Thermogravimetric kinetic analysis of the combustion of biowastes

Renewable Energy 34 (2009) 1622–1627

Contents lists available at ScienceDirect

Renewable Energy journal homepage: www.elsevier.com/locate/renene

Thermogravimetric kinetic analysis of the combustion of biowastes M.E. Sanchez a, M. Otero b, X. Go´mez a, A. Mora´n a, * a b

´n, Avenida de Portugal, 41, 24071 Leo ´n, Spain Department of Chemical Engineering, Institute of Natural Resources (IRENA), University of Leo Department of Chemistry, Centre for Environmental and Marine Studies (CESAM), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal

a r t i c l e i n f o

a b s t r a c t

Article history: Received 26 March 2008 Accepted 17 November 2008 Available online 18 December 2008

Thermogravimetric (TG) analysis was used to study and compare the combustion of sewage sludge (SS), animal manure (AM) and the organic fraction of municipal solid waste (OFMSW). TG curves are in correspondence with the volatiles and carbon content of the materials studied. Non-isothermal thermogravimetric data were used to assess the kinetics of the combustion of these carbonaceous materials. The paper reports on the application of a model-free isoconversional method for the evaluation of the activation energy corresponding to the combustion of these biowastes. The activation energy related to AM combustion (E w 140 kJ mol1) was similar to that corresponding to SS (E w 143 kJ mol1) while the OFMSW showed to have a higher value (E w 173 kJ mol1). Ó 2008 Elsevier Ltd. All rights reserved.

Keywords: Combustion Sewage sludge Animal manure Municipal solid waste Thermogravimetric analysis Kinetics

1. Introduction Environmental legislation becoming more restrictive, management of biowastes such as sewage sludge, animal manure and municipal solid waste is getting a question of great concern. Sewage sludge (biosolids) is an unavoidable byproduct of wastewater treatment. It has valuable attributes but can be odorous and often contains unpleasant constituents that restrict its further use. Land application provides a means of supplying nutrients, such as nitrate and phosphorus, and organic matter (OM) that could be both agriculturally useful and environmentally appropriate [1]. However, the reduced availability of land, the increased public concerns over food chain safety, the associated uncertainties and costs of reuse have required water utilities to explore alternative management options that can contribute to a more sustainable biosolids strategy [2]. Recently, Fytili and Zabaniotou [3] revised the EU legislation concerning sewage sludge and new and old management options. Since aspects such as metal pollution are controlled [4], incineration provides a large volume reduction of sewage sludge and results in improved thermal efficiency [3]. Furthermore, co-combustion of sewage sludge may be also feasible [5]. Most animal manures are land-applied for their nutrient value [6,7] so their impact on the environment has become an issue of concern. Nitrogen (N) and phosphorus (P) runoff from application

* Corresponding author. Tel.: þ34 987291841; fax: þ34 987291839. E-mail address: [email protected] (A. Mora´n). 0960-1481/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2008.11.011

of animal manure are deemed as contributors to non-point pollution [8,9]. Greenhouse gases emissions [10] and the environmental behaviour of trace metals (copper, zinc, arsenic, etc) introduced from animal manure, as a residue of feed additives, have also been reported [11,12]. Lately, biogas production from manure by anaerobic digestion (AD) [13,14] and combined power and heat systems (CHP) [15] has emerged as treatment options for this type of waste. Karmakar et al. [16] published a review on the identification of the most suitable manure management system by integrated decision support systems where environmental regulations are considered. The generation of municipal solid waste (MSW) is a serious problem for urban communities [17]. Only in Spain are generated around 24 million tonnes of MSW annually [18], from which, approximately 40–45% of all MSW is the organic fraction of municipal solid waste (OFMSW) [10]. The composition of the OFMSW is influenced by various factors, including regional differences, climate, collection frequency, season, cultural practices and changes in composition [19]. MSW is affronting more restrictive legislation with respect to landfill disposal of the biodegradable fraction [20] as, according to the European landfill directive EC-99/ 31/EC waste must be treated before being landfilled to cut methane emissions [21]. The potential environmental pollution caused by heavy metals leached from this waste landfill has been one of the serious problems in many countries around the world. Different management options exist for MSW [22,23] and incineration is among them, although the necessary emissions control must be taken [24]. Among the several ways of disposing biowastes which could be considered, it must be tried to make use of their properties and

