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Modification of properties of energy crops under Polish condition as an effect of sewage sludge application onto degraded soil
Journal of Environmental Management 217 (2018) 509e519
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Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Modification of properties of energy crops under Polish condition as an effect of sewage sludge application onto degraded soil Krzysztof Fijalkowski, Karolina Rosikon, Anna Grobelak, Dylan Hutchison, Malgorzata J. Kacprzak* Institute of Environmental Engineering, Czestochowa University of Technology, Czestochowa, Poland
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 December 2017 Received in revised form 17 March 2018 Accepted 31 March 2018
Energy crops are one of the possible solutions for reclamation of degraded or contaminated terrain. Their cultivation requires adequate fertilization typically containing high content of organic matter, nitrogen and phosphorous. While sewage sludge may be one source of these necessary nutrients, it may also modify some plant biomass properties, such as total carbon content. In our study, we determined whether sewage sludge (containing different value of heavy metals) could be an effective fertilizer to obtain good quality energy crops (such as Miscanthus x gigantheus and reed canary grass, Phalaris arundinacea) and simultaneously play positive role for improvement of phytoremediation. The 3-year experiment was performed on degraded soil from terrain of steel mill of Czestochowa (Silesian region, Poland). During the study, it was confirmed that sewage sludge (also in combination with urea, CH4N2O) influences the mobility of Pb, Zn, Cd in soil solution, however the intensity of the process can be limited by plant species and time. Both miscanthus, and reed canary grass were characterized by the low value of bioconcentration factor (BCF), but because biomass was high, the total concentration of heavy metals in crops was comparable with hyperaccumulators. Additionally, modification of the fertilization affected energetic parameters, such as the content of carbon, S/Cl ratio, unitary CO2 emission. However, this effect was not statistically significant. © 2018 Elsevier Ltd. All rights reserved.
Keywords: Energy crop Sewage sludge Degraded soil Contaminant Phytoremediation Energetic value
1. Introduction Increasing energy requirements have become a key issue to be solved around the world (Long et al., 2013). Therefore, in the previous decade, mandatory national targets were set to start replacing petroleum fuels by 2020 (Mehmood et al., 2017). Currently, global energy demand in the scenario by 2030 (Skevas et al., 2014) is considered to come from energy crops cultivated sustainably on non-usable land and/or degraded land (Tripathi et al., 2016) and by 2050 (Pant et al., 2011) will constitute more than a quarter of global demand. The use of bioenergy can not only fill the shortage of fossil fuels, but also stabilize the concentration of greenhouse gases (Long et al., 2013). In accordance with the objectives of the European Union defined by the Directive of the European Parliament and Council
* Corresponding author. Czestochowa University of Technology, Institute of Environmental Engineering, ul. Brzeznicka 60a, 42-200 Czestochowa, Poland. E-mail addresses: kfi[email protected] (K. Fijalkowski), mkacprzak@is. pcz.czest.pl (M.J. Kacprzak). https://doi.org/10.1016/j.jenvman.2018.03.132 0301-4797/© 2018 Elsevier Ltd. All rights reserved.
Directive 2009/28/EC of April 23rd, 2009 on the promotion of the use of energy from renewable sources as well as amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC, by 2020 Poland should reach a 15% share of electricity generated from renewable energy source (RES) in the gross electricity consumption. Unfortunately, the current energy production is not enough to meet the global energy demand (Pandey et al., 2016), so is needed to looking for more environmentally friendly and economical solutions (Long et al., 2013). To avoid negative competition between the use of land for the production of fuels and food, the marginal land or degraded terrain areas deserve attention recently (Fargione et al., 2010). The concept is based on the newly created so-called “sustainable phytoremediation” of such soils by energetic crops and it means that this crops can be grown in areas contaminated and bring many benefits like: reclamation of pollutants, production of bioenergy, improvement of the quality of the soil substrate, aesthetically pleasing landscape and carbon sequestration (Pandey et al., 2016). The problem of degraded land management occupies an
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important place in policy agenda of developed countries. This primarily due to the mining processing, and energy or chemical industrial activity in the area. For example, in Poland, according to data from the Polish Central Statistical Office, the surface of degraded and devastated lands amounted to 61,958 ha (Central Statistical Office in Poland, 2016). Typically, research regarding phytoremediation of contaminated soil are concerned on the slowly growing plant species (Pandey et al., 2016) while much less attention was given to fast growing perennial plants. Data published in 2015 indicate the positive impact of cultivation of perennial grasses on reducing leaching of heavy metals to groundwater (Fernando et al., 2015) and helped ease the climate in the region (Monti and Cosentino, 2015). There are several species of plants that have potential to be used as energy plants and at the same time have the potential for growth in degraded areas which are low in nutrients and water. These plants called “second generation energy crops” are represented by miscanthus perennial grass, which besides high biomass production potential, has low soil requirements and a deep root system, which has a large impact on the prevention of soil erosion and the spread of pollutants (Pandey et al., 2016). Miscanthus tolerates high temperatures climate, and reed canary grass cool climatic conditions. Currently, Phalaris arundinacea it is considered a promising energy plant also due to the fact that it has an effective internal mechanism of N-recycling from shoots to roots, so it is itself efficient in using nutrients (Partala et al., 2001). Research conducted in England by Lord (2015) indicated that reed canary grass is best adapted energy crop to difficult soil conditions in this climate zone. It is well known that the energy crop cultivation on polluted terrains is technically difficult to conduct, because plant production will be significantly hampered by toxicity of pollutants and depletion of nutrients (Kacprzak et al., 2017). Due to the fact that in the phytoremediation processes, over 20% of the management costs are absorbed by the artificial fertilizers application (Wan et al., 2016) so there is a need to use cheap and equally effective and even better solutions (Ociepa et al., 2017). Replacement of mineral fertilization by the organic fertilizers such as sewage sludge, in addition to enriching the substrate with nutrients (Grobelak, 2016), contributes to the reduction of crop emissions from 0.4 to 1.5 Mg CO2 eq.1 ha year1 (Finnan and Styles, 2013). The use of sewage sludge in the soil seems to be one of the most ecological and costeffective options (Boudjabi et al., 2017). The energy contained in biomass is a key factor influencing the energy production and is generally indicated by the amount of heat generated during the total combustion in the standard state. It is limited by composition of elements, especially carbon content in biomass. Higher and lower heating values (HHV, LHV) are used both for calculating energy potentials in biomass (Long et al., 2013). Pandey et al. (2016) indicated in the proposed strategy of “sustainable phytoremediation” an assessment of the quality of biomass in terms of energy, which was produced from contaminated areas. Researchers from India Kumar et al. (2015) pointed out that in order to consider the energy usefulness of plants should be examined its calorific value and carbon content. Unfortunately, currently there is no data from this scientific area, mainly the assessment of the impact of organic waste (sewage sludge and other biosolids) on the calorific value and carbon content in biomass of energy crops cultivated in degraded areas, which is the subject of this study. Hence the aim of the work was to determine whether the use of modifications of fertilization (combination of sewage sludge with additional foliar mineral fertilization by urea) can be useful tools for “hybrid” monitoring of “sustainable phytoremediation” properties with the energy potential of crop plants such as miscanthus or reed
canary grass. 2. Materials and methods 2.1. Materials The soil originated from the terrain of Czestochowa Steelworks (Poland, Silesia region). The sewage sludge was taken from municipal (OW) and industrial (OJ, food processing) wastewater treatment plants WWTP's (Table 1). 2.2. Experiment conditions The experiments were carried out under semi-controlled conditions (containers) over the course of 2.5 years. A total of 12 containers were used throughout the experiment, each with a carrying-capacity of 240 dm3. All containers were equipped with a drainage and hose system that allow them to collect soil leachates. The top layer of soil in 8 of these containers was fertilized with sewage sludge with a composition of 10% of dry matter by weight (equivalent to 45 Mg ha1 3years1, according to the Polish law's permissible value) to the depth of 30 cm. In the first 4 containers, the topsoil layer of soil was mixed with municipal sewage sludge (OW) and in the next 4, with industrial sewage sludge (OJ). The remaining 4 containers were controls. Two plant species: miscanthus (Miscanthus x gigantheus L.) and reed canary grass (Phalaris arundinacea L.), were used as test plants due to their use as highvalue energy potential. After 2 weeks of geochemical equilibration, the miscanthus seedlings were planted (5 plants per container) in 6 of the containers, while seeds of reed canary grass (in the amount of 20 kg ha1) were planted in the remaining 6 containers. At the beginning of the second vegetation period, foliar mineral fertilization with nitrogen (urea) was carried out with a dose of 60 kg N ha1 and 80 kg N ha1 in miscanthus and reed canary grass, respectively. 2.3. Sampling To determine pertinent physio-chemical properties, the soil and sewage sludge samples were air-dried, sieved through a mesh with
Table 1 Characteristic of soil and sewage sludge used in experiments. Parameter
Value
Average
Soil pH in H2O pH in 1 M KCl CEC (cation exchange capacity) C N P Cd Cr Cu Ni Pb Zn
e e cmol kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. P2O5 mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m.
7.88 ± 0.01 7.40 ± 0.01 19.00 ± 0.14 17.45 ± 0.95 481.00 ± 4.9 15.00 ± 1.40 2.30 ± 0.33 26.32 ± 2.83 29.44 ± 0.01 28.99 ± 1.70 46.57 ± 5.25 112.00 ± 9.83
Sewage sludge Metal
value
Cd Cr Cu Ni Pb Zn
mg mg mg mg mg mg
kg1 kg1 kg1 kg1 kg1 kg1
d.m. d.m. d.m. d.m. d.m. d.m.
