Full Chain Energy Analysis of Biodiesel from Jatropha curcas L. in

Mar 19, 2008 - renewable energy share from 0.5% presently to 8% by the year 2011 (1). ... renewable energy sources being promoted. ... JCL oil (2). Ho...
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Environ. Sci. Technol. 2008, 42, 3388–3393

Full Chain Energy Analysis of Biodiesel from Jatropha curcas L. in Thailand KRITANA PRUEKSAKORN AND SHABBIR H. GHEEWALA* The Joint Graduate School of Energy and Environment, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand

Received September 5, 2007. Revised manuscript received December 19, 2007. Accepted January 22, 2008.

Biodiesel production from Jatropha curcas Linnaeus (JCL) has been considered for partial substitution of diesel fuel for transportation in Thailand. The aim of this study is to investigate the energy consumption for long-term investment (20 years) of Jatropha Methyl Ester (JME) production in Thailand using a life cycle approach. Apart from the average result, two scenariossbest and worst casesare set up to illustrate the range of results due to the variety of management practices. The main contributors to the energy use are JCL cultivation, transesterification, and transportation process. The net energy gain (NEG) and net energy ratio (NER) of biodiesel and coproducts from the life cycle of JCL are 4720 GJ/ha and 6.03, respectively. Even if only biodiesel is considered without coproducts, the NER is 1.42, still higher than 1. The study will support decision makers in the energy policy sector to make informed decisions vis-à-vis promotion of JCL plantations for biodiesel.

1. Introduction The Thai government has planned to increase the national renewable energy share from 0.5% presently to 8% by the year 2011 (1). To this end, biodiesel is one of the important renewable energy sources being promoted. Along with oil palm and used oil, Jatropha curcas Linnaeus (JCL) oil has been considered as a prospective feedstock for biodiesel production, particularly due to the possibility of cultivation in dry and marginal lands. Direct use of JCL oil in one piston engines is promoted by the Department of Agricultural ExtensionsThailand because of the good properties of the JCL oil (2). However, for use in automobiles, the JCL oil needs to be converted to biodiesel. Currently, transesterification is one of the most selected chemical methods to adjust oil characteristics for use in cars. Before any policy measures promoting a particular renewable energy can be adopted, it is imperative to consider a full chain energy analysis as a first step to address energy gain or loss of renewable energy production (3). This study is, therefore, focused on evaluation of energy balance of JCL biodiesel production in Thailand using a life cycle approach for supporting the policy-makers. The geographical scope of the study is Thailand, but the results may reflect the trends in other countries in southeast Asia and nearby since almost all the cultivation data collected correspond well with literature values. A rigorous energy analysis is especially important because Jatropha is being planned for large-scale use as biodiesel feedstock in several * Corresponding author e-mail: [email protected]. 3388

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countries in the region; however, most energy balance studies reported in literature to date have been on other feedstocks such as palm, rapeseed, and soyabean oil.