M.E. Sanchez et al. / Renewable Energy 34 (2009) 1622–1627

characteristics so to turn them into a resource, for example through the production of biomethane or biohydrogen [25]. However, this is not always feasible. Then, the combustion of biowastes may have very significant benefits in reducing the volume of waste materials and producing energy [26]. As long as emissions are below the best practical means (BPM) specified legislative limits, the changing energy policy climate lends support to the use of biomass and locally generated waste as fuel, as part of a move toward the low carbon economy. However, the classification of these materials as ‘‘waste’’ usually constrains its onward use [27,28]. Research on biowastes incineration and information campaigns is essential actions to avoid systematic public opposition. The main purpose of this work was to approach the incineration of sewage sludge, animal manure and the organic fraction of municipal solid waste by thermogravimetric analysis. Furthermore the present study provides a novel kinetic assessment of the combustion of these materials. The Ozawa–Flynn–Wall [29,30] model was applied to treat non-isothermal TG data in order to calculate the activation energy of these biowastes combustion. 2. Experimental 2.1. Materials The sewage sludge (SS) used in this work comes from an urban wastewater treatment plant where an aerobic suspended-growth treatment process is carried out. It goes through a stabilization treatment by anaerobic digestion, dehydration and thermal drying in the wastewater treatment plant of origin. Dried pellets of sewage sludge from the wastewater treatment plant were grinded in a ball mill. Animal manure (AM) comes from cow cattle and it is not submitted to any treatment apart from air drying. Dried animal manure was manually disaggregated and grinded in a ball mill. About the municipal solid waste, the raw material used in this work was the source sorted organic fraction of municipal solid waste (OFMSW) consisting only in the green waste and without any further treatment apart from drying. The dried OFMSW was manually disaggregated and grinded in a laboratory mill. The samples were sieved so the particle diameter of the materials used for this study was 0.105 mm < diameter < 0.210 mm, which is in the size range commonly used in CFB reactors ([5], and references therein). For coal particles, Ko¨k et al. [31] found that fractions between 0.037 mm < diameter < 1.651 mm, where it is comprised the particle size used for this study, showed very slight differences in heat of combustion values. Moreover, Gentziz and Chambers [32] observed that coal particulate sizes higher than 100 mm and heating rates below 600  C/min favour homogeneous ignition. Before thermogravimetric analysis, samples corresponding to each kind of biowastes were analysed to determine the main properties that affect thermal conversion. Moisture content was determined gravimetrically by the oven drying method. Higher heating value (HHV) at a constant volume was measured by means of an adiabatic oxygen bomb calorimeter. Proximate determinations were made according to modified procedures from ASTM D 3172 to D 3175 (Standard Practice for Proximate Analysis of Coal and Coke), E 870 (Standard Methods for Analysis of Wood Fuels), D 1102 (ash in wood) and E 872 (volatile matter). For the elemental determination, a LECO equipment model CHN-600 was used to determine the carbon, hydrogen and nitrogen content. Sulphur was determined by means of a LECO equipment model SC-132. 2.2. TG analysis Thermogravimetric analysis was carried out in a TA Instruments equipment model SDT2960. Combustion of the samples was