OW
OJ
6.1 ± 0.46 341.0 ± 3.4 293.4 ± 1.4 116.9 ± 1.0 153.8 ± 3.5 2,6 ± 2.8
0.36 ± 0.1 90.6 ± 0.3 61.6 ± 3.6 18.3 ± 0.5 25.4 ± 0.1 299.2 ± 5.3
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Table 2 The classification of high-temperature corrosion on the base of biomass composition. Fuel indicator of corrosion PWK
Characteristic of biomass
The threat of chloride corrosion
0 1 2 3 4
Cl < 0,02% S/Cl 2,2 S/Cl and K high S/Cl low S/Cl low and K high
no very low low high very high
2 mm diameter holes and stored in plastic bags. The leachates (soil solution) samples were collected monthly, filtered through membrane filters (Sartorius) and acidified to a pH of 2 to perform metal content analysis. After the end of vegetation period the plants were cut down at a height of 5 cm above the ground, weighed, dried at 105 C, and then ground to fine powder in stainless steel grinder (Spex SamplePrep Freezer Mill 6875D) and stored in plastic bags. Thus prepared, the plant material was then used to determine the metal content and energetic parameters (C content and calorific value). Grain size distribution of soil was determined via sieving in accordance with the standard ISO-11277: 2005. Moisture content of soil, sewage sludge and biomass were determined by dryingweighing method in accordance with ISO-11465: 1999. The pH value was determined by a potentiometric analysis in an aqueous solution (pH H2O - active acidity) and 1 M KCl solution (pH KCl exchangeable acidity) with a pH meter CyberScan according to ISO10390: 1997. The total nitrogen content (Kjeldahl nitrogen) was determined by mineralizer BUCHI 426 and distillation apparatus BUCHI 323 according to ISO-11261: 2002. The amount of total carbon determined after dry combustion in the analyzer multi N/C 2100 Analytic Jena AG in accordance with PN-ISO-10694: 2002. Available phosphorus was determined by the colorimetric Egner-Riehm method in accordance with PN-R-04023: 1996 with a HACH spectrophotometer, wavelength of l ¼ 690 nm. Cation exchange capacity (CEC) was determined by the Kappen method according to PN-R-04027: 1997. To determine total heavy metal (Cd, Cr, Cu, Ni, Pb and Zn) content, the soil, soil solution and biomass samples were mineralized in ultra-pure nitric acid (Speed Wave MWS-2 Berghof microwave pressure digestion system). The mineralized samples were analyzed by Atomic Emission Spectrometry with Inductively Coupled Plasma (SPECTRO ICP-OES) according to PN-ISO 11042:2001 protocol. The heat of combustion of biomass was determined using a bomb calorimeter KL-11 Mikado in accordance with PN-81/G04513. The sulfur content in the plant biomass was determined in accordance with PN-G-04584: 2001P using LECO analyzer S TrupSpec. Chlorine plant biomass was determined in accordance with PNISO-587: 2000. 2.3.1. Quality control and quality assurance All the glassware used during experiments were of high quality, acid resistant duran glass. The analytical grade reagents with a certified purity of 99% and stock metal standard solution (1000 ppm) for SPECTRO ICP-OES were produced from SigmaAldrich (Germany). The calibration method for ICP was internal standard method and was measure in triplicate to insure precision of quantitative results. Working standards were prepared by appropriate dilutions of stock standard solutions with double distilled water. The pH meter was calibrated often by standard solutions of pH 4 and 7. The Bomb calorimeter was calibrated before each batch of
samples to be analyzed. Standardization process was done by the combustion a weighed sample of a pure compound of known heat combustion, such as benzoic acid. Then, by dividing this value by the temperature rise produced in the test, we obtain a resultant energy equivalent for this particular calorimeter. The multi N/C 2100 analyzer was calibrated before each batch of samples to be analyzed. Standardization process was done by the calibration method of inserts of different weights of the pure glucose into the reactor, resulting in the generation of a highly linear calibration curve in the ug$g1 range. 2.4. Mathematical analysis 2.4.1. Bioconcentration factor and calorific value of the biomass To evaluate the mobility of heavy metals from the soil to the plant used bioconcentration factor, which was calculated by the formula (Ghosh and Singh, 2005):
BCF ¼
metal concentration in plant shots; mg kg1 metal concentration in soil; mg kg1
(1)
2.4.2. The calorific value of biomass Calorific value of the dried product at 105 C biomass (GCV) was calculated according to the formula (Zhuang et al., 2007):
LHV ¼ Qc 24:42ðWtot þ 8:9HÞ; kJ kg1 d:m:1
(2)
where: Qc - heat of combustion, kJ kg1 e is a net caloric value was measures with a bomb calorimeter Wtot - total moisture, % - for the biomass dried at 105 C, Wtot ¼ 0, H - hydrogen content in biomass, % - H ¼ 6% for the miscanthus, H ¼ 6.3% for reed canary grass (Vassilev et al., 2012), 24.42 - heat of vaporization at 25 C, drain 1% of the water contained in the biomass kJ kg1 8.9 - conversion factor of hydrogen to water.
2.4.3. Fuel indicator of corrosion and free alkali index Fuel indicator of corrosion (PWK) was determined on the basis of the S/Cl ratio and the percentage of potassium in the fuel according to (Wasielewski and Hrabak, 2015): Free alkali index (Af) was estimated according to the formula (Blomberg, 2006):
Af ¼
Na þ K ð2 x S þ ClÞ LHV
where: Af - free alkali index, mol MJ1, mol GJ1
(3)
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Na - acetic acid soluble, or total sodium, mol kg1 K - acetic acid soluble, or total potassium, mol kg1 S - sulfur content of the fuel, mol kg1 Cl - chlorine content of the fuel, mol kg1 LHV - lower heating value, MJ kg1
2.4.4. Unit CO2 emission (ECO2) Unit CO2 emissions per unit of chemical energy during the combustion of biomass, calculated according to the formula (Kobyłecki, 2014):
ECO2 ¼
44 C x ; kgCO2 MJ1 12 LHV
(4)
where: C - The carbon content in the biomass, kg kg1 LHV - lower heating value, MJ kg1 2.5. Statistical analysis A One-way ANOVA test was used to identify differences among groups of variables using Tukey's post hoc with a significance <0,05. Additionally, the data were also submitted to nonparametric Kruskal-Wallis test. Variables with similar behaviors will be presented with the same letter (a, b, c). Therefore, different letters represent the existence of statistically significant differences among groups of variables. All statistical analyses were generated with the software Statistica 10.0, while the standard deviations were determined via Microsoft Office Excel. Bars on charts indicate sample standard deviation where significant differences from the control exceeded p < 0,05. 3. Results and discussion 3.1. The pH value changes in soil solution While sewage sludge may be an excellent fertilizer, it may also contain high concentrations of environmental contaminants such as heavy metals with ions that migrate in soil solutions, and leach into groundwater reservoirs. Concentration fluctuations of heavy metals in these soils closely correlate with the pH; A decrease in pH usually increased the release of heavy metal ions to soil solution. In the first year of the experiment, it was found that the addition of sewage sludge resulted in a decrease of pH in the soil solution under both crops as compared to the control (Figs. 1 and 2). Similar changes in soil pH value following sewage sludge/biosoilds application are common described (Alvarenga et al., 2016). The decrease of pH value is usually explained as an acidification of decomposable products of sewage sludge and simultaneous production of humic acids. In our study, however, the pH value generally increased slightly in time; This pH change was more visible under miscanthus crops and reached a maximum after 24 months. The pH then regressed to values in the range of 7.1e7.3; depending on container. 3.2. Heavy metal mobilization in soil solution Our study confirmed that application of sewage sludge onto degraded land may lead to an increase of heavy metal mobilization in soil solutions. However, this process depends on length of application and plant species. 3.2.1. Cadmium At the beginning of the experiment, an increase in the
concentration of Cd ions in leachate collected from both the cultivation of miscanthus (Fig. 3) and reed canary grass (Fig. 4) was observed. This Cd ion content increase in the soil solution lasted for 6 months of the experiment, but then subsequently decreased. The maximum concentration of ions in the tested permeates under the miscanthus conditions was recorded in the control (0.7 mg dm3), while under the canary - fertilized - OJ 0.43 mg dm3. It was noted, however, that the ion concentration of Cd in the soil solution of all combinations was lower as compared to the control. There was no apparent impact from the applied modification fertilization (introduction of foliar fertilization with urea) to change the concentration of Cd in the soil solution. 3.2.2. Lead At the beginning of the experiment, the highest content of Pb ions (1.99 g dm3) for miscanthus was recorded in leachates taken from sample fertilized OW and was higher than the control (Fig. 5). In the case of the canary, however, the highest concentration of Pb ions was recorded for the non-fertilized samples in the 6th week of the process with a value of 3.12 g dm3 (Fig. 6). In the case of miscanthus (Fig. 5), the Pb content in all combinations was lower relative to the controls. After 18 months this process is decreased, with 30 months experience minimum value. As for the cases of both the reed canary grass (Fig. 6) and the miscanthus, it was observed that after 18 months the process caused a decrease in the concentration of Pb in the soil solutions of all the combinations that were maintained on the same level. 3.2.3. Zinc In the first year after of the experiment (from 2 to 11 months), miscanthus fertilized OW concentration of Zn ions in the soil solution was higher in comparison to the control sample and fertilized OJ (Fig. 7). In the case of canary grass, we observed the opposite reaction e a higher concentration of Zn ions were observed after fertilization with OJ and lower after fertilization with OW (Fig. 8). In addition, generally higher concentrations of Zn were detected in the soil solution associated with canary grass rather than with miscanthus. After modifying the method of fertilization (the second year of the experiment), we observed some fluctuations of the content of Zn ions in the soil leachates in all combinations (Figs. 7 and 8). It was also observed that after the 14th month, the concentration of Zn in the soil solution increased. However, we didn't observe a clear relationship between fertilizer modification and changes of Zn ion concentration in soil leachates. 3.3. The accumulation of heavy metals in biomass One important indicator of the effectiveness of the phytoremediation process is the bioconcentration factor (BCF). The BCF's for all studied metals (i.e. Cd, Cr, Cu, Ni, Pb, Zn) in all samples, resulted in values <1 (Table 3) and this indicates the metal tolerance occurred via the exclusion mechanism, while values >1 indicate that the metal accumulates in the plant biomass (Gerhardt et al., 2017). In our studies the highest BCFI ratio determined for Cr in the first and third year of the iscanthus experiment were for Cr ¼ 0.975 and BCFIII for Cr ¼ 0.631. For reed canary grass, the highest bioconcentration was determined for zinc in the first year of the experiment in the control (BCFI for Zn ¼ 0.616) and with the soil fertilized with sewage sludge (BCFI for Zn ¼ 0.64). These data confirmed that energy crops are not likely to accumulate heavy metals and translocate them to aerial portions of a plant. According to researchers, miscanthus accumulates heavy metals most effectively from all energy grasses (Lyubun and Tychinin, 2007) and reed canary grass uptake Zn more than other metals (Cd, Cu
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Fig. 1. The changes of pH values in soil leachates under miscanthus crops, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 2. The changes of pH in soil solution of container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
and Pb) (Baryła et al., 2009). The research carried out confirms these reports which is also confirmed by Nsanganwimana et al. (2015) who reported the even lower range of BCFs values mainly for the same heavy metals. Also Wanat et al. (2013) noticed that metalloid concentrations in aerial parts of miscanthus grown on contaminated soils are low compare to the soil contamination rate. For reed canary grass the same range of heavy metals BCFs was ska and Klink (2014)and this researchers also received by Polechon suggest that reed canary grass can be suitable for phytostabilization. However, noteworthy is that total metals content in energy crops biomass can be high if taking into consideration the total biomass production yield which can be achieved. Our results suggest that these crops may be good candidates for phytostabilisation (instead of typical phytoextraction) of heavy metals-contaminated soils for use in energy production which is also confirmed by Zorer Çelebi et al. (2018). The achieved positive effect is the prevention of the pollutants migration in the soil profile and low concentration of heavy metals in ashes after biomass incineration.