2. Materials and Methods 2.1. Goal-Objective and Scope of Work. The goal of this study is to evaluate the life cycle energy balance for biodiesel production from JCL in Thailand. Net energy gain (NEG), the difference between the total energy outputs and total energy inputs, is one of the accepted indices for analyzing the energy efficiency of biofuels (3). In the same way, net energy ratio (NER), the ratio of total energy outputs to total energy inputs, reflects the energy efficiency of the process. Both NEG and NER will be used as indicators for investigating the results of this full chain energy analysis. The analysis includes JCL cultivation, oil extraction, biodiesel production, and transportation at all stages. The analysis excludes the assessments of energy consumption associated with facilities construction i.e. manufacturing machines, irrigating structures, vehicles, etc. as well as with manual labor, i.e., new planting, pruning, harvesting, driving etc. The calculations are based on 1 ha of JCL farming area for 20 years. The main result is the estimate of overall energy requirements for best and worst cases. The information is obtained from 14 research sites and 10 practical sites (size of farming area ranges from lower than 1 ha to around 20 ha) in Thailand during the year 2006–2007. The allocation of environmental burdens to coproducts is done based on energy. Although parts of the JCL tree can be exploited for a number of uses such as medicine, insecticide, mollusciside, raw material of dye production, raw material of paper production (4), this study views them as coproducts used for energy purposes except seed cake that will be considered both for fuel stock and fertilizer because of its high nutrient content. The system boundary of this study is shown in Figure 1. 2.2. Process Inventory. The inventory, data sources, calculation unit, detailed explanations and assumptions for the study are presented in this section. 2.2.1. JCL Plantation. JCL is renowned as a tropical, toxic, drought-resistant oil plant. However, the fruit yield is low in dry climates because the leaves shed. For a good yield of JCL fruits, an average rainfall of about 900–1200 mm is desirable (5). There are a number of JCL plantation manuals from several sources presenting different farming management options for optimum yield. To cover the whole representation, a range of numerical data and assumptions of JCL cultivation from more than 20 provinces including farms and research sites in Thailand as well as local and international literature sources are considered in this study. Plantation period is assumed to be 20 years based on previous studies (6–8). 2.2.1.1. Crop Density. Quantity of trees per unit area affects the amount of fruit yield but it is difficult to estimate fruit yield based only on crop density because the yield varies with annual rainfall, nutrient level of the soil, and so on. Hence, the data collection covers all the sources in the range 1100–3300 trees/ha ((8), on-site data). 2.2.1.2. Propagation. Husk, soil, sand, manure, and manual watering required for new breeding are neglected in this analysis. For long-term plantation, seeding is recommended rather than cutting in order to get taproots for holding soil strongly ( (8, 9), on-site data). 2.2.1.3. Land Preparation. Land preparation comprises of ploughing, harrowing, and furrowing to adjust soil conditions. However, some sites do not perform all the activities depending on land characteristics, available equip10.1021/es7022237 CCC: $40.75

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FIGURE 1. Life cycle scheme for the studied system. ment, etc. Rate of diesel use for land preparation is around 25–40 L/time/ha (on-site data). 2.2.1.4. Irrigation. Without enough watering, JCL can yield just 1 period/year (3–7 months per period depending on land characteristics [Faculty of Agriculture, Kasetsart University (KU)]. To increase fruiting period, irrigation is necessary. Amounts of water and diesel consumption for irrigation by pumping method are from KU and a private company as follows: time of irrigation ≈ 12.5 h/ha/time, frequency of irrigation ≈ 15 day/time for dry season only, and rate of diesel consumption ≈ 0.63 L/hour. This irrigation model represents the irrigation in low rainfall areas, and it is assumed that rainy season for 1 year ≈ 3 months for present Thailand weather. However, irrigation at some sites does not consume diesel, i.e., siphon system, drip irrigation system, labor, etc. Also, for some areas in Thailand with a high annual rainfall level of more than 2500 mm (10), irrigation is not necessary. 2.2.1.5. Fertilization. A wide range of data on fertilizer use is obtained from various sources. Two formulas of chemical fertilizer have been identified for this analysis to represent the worst and best case. For the worst case (poor land); literature data (Openshaw, 2000) corresponding to onsite data in Thailand, is selected since not only the amount of chemical fertilizer, but also the amount of fruit yield is identified year by year. The amount of chemical fertilizer for years 1, 2, 3, 4, 5, 6, and onward is 160, 25.5, 63, 126, 252, 378, and 378 kg of N:P:K (40:20:10), respectively. From second year to 20th year of plantation, JCL seed cake is used instead of chemical fertilizers. 1.0 kg of seed cake is equivalent to 0.15 kg of N:P:K (40:20:10) chemical fertilizer (8). For the best case (fertile land), a common amount of chemical fertilizer used for general farming in Thailand viz. 312.5 kg of N:P:K (15:15:15) per year is selected (on-site data). 2.2.1.6. Weeding. To remove weeds at the farm, the methods which can be used are labor, machine, and herbicides. Some farms use all but others use none since grass weed is grazed by cows. The calculations consider both cases. For the calculation, selected kinds of herbicide follow the JCL plantation manual (9), and the amount of use is based on on-site data as follows: (1) glyphosate (48% w/v) for rainy season ≈ 0–4.2 L/year/ha and (2) paraquat (27.6% w/v) for dry season ≈ 0–2.5 L/year/ha. Diesel consumption rate for the weeding machine depends on horse power, condition, maintenance, etc. On-site data is as follows: (1) diesel consumption rate ≈ 4–7 L/time/ha and (2) frequency ≈ 0–1 time/year (≈ 4 h/time). 2.2.1.7. Insecticide. Although insecticide use is recommended by some pilot farms and research institutes, it is seldom used for the actual JCL farms due to the following reasons: (1) JCL is disease-resistant, and its parts have been

