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Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e8
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Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis Hanwei Liang a, Jingzheng Ren a,b,*, Liang Dong a,c,d, Zhiuqiu Gao e,**, Ning Zhang f,g, Ming Pan h a
Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster, School of Geography and Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China b Centre for Engineering Operations Management, Department of Technology and Innovation, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark c CML, Leiden University, Leiden, The Netherlands d Center for Social and Environmental Systems Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba-City, Ibaraki 305-8506, Japan e State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China f Department of Economics, Jinan University, Guangzhou, Guangdong 510632, China g Institute of Resource, Environment and Sustainable Development, Jinan University, Guangzhou, Guangdong 510632, China h Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA, UK
article info
abstract
Article history:
The Sustainability performance of biomass-based hydrogen is in debate. This study aims at
Received 10 March 2016
using Emergy Theory to investigate the sustainability hydrogen production from corn
Received in revised form
stalks by supercritical water gasification, all the inputs including renewable resources,
3 April 2016
non-renewable resources, purchased inputs in the whole life cycle of hydrogen have been
Accepted 13 April 2016
incorporated and transformed into emergy. The emergy indices with respect to this
Available online xxx
technology can be summarized as follows: the transformity is 5.5323E þ 13 sej/kg, the emergy yield ratio (EYR) which is a measure of the ability of the system to exploit and make
Keywords:
local resources available by investing in outside resources is 1.0117, the environmental load
Emergy analysis
ratio (ELR) which indicates the load on the environment by the system is 5.0684, the
Hydrogen
environmental investment ratio (EIR) which can measure the utilization level of the
Supercritical water gasification
invested emergy is 85.8303 and the emergy index of sustainability (ESI) which is a measure
Sustainability
of the sustainability of a product, a process or a service is 0.1996. Therefore, it is not sustainable in the long term perspective for hydrogen production from corn stalks by supercritical water gasification in the current situation of Huaibei city in China. According to the results of sensitivity analysis, two implications are obtained for enhancing the
* Corresponding author. School of Geography and Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China. Tel./fax: þ86 25 5869567. ** Corresponding author. E-mail addresses: [email protected], [email protected] (J. Ren), [email protected] (Z. Gao). http://dx.doi.org/10.1016/j.ijhydene.2016.04.082 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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sustainability of hydrogen from corn stalks: one is developing innovative agricultural system to reduce the consumption of nitrogenous fertilizer and phosphate, and another is to improve the yield and utilization efficiency of corn stalks. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Introduction Energy like the freshwater is a fundamental resource that guarantees the normal life of well-being and the economy development all over the world [17]. Hydrogen has been recognized as a promoting potential energy carrier of the future for its advantage of zero CO2 emissions during its oxidation [23]. Due to the use of non-renewable sources, the traditional pathways for hydrogen production such as natural gas by steam reforming, coal gasification and water electrolysis cannot fulfill the target of sustainable development. Hydrogen production from biomass has received more and more interests and attentions, for biomass is not only the fourth largest source of energy in the world accounting for 15% of the world's primary energy consumption, but also a kind of renewable energy resource [9]. Hydrogen production from biomass has been recognized as a promising technology, however, it also has major challenges, and there are no completed technology demonstrations [10]. Balat had pointed out that biomass to hydrogen has three main limitations, namely seasonal availability and high costs of handling, non-total solid conversion and tars production and process limitations such as corrosion, pressure resistance and hydrogen aging [2]. Therefore, there is a difficult question: is the biomass to hydrogen really sustainable? There are many studies that focus on the sustainability of hydrogen production pathways. For instance, Manzardo et al. [16] established a model by combining gray-based multicriteria decision making method and life cycle thinking for sustainability assessment of hydrogen technologies. Hacatoglu et al. [7] developed a novel sustainability assessment methodology for hybrid energy system with hydrogen-based storage using life cycle emission factors and sustainability indicators. Ren et al. [24] established a sustainability decision making framework for the prioritization of hydrogen production pathways based on fuzzy Analytic Network Process and PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations) method with the considerations of both hard and soft criteria. There are also many studies specially focusing on the sustainability of biomass-based hydrogen production. For instance Balat and Kırtay [33], had a comprehensive review of hydrogen from biomass, and they pointed out that biomass gasification offers the earliest and most economical route for the production of renewable hydrogen. Ren et al. [19] developed a sustainability framework which consists of fifteen criteria in economic, environmental, technological, and social-political aspects for sustainability assessment of biomass-based technologies for hydrogen production. In order to investigate whether ‘biomass to hydrogen’ is really sustainable or not, an index which can
represent the sustainability is prerequisite. Emergy analysis which has the ability to measure the sustainability of a process, a service or a product has been widely used in various fields [1,20,27]. However, there are few studies focusing on using emergy analysis for investigating the sustainability of biomass-based hydrogen, but it had been demonstrated that emergy analysis has the ability to measure the sustainability of hydrogen production pathways [15]. In the emergy analysis, emergy index of sustainability (ESI) is an index to measure the sustainability of a process or a service. However, the traditional emergy theory does not include the life cycle thinking, a life cycle emergy analysis method has been developed in this study for investigating the sustainability of biomass-based hydrogen. The objective of this study is to use life cycle emergy analysis to analyze the sustainability of biomass to hydrogen, and an illustrative case, namely vaporization hydrogen production from corn stalks by super-critical water in Huaibei city of China has been studied.
Emergy analysis In this section, the emergy theory and emergy indices were firstly introduced, and hydrogen production from corn stalks by supercritical water gasification was analyzed by this method.
Emergy theory and emergy indices Emergy as a new concept is an expression of all the energy, resources and services used in the work process that generate a product or services in units of one type of energy [31]. Solar equivalent joules (sej) is the common basis that has been usually used to account all the directly and indirectly energy contributions to obtain a certain product or a service [12]. The link between the various types of resources and emergy is transformity, and transformity is a concept that represents the “energy quality” and “energy transformation ratio”, the corresponding emergy can be calculated by using the consumption of each item (energy quantities or mass quantities) multiply the corresponding transformity [18,25]. Due to different units of the resources, the units of the transformities will vary as the format of sej/unit of the resource, when the unit of the resource is J, then the unit of the transformity is sej/ J, when the unit of the resource is kg, then the unit of the transformity is sej/kg. The inputs and outputs emergy flows of a system in the traditional emergy analysis method has been shown in Fig. 1 and the emergy indices and corresponding calculated methodology used in this paper has been shown in Table 1.
