Environmental sustainability assessment of biodiesel production from Jatropha curcas L. seeds oil in Pakistan

According to IPCC Annual Report (AR-5), environmental impact assessment of any product prototype is recommended before its large-scale commercialization; however, no environmental profile analysis of any biodiesel prototype has been conducted in Pakistan. Therefore, objective of this study was to conduct a comprehensive life cycle assessment (LCA), water footprint and cumulative energy demand (CED) of biodiesel production from Jatropha curcas L. (JC) seeds oil in Pakistan. A cradle-to-gate LCA approach was applied for 400 liter (L) JC biodiesel produced in Pakistan. JC biodiesel production chain was divided into three stages i.e., 1). cultivation of JC crop 2). crude oil extraction from JC seeds and 3). crude oil conversion to biodiesel. Primary data for all the stages were acquired through questionnaire surveys, field visits and measurements in the field. Potential environmental impacts were calculated in SimaPro v.9.2 software using Eco-indicator 99 methodology. Results showed that crude oil extraction stage accounted for highest emissions (77%) to the overall environmental impact categories evaluated, followed by oil conversion stage (21%) and JC cultivation stage (02%), respectively. The three stages of JC biodiesel production chain are major contributor to ecotoxicity with a contribution of 57% to this impact category. Higher contribution to ecotoxicity was due to agrochemicals used in the JC cultivation. Similarly, fossil fuels impact category was responsible for 38% of overall environmental impacts. In addition, water footprint of JC biodiesel production chain was 2632.54 m3/reference unit. Cumulative energy required for 400L JC biodiesel production chain was 46745.70 MJ in Pakistan. Fossil diesel consumption, synthetic fertilizers use and purchased electricity were major hotspot sources to environmental burdens caused by JC biodiesel production in Pakistan. By performing sensitivity analysis at 20% reduction of the baseline values of fossil diesel used, synthetic fertilizers and purchased electricity, a marked decrease in environmental footprint was observed. It is highly recommended that use of renewable energy instead of fossil energy would provide environmental benefits such as lower greenhouse gases and other toxic emissions as compared to conventional petroleum fuels. It is also recommended that JC as a biofuel plant, has been reported to have many desired characteristics such as quick growth, easy cultivation, drought resistance, pest and insect resistance, and mainly great oil content in JC seeds (27–40%). Therefore, JC plant is highly recommended to Billion Tree Afforestation Project (BTAP) for plantation on wasteland because it has multipurpose benefits.


Introduction
products of JC biodiesel production chain are glycerine and press cake. Glycerine can be used in medicines for skin care, cosmetics and soap making, whereas press cake can be used as a food for fishes and organic fertilizer such as bio-compost [29,30].
Pakistan is fossil fuels importing country and 17.20 million tons of crude oil were imported in the fiscal year 2018-2019 [31,32]. In Pakistan transport and electricity sectors are the key user of fossil fuel and would need about 50 percent extra energy for electricity and transport sector in near future [33]. Main energy consumption sector of Pakistan includes residential, private, agriculture, manufacturing, forestry, transportation and other government sectors [34]. Pakistan desires to blend 10 percent biodiesel in fossil diesel by 2025 [35]. Thus, research work on the lab-scale has been conducted on biodiesel production in numerous universities and organizations in the country [36][37][38][39][40]. Over the past twenty year's biodiesel has undergone several research and improvement studies [12,13,41]. According to Chakrabarti et al., 2012 many organisations have been working on production of biodiesel prototypes development from different biomass sources in Pakistan. So far, biodiesel is produced as a prototype in Pakistan which proves to be a good source of renewable and sustainable energy. The Quaid-e-Awam University (QUEST) at Nawabshah [42], The University of Engineering and Technology (UET) Lahore [43], The Institute of Chemistry at Punjab University [44], The Quaid-e-Azam University Islamabad [45], NUST Islamabad [46], NED University of Engineering and Technology, Karachi [47], The University of Agriculture, Faisalabad [44], and University of Science and Technology, Bannu, Khyber Pakhtunkhwa has prepared biodiesel prototypes from Jatropha curcas seeds oil in Pakistan. However, there has been no environmental analysis of any of the biodiesel prototypes developed in Pakistan. Therefore, the objective of this study was to conduct a comprehensive life cycle assessment (LCA) of a biodiesel prototype produced from Jatropha curcas seeds oil in Pakistan, which included calculation of material and energy flows, water footprint, cumulative energy demand (CED) and emissions to soil, water and air. Moreover, sensitivity analysis was also conducted to evaluate the potential impacts of JC biodiesel production if applied on a large-scale in Pakistan.