3.4. Energy properties of biomass 3.4.1. Calorific of biomass The addition of organic fertilizers to energy crops generally has a positive effect on their pertinent energetic properties. Both the use of sewage sludge and composts significantly improved the quality of biomass in energy crops. Analysing the biomass energetic parameters, it was found that influence of the origin of sewage sludge and the additional nitrogen fertilization on the energy values of biomass of miscanthus and reed canary grass occurred (Fig. 9). Under sewage sludge in the first year of the experiment, the calorific value of miscanthus decreased, whereas for reed canary grass, it was observed that the calorific value was influenced by the origin of sewage sludge, e.g., sludge from municipal wastewater treatment plants, which resulted in a reduction of this parameter; On the contrary, sewage sludge from the food industry resulted in an increase. In the second year of the experiment, calorific value of miscanthus biomass ranged from 12,290 to 14,507 kJ kg1d.m., and reed canary grass' from 13,681 to 16,249 kJ kg1d.m. and was
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Fig. 3. The changes of Cd concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 4. The changes of [Cd] in the soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 5. The changes of Pb concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
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Fig. 6. The changes of Pb concentration in soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 7. The changes of Zn concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 8. The changes of Zn concentration in soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
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Table 3 Bioconcentration factor values for the aerial parts of the plants in the container experiment. BCF
1st Year C
2nd Year OW
MISCANTHUS 0.113c Cd 0.112a Cr 0.975c 0.418c Cu 0.144c 0.084b Ni 0.172c 0.113c Pb 0.050a 0.051a Zn 0.189c 0.079a REED CANARY GRASS Cd 0.138c 0.106b Cr 0.471c 0.242b Cu 0.245c 0.135b Ni 0.113b 0.090b Pb 0.048a 0.049a Zn 0.616c 0.328b
3rd Year
OJ
C
CþM
OW
OW þ M
OJ
OJ þ M
C
CþM
OW
OW þ M
OJ
OJ þ M
0.134c 0.613c 0.136b 0.114c 0.044a 0.121b
0.088c 0.132a 0.127b 0.057a 0.044a 0.090b
0.070b 0.179b 0.100b 0.040a 0.044a 0.120b
0.019a 0.093a 0.050a 0.023a 0.029a 0.032a
0.028a 0.086a 0.055a 0.020a 0.030a 0.025a
0.023a 0.099a 0.077a 0.023a 0.029a 0.043a
0.012a 0.109a 0.079a 0.030a 0.027a 0.042a
0.058b 0.293b 0.080a 0.035a 0.052a 0.128b
0.049b 0.631c 0.069a 0.077b 0.033a 0.242c
0.041b 0.245b 0.048a 0.045a 0.024a 0.090a
0.018a 0.108a 0.038a 0.017a 0.024a 0.035a
0.044b 0.204b 0.074a 0.033a 0.032a 0.075a
0.030a 0.216b 0.058a 0.032a 0.028a 0.080a
0.144c 0.284b 0.223c 0.087b 0.043a 0.640c
0.022a 0.281b 0.161b 0.088b 0.046a 0.270b
0.029a 0.095a 0.158b 0.030a 0.046a 0.279b
0.018a 0.049a 0.108a 0.030a 0.035a 0.100a
0.017a 0.082a 0.085a 0.031a 0.035a 0.105a
0.017a 0.068a 0.168b 0.053a 0.039a 0.297b
0.017a 0.101a 0.132b 0.040a 0.037a 0.229b
0.048a 0.183a 0.125b 0.035a 0.040a 0.320b
0.025a 0.141a 0.095a 0.023a 0.033a 0.304b
0.033a 0.067a 0.078a 0.025a 0.024a 0.115a
0.024a 0.072a 0.073a 0.014a 0.022a 0.106a
0.036a 0.128a 0.117a 0.043a 0.032a 0.411b
0.035a 0.115a 0.114a 0.037a 0.029a 0.311b
C: control; OW: municipal sewage sludge; OJ: food processing sewage sludge; M: urea. abc: lowercase different letters indicate significant differences (p < 0,05) between means of each metal BCF factor for the different container in 3 years period.
Fig. 9. The calorific value of miscanthus (left) and reed canary grass (right) in the container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
dependent on both the origin of sewage sludge and additional N fertilizer. In the third year, the calorific value of miscanthus ranged from 13,102 to 14,197 kJ kg1d.m., while the value of the reed canary grass ranged from 13,527 to 15,846 kJ kg1d.m. Like the second year, the calorific value was dependent on the origin of sewage
sludge and nitrogen fertilization. The results obtained in this study were also confirmed by other researchers e.g caloric value of miscanthus and reed canary grass respectively for both crops were 19.100 and 18.000 kJ kg1d.m. (compost fertilization) (Lord, 2015); (artificial fertilizers) 17,800
Fig. 10. The total carbon concentration in miscanthus (left) and reed canary grass (right) of the container experiment with two sewage sludge from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
0.5 0.4121a 3 high 0.0056 0.56 0.656b 3 high 0.0051 0.67 0.3501a 3 high 0.0065 0.29 0.5278b 3 high 0.0013 C: control; OW: municipal sewage sludge; OJ: food processing sewage sludge; M: urea. abc: lowercase different letters indicate significant differences (p < 0,05) between means of each K present for the different container in 3 years period.
0.57 0.3972a 3 high 0.0025 0.37 0.3554a 3 high 0.0039 0.28 0.7467c 3 high 0.0161 0.05 0.9688c 3 high 0.0022 0.29 0.5248b 3 high 0.012 0.42 0.7498c 3 high 0.0169 0.17 0.8372c 3 high 0.0032 0.31 0.5408b 3 high 0.0014 0.56 0.6602b 3 high 0.0036
0.12 0.8471c 3 high 0.0046
0.22 0.2296bc 3 high 0.00047 0.05 0.1152c 3 high 0.00003 0.11 0.0927c 3 high 0.00095 0.03 1.746c 3 high 0.00057 0.11 0.2124a 3 high 0.00076 0.17 0.1783a 3 high 0.0011 0.2 0.6577b 3 high 0.0033 0.08 0.4563ab 3 high 0.0017 0.05 0.4725ab 3 high 0.0028 0.25 0.6504b 3 high 0.0016 0.11 0.5789b 3 high 0.0018 0.12 0.4602ab 3 high 0.003 0.11 0.3852a 3 high 00033 0.09 0.3993a 3 high 0.0011
OJ OW þ M OW CþM C OJ þ M OJ OW þ M OW CþM C OJ OW C
517
MISCANTHUS S/Cl 0.14 K, % 0.3745a PWk 3 risk of corrosion high Af, mol MJ1 0.0018 REED CANARY GRASS S/Cl 0.19 K, % 0.544b PWk 3 risk of corrosion high Af, mol MJ1 0.0041
3rd Year 2nd Year
3.4.3. Risk of chloride corrosion The most important is corrosion risk assessment resulting from the combustion of biomass is the content estimation of chlorine, sulfur, potassium and sodium. These elements are the basis for the determination of the fuel indicator parameter of chloride corrosion (ICV) and the index of free alkali (Af). An important criterion for energetic assessment of biomass for, next to the energy performance, including whether its burning causes corrosion risks. The combustion of fuels such as biomass in boilers results in an accelerated consumption of steel compounds via the corrosive effect of molecular chlorine (Cl2) and hydrogen chloride (HCl). Corrosion is caused primarily by Cl2, which is a product of the oxidation of HCl located in the exhaust gas, but also by the alkaline metal chlorides contained in significant quantities in biofuels, such as Na, K and S. This type of corrosion is referred to as chemical corrosion or chlorohigh-temperature corrosion and is much faster than the oxidation process (Persson et al., 2007). Therefore, to determine whether a tested plant-biomass poses such a threat, the content of elements in plants was examined and then index excess alkali (Af) and indicator of chloride corrosion (PWk) were calculated. The S/Cl ratio was in the range from 0.03 to 0.25 and from 0.12 to 0.67 in the
1st Year
3.4.2. Carbon content in biomass The decrease of carbon content in plants growing on the soil with sewage sludge was noted; However, the results were different because they were dependent on the use of sewage sludge from different origin (Fig. 10). The use of OW was associated with a decrease in the concentration of biomass total carbon content of miscanthus, while with OJ an increase was observed. However, in reed canary grass cultivation, the concentration of carbon in the biomass remained at a similar level and maintained in the range from 342.550 to 359.850 g kg1d.m (34.25e35.98%). Additionally, N fertilization application either resulted in an increase or decrease in the concentration of carbon in the biomass of miscanthus and reed canary grass, depending on the origin of sewage sludge. In the third year of the experiment, the concentration of carbon in the biomass of miscanthus and reed canary grass increased in comparison with the first and second year of research and remained at a similar level in all combinations. In our study carbon content in biomass was not much lower the presented by the other researchers which received values (%) for miscanthus and reed canary grass: 43, 44 (Mehmood et al., 2017); 45, 40 (Lord, 2015) respectively. From polish climate condition research conducted for reed canary grass conducted by Kołodziej et al. (2016) the carbon content in biomass was not measured.