1623

performed in the furnace of the thermobalance under controlled temperature to obtain the corresponding thermogravimetric (TG) and differential thermogravimetric (DTG) combustion curves. Non-isothermal combustion of the separate samples was performed in the furnace of the thermogravimetric equipment under controlled temperature. For each run, each material was separately subjected to increasing temperatures at a constant heating rate up to 900 K. For each sample, four different heating rates (ß ¼ dT=dt) were used to carry out separate dynamic runs. The following b were applied: 5 K min1, 10 K min1, 25 K min1 and 50 K min1, which are low enough to favour homogeneous ignition [32] and to minimize mass transfer effects, as it is known that high heating rates cause large temperature gradients throughout the sample, thereby affecting kinetics [33,34]. For each sample and heating rate, three repetitive TG curves were obtained in order to assure reproducibility of the results. All dynamic runs were carried out in a pan containing 25  1 mg of the corresponding sample and a reference crucible containing calcined calcium oxide. Oxidizing atmosphere inside the furnace during temperature-programmed combustion was determined by means of a continuous airflow of 100 cm3 min1 at a gauge pressure of 101 kPa. 2.3. Theory Kinetic analysis techniques have been classified as either modelfitting (i.e., identification of a kinetic reaction model) or isoconversional (i.e., model-free). Modern thermal analysis appears to prefer the use of the latter methods for two main reasons [35]: 1) model-free kinetics is sufficiently flexible to allow for a change of mechanism during the course of the reaction; 2) mass transfer limitations are reduced by the use of multiple heating rates. By contrast, model-fitting kinetic methods generally involve a single heating rate, the disadvantage being that activation energy varies with heating rate due to mass/energy transfer effects. Providing differential conditions are practised in thermal analysis, it gives data related to chemical kinetics and mass transport which are essentially intrinsic or intra-particle [36]. Therefore, the results of thermal analysis under differential conditions are relevant to any fuel combustion system since effects external to the reacting particles are eliminated. Of course, this is an approach, and, for each specific case, such results should be combined with the transport conditions of a particular combustion system so that the real rates of reaction can be found. In this work intrinsic reaction rate coefficients are obtained for the combustion of biowastes under differential oxidizing conditions as follows: The rate of heterogeneous solid-state reactions can generally be described by,

da ¼ kðTÞf ðaÞ dt

(1)

where t is time, k(T) the temperature-dependent constant and f(a) a function called the reaction model, which describes the dependence of the reaction rate on the extent of reaction, a. The temperature dependence of the rate constant is described by the Arrhenius equation. Thus, the rate of a solid-state reaction can generally be described by,

da ¼ AeE=RT f ðaÞ dt

(2)

where A is the pre-exponential Arrhenius factor, E the activation energy and R the gas constant. For dynamic data obtained at a constant heating rate (ß ¼ dT=dt ¼ constant), this term is inserted in Eq. (2) so the above rate expression can be transformed into non-isothermal rate

1624

M.E. Sanchez et al. / Renewable Energy 34 (2009) 1622–1627

expressions describing reaction rates as a function of temperature at a constant b.

da 1 ¼ AeE=RT f ðaÞ b dT

10%

(3)

(4)

Isoconversional methods involve carrying out a series of experiments at different heating rates [37,38]. In this work, activation energy from dynamic data was obtained from isoconversional method by Flynn, Wall and Ozawa [29,33,39] using the Doyle’s approximation of p(x) [40], which involves measuring the temperatures corresponding to fixed values of a from experiments at different heating rates.

 AE E  5:331  1:052 RgðaÞ RT



mass (%)

30%

Z a Z da A T E=RT e dT ¼ gðaÞ ¼ b T0 0 f ðaÞ

0 300

Taking the double logarithm of both sides of Eq. (6), with kðTÞ ¼ AeE=RT , gives

E ln½  lnð1  aðTÞÞ ¼ ln A   n ln b RT

400

500

600

700

800

Temperature (K) AM

100 10% 20%

80

mass (%)

(6)

bn

50%

20

(5)

  kðTÞ

40%

60

40

From this equation, the activation energy E may be estimated by plotting ln (b) vs. 1/T. In order to determine the reaction order, Avrami’s theory was extended to describe non-isothermal cases, where variation of the degree of conversion with temperature and heating rate can be described as

aðTÞ ¼ 1  exp

20%

80

Integrating up to conversion, a, Eq. (3) gives,

lnðbÞ ¼ ln

SS

100

30% 40%

60

50%

40

(7) 20

Hence, a plot of ln [ln (1  a(T))] vs. ln b, which is obtained at the same temperature from a number of isotherms taken at different heating rates, should yield straight lines whose slope will have the value of the reaction order or the Flynn–Wall–Ozawa exponent n [29,30]. Additional details of the method applied to study the process are described elsewhere [33].