System boundary and reference unit
The system boundary of the present study is presented in (Fig 1). The biodiesel production chain was divided into three stages i.e., 1). Cultivation, 2). Oil extraction and 3). Oil conversion to biodiesel. A cradle-to-gate LCA approach was followed in the present study. The reference unit was defined as 400 litres of biodiesel produced from JC seeds at the production facility in the Biodiesel Laboratory of UST, Bannu, Pakistan.

Life cycle inventory and impact assessment
A detailed questionnaire regarding the inputs and outputs of biodiesel production chain was sent to the Biodiesel Laboratory of the Department of Botany, University of Science and Technology (UST), Bannu, KP, Pakistan. The primary data were collected for cultivation, lab-based biodiesel production (crude oil extraction stage and oil conversion to biodiesel stage) as presented in (Table 1). The secondary data were taken from published literature and Ecoinvent database. The data were modelled using SimaPro 9.0 software and applying Eco-indicator 99E methodology. Sensitivity analysis was conducted as per ISO 2006 protocol 14040-14043 to examine the impact of varying an input parameter such as diesel fuel consumed in transport of materials, synthetic fertilizers applied in the JC nursery and cultivation stage and purchased electricity consumed in machinery at the oil conversion stage.

Mass and economic allocation and assumptions
If a process generates more than one valuable output, allocation of environmental impacts to each output is essential [45]. In the present study, both mass and economic based allocation were applied. In the oil extraction stage of biodiesel production from JC seeds, the mass-based allocation was applied for the main product (crude oil, 58%) and the co-product (seedcake, 42%), whereas in the oil conversion stage, economic allocation was applied for the main product (biodiesel oil) and co-product (glycerine). JC biodiesel was accounted for 95% of environmental burdens (0.957 US $/L biodiesel in 2019) and purified glycerine was for 5% (0.209 US $/L in 2019) based on economic allocation.
Further assumptions for this study included; b. Heat required during the oil conversion stage was converted to joules (J) and mega joules (MJ) using the formula (Q = c � m � ΔT) Where, Q is the quantity of heat, c is specific heat of the substance or solution and its unit is joules per gram Celsius, m is the mass of the substance or solution in kg (kilogram) and ΔT is change in Temperature and its unit is kelvin. c. Soya bean oil process data present in Ecoinvent database was used instead of JC crude oil in oil conversion stage, because the JC crude oil was not available in the SimaPro v 9.2 software.