Table 4 Fuel chloride corrosion ratio (PWk) and free alkali index (Af) of container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
and 16,300 kJ kg1d.m. (Mehmood et al., 2017) (sewage sludge fertilization) 15,680 kJ kg1d.m. for only reed canary grass (Kołodziej et al., 2016). Fertilizing with N resulted in a decrease in the calorific value of the examined plant species in the second as well as in the third year of the experiment. In addition, the impact of fertilization was decreasing in second and third year of the experiment. This phenomena was also described by Kołodziej et al. (2016) where sewage sludge dose was from 0 to 60 Mg ha1 and received caloric value of reed canary grass in the range 15,680e15,509 kJ kg1d.m. It should be also noted that the biomass caloric value is significantly affected by the biomass humidity, which, according to many researchers, is related to the harvest date (Bassam, 2013) and the humidity value obtained in this experiment was at the level of 23e50% for misanthus and 39e68% for reed canary grass (data not published) because autumn harvests were used. Therefore, a not much lower biomass caloric values in relation to others cited researcher could have resulted from the higher water content and the type of sewage sludge used.
OJ þ M
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Fig. 11. The unit emissions of CO2 during the combustion of (left) and reed canary grass (right) biomass of the container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
cultivation of miscanthus and reed canary grass, respectively (see Table 2). On the base of these values (a low S/Cl ratio), all samples were classified as causing a high risk of PWk. In addition, the calculated Af in the cultivation of canary, throughout the process was negative. However, under miscanthus, negative Af values were obtained only in the third year of the experiment for plants both fertilized with urea and grown on soil with municipal sewage sludge (OW þ M) treatment, and on soil amended with sewage sludge from the food industry alone, while remaining positive for other combinations (see Table 4).
3.4.4. Unitary CO2 emission (ECO2) during the combustion of biomass The combustion process entails an increase in CO2 emissions into the atmosphere. Many researchers suggest the ability to counteract the increase in anthropogenic CO2 emissions from energy conversion processes by thermal treatment of biomass (Lehmann and Joseph, 2015). Energy from biomass burning is treated as “pure” because the accompanying CO2 emissions are equal to zero. Kobyłecki (2014) have shown, however, that from the environmental point of view this approach is wrong, because the source of the fuel does not affect the properties of the CO2 generated from energy conversion processes. Our results support their conclusion. Specific emission of CO2 in the experiment was in the range from 0.094 to 0.105 kgCO2 MJ1 for and from 0.084 to 0.102 kgCO2 MJ1 for reed canary grass, respectively. However, we didn't observe a clear influence of fertilizer and plant species on the changes of specific emission of carbon dioxide. Literature data indicate that the combustion 1 kg of coal results in CO2 emissions at the level of 1.14 kgCO2 MJ1, while burning 1 kg of methane - 0.055 kgCO2 MJ1 (Kobyłecki, 2014). In the case of biomass, CO2 emission accompanying the combustion is lower than that achieved during the combustion of coal and higher than that obtained during the combustion of methane. In our experiment, the highest values of CO2 emissions (within the range of 0.106e0.115 kgCO2 MJ1) were detected in the third year of the process, while the lowest (from 0.089 to 0.096 kgCO2 MJ1) were detected in the second year (Fig. 11). In addition, it was observed that the additional foliar nitrogen fertilization increased estimated CO2 emissions both in the second and in the third year of experiment. However, in the first year of the experiment, we found minimal emission of CO2 in trials of biomass grown on soil fertilized with sewage sludge. In the case of reed canary grass (Fig. 11), for the first year of the experiment, soil fertilization with sewage sludge applied at minimal level reduced the estimated unit CO2 emissions, which ranged
from 0.097 to 0.1 kgCO2 MJ1. In the second year of the process, the decline of ECO2 values was more apparent (as compared to nonfertilized control). In the third year, we observed a different reaction: an increase of ECO2 in treated samples. Only in combination with foliar fertilization the decrease of ECO2 was observed as compared to control.
4. Conclusion The use of degraded land for cultivation of long-term grasses for energy purposes ensures increased energy security by reducing dependence on other crops and a number of environmental benefits. Such soils are ideally suited for non-food crops such as energy crops so that they can have an energy source, which has comparable energy characteristics, comparable to conventional ones, and in addition extremely cheap to obtain and relatively safe for the environment. However, there is a notable problem in the management of degraded soils: they are relatively poor in nutrients necessary for proper plant functioning. Therefore, it is important to ensure proper fertilization of soils providing all the necessary nutrients. Undoubtedly, one of these is the use of sewage sludge since it has excellent fertilizer properties. The use of sewage sludge as a replacement for fertilizers favors the formation and stabilization of the soil through the decomposition of organic matter which is heavily disturbed in areas contaminated with heavy metals. Its ecological capabilities also affect the physical and chemical properties of the soil (improving aggregation and infiltration capacity and increasing the availability of nutrients), even if it is possible to increase the mobility of metals and metalloids - which could be captured by the energy crops root system. Our studies, however, indicate that any fertilizer modification on degraded land leads to changes in both phytoremediation and energy properties of plants. It is probably connected with the poor soil buffer capacity of degraded land, nutrient depletion, loss of soil organic carbon. Hence, the use of sewage sludge could help stop these negative processes, but the quality of sewage sludge introduced into the soil is an important determining factor in its efficacy. Fulfilling these conditions does not only lead to the restoration of degraded soils, but also allows for an additional source of renewable energy, which is extremely important given the continuous and systematic depletion of conventional sources. From conducted study, results evidenced that metal and metalloid uptake by miscanthus and reed canary grass is lower than typical hyperaccumulators as well as the transfer from soil to aerial parts. This behaviour makes this crops potential for the
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“sustainable phytoremediation” energy culture on degraded terrains, as a part of phytostabilisation process which are general. This kind of land are not usable for any other activities and they are a threat to surroundings. Data received indeed shows that miscanthus and reed canary grass could be mainly able to reduce wind erosion, to immobilize a part of contaminants by adsorption or accumulation in roots, and to limit the transfer to aerial parts. And also, as we indicated the clean energy profit as well as clean sewage sludge (biosolids) sustainable management. It is important that perennial crops could provide the additional sequestration of carbon in the soil at high yields. Hence, in that case greenhouse gas emissions will be lower because of application of biosolids fertilizers, which leads to higher carbon formation for crops with high biomass production. Acknowledgments The study was supported by an internal grant of the Czestochowa University of Technology, Poland: BS/PBe401e304/11. Karolina Rosikon, received the grant within the project DoktoRIS-Scholarship program for innovative Silesia, co-financed by the European Union under the European Social Fund. References Alvarenga, P., Farto, M., Mourinha, C., Palma, P., 2016. Beneficial use of dewatered and composted sewage sludge as soil amendments: behaviour of metals in soils and their uptake by plants. Waste Biomass Valorization 7, 1189e1201. https:// doi.org/10.1007/s12649-016-9519-z. ska, H., 2009. Content of components in some Baryła, R., Sawicka, J., Kulik, M., Lipin grass species irrigated with purified sewage. J. Elemntology. https://doi.org/ 10.5601/jelem.2009.14.1.01. Bassam, N.E., 2013. Energy Plant Species. Routledge. Blomberg, T., 2006. Which are the right test conditions for the simulation of high temperature alkali corrosion in biomass combustion? Mater. Corros. 57, 170e175. https://doi.org/10.1002/maco.200503905. Boudjabi, S., Kribaa, M., Chenchouni, H., 2017. Sewage sludge fertilization alleviates drought stress and improves physiological adaptation and yield performances in Durum Wheat (Triticum durum): a double-edged sword. J. King Saud Univ. Sci. 1e9 https://doi.org/10.1016/j.jksus.2017.12.012. Central Statistical Office in Poland, 2016. The CSO Report 2016. Fargione, J.E., Plevin, R.J., Hill, J.D., 2010. The ecological impact of biofuels. Annu. Rev. Ecol. Evol. Syst. 41, 351e377. https://doi.org/10.1146/annurev-ecolsys102209-144720. o, S., Barbosa, B., Costa, J., Duarte, M.P., Monti, A., 2015. Perennial Fernando, A.L., Bole grass production opportunities on marginal mediterranean land. BioEnergy Res. 8, 1523e1537. https://doi.org/10.1007/s12155-015-9692-0. Finnan, J., Styles, D., 2013. Hemp_ A more sustainable annual energy crop for climate and energy policy. Energy Policy 58, 152e162. https://doi.org/10.1016/ j.enpol.2013.02.046. Gerhardt, K.E., Gerwing, P.D., Greenberg, B.M., 2017. Opinion: taking phytoremediation from proven technology to accepted practice. Plant Sci. 256, 170e185. https://doi.org/10.1016/j.plantsci.2016.11.016. Ghosh, M., Singh, S.P., 2005. A comparative study of cadmium phytoextraction by accumulator and weed species. Environ. Pollut. 133, 365e371. https://doi.org/ 10.1016/j.envpol.2004.05.015. Grobelak, A., 2016. Organic Soil Amendments in the Phytoremediation Process, in: Phytoremediation. Springer International Publishing, Cham, pp. 21e39. https:// doi.org/10.1007/978-3-319-41811-7_2. Kacprzak, M., Neczaj, E., Fijałkowski, K., Grobelak, A., Grosser, A., Worwag, M., Rorat, A., Brattebo, H., Almås, Å., Singh, B.R., 2017. Sewage sludge disposal strategies for sustainable development. Environ. Res. 156, 39e46. https:// doi.org/10.1016/j.envres.2017.03.010. Kobyłecki, R., 2014. Environmental Aspects of Biomass Thermolysis. Monoraphy. Czestochowa University of Technology, Czestochowa.