0 300

400

500

600

700

800

Temperature (K) OFMSW 100

3. Results and discussion

10%

3.1. Characterization of materials

Table 1 Proximate analysis, elementary analysis, and calorific values corresponding to the SS, AM and OFMSW used in this study. Biowaste Moisture (%)

Volatilesa (%)

Ashesa (%)

Cb (%)

Hb (%)

Nb (%)

Sa,b (%)

Ob,c (%)

HHVa (MJ kg1)

SS 6.8 AM 6.9 OFMSW 10.8

59.2 70.3 76.9

32.4 13.7 7.7

55.3 7.8 49.9 6.4 52.3 6.5

9.7 3.5 2.7

1.4 0.6 0.3

25.6 38.8 38.3

16.5 17.8 19.9

30%

mass (%)

The results of the elementary and proximate analysis for the sewage sludge, animal manure and municipal solid waste here used are shown in Table 1. It must be pointed out that the ash yield of OFMSW (7.7 wt%) is quite lower than those of AM (13.7 wt%) and SS (32.4 wt%). Furthermore, OFMSW yields higher amount of volatiles (76.9 wt%) than AM (70.3 wt%), while the SS yields 59.2 wt%. The three types of biowastes have very similar values of carbon but SS

HHV, high heat value. a Dry basis. b Dry ash free basis. c Calculated by difference.

20%

80

40%

60

50% 40

20

0 300

400

500

600

700

800

Temperature (K) 5 K min-1

10 K min-1

25 K min-1

50 K min-1

Fig. 1. TG curves corresponding to the combustion of SS, AM, and OFMSW at different heating rates.

M.E. Sanchez et al. / Renewable Energy 34 (2009) 1622–1627

0

10%

20%

30%

40%

Table 2 Slopes and correlation coefficients (R2) corresponding to linear fittings in Fig. 2 together with the resultant activation energy (E) values.

50% SS

Biowaste

Conversion (%)

Slope

E (kJ mol1)

SS

50 40 30 20 10 50 40 30 20 10 50 40 30 20 10

16.91 19.57 19.11 16.96 16.23 21.31 18.71 19.42 18.26 12.96 25.38 23.91 21.21 23.67 15.85

133.66 154.68 151.08 134.05 128.30 168.44 147.91 153.51 144.36 102.44 200.69 188.99 167.70 187.13 125.31

-0.5

ln [β (Ks-1)]

-1

AM

-1.5 OFMSW

-2 -2.5 -3 1.2

1.4

1.6

1.8

2

2.2

103T-1(K-1) 10%

20%

30%

40%

50%

3.2. TG results

ln [β (Ks-1)]

-0.8

-1.3

-1.8

-2.3

1.5

1.6

1.7

1.8

103T 10%

20%

1.9

2

(K-1)

30%

40%

50% OFMSW

-0.3

-0.8

ln [β (Ks-1)]

showed a higher H, N and S content than both AM and OFMSW, which displayed comparable contents of these elements. About the HHV value, SS has a lower value (16.5 MJ kg1) than AM (17.8 MJ kg1) and than OFMSW, which has a heating value slightly higher (19.9 MJ kg1).