considered and used for insect control (8, 11–13). The damage from attack of insects is not significant. (2) Many kinds of insects (i.e., bees) pollinate flowers to produce fruit, and use of insecticide may kill those pollinators and thus negatively affect productivity. Therefore, this study assumes that no insecticides are used. 2.2.1.8. Harvesting. For the first year, there is no harvest at some sites because fruit yield is too low. On the other hand; at some sites, crop density of 1 × 1 m2 for the first year yields a reasonable harvest. Then, in the second year, 75% of the JCL trees are cut leaving a crop density of around 2 × 2 m2 to avoid interference of photosynthesis by the surrounding trees. JCL wood here is counted as coproduct. 2.2.2. JCL Oil Refinery. After drying by sunlight, JCL dry fruit is transformed to JCL oil, seed cake, and dry peel by cracking, pressing, and filtrating processes. The promoted trend is to produce and use oil in rural areas with a smallscale design ( (5, 13, 14), on-site data). The selected engine specifications for calculation are referred from a private company cooperating with a government institute. The specification details are 2 hp cracking machine with capacity 100–120 kg of seed/hour, 5 hp screw pressing machine with capacity 12.5–20 L (11.5–18.4 kg) of oil/hour, and 2 hp filtrating machine with capacity 150–170 L (138–156.4 kg) of oil/hour (specific gravity of JCL crude oil ) 0.92) (8). 2.2.3. JCL Biodiesel Production. JCL crude oil can be directly used in agricultural machinery without oil and engine modification. Nevertheless, the oil quality will be better and there will be less long-term problems if it is first converted into biodiesel (15). In the near future, small scale biodiesel plants in remote areas are expected to increase more than large-scale centralized ones because they can be easily operated by peasant proprietors without the need for complicated control and also distribution cost is reduced. The selected engine specifications for calculation are referred from a site producing 100% JME from JCL by transesterification using CH3OH (23% v/v) and NaOH (0.7–0.9% w/v) which is the major trend in Thailand due to lower prices than C2H5OH and KOH. This model has been developed and supported by the Department of Mechanical Engineering at the Prince of Songkla University (PSU) in Thailand. The capacity is 80 L of oil/batch with rate of electricity consumption around 3.8–4.1 kWh/batch. Efficiency of the process reaches 95.0–97.5% by weight of conversion rate. 2.2.4. Transportation. Transportation distance and frequency for the analysis are estimated from a number of study sites in Thailand. Educated assumptions are used for filling some information gaps. For instance, the utilization of JCL coproducts for energy purposes is not done at all sites. It is assumed that the biodiesel production factory would be sited close to the oil refinery. Therefore, this study assumes no transportation during that phase. Normally, agricultural materials will not be bought and carried for only a JCL farm. Thus, for this part, the selected data is from a community growing JCL on only around 15 ha. The estimated rate of diesel consumption for a pick-up and a 10-wheel truck are around 6–12 and 3.2–4 km/L with a carry load around 1–2 and 12–14 tons, respectively (Naval Dockyard Department, Thailand and a logistics company). The data for transportation by ship for imported material have been acquired from Rayong bulk terminal company as follows: Carry load ≈ 20 000–60 000 ton/trip, Fuel consumption ≈ 690–900 ton diesel/round trip (U.S.-Thailand). The details of transportation are summarized in Table 1. 2.2.5. Product Output. Masses of all JCL products are collected from many sources. Compositional analysis of JCL tree and fruit in Thailand were obtained from EGAT (Electricity Generating Authority of Thailand) and correspond to those reported in the literature (Openshaw, 2000). Although JCL is being planted in Thailand for more than a decade, VOL. 42, NO. 9, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 1. Numerical Details and Assumptions for Calculation for Transportation Part (Per Ha for 20 Years)a detail of transportation

distance (km/round)

frequency (time/year)