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Biomass Bioenergy 78, 110e125. https:// doi.org/10.1016/j.biombioe.2015.04.015. Lyubun, Y.V., Tychinin, D.N., 2007. Phytoremediation in Russia. In: Phytoremediation, Methods in Biotechnology. Humana Press, Totowa, NJ, pp. 423e434. https://doi.org/10.1007/978-1-59745-098-0_29. Mehmood, M.A., Ibrahim, M., Rashid, U., Nawaz, M., Ali, S., Hussain, A., Gull, M., 2017. Biomass production for bioenergy using marginal lands. Sustain. Prod. Consum. 9, 3e21. https://doi.org/10.1016/j.spc.2016.08.003. Monti, A., Cosentino, S.L., 2015. Conclusive results of the European project OPTIMA: optimization of perennial grasses for biomass production in the mediterranean area. BioEnergy Res. 8, 1459e1460. https://doi.org/10.1007/s12155-015-9679-x. Nsanganwimana, F., Pourrut, B., Waterlot, C., Louvel, B., Bidar, G., Labidi, S., s-Hadj Sahraoui, A., Fourrier, H., Douay, F., Fontaine, J., Muchembled, J., Loune 2015. 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Research article
Modification of properties of energy crops under Polish condition as an effect of sewage sludge application onto degraded soil Krzysztof Fijalkowski, Karolina Rosikon, Anna Grobelak, Dylan Hutchison, Malgorzata J. Kacprzak* Institute of Environmental Engineering, Czestochowa University of Technology, Czestochowa, Poland
a r t i c l e i n f o
a b s t r a c t
Article history: Received 30 December 2017 Received in revised form 17 March 2018 Accepted 31 March 2018
Energy crops are one of the possible solutions for reclamation of degraded or contaminated terrain. Their cultivation requires adequate fertilization typically containing high content of organic matter, nitrogen and phosphorous. While sewage sludge may be one source of these necessary nutrients, it may also modify some plant biomass properties, such as total carbon content. In our study, we determined whether sewage sludge (containing different value of heavy metals) could be an effective fertilizer to obtain good quality energy crops (such as Miscanthus x gigantheus and reed canary grass, Phalaris arundinacea) and simultaneously play positive role for improvement of phytoremediation. The 3-year experiment was performed on degraded soil from terrain of steel mill of Czestochowa (Silesian region, Poland). During the study, it was confirmed that sewage sludge (also in combination with urea, CH4N2O) influences the mobility of Pb, Zn, Cd in soil solution, however the intensity of the process can be limited by plant species and time. Both miscanthus, and reed canary grass were characterized by the low value of bioconcentration factor (BCF), but because biomass was high, the total concentration of heavy metals in crops was comparable with hyperaccumulators. Additionally, modification of the fertilization affected energetic parameters, such as the content of carbon, S/Cl ratio, unitary CO2 emission. However, this effect was not statistically significant. © 2018 Elsevier Ltd. All rights reserved.
Keywords: Energy crop Sewage sludge Degraded soil Contaminant Phytoremediation Energetic value
1. Introduction Increasing energy requirements have become a key issue to be solved around the world (Long et al., 2013). Therefore, in the previous decade, mandatory national targets were set to start replacing petroleum fuels by 2020 (Mehmood et al., 2017). Currently, global energy demand in the scenario by 2030 (Skevas et al., 2014) is considered to come from energy crops cultivated sustainably on non-usable land and/or degraded land (Tripathi et al., 2016) and by 2050 (Pant et al., 2011) will constitute more than a quarter of global demand. The use of bioenergy can not only fill the shortage of fossil fuels, but also stabilize the concentration of greenhouse gases (Long et al., 2013). In accordance with the objectives of the European Union defined by the Directive of the European Parliament and Council
* Corresponding author. Czestochowa University of Technology, Institute of Environmental Engineering, ul. Brzeznicka 60a, 42-200 Czestochowa, Poland. E-mail addresses: kfi[email protected] (K. Fijalkowski), mkacprzak@is. pcz.czest.pl (M.J. Kacprzak). https://doi.org/10.1016/j.jenvman.2018.03.132 0301-4797/© 2018 Elsevier Ltd. All rights reserved.
Directive 2009/28/EC of April 23rd, 2009 on the promotion of the use of energy from renewable sources as well as amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC, by 2020 Poland should reach a 15% share of electricity generated from renewable energy source (RES) in the gross electricity consumption. Unfortunately, the current energy production is not enough to meet the global energy demand (Pandey et al., 2016), so is needed to looking for more environmentally friendly and economical solutions (Long et al., 2013). To avoid negative competition between the use of land for the production of fuels and food, the marginal land or degraded terrain areas deserve attention recently (Fargione et al., 2010). The concept is based on the newly created so-called “sustainable phytoremediation” of such soils by energetic crops and it means that this crops can be grown in areas contaminated and bring many benefits like: reclamation of pollutants, production of bioenergy, improvement of the quality of the soil substrate, aesthetically pleasing landscape and carbon sequestration (Pandey et al., 2016). The problem of degraded land management occupies an
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important place in policy agenda of developed countries. This primarily due to the mining processing, and energy or chemical industrial activity in the area. For example, in Poland, according to data from the Polish Central Statistical Office, the surface of degraded and devastated lands amounted to 61,958 ha (Central Statistical Office in Poland, 2016). Typically, research regarding phytoremediation of contaminated soil are concerned on the slowly growing plant species (Pandey et al., 2016) while much less attention was given to fast growing perennial plants. Data published in 2015 indicate the positive impact of cultivation of perennial grasses on reducing leaching of heavy metals to groundwater (Fernando et al., 2015) and helped ease the climate in the region (Monti and Cosentino, 2015). There are several species of plants that have potential to be used as energy plants and at the same time have the potential for growth in degraded areas which are low in nutrients and water. These plants called “second generation energy crops” are represented by miscanthus perennial grass, which besides high biomass production potential, has low soil requirements and a deep root system, which has a large impact on the prevention of soil erosion and the spread of pollutants (Pandey et al., 2016). Miscanthus tolerates high temperatures climate, and reed canary grass cool climatic conditions. Currently, Phalaris arundinacea it is considered a promising energy plant also due to the fact that it has an effective internal mechanism of N-recycling from shoots to roots, so it is itself efficient in using nutrients (Partala et al., 2001). Research conducted in England by Lord (2015) indicated that reed canary grass is best adapted energy crop to difficult soil conditions in this climate zone. It is well known that the energy crop cultivation on polluted terrains is technically difficult to conduct, because plant production will be significantly hampered by toxicity of pollutants and depletion of nutrients (Kacprzak et al., 2017). Due to the fact that in the phytoremediation processes, over 20% of the management costs are absorbed by the artificial fertilizers application (Wan et al., 2016) so there is a need to use cheap and equally effective and even better solutions (Ociepa et al., 2017). Replacement of mineral fertilization by the organic fertilizers such as sewage sludge, in addition to enriching the substrate with nutrients (Grobelak, 2016), contributes to the reduction of crop emissions from 0.4 to 1.5 Mg CO2 eq.1 ha year1 (Finnan and Styles, 2013). The use of sewage sludge in the soil seems to be one of the most ecological and costeffective options (Boudjabi et al., 2017). The energy contained in biomass is a key factor influencing the energy production and is generally indicated by the amount of heat generated during the total combustion in the standard state. It is limited by composition of elements, especially carbon content in biomass. Higher and lower heating values (HHV, LHV) are used both for calculating energy potentials in biomass (Long et al., 2013). Pandey et al. (2016) indicated in the proposed strategy of “sustainable phytoremediation” an assessment of the quality of biomass in terms of energy, which was produced from contaminated areas. Researchers from India Kumar et al. (2015) pointed out that in order to consider the energy usefulness of plants should be examined its calorific value and carbon content. Unfortunately, currently there is no data from this scientific area, mainly the assessment of the impact of organic waste (sewage sludge and other biosolids) on the calorific value and carbon content in biomass of energy crops cultivated in degraded areas, which is the subject of this study. Hence the aim of the work was to determine whether the use of modifications of fertilization (combination of sewage sludge with additional foliar mineral fertilization by urea) can be useful tools for “hybrid” monitoring of “sustainable phytoremediation” properties with the energy potential of crop plants such as miscanthus or reed
canary grass. 2. Materials and methods 2.1. Materials The soil originated from the terrain of Czestochowa Steelworks (Poland, Silesia region). The sewage sludge was taken from municipal (OW) and industrial (OJ, food processing) wastewater treatment plants WWTP's (Table 1). 2.2. Experiment conditions The experiments were carried out under semi-controlled conditions (containers) over the course of 2.5 years. A total of 12 containers were used throughout the experiment, each with a carrying-capacity of 240 dm3. All containers were equipped with a drainage and hose system that allow them to collect soil leachates. The top layer of soil in 8 of these containers was fertilized with sewage sludge with a composition of 10% of dry matter by weight (equivalent to 45 Mg ha1 3years1, according to the Polish law's permissible value) to the depth of 30 cm. In the first 4 containers, the topsoil layer of soil was mixed with municipal sewage sludge (OW) and in the next 4, with industrial sewage sludge (OJ). The remaining 4 containers were controls. Two plant species: miscanthus (Miscanthus x gigantheus L.) and reed canary grass (Phalaris arundinacea L.), were used as test plants due to their use as highvalue energy potential. After 2 weeks of geochemical equilibration, the miscanthus seedlings were planted (5 plants per container) in 6 of the containers, while seeds of reed canary grass (in the amount of 20 kg ha1) were planted in the remaining 6 containers. At the beginning of the second vegetation period, foliar mineral fertilization with nitrogen (urea) was carried out with a dose of 60 kg N ha1 and 80 kg N ha1 in miscanthus and reed canary grass, respectively. 2.3. Sampling To determine pertinent physio-chemical properties, the soil and sewage sludge samples were air-dried, sieved through a mesh with
Table 1 Characteristic of soil and sewage sludge used in experiments. Parameter
Value
Average
Soil pH in H2O pH in 1 M KCl CEC (cation exchange capacity) C N P Cd Cr Cu Ni Pb Zn
e e cmol kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. P2O5 mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m. mg kg1 d.m.
7.88 ± 0.01 7.40 ± 0.01 19.00 ± 0.14 17.45 ± 0.95 481.00 ± 4.9 15.00 ± 1.40 2.30 ± 0.33 26.32 ± 2.83 29.44 ± 0.01 28.99 ± 1.70 46.57 ± 5.25 112.00 ± 9.83
Sewage sludge Metal
value
Cd Cr Cu Ni Pb Zn
mg mg mg mg mg mg
kg1 kg1 kg1 kg1 kg1 kg1
d.m. d.m. d.m. d.m. d.m. d.m.