Estimation of water footprint of JC biodiesel production chain
The data for the JC cultivation stage, i.e., crop phenology, irrigation, and field management, were collected from field experiments that took place at the University of Science and Technology, Bannu, Pakistan during 2019-2020. The annual green and blue water footprint for the JC cultivation stage was estimated using AquaCrop Model version 6.1 developed by FAO (Food and Agriculture Organization) [46,47]. According to the Hoekstra et al., 2011 blue water footprint is indicator of freshwater use (surface and groundwater) for person or community development of goods and services and green water footprint is utilization of rainwater, which does not run off, or refill the groundwater but is retained as soil moisture within the soil. Then, the green and blue water footprint of JC plantation for Bannu was summed up with the blue water footprint of Lab-based JC biodiesel production stage. For Lab-based JC biodiesel production stage, blue water footprint was estimated using Hoekstra et al. 2011 method present by-default in SimaPro version 9.0 software. The blue and green water footprint of JC crop was estimated following the global water footprint accounting standards [44]. The AquaCrop model of FAO (version 6.1) was used to simulate the soil water balance and JC productivity [49,50]. This model estimates the evapotranspiration (ET) and JC yield by simulating the dynamic soil water balance and biomass growth on a daily basis (Eq 1).
Where; S is soil water content (mm) on day i, R is rainfall (mm), I is mean irrigation (mm), CR is capillary rise (mm), RO is mean surface runoff, Dr is drainage (mm) and ET is evapotranspiration [51]. The output of the AquaCrop simulation-crop growth characteristics and water fluxes were partitioned into blue and green parts using the method introduced by [52]. The blue and green components of JC crop water use (CWU) was assessed by summing the blue and green ET over the JC crop growing period as shown in Eqs 2 and 3.
Where, CWU b and CWU g are blue and green water consumption (m 3 ), S bt and S gt are change in blue and green soil water stock over the growing season and 10 is the conversion factor from mm to m 3 . The WF b and WF g were obtained by dividing CWU by the crop yield Y using Eqs 4 and 5 [52].
Sensitivity analysis for identification of clean and green options in JC biodiesel production chain A sensitivity analysis was conducted as per ISO protocol 2006; 14000 series that involve examining the impact of varying an input parameter. Sensitivity analysis was performed for identification of clean and green options in the JC biodiesel production chain using SimaPro v9.1 software. A 20% reduction in the baseline values for fossil diesel use, synthetic fertilizers and purchased electricity was applied to check its effect on the emissions reduction or improvement in the environmental profile of the JC biodiesel production in Pakistan. A sensitivity analysis was carried out to reduce the hotspot sources to environmental impacts caused by JC biodiesel production without going to deteriorate the quality of the biodiesel to encourage clean and green production of biodiesel from JC seeds in Pakistan.