Seedling. For new plantings, seedlings are transported from nursery to farmland. At some sites, the nursery and farmland are located nearby. The transportation of seedlings to the seller is not included. Weeding (chemical). For herbicides, water for mixing with the chemical has to be carried from warehouse/water pipe to farm in case there is no pipeline or any irrigation system at the farm (mixing rate of glyphosate and paraquat to water are 1:100 and 5–6.25:1000). Agricultural materials. Chemical fertilizers, herbicides, diesel fuel, and agricultural equipment related to JCL plantation are transported from shop to farm. Chemical materials. Chemicals related to JME production (NaOH, CH3OH, etc.) are transported from chemical shop to biodiesel production factory. Imported materials. Chemical fertilizers, herbicides, and any materials associated with the whole activities of JME production are assumed to be imported by ship with an estimated weight of around 6–11 ton of material per 1 ha per 20 years. JCL fruit. JCL fruit is transported from the farm to the JCL oil refinery and biodiesel production facilities. Some investors have set the JCL farmland and JCL oil refinery near to each other. JCL wood. JCL wood is carried from farm to power plant.

0–6 (a)

1 (only first year)

0–6 (a)

1–2 (per 0.5–2 ha)

≈ 20 (a)

1 (per 15 ha)

10–120 (a)

1–2

All JCL products (JME, peel, seed cake, and glycerin except wood). All JCL products after transformation are assumed to be transported the same distance as JCL wood.

0–200 (a)

a

U.S.-Thailand (b)

0–200 A -

4–10

50–200 (c)

0–2 (first year) 1 (20th year) 4–10

Note: transportation by (a), pick-up; (b), ship; (c), 10-wheel truck.

TABLE 2. Factors for Energy Calculations along the Life Cycle of Biodiesel Production from JCL subject fertilizer production nitrogen (N) phosphorus (P) potassium (K) diesel use fuel energy per kg of diesel energy for producing diesel (specific gravity of diesel ) 0.845 kg/L)(19)

energy factor (MJ/kg) 87.9(18) 26.4(18) 10.5(18) 43.1 (36.4 MJ/L)(20) 9.6 (8.1 MJ/L)(21)

subject herbicides production glyphosate paraquat

energy factor (MJ/kg) 452.5(18) 458.4(18)

electricity use based on the present electricity mix in Thailand, 100 MJ of primary energy are required to produce 36 MJ (or 10 kWh) electricity(22).

sodium Hhydroxide (NaOH)

19.87(23, 24)

methanol (MeOH)

38.08(23)

wood (air-dry)

16.54a to 16.8(8)

peel (air-dry)

11.1(8) to 13.07a

JCL biodiesel (specific gravity of JME ) 0.88 kg/L) (7, 25)

37.3

crude glycerin (waste glycerin from JME production process)

25.6

seed cake (as fuel stock)

18.81(8) to 25.1a

seed cake (as fertilizer)

a

EGAT, (2006).

b

Energy factor is computed assuming that 1 kg of seed cake ≈ 0.15 kg of N:P:K-40:20:10 (8).

complete numerical record for amount of fruit is unavailable. Ranges of data obtained from Thailand on-site are about 0–5000; 350–12 500; and 880–12 500 kg JCL seed for years 1, 2, and 3, respectively. The lowest values for the first three years correspond to ref 8. Therefore, the data for year 4–20 from this source are referred as the representative of the worst case. The highest value for first year corresponds to the study result of KU. The shortest time to reach full potential of JCL fruiting is around 2–3 years, and it can keep yielding the same amount until 20 years (6, 13, 16). The amount of highest possible seed yield corresponds to refs 13 and 17. Therefore, it is assumed that the amount of JCL seed for year 4–20 is 12 500 kg/year. The average JCL biodiesel yield for best case is 2.7 ton/ha/year, almost the same as the value obtained from D1 Oils Company, a major producer of JCL biodiesel. 3390