OW
OJ
6.1 ± 0.46 341.0 ± 3.4 293.4 ± 1.4 116.9 ± 1.0 153.8 ± 3.5 2,6 ± 2.8
0.36 ± 0.1 90.6 ± 0.3 61.6 ± 3.6 18.3 ± 0.5 25.4 ± 0.1 299.2 ± 5.3
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Table 2 The classification of high-temperature corrosion on the base of biomass composition. Fuel indicator of corrosion PWK
Characteristic of biomass
The threat of chloride corrosion
0 1 2 3 4
Cl < 0,02% S/Cl 2,2 S/Cl and K high S/Cl low S/Cl low and K high
no very low low high very high
2 mm diameter holes and stored in plastic bags. The leachates (soil solution) samples were collected monthly, filtered through membrane filters (Sartorius) and acidified to a pH of 2 to perform metal content analysis. After the end of vegetation period the plants were cut down at a height of 5 cm above the ground, weighed, dried at 105 C, and then ground to fine powder in stainless steel grinder (Spex SamplePrep Freezer Mill 6875D) and stored in plastic bags. Thus prepared, the plant material was then used to determine the metal content and energetic parameters (C content and calorific value). Grain size distribution of soil was determined via sieving in accordance with the standard ISO-11277: 2005. Moisture content of soil, sewage sludge and biomass were determined by dryingweighing method in accordance with ISO-11465: 1999. The pH value was determined by a potentiometric analysis in an aqueous solution (pH H2O - active acidity) and 1 M KCl solution (pH KCl exchangeable acidity) with a pH meter CyberScan according to ISO10390: 1997. The total nitrogen content (Kjeldahl nitrogen) was determined by mineralizer BUCHI 426 and distillation apparatus BUCHI 323 according to ISO-11261: 2002. The amount of total carbon determined after dry combustion in the analyzer multi N/C 2100 Analytic Jena AG in accordance with PN-ISO-10694: 2002. Available phosphorus was determined by the colorimetric Egner-Riehm method in accordance with PN-R-04023: 1996 with a HACH spectrophotometer, wavelength of l ¼ 690 nm. Cation exchange capacity (CEC) was determined by the Kappen method according to PN-R-04027: 1997. To determine total heavy metal (Cd, Cr, Cu, Ni, Pb and Zn) content, the soil, soil solution and biomass samples were mineralized in ultra-pure nitric acid (Speed Wave MWS-2 Berghof microwave pressure digestion system). The mineralized samples were analyzed by Atomic Emission Spectrometry with Inductively Coupled Plasma (SPECTRO ICP-OES) according to PN-ISO 11042:2001 protocol. The heat of combustion of biomass was determined using a bomb calorimeter KL-11 Mikado in accordance with PN-81/G04513. The sulfur content in the plant biomass was determined in accordance with PN-G-04584: 2001P using LECO analyzer S TrupSpec. Chlorine plant biomass was determined in accordance with PNISO-587: 2000. 2.3.1. Quality control and quality assurance All the glassware used during experiments were of high quality, acid resistant duran glass. The analytical grade reagents with a certified purity of 99% and stock metal standard solution (1000 ppm) for SPECTRO ICP-OES were produced from SigmaAldrich (Germany). The calibration method for ICP was internal standard method and was measure in triplicate to insure precision of quantitative results. Working standards were prepared by appropriate dilutions of stock standard solutions with double distilled water. The pH meter was calibrated often by standard solutions of pH 4 and 7. The Bomb calorimeter was calibrated before each batch of
samples to be analyzed. Standardization process was done by the combustion a weighed sample of a pure compound of known heat combustion, such as benzoic acid. Then, by dividing this value by the temperature rise produced in the test, we obtain a resultant energy equivalent for this particular calorimeter. The multi N/C 2100 analyzer was calibrated before each batch of samples to be analyzed. Standardization process was done by the calibration method of inserts of different weights of the pure glucose into the reactor, resulting in the generation of a highly linear calibration curve in the ug$g1 range. 2.4. Mathematical analysis 2.4.1. Bioconcentration factor and calorific value of the biomass To evaluate the mobility of heavy metals from the soil to the plant used bioconcentration factor, which was calculated by the formula (Ghosh and Singh, 2005):
BCF ¼
metal concentration in plant shots; mg kg1 metal concentration in soil; mg kg1
(1)
2.4.2. The calorific value of biomass Calorific value of the dried product at 105 C biomass (GCV) was calculated according to the formula (Zhuang et al., 2007):
LHV ¼ Qc 24:42ðWtot þ 8:9HÞ; kJ kg1 d:m:1
(2)
where: Qc - heat of combustion, kJ kg1 e is a net caloric value was measures with a bomb calorimeter Wtot - total moisture, % - for the biomass dried at 105 C, Wtot ¼ 0, H - hydrogen content in biomass, % - H ¼ 6% for the miscanthus, H ¼ 6.3% for reed canary grass (Vassilev et al., 2012), 24.42 - heat of vaporization at 25 C, drain 1% of the water contained in the biomass kJ kg1 8.9 - conversion factor of hydrogen to water.
2.4.3. Fuel indicator of corrosion and free alkali index Fuel indicator of corrosion (PWK) was determined on the basis of the S/Cl ratio and the percentage of potassium in the fuel according to (Wasielewski and Hrabak, 2015): Free alkali index (Af) was estimated according to the formula (Blomberg, 2006):
Af ¼
Na þ K ð2 x S þ ClÞ LHV
where: Af - free alkali index, mol MJ1, mol GJ1
(3)
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Na - acetic acid soluble, or total sodium, mol kg1 K - acetic acid soluble, or total potassium, mol kg1 S - sulfur content of the fuel, mol kg1 Cl - chlorine content of the fuel, mol kg1 LHV - lower heating value, MJ kg1
2.4.4. Unit CO2 emission (ECO2) Unit CO2 emissions per unit of chemical energy during the combustion of biomass, calculated according to the formula (Kobyłecki, 2014):
ECO2 ¼
44 C x ; kgCO2 MJ1 12 LHV
(4)
where: C - The carbon content in the biomass, kg kg1 LHV - lower heating value, MJ kg1 2.5. Statistical analysis A One-way ANOVA test was used to identify differences among groups of variables using Tukey's post hoc with a significance <0,05. Additionally, the data were also submitted to nonparametric Kruskal-Wallis test. Variables with similar behaviors will be presented with the same letter (a, b, c). Therefore, different letters represent the existence of statistically significant differences among groups of variables. All statistical analyses were generated with the software Statistica 10.0, while the standard deviations were determined via Microsoft Office Excel. Bars on charts indicate sample standard deviation where significant differences from the control exceeded p < 0,05. 3. Results and discussion 3.1. The pH value changes in soil solution While sewage sludge may be an excellent fertilizer, it may also contain high concentrations of environmental contaminants such as heavy metals with ions that migrate in soil solutions, and leach into groundwater reservoirs. Concentration fluctuations of heavy metals in these soils closely correlate with the pH; A decrease in pH usually increased the release of heavy metal ions to soil solution. In the first year of the experiment, it was found that the addition of sewage sludge resulted in a decrease of pH in the soil solution under both crops as compared to the control (Figs. 1 and 2). Similar changes in soil pH value following sewage sludge/biosoilds application are common described (Alvarenga et al., 2016). The decrease of pH value is usually explained as an acidification of decomposable products of sewage sludge and simultaneous production of humic acids. In our study, however, the pH value generally increased slightly in time; This pH change was more visible under miscanthus crops and reached a maximum after 24 months. The pH then regressed to values in the range of 7.1e7.3; depending on container. 3.2. Heavy metal mobilization in soil solution Our study confirmed that application of sewage sludge onto degraded land may lead to an increase of heavy metal mobilization in soil solutions. However, this process depends on length of application and plant species. 3.2.1. Cadmium At the beginning of the experiment, an increase in the
concentration of Cd ions in leachate collected from both the cultivation of miscanthus (Fig. 3) and reed canary grass (Fig. 4) was observed. This Cd ion content increase in the soil solution lasted for 6 months of the experiment, but then subsequently decreased. The maximum concentration of ions in the tested permeates under the miscanthus conditions was recorded in the control (0.7 mg dm3), while under the canary - fertilized - OJ 0.43 mg dm3. It was noted, however, that the ion concentration of Cd in the soil solution of all combinations was lower as compared to the control. There was no apparent impact from the applied modification fertilization (introduction of foliar fertilization with urea) to change the concentration of Cd in the soil solution. 3.2.2. Lead At the beginning of the experiment, the highest content of Pb ions (1.99 g dm3) for miscanthus was recorded in leachates taken from sample fertilized OW and was higher than the control (Fig. 5). In the case of the canary, however, the highest concentration of Pb ions was recorded for the non-fertilized samples in the 6th week of the process with a value of 3.12 g dm3 (Fig. 6). In the case of miscanthus (Fig. 5), the Pb content in all combinations was lower relative to the controls. After 18 months this process is decreased, with 30 months experience minimum value. As for the cases of both the reed canary grass (Fig. 6) and the miscanthus, it was observed that after 18 months the process caused a decrease in the concentration of Pb in the soil solutions of all the combinations that were maintained on the same level. 3.2.3. Zinc In the first year after of the experiment (from 2 to 11 months), miscanthus fertilized OW concentration of Zn ions in the soil solution was higher in comparison to the control sample and fertilized OJ (Fig. 7). In the case of canary grass, we observed the opposite reaction e a higher concentration of Zn ions were observed after fertilization with OJ and lower after fertilization with OW (Fig. 8). In addition, generally higher concentrations of Zn were detected in the soil solution associated with canary grass rather than with miscanthus. After modifying the method of fertilization (the second year of the experiment), we observed some fluctuations of the content of Zn ions in the soil leachates in all combinations (Figs. 7 and 8). It was also observed that after the 14th month, the concentration of Zn in the soil solution increased. However, we didn't observe a clear relationship between fertilizer modification and changes of Zn ion concentration in soil leachates. 3.3. The accumulation of heavy metals in biomass One important indicator of the effectiveness of the phytoremediation process is the bioconcentration factor (BCF). The BCF's for all studied metals (i.e. Cd, Cr, Cu, Ni, Pb, Zn) in all samples, resulted in values <1 (Table 3) and this indicates the metal tolerance occurred via the exclusion mechanism, while values >1 indicate that the metal accumulates in the plant biomass (Gerhardt et al., 2017). In our studies the highest BCFI ratio determined for Cr in the first and third year of the iscanthus experiment were for Cr ¼ 0.975 and BCFIII for Cr ¼ 0.631. For reed canary grass, the highest bioconcentration was determined for zinc in the first year of the experiment in the control (BCFI for Zn ¼ 0.616) and with the soil fertilized with sewage sludge (BCFI for Zn ¼ 0.64). These data confirmed that energy crops are not likely to accumulate heavy metals and translocate them to aerial portions of a plant. According to researchers, miscanthus accumulates heavy metals most effectively from all energy grasses (Lyubun and Tychinin, 2007) and reed canary grass uptake Zn more than other metals (Cd, Cu
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Fig. 1. The changes of pH values in soil leachates under miscanthus crops, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 2. The changes of pH in soil solution of container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
and Pb) (Baryła et al., 2009). The research carried out confirms these reports which is also confirmed by Nsanganwimana et al. (2015) who reported the even lower range of BCFs values mainly for the same heavy metals. Also Wanat et al. (2013) noticed that metalloid concentrations in aerial parts of miscanthus grown on contaminated soils are low compare to the soil contamination rate. For reed canary grass the same range of heavy metals BCFs was ska and Klink (2014)and this researchers also received by Polechon suggest that reed canary grass can be suitable for phytostabilization. However, noteworthy is that total metals content in energy crops biomass can be high if taking into consideration the total biomass production yield which can be achieved. Our results suggest that these crops may be good candidates for phytostabilisation (instead of typical phytoextraction) of heavy metals-contaminated soils for use in energy production which is also confirmed by Zorer Çelebi et al. (2018). The achieved positive effect is the prevention of the pollutants migration in the soil profile and low concentration of heavy metals in ashes after biomass incineration.