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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The resources in the traditional emergy analysis can be divided into four categories, namely renewable environmental resources (R), non-renewable environmental resources, purchased (economic) inputs (F) and Product (P), and the purchased inputs can also be divided into two categories, namely renewable purchased input (FR) and non-renewable purchased output (FN). The renewable environmental resources (R) represent the resources that are renewable and obtained from the environment which mainly consist of sun radiation, rain chemical potential, rain geopotential and wind, while the nonrenewable environmental resources (N) represent the resources that are non-renewable and obtained from the environment which mainly refer to net topsoil loss. The purchased inputs (F) represent the resources bought from the market, the renewable purchased inputs (FR) refer to the renewable resources bought from the market such as hydroelectricity, seed, labor and water, while the non-renewable purchased inputs (FN) refer to the non-renewable resources bought from the market such as coal, petroleum, diesel, and Nitrogenous fertilizer et al. Product (P) represents the target product of an industrial system, i.e. hydrogen in hydrogen production system and bioethanol in biofuel production system.
3
Based on the four categories of resources, the following indices can be defined as follows [3,4,28,]: The index yield(Y) is the sum of renewable environmental resources, non-renewable environmental resources and purchased (economic) inputs. Yield represents the total needed emergy for a product or a service. The emergy yield ratio (EYR) is the ratio of yield (Y) to the purchased inputs, it is a measure of the ability of the system to exploit and make local resources available by investing in outside resources. The transformity (Tr) is the yield (Y)divided by the product (P), it is a measure of the emergy consumption per unit of product. The environmental load ratio (ELR) is ratio of the sum of non-renewable resources (N) and non-renewable purchased inputs (FN) to the sum of renewable resources (R) and renewable purchased inputs (FR). It is a measure of the load on the environment by the system. The environmental investment ratio (EIR) is ratio of the purchased inputs to the sum of renewable resources (R) and non-renewable resources (N), and it is a measure of the utilization level of the emergy that is invested. The emergy index of sustainability (ESI) is the ratio of the emergy yield ratio (EYR) to environmental load ratio (ELR), it is a measure of the sustainability of a product, a process or a service. When ESI < 1, the corresponding product or process is not sustainable in the long term, when 1 < ESI < 5, the corresponding product or process has a sustainable contribution to the economy for medium periods and the product or process with ESI > 5 can be recognized as sustainable in the long term [6].
Hydrogen production from corn stalks by supercritical water gasification
Fig. 1 e Traditional Inputs and outputs emergy flows of the production system.
Table 1 e Emergy indices and corresponding calculated methodology in the traditional and improved emergy analysis. Name Renewable environmental resources Non-renewable environmental resources Renewable purchased inputs Non-renewable purchased inputs Product (mass or energy) Yield Transformity Emergy yield ratio Environmental load ratio Environmental investment ratio Emergy index of sustainability
Abbreviation
Formula
R
R
N
N
FR
FR
FN
FN
P Y Tr EYR ELR EIR
P Y ¼ R þ N þ FR þ FN Tr ¼ Y/P EYR ¼ Y/(FR þ FN) ELR ¼ (FN þ N)/(R þ FR) EIR ¼ (FR þ FN)/(R þ N)
ESI
ESI ¼ EYR/ELR
Supercritical water gasification (SCWG) can advantageously avoid high drying costs, and more attention has been paid to SCWG recently [14]. And Biomass gasification in supercritical water can lead to zero CO2 emission in a very short life cycle period since carbon in the form of CO2 and energy are fixed by photosynthesis during biomass growth [13]. However, there is not a solid proof for the sustainability of hydrogen production by biomass gasification in supercritical water. An illustrative case using supercritical water gasification technology for hydrogen production from corn stalks has been studied by emergy analysis. The whole hydrogen production system has been fixed in Huaibei City, Anhui Province of China, it is a city with the area of 14,500 ha and the population of 0.40 million in the north of Anhui Province, this city located at 116 230 -117 020 E and 33 160 -34 140 N, the average annual temperature is 14.8 C, and the yearly precipitation is about 830 mm. The yield of corn is 4153.0 kg/hm2. The data of each input flow of hydrogen are obtained from three parts: i) published work; ii) survey from the corresponding agencies; iii) estimation according to published work. The function unit is 1000 kg of hydrogen. The life cycle boundary of hydrogen production comprises of corn plantation, stalks acquisition, transportation from the farmland to farm-warehouse, transportation from farm-warehouse to
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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factory and hydrogen production. It needed to be pointed out that, due to the countryside road, tractor are used to transfer the corn stalks from the farmland to the farm-warehouse, and trucks are used to transfer the corn stalks from the farmwarehouse. In the hydrogen production process, the catalysts are neglected.
Results and discussion After categorizing each item into renewable or non-renewable resources, or purchased inputs, the results of emergy analysis of hydrogen production by super-critical water gasification can be obtained, as shown in Table 2, and the specific procedures have been shown in the Appendix. Then with the emergies in Table 2 and the formulas shown in Table 1, all the emergy indices can be calculated, the transformity can be determined by calculating the ratio of yield (Y) to the product (P) and it is 5.5323E þ 13 sej/kg, it means that 5.5323E þ 13 sej of emergy is needed to produce 1 kg hydrogen. The emergy yield ratio (EYR) is 1.0117, the environmental load ratio (ELR) is 5.0684, the environmental investment ratio (EIR) is 85.8303 and the emergy index of sustainability (ESI) is 0.1996. It is apparent that the ELR is low, and systems are allowed to exploit more resources from the environmental, and the EIR is high, it means that this system mainly replies on the purchased inputs. Meanwhile ESI < 1, it
denotes that hydrogen production by super-critical water gasification from corn stalks is not sustainable in the long term. The emergy proportion of the four kinds of emergy types in the total emergy has been presented in Fig. 2. It is apparent that the purchased inputs contribute the most part in the total emergy of the system, it means that the emergy for hydrogen production mainly reply on the purchased inputs. The emergy proportion of each flow in the total nonrenewable purchased inputs has been presented in Fig. 3,
Fig. 2 e The proportion of the four categories of emergy flows.