Results
Environmental impacts of JC biodiesel production chain. The results of life cycle impact assessment for 400L JC biodiesel production are presented in this section. In this study, the US-EPA top ten most wanted environmental impact categories were evaluated i.e., carcinogens, respiratory organics, respiratory inorganics, climate change, ozone layer depletion, eco toxicity, acidification/ eutrophication, and fossil fuels [53,54]. The overall results for environmental impact categories of three stages i.e. JC cultivation stage, oil extraction and oil conversion stage are presented in Table 2. Among the three stages, the oil extraction stage has major contribution (77%) to all the environmental impact categories, followed by the oil conversion stage (21%), respectively. The cultivation stage has minor contribution (2%) to all the environmental impact categories as can be seen in Fig 2. The highest environmental impact of the three stages of biodiesel production from JC seeds was posed by ecotoxicity (3828.784 PAF � m2yr), followed by fossil fuels (2502.347 MJ surplus) and acidification/eutrophication (341.231 PDF � m2yr). The carcinogens (0.0216 DALY), respiratory inorganics (6.6E-03 DALY), climate change (1.2E-03 DALY), respiratory organics (5.2E-06 DALY) and ozone layer depletion (2.3E-07 DALY) accounted for minor environmental impacts. The overall results showed that the three stages of biodiesel production (JC cultivation, crude oil extraction and oil conversion) were major contributor to ecotoxicity impact category with a contribution of 57% to the overall impact categories evaluated. Similarly, the overall emissions accounted for 38% of the environmental burdens in the fossil fuels impact category. Moreover, the contribution of cultivation stage, oil extraction stage and oil conversion stage to acidification/eutrophication was 5% to all the environmental impact categories as can be seen in Fig 3. Emissions to different environmental compartments such as air, water and soil from the three stages of JC biodiesel production chain in Pakistan are summarized in the S1-S9 Tables.
Cumulative energy demand (CED) for JC biodiesel production chain. The CED results and related hotspots of the three stages of JC biodiesel production are presented in Table 3. The total CED required for the three stages were amounted to 46745.70 MJ from energy sources i.e., non-renewable fossil, non-renewable nuclear, non-renewable biomass and renewable water. However, among the energy sources, non-renewable fossil had the highest contribution i.e., 32982.40 MJ to the total energy removed from the nature to produce 400 L JC biodiesel as a prototype in Pakistan. The major consumption from the non-renewable fossil fuel source was in oil extraction stage of JC biodiesel production, followed by oil conversion stage, and cultivation stage, respectively. Whereas, non-renewable biomass was the second largest source with contribution of 9829.50 MJ energy use. Likewise, highest energy was consumed by oil conversion stage from non-renewable biomass, followed by oil extraction stage, and cultivation stage for 400 L biodiesel production from JC seeds. The renewable water had the contribution 1212.7 MJ to the total energy used by the process. The conversion stage was the single major contributor to renewable water, followed by extraction stage, and cultivation stage. Concisely, most of the energy was used from non-renewable fossil during the production of biodiesel from JC seeds. Maximum energy was consumed by oil conversion stage (59%), followed by oil extraction stage (38%), and cultivation stage (3%) as can be seen (Fig 4). Sensitivity analysis for clean and green options in JC biodiesel production chain. Around 20% reduction of fossil diesel use with respect to its baseline value was assumed which leads to 17.32% decrease in environmental burdens in the ozone layer depletion, 15.57% in respiratory organic, 15.42% in fossil fuels, 8.09% in respiratory inorganic, 6.32% in climate change, 5.99%, 4.21% and 1.80%, in ecotoxicity, carcinogens and acidification potential/eutrophication potential, respectively. Similarly, the use of urea was also assumed to be decrease by 20% from its baseline value, the impacts of urea in acidification potential /eutrophication potential was dropped by 5.17%, carcinogens was decreased up to 4.16%, respiratory inorganic was decreased by 1.53%, 1.2% decrease occurred in climate change, ozone layer depletion was decreased by 1.14%, respiratory organic was decreased by 0.6% and ecotoxicity was decrease up to 0.47% as summarized in (Table 4). Similarly, 20% reduction in the use of DAP, all-environmental impact categories were decreased i.e., acidification potential/eutrophication potential (6.03%) carcinogens (4.16%), respiratory inorganic (2.65%), climate change (1.77%), fossil fuels (1.19%), ozone layer depletion (1.10%), respiratory organic (1.09%) and the reduction in impact to the ecotoxicity was (0.01%). The reduction in potassium fertilizer uses by 20% leads to the maximum percentage of decrease in carcinogens (23%), followed by AP/EP (8.09%), respiratory inorganic (2.62%), ecotoxicity (1.30%), climate change (1.07%), ozone layer depletion (1.01%), respiratory organic (1%) and fossil fuel (0.21%), respectively. In the oil conversion stage, the use of electricity was reduced by 20%, so the climate change impact was decreased by 20.12%, followed by the reduction in the respiratory inorganic environmental impact category (12.59%). With the 20% reduction in the electricity, the 11.22% decrease occurred in carcinogens impact category and ecotoxicity was reduced up to 10.81%, respectively. The reduction occurred in fossil fuels was (9.79%), acidification potential /eutrophication potential was 6.70%, ozone layer depletion (5.34%) and respiratory organic was decrease up to (0.49%) as presented in (Table 4).
Water footprint (WF) of JC biodiesel production chain. The total WF for the three stage of JC biodiesel production was equal to 2632.54 m 3 /400L biodiesel production in Pakistan with most of the water consumption occurred in the cultivation stage. Among the three stages of JC biodiesel production chain, the total WF for cultivation stage was estimated to 2460 m 3 /400L biodiesel, whereas the total WF for crude oil extraction stage and oil conversion stage was equal to 154 m 3 and 18.54 m 3 per 400L biodiesel from JC seeds. Maximum water was consumed by cultivation stage, followed by oil extraction stage and then oil conversion stage as can be seen in (Fig 5).