AM

-0.3

-2.8

1625

-1.3

-1.8

The TG curves obtained from the temperature programmed combustions of the samples at the heating rates (b) of 5 K min1, 10 K min1, 25 K min1 and 50 K min1 are depicted in Fig. 1. As it may be observed, on raising the temperature, combustion of the sample takes place with an associated mass loss. Once the fuel content of the biowaste is exhausted, the mass corresponding to the ashes remains stable. Five different percentages of conversion (a) are pointed out in each curve: 10, 20, 30, 40 and 50%. The plots of log b vs. 1/T corresponding to the several conversion degrees of the process are shown in Fig. 2 for SS, AM and OFMSW. Mostly there is linearity for the several conversion percentages so the activation energy E may be calculated from the corresponding slope according to the Ozawa–Flynn–Wall kinetic method [29,33,39,40]. The slopes of linear fittings showed in Fig. 2 are shown in Table 2 and Table 3 shows the values of E calculated by the Ozawa–Flynn–Wall method. Resembling the HHV, the activation energy corresponding to the sewage sludge (w140 kJ mol1) is only slightly lower than that corresponding to the animal manure (w143 kJ mol1), and both are lower than the E corresponding to the organic fraction of municipal solid waste (w174 kJ mol1). Thus, OFMSW had a relative high volatiles and carbon contents together with the highest HHV, and the activation energy corresponding to its combustion is higher than that corresponding to SS and AM. Isoconversional methods have been used to study the thermal decomposition kinetics of carbonaceous materials. Activation energies corresponding to the biowastes here used are higher than those found for low rank coals [41] but lower than E values for

-2.3

-2.8

1.4

1.6

1.8

103T

2

2.2

(K-1)

Fig. 2. Curves of fitting to kinetic model proposed by Ozawa–Flynn–Wall to various conversion percentages corresponding to the combustion of SS, AM and OFMSW at different heating rates.

Table 3 Values of activation energy obtained by the Ozawa–Flynn–Wall isoconversional method. Biowaste

Activation energy (kJ mol1)

a

SS AM OFMSW

140.36 143.33 173.96

a The activation energy E was calculated as the arithmetic average of the several E values obtained for the different a in Fig. 2.

1626

M.E. Sanchez et al. / Renewable Energy 34 (2009) 1622–1627

1

473

523

573

623

673

0.6 SS

SS

AM

OFMSW

0.5

DTG (%s-1)

ln [-ln(1-α(T)]

0 -1 -2 -3

-2.1

-1.6

-1.1

ln [β (K 473

523

-0.6

573

623

673

ln [-ln(1-α(T)]

-2 -3

-2.1

-1.6

-1.1

-0.6

ln [β (K s-1)] 473

523

573

623

673 OFMSW

0 -1 -2 -3 -4 -2.6

-2.1

-1.6

373

473

573

673

773

873

T (K)

-1

-4 -2.6

0 273

-0.1

0

ln [-ln(1-α(T)]

0.2

s-1)]

AM

1

0.3

0.1

-4 -2.6

1

0.4

-1.1

-0.6

ln [β (K s-1)] Fig. 3. Curves of fitting corresponding to the reaction order n for different temperatures along the combustion of SS, AM and OFMSW at different heating rates.

Fig. 4. Combustion DTG curves corresponding to SS, AM and OFMSW (b ¼ 50 K min1).

materials such as rubber [42], sugarcane bagasse [43], residues from composting [44] or urban solid residues composting [45]. For the computation of the reaction order, the plots of ln [ln (1  a (T))] vs. ln b have been represented in Fig. 3. The n values as a function of temperature for SS, AM and OFMSW combustion are shown in Table 4. Variation of the n value with temperature is parallel for SS and AM but different from that obtained for OFMSW. The values ranged from very close to zero (pseudo zero-order reaction) to around 0.4 and are dependent on the extent of the reaction, i.e., not constant during the reaction, which is evidence of the multiple step process. The AM showed higher n values than both the SS and the OFMSW in the temperature range of combustion. It is worth noting that although n is dependent on the type of carbonaceous material, for a specific material its value is not integral (fractional order), which indicates the complexity of the degradation process of all these materials. There is not any linear relationship between the Flynn–Wall–Ozawa exponent n and the activation energy. SS and AM had comparable activation energy values while OFMSW had a higher E value. Still SS and OFMSW had comparable n values while AM had a higher one. The DTG results obtained from the temperature programmed combustions (50 K min1) of the biowastes here studied are shown in Fig. 4. The corresponding characteristic parameters are displayed in Table 5. As it may be seen by the Tv, Tm and Tf, the combustion of the biowastes here studied occurs in quite alike ranges of temperature. It could be said that OFMSW starts and ends combustion at slightly lower temperatures than SS and AM, but differences are very small. However the ranges of temperature are very similar, the combustion profiles corresponding to these materials are quite different. First, the intensity of the DTG peak (DTGmax) is much higher for AM than for OFMSW and especially than for SS. Secondly, once moisture has been eliminated, weight loss associated to the combustion process of SS and AM occurs in two not coincident stages while that of OFMSW Table 5 Characteristic parameters obtained from DTG combustion profiles (50 K min1) corresponding to SS, AM and OFMSW.