Table 2 e Emergy analysis of hydrogen production by super-critical water gasification. Stage Plantation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Transport 16 17 Transport 18 19 Production 20 21 22
Item (unit) R Sun radiation (J) Rain chemical potential (J) Rain geopotential (J) Wind (J) N Net topsoil loss (J) FR Seed (kg) Labor (h) Management fees ($) Water (kg) FN Herbicides Insecticides pesticides Nitrogenous fertilizer (kg) Phosphate (kg) Potash (kg) Diesel (kg) FR Labor (h) FN Diesel (kg) FR Labor (h) FN Diesel (kg) FR Water (kg) Hydroelectricity (kJ) FN Coal electricity (kJ)
Data
Transformity (sej/unit)
Reference
13 10 08 10
1 3.05E þ 04 4.70E þ 04 2.45E þ 03
Definition [29] [29] [29]
2.4780E 3.7274E 2.0510E 2.6041E
2.6090E þ 09
7.40E þ 04
[29]
1.9307E þ 14
65.9680 2473.8 131.7252 7.9162Eþ06
3.36E 1.10E 4.45E 6.64E
05 12 12 08
[30] [29] [29] [29]
2.2165E 2.7201E 5.8618E 5.2564E
12.3690 2.4738 742.14 1319.4 824.600 197.9040
2.40E þ 10 2.40E þ 10 2.41E þ 13 2.02E þ 13 1.74Eþ12 6.60E þ 04
[31] [29] [29] [29] [29] [29]
2.9686E þ 11 5.9371E þ 11 1.7886E þ 16 2.6652E þ 16 1.4348Eþ15 1.3062E þ 07
50.2465
1.10E þ 12
[29]
5.5271E þ 13
3.6676
6.60E þ 04
[29]
2.4206E þ 05
4.6231
1.10E þ 12
[29]
5.0854E þ 12
174.6538
6.60E þ 04
[29]
1.1527E þ 07
5.273Eþ04 232,500
6.64E þ 08 6.23E þ 07
[29] [29]
3.5013E þ 13 1.4485E þ 13
232,500
1.71E þ 08
[29]
3.9758E þ 13
2.4780E 1.2221E 4.3638E 1.0629E
þ þ þ þ
þ þ þ þ
Emergy (sej) þ þ þ þ
þ þ þ þ
13 14 13 13
07 15 14 15
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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ESI
Fig. 3 e The emergy proportion of each flow in the total non-renewable purchased inputs.
0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
Nitrogen Phosphate
0%
20%
40%
60%
80%
0.2008 0.2006 0.2004
ESI
and the nitrogenous fertilizer and phosphate contribute 38.90% and 57.97% of the total non-renewable purchased inputs, respectively. The transformities of nitrogenous fertilizer and phosphate are the highest among all the non-renewable purchased inputs. Therefore, in order to reduce the emergy consumption in hydrogen production system, it is prerequisite to develop novel agricultural system which needs lower nitrogenous fertilizer and phosphate consumption than the traditional system. In order to investigate the effects of the consumption of nitrogenous fertilizer and phosphate and the yield of corn stalks on the sustainability of hydrogen, sensitivity analysis was carried out to study how ESI varies by changing the fertilizer utilization percentage and the yield of corn stalks. Nitrogenous fertilizer and phosphate have significant positive impacts on the total emergy of the whole hydrogen production system, and the sensitivity analysis of the two factors on emergy index of sustainability has been carried out, the result has been shown in Fig. 4. The use of the two fertilizers decrease comparing to the initial situation, the emergy index of sustainability will increase. Hence, the novel agricultural system which consumes less nitrogenous fertilizer and phosphate is urgently needed to make the hydrogen production system more sustainable. The yield of corn stalks has significant positive impacts on the total emergy of the whole hydrogen production system,
0.2002 0.2 0.1998 0.1996 0.1994
100%
120%
140%
160%
180%
200%
Yield Percentage of corn stalks Fig. 5 e Sensitivity analysis of yield of corn stalks on ESI. and the sensitivity analysis of yield of corn stalks on ESI has been shown in Fig. 5, it is apparent that ESI is approximate direct proportion to the yield of corn stalks. Therefore, the improvement of the yield of the stalks and the utilization efficiency of corn stalks is beneficial to make the hydrogen system more sustainable.
Conclusion Emergy analysis has been carried out to analyze hydrogen production from corn stalks by supercritical water gasification in this study. The transformity is 5.5323E þ 13 sej/kg, EYR is 1.0117, ELR is 5.0684, EIR is 85.8303 and ESI is 0.1996. Accordingly, the hydrogen production from corn stalks by supercritical water gasification is not sustainable in the long term. According to the results of the sensitivity analysis, there are two ways to increase the emergy index of sustainability and make hydrogen production from corn stalks by supercritical water gasification more sustainable, one is developing innovative agricultural system to reduce the consumption of nitrogenous fertilizer and phosphate, and another is to improve the yield and utilization efficiency of corn stalks. In more details, there are two implications: (1) developing and adopting advanced agricultural technologies for corn production for reducing the consumption of nitrogenous fertilizer and phosphate is beneficial for sustainable hydrogen production from corn stalks by supercritical water gasification. Accordingly, more and more Research, Development, and Demonstration (R&DD) projects are needed for the saving of nitrogenous fertilizer and phosphate in corn cultivation; (2) improving the yield and utilization efficiency of corn stalks is also beneficial for sustainable hydrogen production from corn stalks by supercritical water gasification. Accordingly, measures for the improvement of the collection rate of corn stalks and technologies for the improvement of the conversion efficiency are needed.
100%
Fertilizer percentage
Fig. 4 e Sensitivity analysis of nitrogenous fertilizer and phosphate on ESI.
Emergy index of sustainability as single index was employed for measuring the sustainability of hydrogen production from corn stalks by supercritical water gasification; it is convenient for the stakeholders to judge the
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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sustainability performance of hydrogen production pathways directly. However, there are also some drawbacks in this study: (1) Emergy index of sustainability is usually used for measuring eco-sustainability, but sustainability of industrial processes usually considers three pillars including economic prosperity, environmental cleanness, and social responsibility, thus, ESI sometime cannot completely indicate the sustainability of industrial processes; (2) The data were collected based on survey and literature reviews, thus, there are some inconsistencies between the data sources, and however the accuracy of the data has significant effect on the results. The future work of the authors is to combine multi-criteria decision making methods [21,22] and emergy theory and to develop the methods for analyzing the deviations of the results caused by data inconsistency for addressing the abovementioned two drawbacks.
2. Rain chemical potential Area ¼ 16492 m2, Rainfall ¼ 0.15 m, Density ¼ 1000 kg/m3, Gibbs free energy ¼ 4940 J/kg, Energy(J)¼(Area) (Rainfall) (Density) (Gibbs free energy) ¼ 1.2221E þ 10 J. 3. Rain geopotential Area ¼ 16492 m2, Rainfall ¼ 0.15 m, Rainoff rate ¼ 0.20, Average elevation ¼ 90 m, Density ¼ 1000 kg/m3, Gravity ¼ 9.80 s/m2, Energy(J)¼(Area) (Rainfall) (Rainoff rate) (Average elevation) Density Gravity ¼ 4.3638E þ 08 J. 4. Wind Area ¼ 16492 m2, Air Density ¼ 1.23 kg/m3, Drag coefficient ¼ 0.001, Average annual wind velocity ¼ 2 m/s, Geostrophic wind ¼ 10 Average annual wind velocity/ 6 ¼ 3.33 m/s, T ¼ 0.45yr, Energy (J)¼(Area) (Air Density) (Drag coefficient) (Geostrophic wind)3 (3600 24 365 0.45) ¼ 1.0629 E þ 10 J. 5. Topsoil loss
Acknowledgments This work is financially supported by the International Network Programme funded by Styrelsen for Forskning og Innovation (95- 460-54298), the Startup Foundation for Introducing Talent of NUIST (2243141501003-2015r003) of China and the Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration (UES2015A04) of China.