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Ratio of JCL air-dried fruit yield to seed is 10/7 ((8); N.R. Industry Co., Ltd.; KU). Ratio of JCL seed to oil (oil extracted by motor press) is 10/2.3 ((5); KU). Conversion rate of biodiesel product is about 95% and ratio of biodiesel/crude glycerin is 7.8/2.2 (PSU). Weight of air-dried fruit yield minus weight of seed is the weight of JCL air-dried peel. Weight of seed minus weight of oil is weight of seed cake. Dry wood for the first and last years, around 18 375 kg and 4000 kg, respectively, are counted as coproducts (KU, ref 8). The factors used for energy calculations are shown in Table 2. Energy factors for the chemical production are mainly referred from literature because most of the chemicals used are imported. On the other hand, energy factors for the agricultural product outputs are referred to both from Thailand and checked with literature values to ensure data reliability.

FIGURE 2. Energy consumption for producing JME and coproducts per ha for 20 years.

FIGURE 3. Energy gain from the whole process of JME production per 1 ha for 20 years.

3. Results and Discussion 3.1. Net Energy Results. The energy consumption in each process to produce biodiesel per ha for 20 years is shown in Figure 2. The agriculture phase has the highest average energy consumption and oil refining the lowest. The range of energy consumption for transportation phase is quite high because some sites have to transport products for sale through large distances while some sites operate all activities in their community area. The specification of engines in the oil refinery and biodiesel production phases for the best and worst cases is set to be the same. The energy consumption of the best case is higher than the worst case due to a higher JCL fruit yield. Apart from the transportation phase, the main contributors to the energy use are biodiesel production phase for the case of highest productivity (best case). It can be seen that the average conditions for JCL cultivation are closer to the worst case, and the energy consumption for average and worst case is more than double that of the best case. This is due to the need for irrigation and fertilization. It implies the JCL grown on poor land consumes twice the energy as that grown on fertile land for obtaining a similar yield. All JCL outputs are assumed to be used for energy purposes. Details of the energy output from each phase are shown in Figure 3. Ranges of the total energy output from JME and all products used (per ha for 20 years) are 695–1978 GJ and 2534–8784 GJ, respectively. The highest energy gain is from seed cake as fuel stock because the total weight of seed cake is more than 3 times that of JME. However, due to its high nutrient content it is anticipated that the seed cake will be promoted to be used as fertilizer. When it is used as fertilizer, the energy output is the reduction of energy consumption for producing the chemical fertilizer which it would substitute. The energy gain from the use of seed cake as fuel is about 3 times that of its use as fertilizer. However, this cannot be used as a justification for the use of seed cake as fuel because the air emissions from burning of seed cake as well as environmental benefits of chemical fertilizer

substitution should also be considered in addition to energy output. In practice, the selection will also be governed by the market price. Energy gain from firewood is lowest because it can be harvested only in the first and last year (year 1 and 20). Small branches and leaves, which should be pruned occasionally for maintaining the height and spacing between JCL trees to be around 2 m (for convenience of collecting JCL fruits), are not included in the energy calculation because, with their low weight, there is no economic advantage of collecting them for sale. These are normally viewed as soil conditioner though suitable sizes and ages of branch can be used for new plantings. In this sense, they can be considered coproducts in economic terms but do not directly provide an energy output. In case seed cake is used as fuel stock, ranges of NEG and NER from the whole production cycle are 1222–8051 GJ per ha for 20 years and 1.93–11.99, respectively. If the coproducts are not utilized, the range of NER of JME is 0.53–2.70. 3.2. Process Analysis. To identify the main energy burdens of the whole process, the energy consumptions in each activity per ha for 20 years are presented in Figure 4. Transportation is not considered in this part as it is highly variable depending on very site-specific conditions. The main contributors to energy use are methanol production, fertilizer production, and irrigation process contributing approximately 36, 30, and 13%, respectively. The quite high range of the three highest contributors points to opportunities for substantially reducing energy use with proper planning. For instance, 260 GJ of energy consumption for chemical fertilizer production can be reduced with the utilization of manure, i.e., JCL seed cake or waste from cows and chicken. Or 127 GJ of diesel consumption for irrigation can be reduced if JCL is grown in the areas with adequate rainfall or if gravity irrigation is used. Range of total energy consumption for transportation based on data collection in Thailand is approximately 7–648 GJ. The range of total energy consumption is so high since VOL. 42, NO. 9, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 4. Energy consumption in each activity for producing JME and coproducts per 1 ha for 20 years.