Table 4 Reaction order (n) as a function of temperature corresponding to SS, AM and OFMSW. Temperature (K)

SS

AM

OFMSW

473 523 573 623 673 Average n

0.14 0.21 0.23 0.17 0.08 0.17

0.27 0.36 0.39 0.16 0.04 0.25

0.21 0.14 0.23 0.12 0.01 0.14

Biowaste

SS AM OFMSW

Tv

Tm

Tf

DTGmax 1

(K)

(K)

(K)

(% s

410 425 400

630 630 610

930 950 910

0.23 0.54 0.40

)

tq (s) 624 630 612

Tv, onset temperature for volatile release and weight loss; Tm, temperature of maximum weight loss rate; Tf, final combustion temperature detected as weight stabilization; DTGmax, maximum weight loss rate; tq, burning time, time interval from the moment the dried sample starts to lose weight until the moment combustion ends and weight stabilizes.

M.E. Sanchez et al. / Renewable Energy 34 (2009) 1622–1627

occurs in three stages. This fact is quite relevant for energy recovery since heat is released nearly simultaneously to mass loss [46]. 4. Conclusions Differences were found between the combustion of the biowastes here studied: sewage sludge, animal manure and organic fraction of municipal solid waste. The TG curves are in correspondence with the proximate analysis of the materials studied. The activation energy corresponding to AM (E w; 140 kJ mol1) was similar to that corresponding to SS (E w 143 kJ mol1) while the OFMSW showed to have a higher value (E w 173 kJ mol1). These values are higher than those found in the literature for low rank coal but lower than those found for some other carbonaceous wastes. The reaction order was found to vary along the reaction pathway. The n values dependence of temperature was similar for SS and AM but diverged from OFMSW. The average reaction order corresponding to SS and OFMSW (0.14 and 0.17, respectively) was comparable and lower than that corresponding to AM (0.25). DTG curves showed that the combustion of the biowastes here studied occurs in coincident ranges of temperature. However, stages of the combustion process and the peaks height are quite different, being especially noticeable the DTG peak corresponding to AM. This work shows that the combustion of these biowastes is a complex process characteristic for each kind of material. Apart from the specific SS, AM and OFMSW here studied, conclusions cannot be generalized for the combustion of these types of biowastes. The kinetic parameters derived in this work come from reaction rates characterized only by temperature, irrespective of mass transfer and structural transient variations so specific combustion operation conditions should be further studied in a combustion reactor. Anyway, the present study proves that thermogravimetric analysis is a very useful tool for a first, simple and fast assessment of such biowaste’s fuel properties before planning their incineration. References [1] Vogeler I, Green SR, Mills T, Clothier BE. Modelling nitrate and bromide leaching from sewage sludge. Soil Till Res 2000;89:177–84. [2] Cartmell E, Gostelow P, Riddell-Black D, Simms N, Oakey J, Morris J, et al. Biosolids - a fuel or a waste? An integrated appraisal of five co-combustion scenarios with policy analysis. Environ Sci Technol 2006;40:649–58. [3] Fytili D, Zabaniotou A. Utilization of sewage sludge in EU application of old and new methods – a review. Renew Sust Energ Rev 2008;12:116–40. [4] Dewil R, Baeyens J, Appels L. Enhancing the use of waste activated sludge as bio-fuel through selectively reducing its heavy metal content. J Hazard Mat 2007;144:703–7. [5] Van de Velden M, Baeyens J, Dougan B, McMurdo A. Investigation of operational parameters for an industrial CFB combustor of coal, biomass and sludge. China Particuology 2007;5:247–54. [6] Garbarino JR, Bedna AJ, Rutherford DW, Beyer RS, Wershaw RL. Environmental fate of roxarsone in poultry litter. I. Degradation of roxarsone during composting. Environ Sci Technol 2003;37:1509–14. [7] Jackson BP, Seaman JC, Bertsch PM. Fate of arsenic compounds in poultry litter upon land application. Chemosphere 2006;65:2028–34. [8] Allen SC, Nair VD, Graetz DA, Jose S, Ramachandran NPK. Phosphorus loss from organic versus inorganic fertilizers used in alley cropping on a Florida Ultisol. Agr Ecosyst Environ 2006;117:290–8. [9] Anderson R, Xia L. Agronomic measures of P, Q/I parameters and lysimetercollectable P in subsurface soil horizons of a long-term slurry. Chemosphere 2001;42:171–8. [10] Zhou JB, Jiang MM, Chen GQ. Estimation of methane and nitrous oxide emission from livestock and poultry in China during 1949-2003. Energy Policy 2007;35:3759–67. [11] Bednar AJ, Garbarino JR, Ferrer I, Rutherford DW, Wershaw RL, Ranville JF, et al. Photodegradation of roxarsone in poultry litter leachates. Sci Total Environ 2003;302:237–45. [12] Zhou D, Hao X, Wang Y, Dong Y, Cang L. Copper and Zn uptake by radish and pakchoi as affected by application of livestock and poultry manures. Chemosphere 2005;59:167–75. [13] Cue´llar AD, Webber ME. Cow power: the energy and emissions benefits of converting manure to biogas. Environ Res Lett 2008;3. 034002.