Area ¼ 16492 m2, Erosion rate ¼ 350 g/year.m2, Organic soil percentage ¼ 2%, Energy of organic soil ¼ 5.4E þ 06kal/ t 4186 J/kal ¼ 2.26E þ 10 J/t, Energy(J)¼(Area) Erosion rate Organic soil percentage Energy of organic soil T ¼ 2.6090 E þ 09 J 6. Seed 40 kg corn seeds are needed to plant 1 ha of corn, the plant area is Area ¼ 16492 m2
Appendix Notes to Table 2
Seed ¼ 40 1.6492 ¼ 65.9680 The data used in the calculation come form i) published work [5,8,11,32]; ii) survey from the corresponding agencies; iii) estimation according to published work [26]. Area ¼
1000 S0 Cy SCr
(1)
where Area is the needed farmland for production 1000 kg of hydrogen, S0 is the needed corn stalks for production 1 kg hydrogen, Cy is the corn yield per ha, SCr is the ratio of stalks to corn yield. Substitute S0, Cy, and SCr (S0 ¼ 8.219 kg/kgH2, Cy ¼ 4153.0 kg/hm2, Scr ¼ 1.2 [1e3]), then the needed farmland is 1.6492 hm2. 1. Sun radiation Area ¼ 16492 m2, Insolation ¼ 4.77E þ 9 J/m2/yr, Albedo ¼ 0.3, T ¼ 0.45yr
7. Labor It needs 1500 men's hours for planting and reaping 1 ha corn, the plant area is Area ¼ 16492 m2
Labor ¼ 1500 1.6492 ¼ 2473.8 h
8. Management fee The management fee for 1 ha corn is 500 Yuan¥, the ratio of USD and ¥ is 6.26, the plant area is Area ¼ 16492 m2
Management fee ¼ 500 1.6492/6.26 ¼ 131.7252$ 9. Irrigation Water
Energy (J) ¼ (Area) (Insolation) (1 Albedo) T ¼ 2.4780 Eþ13 J
It needs 4800 m3 of water for irrigation of 1 ha corn, the plant area is Area ¼ 16492 m2
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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Water Density ¼ 1000kg/m3
7
The time for transport ¼ (1000 S0/Tractor capacity) average distance from farmland to warehouse / Tractor velocity ¼ 0.6164 h
Irrigation water ¼ 4800 1.6492 1000 ¼ 7.9162 E þ 06 kg 10. Herbicides Needed herbicides per ha corn ¼ 7.5 kg, Area ¼ 1.6492ha
Pesticide ¼ Needed pesticide per ha corn Area ¼ 12.3690 kg 11. Needed insecticides pesticides per ha corn ¼ 1.5 kg, Area ¼ 1.6492ha
Insecticides pesticides ¼ Needed insecticides pesticides per ha corn Area ¼ 2.4738 kg
Labor ¼ The time for the package of stalks þ The time for transport ¼ 50.2565 h 17. Diesel Tractor diesel consumption ¼ 35 L/100 km, Tractor capacity ¼ 2 t, average distance from farmland to warehouse ¼ 3 km, Diesel density ¼ 0.85 kg/L
Diesel ¼ (1000 S0/Tractor capacity) average distance from farmland to warehouse Tractor diesel consumption Diesel density ¼ 3.6676 kg 18. Labor
12. Phosphate Plantation 1 ha needs Nitrogenous fertilizer 450 kg. 13. Nitrogenous fertilizer Plantation 1 ha needs Nitrogenous fertilizer 800 kg, the plant area is Area ¼ 16492 m2
Truck diesel consumption ¼ 0.05 L (t km)1, Truck capacity ¼ 8 t, average distance from warehouse to factory ¼ 500 km, Truck velocity ¼ 200 km/h, The time for loading per truck ¼ 2 h
The time for loading ¼ The time for loading per truck (1000 S0/Truck capacity) ¼ 2.0547h
Nitrogenous fertilizer ¼ 800 kg/ha 1.6492ha ¼ 742.14 kg 14. Potash fertilizer Plantation 1 ha needs Potash fertilizer 500 kg, the plant area is Area ¼ 16492 m2
Potash fertilizer ¼ 500 kg/ha 1.6492ha ¼ 824.600 kg 15. Diesel The needed biodiesel is 120 kg for producing 1 ha corn, he plant area is Area ¼ 16492 m2
Diesel ¼ 120 1.6492 ¼ 197.9040 16. Labor
The time for transport ¼ (1000 S0/Truck capacity) average distance from warehouse to factory / Truck velocity ¼ 2.5684 h
Labor ¼ The time for loading þ The time for transport ¼ 4.6231 h 19. Diesel Truck diesel consumption ¼ 0.05 L (t km)1, average distance from warehouse to factory ¼ 500 km, Diesel density ¼ 0.85 kg/L
Diesel ¼ 1000 S0 average distance from warehouse to factory Truck diesel consumption Diesel density ¼ 174.6538 kg 20. Water
The needed hours for package for the corn stalks of 1 ha is 30 h, Tractor velocity ¼ 20 km/h, average distance from farmland to warehouse is 3 km, Transportation capacityis2t
Water consumption per kg hydrogen ¼ 52.73 kg, Hydrogen production ¼ 1000 kg
The time for the package of stalks ¼ The needed hours for package for the corn stalks of 1 ha Area ¼ 49.4760 h
Water ¼ Water consumption per kg hydrogen Hydrogen production ¼ 5.273 E þ 04 kg
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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21. Hydroelectricity Electricity consumption per kg hydrogen ¼ 0.465 MJ, assume the proportion of hydroelectricity ¼ 50%
Hydroelectricity ¼ Electricity consumption per kg hydrogen Proportion of hydroelectricity 1000 ¼ 232,500 kJ 21. Coal-electricity
[15]
[16]
[17]
Electricity consumption per kg hydrogen ¼ 0.465 MJ, assume the proportion of coal-electricity ¼ 50%
[18]
Coal-electricity ¼ Electricity consumption per kg hydrogen Proportion of coal-electricity 1000 ¼ 232,500 kJ
[19]
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Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis Hanwei Liang a, Jingzheng Ren a,b,*, Liang Dong a,c,d, Zhiuqiu Gao e,**, Ning Zhang f,g, Ming Pan h a
Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster, School of Geography and Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China b Centre for Engineering Operations Management, Department of Technology and Innovation, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark c CML, Leiden University, Leiden, The Netherlands d Center for Social and Environmental Systems Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba-City, Ibaraki 305-8506, Japan e State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China f Department of Economics, Jinan University, Guangzhou, Guangdong 510632, China g Institute of Resource, Environment and Sustainable Development, Jinan University, Guangzhou, Guangdong 510632, China h Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA, UK
article info
abstract
Article history:
The Sustainability performance of biomass-based hydrogen is in debate. This study aims at
Received 10 March 2016
using Emergy Theory to investigate the sustainability hydrogen production from corn
Received in revised form
stalks by supercritical water gasification, all the inputs including renewable resources,
3 April 2016
non-renewable resources, purchased inputs in the whole life cycle of hydrogen have been
Accepted 13 April 2016
incorporated and transformed into emergy. The emergy indices with respect to this
Available online xxx
technology can be summarized as follows: the transformity is 5.5323E þ 13 sej/kg, the emergy yield ratio (EYR) which is a measure of the ability of the system to exploit and make
Keywords:
local resources available by investing in outside resources is 1.0117, the environmental load
Emergy analysis