3.4. Energy properties of biomass 3.4.1. Calorific of biomass The addition of organic fertilizers to energy crops generally has a positive effect on their pertinent energetic properties. Both the use of sewage sludge and composts significantly improved the quality of biomass in energy crops. Analysing the biomass energetic parameters, it was found that influence of the origin of sewage sludge and the additional nitrogen fertilization on the energy values of biomass of miscanthus and reed canary grass occurred (Fig. 9). Under sewage sludge in the first year of the experiment, the calorific value of miscanthus decreased, whereas for reed canary grass, it was observed that the calorific value was influenced by the origin of sewage sludge, e.g., sludge from municipal wastewater treatment plants, which resulted in a reduction of this parameter; On the contrary, sewage sludge from the food industry resulted in an increase. In the second year of the experiment, calorific value of miscanthus biomass ranged from 12,290 to 14,507 kJ kg1d.m., and reed canary grass' from 13,681 to 16,249 kJ kg1d.m. and was
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Fig. 3. The changes of Cd concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 4. The changes of [Cd] in the soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 5. The changes of Pb concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
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Fig. 6. The changes of Pb concentration in soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 7. The changes of Zn concentration in soil solution of the container experiment with miscanthus, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
Fig. 8. The changes of Zn concentration in soil solution of the container experiment with reed canary grass, two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
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Table 3 Bioconcentration factor values for the aerial parts of the plants in the container experiment. BCF
1st Year C
2nd Year OW
MISCANTHUS 0.113c Cd 0.112a Cr 0.975c 0.418c Cu 0.144c 0.084b Ni 0.172c 0.113c Pb 0.050a 0.051a Zn 0.189c 0.079a REED CANARY GRASS Cd 0.138c 0.106b Cr 0.471c 0.242b Cu 0.245c 0.135b Ni 0.113b 0.090b Pb 0.048a 0.049a Zn 0.616c 0.328b
3rd Year
OJ
C
CþM
OW
OW þ M
OJ
OJ þ M
C
CþM
OW
OW þ M
OJ
OJ þ M
0.134c 0.613c 0.136b 0.114c 0.044a 0.121b
0.088c 0.132a 0.127b 0.057a 0.044a 0.090b
0.070b 0.179b 0.100b 0.040a 0.044a 0.120b
0.019a 0.093a 0.050a 0.023a 0.029a 0.032a
0.028a 0.086a 0.055a 0.020a 0.030a 0.025a
0.023a 0.099a 0.077a 0.023a 0.029a 0.043a
0.012a 0.109a 0.079a 0.030a 0.027a 0.042a
0.058b 0.293b 0.080a 0.035a 0.052a 0.128b
0.049b 0.631c 0.069a 0.077b 0.033a 0.242c
0.041b 0.245b 0.048a 0.045a 0.024a 0.090a
0.018a 0.108a 0.038a 0.017a 0.024a 0.035a
0.044b 0.204b 0.074a 0.033a 0.032a 0.075a
0.030a 0.216b 0.058a 0.032a 0.028a 0.080a
0.144c 0.284b 0.223c 0.087b 0.043a 0.640c
0.022a 0.281b 0.161b 0.088b 0.046a 0.270b
0.029a 0.095a 0.158b 0.030a 0.046a 0.279b
0.018a 0.049a 0.108a 0.030a 0.035a 0.100a
0.017a 0.082a 0.085a 0.031a 0.035a 0.105a
0.017a 0.068a 0.168b 0.053a 0.039a 0.297b
0.017a 0.101a 0.132b 0.040a 0.037a 0.229b
0.048a 0.183a 0.125b 0.035a 0.040a 0.320b
0.025a 0.141a 0.095a 0.023a 0.033a 0.304b
0.033a 0.067a 0.078a 0.025a 0.024a 0.115a
0.024a 0.072a 0.073a 0.014a 0.022a 0.106a
0.036a 0.128a 0.117a 0.043a 0.032a 0.411b
0.035a 0.115a 0.114a 0.037a 0.029a 0.311b
C: control; OW: municipal sewage sludge; OJ: food processing sewage sludge; M: urea. abc: lowercase different letters indicate significant differences (p < 0,05) between means of each metal BCF factor for the different container in 3 years period.
Fig. 9. The calorific value of miscanthus (left) and reed canary grass (right) in the container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
dependent on both the origin of sewage sludge and additional N fertilizer. In the third year, the calorific value of miscanthus ranged from 13,102 to 14,197 kJ kg1d.m., while the value of the reed canary grass ranged from 13,527 to 15,846 kJ kg1d.m. Like the second year, the calorific value was dependent on the origin of sewage
sludge and nitrogen fertilization. The results obtained in this study were also confirmed by other researchers e.g caloric value of miscanthus and reed canary grass respectively for both crops were 19.100 and 18.000 kJ kg1d.m. (compost fertilization) (Lord, 2015); (artificial fertilizers) 17,800
Fig. 10. The total carbon concentration in miscanthus (left) and reed canary grass (right) of the container experiment with two sewage sludge from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
0.5 0.4121a 3 high 0.0056 0.56 0.656b 3 high 0.0051 0.67 0.3501a 3 high 0.0065 0.29 0.5278b 3 high 0.0013 C: control; OW: municipal sewage sludge; OJ: food processing sewage sludge; M: urea. abc: lowercase different letters indicate significant differences (p < 0,05) between means of each K present for the different container in 3 years period.
0.57 0.3972a 3 high 0.0025 0.37 0.3554a 3 high 0.0039 0.28 0.7467c 3 high 0.0161 0.05 0.9688c 3 high 0.0022 0.29 0.5248b 3 high 0.012 0.42 0.7498c 3 high 0.0169 0.17 0.8372c 3 high 0.0032 0.31 0.5408b 3 high 0.0014 0.56 0.6602b 3 high 0.0036
0.12 0.8471c 3 high 0.0046
0.22 0.2296bc 3 high 0.00047 0.05 0.1152c 3 high 0.00003 0.11 0.0927c 3 high 0.00095 0.03 1.746c 3 high 0.00057 0.11 0.2124a 3 high 0.00076 0.17 0.1783a 3 high 0.0011 0.2 0.6577b 3 high 0.0033 0.08 0.4563ab 3 high 0.0017 0.05 0.4725ab 3 high 0.0028 0.25 0.6504b 3 high 0.0016 0.11 0.5789b 3 high 0.0018 0.12 0.4602ab 3 high 0.003 0.11 0.3852a 3 high 00033 0.09 0.3993a 3 high 0.0011
OJ OW þ M OW CþM C OJ þ M OJ OW þ M OW CþM C OJ OW C
517
MISCANTHUS S/Cl 0.14 K, % 0.3745a PWk 3 risk of corrosion high Af, mol MJ1 0.0018 REED CANARY GRASS S/Cl 0.19 K, % 0.544b PWk 3 risk of corrosion high Af, mol MJ1 0.0041
3rd Year 2nd Year
3.4.3. Risk of chloride corrosion The most important is corrosion risk assessment resulting from the combustion of biomass is the content estimation of chlorine, sulfur, potassium and sodium. These elements are the basis for the determination of the fuel indicator parameter of chloride corrosion (ICV) and the index of free alkali (Af). An important criterion for energetic assessment of biomass for, next to the energy performance, including whether its burning causes corrosion risks. The combustion of fuels such as biomass in boilers results in an accelerated consumption of steel compounds via the corrosive effect of molecular chlorine (Cl2) and hydrogen chloride (HCl). Corrosion is caused primarily by Cl2, which is a product of the oxidation of HCl located in the exhaust gas, but also by the alkaline metal chlorides contained in significant quantities in biofuels, such as Na, K and S. This type of corrosion is referred to as chemical corrosion or chlorohigh-temperature corrosion and is much faster than the oxidation process (Persson et al., 2007). Therefore, to determine whether a tested plant-biomass poses such a threat, the content of elements in plants was examined and then index excess alkali (Af) and indicator of chloride corrosion (PWk) were calculated. The S/Cl ratio was in the range from 0.03 to 0.25 and from 0.12 to 0.67 in the
1st Year
3.4.2. Carbon content in biomass The decrease of carbon content in plants growing on the soil with sewage sludge was noted; However, the results were different because they were dependent on the use of sewage sludge from different origin (Fig. 10). The use of OW was associated with a decrease in the concentration of biomass total carbon content of miscanthus, while with OJ an increase was observed. However, in reed canary grass cultivation, the concentration of carbon in the biomass remained at a similar level and maintained in the range from 342.550 to 359.850 g kg1d.m (34.25e35.98%). Additionally, N fertilization application either resulted in an increase or decrease in the concentration of carbon in the biomass of miscanthus and reed canary grass, depending on the origin of sewage sludge. In the third year of the experiment, the concentration of carbon in the biomass of miscanthus and reed canary grass increased in comparison with the first and second year of research and remained at a similar level in all combinations. In our study carbon content in biomass was not much lower the presented by the other researchers which received values (%) for miscanthus and reed canary grass: 43, 44 (Mehmood et al., 2017); 45, 40 (Lord, 2015) respectively. From polish climate condition research conducted for reed canary grass conducted by Kołodziej et al. (2016) the carbon content in biomass was not measured.