1627

[14] Kaparaju P, Ellegaard L, Angelidaki I. Optimisation of biogas production from manure through serial digestion: lab-scale and pilot-scale studies. Bioresour Technol 2009;100:701–9. [15] Mueller S. Manure’s allure: variation of the financial, environmental, and economic benefits from combined heat and power systems. Renew Energ 2007;32:248–56. [16] Karmakar S, Lague C, Agnew J, Landry H. Integrated decision support system (DSS) for manure management: a review and perspective. Comput Electron Agr 2007;57:190–201. [17] Forster-Carneiro T, Perez M, Romero LI. Composting potential of different inoculum sources in the modified SEBAC system treatment of municipal solid wastes. Bioresour Technol 2007;98:3354–66. [18] Mace´ S, Bolzonella D, Mata-A´lvarez J. Full scale implementation of AD technology to treat the organic fraction of municipal solid waste in Spain. In: Proceedings of fourth international symposium anaerobic digestion of solid waste, Copenhagen (Denmark); 2005. p. 409–16. [19] Tchobanoglous G, Hilary T, Vigil SA. Integrated solids waste management: engineering principles and management issues. Mc Graw-Hill, Inc; 1997. [20] Gomez X, Cuetos MJ, Cara J, Moran A, Garcia AI. Anaerobic co-digestion of primary sludge and the fruit and vegetable fraction of the municipal solid wastes. Renew Energ 2006;31:2017–24. [21] Council Directive 1999/31/EC of 26 April on the landfill of waste. Official Journal of the European Communities L 182/1-19; 16.07.1999. [22] Erkut E, Karagiannidis A, Perkoulidis G, Tjandra SA. A multicriteria facility location model for municipal solid waste management in North Greece. Eur J Oper Res 2008;187:1402–21. [23] Sharholy M, Ahmad K, Mahmood G, Trivedi RC. Municipal solid waste management in Indian cities – a review. Waste Manage 2008;28:459–67. [24] Everaert K, Baeyens J. The formation and emission of dioxins in large scale thermal processes. Chemosphere 2002;46:439–48. [25] Go´mez X, Mora´n A, Cuetos MJ, Sa´nchez ME. The production of hydrogen by dark fermentation of municipal solid wastes and slaughterhouse waste: a two-phase process. J Power Sources 2006;157:727–32. [26] Cheung WH, Lee VKC, McKay G. Minimizing dioxin emissions from integrated MSW thermal treatment. Environ Sci Technol 2007;41:2001–7. [27] Enright JF. ‘‘Waste’’ or ‘‘product’’? That is the question. In: Papadimitriou K, Stentiford EI, editors. Biodegradable and residual waste management. Leeds: CalRecovery Europe Ltd.; 2004. p. 311. [28] Zheng G, Kozinski JA. Thermal events occurring during the combustion of biomass residue. Fuel 2000;79:181–92. [29] Ozawa T. A new method of analyzing