ratio (ELR) which indicates the load on the environment by the system is 5.0684, the
Hydrogen
environmental investment ratio (EIR) which can measure the utilization level of the
Supercritical water gasification
invested emergy is 85.8303 and the emergy index of sustainability (ESI) which is a measure
Sustainability
of the sustainability of a product, a process or a service is 0.1996. Therefore, it is not sustainable in the long term perspective for hydrogen production from corn stalks by supercritical water gasification in the current situation of Huaibei city in China. According to the results of sensitivity analysis, two implications are obtained for enhancing the
* Corresponding author. School of Geography and Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China. Tel./fax: þ86 25 5869567. ** Corresponding author. E-mail addresses: [email protected], [email protected] (J. Ren), [email protected] (Z. Gao). http://dx.doi.org/10.1016/j.ijhydene.2016.04.082 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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sustainability of hydrogen from corn stalks: one is developing innovative agricultural system to reduce the consumption of nitrogenous fertilizer and phosphate, and another is to improve the yield and utilization efficiency of corn stalks. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Introduction Energy like the freshwater is a fundamental resource that guarantees the normal life of well-being and the economy development all over the world [17]. Hydrogen has been recognized as a promoting potential energy carrier of the future for its advantage of zero CO2 emissions during its oxidation [23]. Due to the use of non-renewable sources, the traditional pathways for hydrogen production such as natural gas by steam reforming, coal gasification and water electrolysis cannot fulfill the target of sustainable development. Hydrogen production from biomass has received more and more interests and attentions, for biomass is not only the fourth largest source of energy in the world accounting for 15% of the world's primary energy consumption, but also a kind of renewable energy resource [9]. Hydrogen production from biomass has been recognized as a promising technology, however, it also has major challenges, and there are no completed technology demonstrations [10]. Balat had pointed out that biomass to hydrogen has three main limitations, namely seasonal availability and high costs of handling, non-total solid conversion and tars production and process limitations such as corrosion, pressure resistance and hydrogen aging [2]. Therefore, there is a difficult question: is the biomass to hydrogen really sustainable? There are many studies that focus on the sustainability of hydrogen production pathways. For instance, Manzardo et al. [16] established a model by combining gray-based multicriteria decision making method and life cycle thinking for sustainability assessment of hydrogen technologies. Hacatoglu et al. [7] developed a novel sustainability assessment methodology for hybrid energy system with hydrogen-based storage using life cycle emission factors and sustainability indicators. Ren et al. [24] established a sustainability decision making framework for the prioritization of hydrogen production pathways based on fuzzy Analytic Network Process and PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations) method with the considerations of both hard and soft criteria. There are also many studies specially focusing on the sustainability of biomass-based hydrogen production. For instance Balat and Kırtay [33], had a comprehensive review of hydrogen from biomass, and they pointed out that biomass gasification offers the earliest and most economical route for the production of renewable hydrogen. Ren et al. [19] developed a sustainability framework which consists of fifteen criteria in economic, environmental, technological, and social-political aspects for sustainability assessment of biomass-based technologies for hydrogen production. In order to investigate whether ‘biomass to hydrogen’ is really sustainable or not, an index which can
represent the sustainability is prerequisite. Emergy analysis which has the ability to measure the sustainability of a process, a service or a product has been widely used in various fields [1,20,27]. However, there are few studies focusing on using emergy analysis for investigating the sustainability of biomass-based hydrogen, but it had been demonstrated that emergy analysis has the ability to measure the sustainability of hydrogen production pathways [15]. In the emergy analysis, emergy index of sustainability (ESI) is an index to measure the sustainability of a process or a service. However, the traditional emergy theory does not include the life cycle thinking, a life cycle emergy analysis method has been developed in this study for investigating the sustainability of biomass-based hydrogen. The objective of this study is to use life cycle emergy analysis to analyze the sustainability of biomass to hydrogen, and an illustrative case, namely vaporization hydrogen production from corn stalks by super-critical water in Huaibei city of China has been studied.
Emergy analysis In this section, the emergy theory and emergy indices were firstly introduced, and hydrogen production from corn stalks by supercritical water gasification was analyzed by this method.
Emergy theory and emergy indices Emergy as a new concept is an expression of all the energy, resources and services used in the work process that generate a product or services in units of one type of energy [31]. Solar equivalent joules (sej) is the common basis that has been usually used to account all the directly and indirectly energy contributions to obtain a certain product or a service [12]. The link between the various types of resources and emergy is transformity, and transformity is a concept that represents the “energy quality” and “energy transformation ratio”, the corresponding emergy can be calculated by using the consumption of each item (energy quantities or mass quantities) multiply the corresponding transformity [18,25]. Due to different units of the resources, the units of the transformities will vary as the format of sej/unit of the resource, when the unit of the resource is J, then the unit of the transformity is sej/ J, when the unit of the resource is kg, then the unit of the transformity is sej/kg. The inputs and outputs emergy flows of a system in the traditional emergy analysis method has been shown in Fig. 1 and the emergy indices and corresponding calculated methodology used in this paper has been shown in Table 1.