Table 4 Fuel chloride corrosion ratio (PWk) and free alkali index (Af) of container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
and 16,300 kJ kg1d.m. (Mehmood et al., 2017) (sewage sludge fertilization) 15,680 kJ kg1d.m. for only reed canary grass (Kołodziej et al., 2016). Fertilizing with N resulted in a decrease in the calorific value of the examined plant species in the second as well as in the third year of the experiment. In addition, the impact of fertilization was decreasing in second and third year of the experiment. This phenomena was also described by Kołodziej et al. (2016) where sewage sludge dose was from 0 to 60 Mg ha1 and received caloric value of reed canary grass in the range 15,680e15,509 kJ kg1d.m. It should be also noted that the biomass caloric value is significantly affected by the biomass humidity, which, according to many researchers, is related to the harvest date (Bassam, 2013) and the humidity value obtained in this experiment was at the level of 23e50% for misanthus and 39e68% for reed canary grass (data not published) because autumn harvests were used. Therefore, a not much lower biomass caloric values in relation to others cited researcher could have resulted from the higher water content and the type of sewage sludge used.
OJ þ M
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Fig. 11. The unit emissions of CO2 during the combustion of (left) and reed canary grass (right) biomass of the container experiment with two sewage sludge samples from municipal (OW) and industrial (OJ, food processing) WWTP's and urea (M).
cultivation of miscanthus and reed canary grass, respectively (see Table 2). On the base of these values (a low S/Cl ratio), all samples were classified as causing a high risk of PWk. In addition, the calculated Af in the cultivation of canary, throughout the process was negative. However, under miscanthus, negative Af values were obtained only in the third year of the experiment for plants both fertilized with urea and grown on soil with municipal sewage sludge (OW þ M) treatment, and on soil amended with sewage sludge from the food industry alone, while remaining positive for other combinations (see Table 4).
3.4.4. Unitary CO2 emission (ECO2) during the combustion of biomass The combustion process entails an increase in CO2 emissions into the atmosphere. Many researchers suggest the ability to counteract the increase in anthropogenic CO2 emissions from energy conversion processes by thermal treatment of biomass (Lehmann and Joseph, 2015). Energy from biomass burning is treated as “pure” because the accompanying CO2 emissions are equal to zero. Kobyłecki (2014) have shown, however, that from the environmental point of view this approach is wrong, because the source of the fuel does not affect the properties of the CO2 generated from energy conversion processes. Our results support their conclusion. Specific emission of CO2 in the experiment was in the range from 0.094 to 0.105 kgCO2 MJ1 for and from 0.084 to 0.102 kgCO2 MJ1 for reed canary grass, respectively. However, we didn't observe a clear influence of fertilizer and plant species on the changes of specific emission of carbon dioxide. Literature data indicate that the combustion 1 kg of coal results in CO2 emissions at the level of 1.14 kgCO2 MJ1, while burning 1 kg of methane - 0.055 kgCO2 MJ1 (Kobyłecki, 2014). In the case of biomass, CO2 emission accompanying the combustion is lower than that achieved during the combustion of coal and higher than that obtained during the combustion of methane. In our experiment, the highest values of CO2 emissions (within the range of 0.106e0.115 kgCO2 MJ1) were detected in the third year of the process, while the lowest (from 0.089 to 0.096 kgCO2 MJ1) were detected in the second year (Fig. 11). In addition, it was observed that the additional foliar nitrogen fertilization increased estimated CO2 emissions both in the second and in the third year of experiment. However, in the first year of the experiment, we found minimal emission of CO2 in trials of biomass grown on soil fertilized with sewage sludge. In the case of reed canary grass (Fig. 11), for the first year of the experiment, soil fertilization with sewage sludge applied at minimal level reduced the estimated unit CO2 emissions, which ranged
from 0.097 to 0.1 kgCO2 MJ1. In the second year of the process, the decline of ECO2 values was more apparent (as compared to nonfertilized control). In the third year, we observed a different reaction: an increase of ECO2 in treated samples. Only in combination with foliar fertilization the decrease of ECO2 was observed as compared to control.
4. Conclusion The use of degraded land for cultivation of long-term grasses for energy purposes ensures increased energy security by reducing dependence on other crops and a number of environmental benefits. Such soils are ideally suited for non-food crops such as energy crops so that they can have an energy source, which has comparable energy characteristics, comparable to conventional ones, and in addition extremely cheap to obtain and relatively safe for the environment. However, there is a notable problem in the management of degraded soils: they are relatively poor in nutrients necessary for proper plant functioning. Therefore, it is important to ensure proper fertilization of soils providing all the necessary nutrients. Undoubtedly, one of these is the use of sewage sludge since it has excellent fertilizer properties. The use of sewage sludge as a replacement for fertilizers favors the formation and stabilization of the soil through the decomposition of organic matter which is heavily disturbed in areas contaminated with heavy metals. Its ecological capabilities also affect the physical and chemical properties of the soil (improving aggregation and infiltration capacity and increasing the availability of nutrients), even if it is possible to increase the mobility of metals and metalloids - which could be captured by the energy crops root system. Our studies, however, indicate that any fertilizer modification on degraded land leads to changes in both phytoremediation and energy properties of plants. It is probably connected with the poor soil buffer capacity of degraded land, nutrient depletion, loss of soil organic carbon. Hence, the use of sewage sludge could help stop these negative processes, but the quality of sewage sludge introduced into the soil is an important determining factor in its efficacy. Fulfilling these conditions does not only lead to the restoration of degraded soils, but also allows for an additional source of renewable energy, which is extremely important given the continuous and systematic depletion of conventional sources. From conducted study, results evidenced that metal and metalloid uptake by miscanthus and reed canary grass is lower than typical hyperaccumulators as well as the transfer from soil to aerial parts. This behaviour makes this crops potential for the
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“sustainable phytoremediation” energy culture on degraded terrains, as a part of phytostabilisation process which are general. This kind of land are not usable for any other activities and they are a threat to surroundings. Data received indeed shows that miscanthus and reed canary grass could be mainly able to reduce wind erosion, to immobilize a part of contaminants by adsorption or accumulation in roots, and to limit the transfer to aerial parts. And also, as we indicated the clean energy profit as well as clean sewage sludge (biosolids) sustainable management. It is important that perennial crops could provide the additional sequestration of carbon in the soil at high yields. Hence, in that case greenhouse gas emissions will be lower because of application of biosolids fertilizers, which leads to higher carbon formation for crops with high biomass production. Acknowledgments The study was supported by an internal grant of the Czestochowa University of Technology, Poland: BS/PBe401e304/11. Karolina Rosikon, received the grant within the project DoktoRIS-Scholarship program for innovative Silesia, co-financed by the European Union under the European Social Fund. References Alvarenga, P., Farto, M., Mourinha, C., Palma, P., 2016. Beneficial use of dewatered and composted sewage sludge as soil amendments: behaviour of metals in soils and their uptake by plants. Waste Biomass Valorization 7, 1189e1201. https:// doi.org/10.1007/s12649-016-9519-z. ska, H., 2009. Content of components in some Baryła, R., Sawicka, J., Kulik, M., Lipin grass species irrigated with purified sewage. J. Elemntology. https://doi.org/ 10.5601/jelem.2009.14.1.01. Bassam, N.E., 2013. Energy Plant Species. Routledge. Blomberg, T., 2006. Which are the right test conditions for the simulation of high temperature alkali corrosion in biomass combustion? Mater. Corros. 57, 170e175. https://doi.org/10.1002/maco.200503905. Boudjabi, S., Kribaa, M., Chenchouni, H., 2017. Sewage sludge fertilization alleviates drought stress and improves physiological adaptation and yield performances in Durum Wheat (Triticum durum): a double-edged sword. J. King Saud Univ. Sci. 1e9 https://doi.org/10.1016/j.jksus.2017.12.012. Central Statistical Office in Poland, 2016. The CSO Report 2016. Fargione, J.E., Plevin, R.J., Hill, J.D., 2010. The ecological impact of biofuels. Annu. Rev. Ecol. Evol. Syst. 41, 351e377. https://doi.org/10.1146/annurev-ecolsys102209-144720. o, S., Barbosa, B., Costa, J., Duarte, M.P., Monti, A., 2015. Perennial Fernando, A.L., Bole grass production opportunities on marginal mediterranean land. BioEnergy Res. 8, 1523e1537. https://doi.org/10.1007/s12155-015-9692-0. Finnan, J., Styles, D., 2013. Hemp_ A more sustainable annual energy crop for climate and energy policy. Energy Policy 58, 152e162. https://doi.org/10.1016/ j.enpol.2013.02.046. Gerhardt, K.E., Gerwing, P.D., Greenberg, B.M., 2017. Opinion: taking phytoremediation from proven technology to accepted practice. Plant Sci. 256, 170e185. https://doi.org/10.1016/j.plantsci.2016.11.016. Ghosh, M., Singh, S.P., 2005. A comparative study of cadmium phytoextraction by accumulator and weed species. Environ. Pollut. 133, 365e371. https://doi.org/ 10.1016/j.envpol.2004.05.015. Grobelak, A., 2016. Organic Soil Amendments in the Phytoremediation Process, in: Phytoremediation. Springer International Publishing, Cham, pp. 21e39. https:// doi.org/10.1007/978-3-319-41811-7_2. Kacprzak, M., Neczaj, E., Fijałkowski, K., Grobelak, A., Grosser, A., Worwag, M., Rorat, A., Brattebo, H., Almås, Å., Singh, B.R., 2017. Sewage sludge disposal strategies for sustainable development. Environ. Res. 156, 39e46. https:// doi.org/10.1016/j.envres.2017.03.010. Kobyłecki, R., 2014. Environmental Aspects of Biomass Thermolysis. Monoraphy. Czestochowa University of Technology, Czestochowa.
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