thermogravimetric data. Bull Chem Soc Jpn 1965;38:1881–6. [30] Flynn JH, Wall LA. A quick, direct method for the determination of activation energy from thermogravimetric data. Polym Lett 1966;4:323–8. ¨ . Effect of particle size on the thermal [31] Ko¨k MV, Ozbas E, Hicyilmaz C, Karacan O and combustion properties of coal. Thermochim Acta 1997;302:125–30. [32] Gentziz T, Chambers A. Physical structure changes of canadian coals during combustion. Energy Sources 1995;17:131–49. [33] Ozawa T. Kinetic analysis of derivative curves in thermal analysis. J Therm Anal 1970;2:301–24. [34] Kneller WA. Physicochemical characterization of coal and coal reactivity: a review. Thermochim Acta 1986;108:357–88. [35] Sima-Ella E, Mays TJ. Analysis of the oxidation reactivity of carbonaceous materials using thermogravimetric analysis. J Therm Anal Calorim 2005;80:109–13. [36] Filho CGS, Milioli FE. A thermogravimetric analysis of the combustion of a brazilian mineral coal. Quim Nova 2008;31:98–103. [37] Khawam A, Flanagan DR. Role of isoconversional methods in varying activation energies of solid-state kinetics: II. nonisothermal kinetic studies. Thermochim Acta 2005;436:101–12. [38] Vyazovkin S. Evaluation of activation energy of thermally stimulated solidstate reactions under arbitrary variation of temperature. J Comput Chem 1997;18:393–402. [39] Flynn JH, Wall LA. General treatment of thermogravimetry of polymers. J Res Nat Bur Stand 1966;70A:487–523. [40] Doyle CD. Estimating isothermal life from thermogravimetric data. J Appl Polym Sci 1962;6:639–42. [41] Ko¨k MV. Temperature-controlled combustion and kinetics of different rank coal samples. J Therm Anal Calorim 2005;79:175–80. [42] Moreno RMB, Medeiros ES, Ferreira FC, Alves N, Gonçalves PS, Mattoso LHC. Thermogravimetric studies of decomposition kinetics of six different IAC Hevea rubber clones using Flynn–Wall–Ozawa approach. Plast Rubber Compos 2006;35:15–21. [43] Ramajo-Escalera B, Espina A, Garcı´a JR, Sosa-Arnao JH, Nebra SA. Model-free kinetics applied to sugarcane bagasse combustion. Thermochim Acta 2006;448:111–6. [44] Silva AR, Crespi MS, Ribeiro CA, Oliveira SC, Silva MRS. Kinetic of thermal decomposition of residues from different kinds of composting. J Therm Anal Calorim 2004;75:401–9. [45] Crespi MS, Silva AR, Ribeiro CA, Oliveira SC, Silva MRS. Composting of urban solid residues (usr) by different dispositions. Kinetics of thermal decomposition. J Therm Anal Calorim 2003;72:1049–56. [46] Otero M, Gomez X, Garcı´a AI, Mora´n A. Effects of sewage sludge blending on the coal combustion: a thermogravimetric assessment. Chemosphere 2007;69:1740–50.