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e8
The resources in the traditional emergy analysis can be divided into four categories, namely renewable environmental resources (R), non-renewable environmental resources, purchased (economic) inputs (F) and Product (P), and the purchased inputs can also be divided into two categories, namely renewable purchased input (FR) and non-renewable purchased output (FN). The renewable environmental resources (R) represent the resources that are renewable and obtained from the environment which mainly consist of sun radiation, rain chemical potential, rain geopotential and wind, while the nonrenewable environmental resources (N) represent the resources that are non-renewable and obtained from the environment which mainly refer to net topsoil loss. The purchased inputs (F) represent the resources bought from the market, the renewable purchased inputs (FR) refer to the renewable resources bought from the market such as hydroelectricity, seed, labor and water, while the non-renewable purchased inputs (FN) refer to the non-renewable resources bought from the market such as coal, petroleum, diesel, and Nitrogenous fertilizer et al. Product (P) represents the target product of an industrial system, i.e. hydrogen in hydrogen production system and bioethanol in biofuel production system.
3
Based on the four categories of resources, the following indices can be defined as follows [3,4,28,]: The index yield(Y) is the sum of renewable environmental resources, non-renewable environmental resources and purchased (economic) inputs. Yield represents the total needed emergy for a product or a service. The emergy yield ratio (EYR) is the ratio of yield (Y) to the purchased inputs, it is a measure of the ability of the system to exploit and make local resources available by investing in outside resources. The transformity (Tr) is the yield (Y)divided by the product (P), it is a measure of the emergy consumption per unit of product. The environmental load ratio (ELR) is ratio of the sum of non-renewable resources (N) and non-renewable purchased inputs (FN) to the sum of renewable resources (R) and renewable purchased inputs (FR). It is a measure of the load on the environment by the system. The environmental investment ratio (EIR) is ratio of the purchased inputs to the sum of renewable resources (R) and non-renewable resources (N), and it is a measure of the utilization level of the emergy that is invested. The emergy index of sustainability (ESI) is the ratio of the emergy yield ratio (EYR) to environmental load ratio (ELR), it is a measure of the sustainability of a product, a process or a service. When ESI < 1, the corresponding product or process is not sustainable in the long term, when 1 < ESI < 5, the corresponding product or process has a sustainable contribution to the economy for medium periods and the product or process with ESI > 5 can be recognized as sustainable in the long term [6].
Hydrogen production from corn stalks by supercritical water gasification
Fig. 1 e Traditional Inputs and outputs emergy flows of the production system.
Table 1 e Emergy indices and corresponding calculated methodology in the traditional and improved emergy analysis. Name Renewable environmental resources Non-renewable environmental resources Renewable purchased inputs Non-renewable purchased inputs Product (mass or energy) Yield Transformity Emergy yield ratio Environmental load ratio Environmental investment ratio Emergy index of sustainability
Abbreviation
Formula
R
R
N
N
FR
FR
FN
FN
P Y Tr EYR ELR EIR
P Y ¼ R þ N þ FR þ FN Tr ¼ Y/P EYR ¼ Y/(FR þ FN) ELR ¼ (FN þ N)/(R þ FR) EIR ¼ (FR þ FN)/(R þ N)
ESI
ESI ¼ EYR/ELR
Supercritical water gasification (SCWG) can advantageously avoid high drying costs, and more attention has been paid to SCWG recently [14]. And Biomass gasification in supercritical water can lead to zero CO2 emission in a very short life cycle period since carbon in the form of CO2 and energy are fixed by photosynthesis during biomass growth [13]. However, there is not a solid proof for the sustainability of hydrogen production by biomass gasification in supercritical water. An illustrative case using supercritical water gasification technology for hydrogen production from corn stalks has been studied by emergy analysis. The whole hydrogen production system has been fixed in Huaibei City, Anhui Province of China, it is a city with the area of 14,500 ha and the population of 0.40 million in the north of Anhui Province, this city located at 116 230 -117 020 E and 33 160 -34 140 N, the average annual temperature is 14.8 C, and the yearly precipitation is about 830 mm. The yield of corn is 4153.0 kg/hm2. The data of each input flow of hydrogen are obtained from three parts: i) published work; ii) survey from the corresponding agencies; iii) estimation according to published work. The function unit is 1000 kg of hydrogen. The life cycle boundary of hydrogen production comprises of corn plantation, stalks acquisition, transportation from the farmland to farm-warehouse, transportation from farm-warehouse to
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factory and hydrogen production. It needed to be pointed out that, due to the countryside road, tractor are used to transfer the corn stalks from the farmland to the farm-warehouse, and trucks are used to transfer the corn stalks from the farmwarehouse. In the hydrogen production process, the catalysts are neglected.
Results and discussion After categorizing each item into renewable or non-renewable resources, or purchased inputs, the results of emergy analysis of hydrogen production by super-critical water gasification can be obtained, as shown in Table 2, and the specific procedures have been shown in the Appendix. Then with the emergies in Table 2 and the formulas shown in Table 1, all the emergy indices can be calculated, the transformity can be determined by calculating the ratio of yield (Y) to the product (P) and it is 5.5323E þ 13 sej/kg, it means that 5.5323E þ 13 sej of emergy is needed to produce 1 kg hydrogen. The emergy yield ratio (EYR) is 1.0117, the environmental load ratio (ELR) is 5.0684, the environmental investment ratio (EIR) is 85.8303 and the emergy index of sustainability (ESI) is 0.1996. It is apparent that the ELR is low, and systems are allowed to exploit more resources from the environmental, and the EIR is high, it means that this system mainly replies on the purchased inputs. Meanwhile ESI < 1, it
denotes that hydrogen production by super-critical water gasification from corn stalks is not sustainable in the long term. The emergy proportion of the four kinds of emergy types in the total emergy has been presented in Fig. 2. It is apparent that the purchased inputs contribute the most part in the total emergy of the system, it means that the emergy for hydrogen production mainly reply on the purchased inputs. The emergy proportion of each flow in the total nonrenewable purchased inputs has been presented in Fig. 3,
Fig. 2 e The proportion of the four categories of emergy flows.