Discussion
Our results are similar with previous research studies, where environmental burdens were primarily associated with fossil diesel use, electricity consumption, and the use of synthetic fertilizer [45,[55][56][57][58][59][60]. Our findings were in accordance with previous studies conducted on biodiesel production from different biomass sources such as JC, soybean, castor oil, waste cooking oil etc, where oil extraction stage accounted for the largest contribution and cultivation stage was responsible for minor emissions to all the environmental impact categories evaluated [61] With respect to GHG emissions, the main impact is related to JC seeds processing (79.3%), whereas 20.7% emissions were caused by cultivation of JC seeds [62]. A comprehensive LCA of biodiesel production from JC in Thailand by [63] also showed that the biodiesel production stage led to higher emissions in all the environmental impact categories relative to cultivation stage of biodiesel production from JC seeds oil. The primary reason for this higher contribution of the production or manufacturing stage of biodiesel to all environmental impact categories is due to the use of chemicals such as sodium hydroxide (NaOH) and methanol, and energy consumption during the manufacturing processes [64]. Ecotoxicity impacts were mainly due to synthetic fertilizers, insecticide and pesticide use in the cultivation stage, and chemicals used in the manufacturing stage [65]. The impact of acidification/eutrophication is mostly because of the emissions of ammonia and nitrogen oxide to air from synthetic fertilizers. The primary reason for these higher emissions was from synthetic fertilizers use, diesel fuel consumed in the vehicle for transportation of saplings to the plantation site and preparation of land for cultivation through tractor mechanization [66]. However, in the present study, JC nursery and JC cultivation field was established within the University of Science and Technology, Bannu, Pakistan, where less distances were covered to transport JC saplings from nursery to cultivation site, JC seeds from field to biodiesel production site/Lab, thus consuming less quantities of fossil fuels and other resources.
Cumulative energy demand refers to the amount of energy extracted from nature to produce a specific product such as biodiesel [67]. Maximum energy was consumed by oil conversion stage (59%), followed by oil extraction stage (38%), and the cultivation stage (3%) in this study. Our results were lower than the [68], where cultivation stage was responsible for 45.7% emissions, followed by oil extraction stage (15.7%) and oil conversion stage (38.5%) stage. The primary reason for lower emissions in the cultivation stage was attributed to the fact that JC nursery and cultivation was established on small-scale on campus site with minimum resource inputs and mechanization as compared to [69]. Furthermore, in the oil conversion stage in JC biodiesel production in Pakistan, mostly purchased electricity and fossil energy was consumed to run equipment/machinery for crude JC oil conversion into JC biodiesel. Energy demand for the processing stage of biodiesel alone accounted for 65% and 85% of the overall energy demand for palm and JC biodiesel manufacturing, respectively [56][57][58][59][60][61][62][63][64][65]. Likewise, according to, JC cultivation stage accounted for 12% to the overall CED, whereas overall transportation of JC saplings to the plantation site, oil cake and unrefined Jatropha oil contributed 15% to the CED in China. Our results were less than [66], because our analysis was based on Lab-based pilot study, where minimal distances were covered and little quantities of chemicals were utilized during the entire production chain of the JC biodiesel. However, our results were in line with Ndong et al. 2009 for manufacturing stage of JC biodiesel production, where transesterification consumed huge quantity of purchased electricity (61%) [67]. Similarly, [65][66][67][68] reported that the JC oil extraction and processing has higher consumption of energy as compare to cultivation stage, which is in accordance with the results of the present study [62]. reported that water footprint is mostly due to cultivation stage in the JC biodiesel production chain, thus irrigation is one of the most significant features for the development of this biofuel plant. In the cultivation stage, water use is higher relative to the manufacturing/Lab stage [69,70] which is similar to our results in the present study.

Conclusions and recommendations
This is the ever first study on the environmental sustainability, water footprint and cumulative energy demand of Jatropha curcas (JC) biodiesel production chain in Pakistan. From the results, it is concluded that most of the hotspot's inputs were from the cultivation stage of the biodiesel production chain such as fossil diesel and synthetic fertilizers like urea, DAP, potassium, whereas from oil conversion stage, purchased electricity consumption was the major contributor to overall environmental footprints. By performing sensitivity analysis at 20% reduction in the baseline values for fossil diesel use, synthetic fertilizers and purchased electricity, a marked decrease in most of the environmental impact categories were observed. The present study provides a benchmark or baseline for future research work to investigate material and energy flows, environmental burdens, water footprint of biofuels production from other bioenergy crops in Pakistan. Besides biodiesel production from JC seeds oil, its by-products can also be used as a value-added raw material in pharmaceutical, soap and bio pesticides manufacture industries.
Supporting information S1