TABLE 3. NER and Main Energy Contributor of the Life Cycle of JME Production source

average result

worst case scenario best case scenario

NER NER (only biodiesel) first contributor second contributor

6.03 1.42 agriculture transesterification

1.93 0.53 transportation transesterification

11.99 2.70 transesterification agriculture

third contributor

transportation

agriculture

oil extraction

the transportation for all parts, i.e., seedling (for new planting), water (for use of herbicide), JCL fruit, and all final products can be avoided with proper planning as the explained in Table 1. For the worst case, NER of only JME is 0.53, which is not promising. However, if only the transportation part can be changed to be the best case (the other parts still being the worst case), NEG and NER of only JME product will already be favorable at 25 GJ and 1.04, respectively. It implies that the promotion of JME production by the Thai government within the community is beneficial from an energy perspective. NER and main contributor to energy use from life cycle of JME in this model are compared to the energy analysis of JCL from other studies in the Table 3. NER for all sources of JCL biodiesel are in the same range as this study. However, NER of best case scenario is higher than the other studies which have considered the growth of JCL trees in arid conditions. It is also possible that maximum seed yield has been overestimated by certain companies promoting JME. However, in practice, the result will obviously not be the best or worst case. The scope of work and grouping of main contributor for each study are slightly different. Coproduct in Tobin’s study is only the seed cake (as fertilizer), whereas coproducts in ref 26 are seed cake (as fuel stock), coat, shell,

FIGURE 5. Sensitivity analysis of factors related to NER. 3392

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(26)

Case 1 (23)

Case 2 (23)

3.74 2.78 2.44 0.68 lime transesterification transesterification oil refinery cultivation/harvesting transportation cultivation/ fertilization oil extraction harvesting

and glycerin. The study models in ref 23, Case 1 and Case 2, assume that JCL biodiesel is sold locally and exported from India to Europe, respectively. That is why the transportation is an important contributor for the Case 2. However, it can be seen that the main contributor in ref 26 is the agricultural phase corresponding to the average result of this work. It can be concluded that the biodiesel production from JCL in Thailand tends to mostly consume energy in the agricultural phase. 3.3. Sensitivity Analysis. Due to variable conditions, a sensitivity analysis has been done as presented in Figure 5 to determine the effect of the following factors on NER: biodiesel yield, coproducts yield, farm energy inputs, energy consumption in oil extraction process, and energy consumption in biodiesel consumption process. The figure shows that the NER results are most sensitive to a change in coproducts yield. A 10% change in coproducts yield changes the NER by about 8%. This is reasonable since, as observed earlier, the coproducts provide the maximum energy output (Figure 3). The effect of changing all the other factors on the NER is less significant. The results of this study are thus robust. 3.4. Interpretation. The net energy value of JME is assessed to evaluate the benefits of using it as a substitute

for diesel. JME is the main product and seed cake, crude glycerin, wood, and peel are also counted in the analysis as they are significant coproducts. The results of the study show a net energy gain from all JME coproducts. In terms of energy, the promotion of JME production in community area yields a positive NER for all scenarios considered. With proper planning, an NER as high as 12 can be obtained. It should be noted that the calculations in this study are done for a long-term plantation of 20 years. The study assesses only energy balance as a first step in evaluating the possibility of JCL as a feedstock for biodiesel. The cost of investment, depletion of resources, environmental impacts, toxicity of JCL, and chemical use should be further studied for an overall assessment. Nevertheless, the results of this study point clearly to the conditions under which maximum benefits of utilizing JCL for biodiesel can be derived. This will serve as a good starting point for policy as well as investment decisions for appropriate infrastructure development and further research needs.

Acknowledgments We thank the Joint Graduate School of Energy and Environment (JGSEE) for supporting this research.

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