Table 2 e Emergy analysis of hydrogen production by super-critical water gasification. Stage Plantation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Transport 16 17 Transport 18 19 Production 20 21 22
Item (unit) R Sun radiation (J) Rain chemical potential (J) Rain geopotential (J) Wind (J) N Net topsoil loss (J) FR Seed (kg) Labor (h) Management fees ($) Water (kg) FN Herbicides Insecticides pesticides Nitrogenous fertilizer (kg) Phosphate (kg) Potash (kg) Diesel (kg) FR Labor (h) FN Diesel (kg) FR Labor (h) FN Diesel (kg) FR Water (kg) Hydroelectricity (kJ) FN Coal electricity (kJ)
Data
Transformity (sej/unit)
Reference
13 10 08 10
1 3.05E þ 04 4.70E þ 04 2.45E þ 03
Definition [29] [29] [29]
2.4780E 3.7274E 2.0510E 2.6041E
2.6090E þ 09
7.40E þ 04
[29]
1.9307E þ 14
65.9680 2473.8 131.7252 7.9162Eþ06
3.36E 1.10E 4.45E 6.64E
05 12 12 08
[30] [29] [29] [29]
2.2165E 2.7201E 5.8618E 5.2564E
12.3690 2.4738 742.14 1319.4 824.600 197.9040
2.40E þ 10 2.40E þ 10 2.41E þ 13 2.02E þ 13 1.74Eþ12 6.60E þ 04
[31] [29] [29] [29] [29] [29]
2.9686E þ 11 5.9371E þ 11 1.7886E þ 16 2.6652E þ 16 1.4348Eþ15 1.3062E þ 07
50.2465
1.10E þ 12
[29]
5.5271E þ 13
3.6676
6.60E þ 04
[29]
2.4206E þ 05
4.6231
1.10E þ 12
[29]
5.0854E þ 12
174.6538
6.60E þ 04
[29]
1.1527E þ 07
5.273Eþ04 232,500
6.64E þ 08 6.23E þ 07
[29] [29]
3.5013E þ 13 1.4485E þ 13
232,500
1.71E þ 08
[29]
3.9758E þ 13
2.4780E 1.2221E 4.3638E 1.0629E
þ þ þ þ
þ þ þ þ
Emergy (sej) þ þ þ þ
þ þ þ þ
13 14 13 13
07 15 14 15
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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ESI
Fig. 3 e The emergy proportion of each flow in the total non-renewable purchased inputs.
0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0
Nitrogen Phosphate
0%
20%
40%
60%
80%
0.2008 0.2006 0.2004
ESI
and the nitrogenous fertilizer and phosphate contribute 38.90% and 57.97% of the total non-renewable purchased inputs, respectively. The transformities of nitrogenous fertilizer and phosphate are the highest among all the non-renewable purchased inputs. Therefore, in order to reduce the emergy consumption in hydrogen production system, it is prerequisite to develop novel agricultural system which needs lower nitrogenous fertilizer and phosphate consumption than the traditional system. In order to investigate the effects of the consumption of nitrogenous fertilizer and phosphate and the yield of corn stalks on the sustainability of hydrogen, sensitivity analysis was carried out to study how ESI varies by changing the fertilizer utilization percentage and the yield of corn stalks. Nitrogenous fertilizer and phosphate have significant positive impacts on the total emergy of the whole hydrogen production system, and the sensitivity analysis of the two factors on emergy index of sustainability has been carried out, the result has been shown in Fig. 4. The use of the two fertilizers decrease comparing to the initial situation, the emergy index of sustainability will increase. Hence, the novel agricultural system which consumes less nitrogenous fertilizer and phosphate is urgently needed to make the hydrogen production system more sustainable. The yield of corn stalks has significant positive impacts on the total emergy of the whole hydrogen production system,
0.2002 0.2 0.1998 0.1996 0.1994
100%
120%
140%
160%
180%
200%
Yield Percentage of corn stalks Fig. 5 e Sensitivity analysis of yield of corn stalks on ESI. and the sensitivity analysis of yield of corn stalks on ESI has been shown in Fig. 5, it is apparent that ESI is approximate direct proportion to the yield of corn stalks. Therefore, the improvement of the yield of the stalks and the utilization efficiency of corn stalks is beneficial to make the hydrogen system more sustainable.
Conclusion Emergy analysis has been carried out to analyze hydrogen production from corn stalks by supercritical water gasification in this study. The transformity is 5.5323E þ 13 sej/kg, EYR is 1.0117, ELR is 5.0684, EIR is 85.8303 and ESI is 0.1996. Accordingly, the hydrogen production from corn stalks by supercritical water gasification is not sustainable in the long term. According to the results of the sensitivity analysis, there are two ways to increase the emergy index of sustainability and make hydrogen production from corn stalks by supercritical water gasification more sustainable, one is developing innovative agricultural system to reduce the consumption of nitrogenous fertilizer and phosphate, and another is to improve the yield and utilization efficiency of corn stalks. In more details, there are two implications: (1) developing and adopting advanced agricultural technologies for corn production for reducing the consumption of nitrogenous fertilizer and phosphate is beneficial for sustainable hydrogen production from corn stalks by supercritical water gasification. Accordingly, more and more Research, Development, and Demonstration (R&DD) projects are needed for the saving of nitrogenous fertilizer and phosphate in corn cultivation; (2) improving the yield and utilization efficiency of corn stalks is also beneficial for sustainable hydrogen production from corn stalks by supercritical water gasification. Accordingly, measures for the improvement of the collection rate of corn stalks and technologies for the improvement of the conversion efficiency are needed.
100%
Fertilizer percentage
Fig. 4 e Sensitivity analysis of nitrogenous fertilizer and phosphate on ESI.
Emergy index of sustainability as single index was employed for measuring the sustainability of hydrogen production from corn stalks by supercritical water gasification; it is convenient for the stakeholders to judge the
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
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sustainability performance of hydrogen production pathways directly. However, there are also some drawbacks in this study: (1) Emergy index of sustainability is usually used for measuring eco-sustainability, but sustainability of industrial processes usually considers three pillars including economic prosperity, environmental cleanness, and social responsibility, thus, ESI sometime cannot completely indicate the sustainability of industrial processes; (2) The data were collected based on survey and literature reviews, thus, there are some inconsistencies between the data sources, and however the accuracy of the data has significant effect on the results. The future work of the authors is to combine multi-criteria decision making methods [21,22] and emergy theory and to develop the methods for analyzing the deviations of the results caused by data inconsistency for addressing the abovementioned two drawbacks.
2. Rain chemical potential Area ¼ 16492 m2, Rainfall ¼ 0.15 m, Density ¼ 1000 kg/m3, Gibbs free energy ¼ 4940 J/kg, Energy(J)¼(Area) (Rainfall) (Density) (Gibbs free energy) ¼ 1.2221E þ 10 J. 3. Rain geopotential Area ¼ 16492 m2, Rainfall ¼ 0.15 m, Rainoff rate ¼ 0.20, Average elevation ¼ 90 m, Density ¼ 1000 kg/m3, Gravity ¼ 9.80 s/m2, Energy(J)¼(Area) (Rainfall) (Rainoff rate) (Average elevation) Density Gravity ¼ 4.3638E þ 08 J. 4. Wind Area ¼ 16492 m2, Air Density ¼ 1.23 kg/m3, Drag coefficient ¼ 0.001, Average annual wind velocity ¼ 2 m/s, Geostrophic wind ¼ 10 Average annual wind velocity/ 6 ¼ 3.33 m/s, T ¼ 0.45yr, Energy (J)¼(Area) (Air Density) (Drag coefficient) (Geostrophic wind)3 (3600 24 365 0.45) ¼ 1.0629 E þ 10 J. 5. Topsoil loss
Acknowledgments This work is financially supported by the International Network Programme funded by Styrelsen for Forskning og Innovation (95- 460-54298), the Startup Foundation for Introducing Talent of NUIST (2243141501003-2015r003) of China and the Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration (UES2015A04) of China.
Area ¼ 16492 m2, Erosion rate ¼ 350 g/year.m2, Organic soil percentage ¼ 2%, Energy of organic soil ¼ 5.4E þ 06kal/ t 4186 J/kal ¼ 2.26E þ 10 J/t, Energy(J)¼(Area) Erosion rate Organic soil percentage Energy of organic soil T ¼ 2.6090 E þ 09 J 6. Seed 40 kg corn seeds are needed to plant 1 ha of corn, the plant area is Area ¼ 16492 m2
Appendix Notes to Table 2
Seed ¼ 40 1.6492 ¼ 65.9680 The data used in the calculation come form i) published work [5,8,11,32]; ii) survey from the corresponding agencies; iii) estimation according to published work [26]. Area ¼
1000 S0 Cy SCr
(1)
where Area is the needed farmland for production 1000 kg of hydrogen, S0 is the needed corn stalks for production 1 kg hydrogen, Cy is the corn yield per ha, SCr is the ratio of stalks to corn yield. Substitute S0, Cy, and SCr (S0 ¼ 8.219 kg/kgH2, Cy ¼ 4153.0 kg/hm2, Scr ¼ 1.2 [1e3]), then the needed farmland is 1.6492 hm2. 1. Sun radiation Area ¼ 16492 m2, Insolation ¼ 4.77E þ 9 J/m2/yr, Albedo ¼ 0.3, T ¼ 0.45yr
7. Labor It needs 1500 men's hours for planting and reaping 1 ha corn, the plant area is Area ¼ 16492 m2
Labor ¼ 1500 1.6492 ¼ 2473.8 h
8. Management fee The management fee for 1 ha corn is 500 Yuan¥, the ratio of USD and ¥ is 6.26, the plant area is Area ¼ 16492 m2
Management fee ¼ 500 1.6492/6.26 ¼ 131.7252$ 9. Irrigation Water
Energy (J) ¼ (Area) (Insolation) (1 Albedo) T ¼ 2.4780 Eþ13 J
It needs 4800 m3 of water for irrigation of 1 ha corn, the plant area is Area ¼ 16492 m2
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e8
Water Density ¼ 1000kg/m3
7
The time for transport ¼ (1000 S0/Tractor capacity) average distance from farmland to warehouse / Tractor velocity ¼ 0.6164 h
Irrigation water ¼ 4800 1.6492 1000 ¼ 7.9162 E þ 06 kg 10. Herbicides Needed herbicides per ha corn ¼ 7.5 kg, Area ¼ 1.6492ha
Pesticide ¼ Needed pesticide per ha corn Area ¼ 12.3690 kg 11. Needed insecticides pesticides per ha corn ¼ 1.5 kg, Area ¼ 1.6492ha
Insecticides pesticides ¼ Needed insecticides pesticides per ha corn Area ¼ 2.4738 kg
Labor ¼ The time for the package of stalks þ The time for transport ¼ 50.2565 h 17. Diesel Tractor diesel consumption ¼ 35 L/100 km, Tractor capacity ¼ 2 t, average distance from farmland to warehouse ¼ 3 km, Diesel density ¼ 0.85 kg/L
Diesel ¼ (1000 S0/Tractor capacity) average distance from farmland to warehouse Tractor diesel consumption Diesel density ¼ 3.6676 kg 18. Labor
12. Phosphate Plantation 1 ha needs Nitrogenous fertilizer 450 kg. 13. Nitrogenous fertilizer Plantation 1 ha needs Nitrogenous fertilizer 800 kg, the plant area is Area ¼ 16492 m2
Truck diesel consumption ¼ 0.05 L (t km)1, Truck capacity ¼ 8 t, average distance from warehouse to factory ¼ 500 km, Truck velocity ¼ 200 km/h, The time for loading per truck ¼ 2 h
The time for loading ¼ The time for loading per truck (1000 S0/Truck capacity) ¼ 2.0547h
Nitrogenous fertilizer ¼ 800 kg/ha 1.6492ha ¼ 742.14 kg 14. Potash fertilizer Plantation 1 ha needs Potash fertilizer 500 kg, the plant area is Area ¼ 16492 m2
Potash fertilizer ¼ 500 kg/ha 1.6492ha ¼ 824.600 kg 15. Diesel The needed biodiesel is 120 kg for producing 1 ha corn, he plant area is Area ¼ 16492 m2
Diesel ¼ 120 1.6492 ¼ 197.9040 16. Labor
The time for transport ¼ (1000 S0/Truck capacity) average distance from warehouse to factory / Truck velocity ¼ 2.5684 h
Labor ¼ The time for loading þ The time for transport ¼ 4.6231 h 19. Diesel Truck diesel consumption ¼ 0.05 L (t km)1, average distance from warehouse to factory ¼ 500 km, Diesel density ¼ 0.85 kg/L
Diesel ¼ 1000 S0 average distance from warehouse to factory Truck diesel consumption Diesel density ¼ 174.6538 kg 20. Water
The needed hours for package for the corn stalks of 1 ha is 30 h, Tractor velocity ¼ 20 km/h, average distance from farmland to warehouse is 3 km, Transportation capacityis2t
Water consumption per kg hydrogen ¼ 52.73 kg, Hydrogen production ¼ 1000 kg
The time for the package of stalks ¼ The needed hours for package for the corn stalks of 1 ha Area ¼ 49.4760 h
Water ¼ Water consumption per kg hydrogen Hydrogen production ¼ 5.273 E þ 04 kg
Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082
8
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e8
21. Hydroelectricity Electricity consumption per kg hydrogen ¼ 0.465 MJ, assume the proportion of hydroelectricity ¼ 50%
Hydroelectricity ¼ Electricity consumption per kg hydrogen Proportion of hydroelectricity 1000 ¼ 232,500 kJ 21. Coal-electricity
[15]
[16]
[17]
Electricity consumption per kg hydrogen ¼ 0.465 MJ, assume the proportion of coal-electricity ¼ 50%
[18]
Coal-electricity ¼ Electricity consumption per kg hydrogen Proportion of coal-electricity 1000 ¼ 232,500 kJ
[19]
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Please cite this article in press as: Liang H, et al., Is the hydrogen production from biomass technology really sustainable? Answer by life cycle emergy analysis, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/j.ijhydene.2016.04.082