Life cycle assessment for evaluating the energy balance of the multi-feedstock biodiesel production process in Indonesia

This study aims to compare the energy balance of the production of biodiesel from multiple feedstocks to the production of biodiesel from palm oil in Indonesia. The energy balance study indicates that the biodiesel multi-feedstock plant is feasible to operate. The renewability of biodiesel from multiple feedstocks is 3.31 and that of palm oil biodiesel is 6.23. It is due to the fact that the energy content and demand of multi-feedstock biodiesel are much lower than palm oil biodiesel. The energy content of biodiesel from multiple feedstocks (and its co-products) is less than that of biodiesel from palm oil (and its co-products), 109,041 MJ vs 130,370 MJ, respectively. The energy demands for the production of biodiesel from multiple feedstocks and biodiesel from palm oil are 35 × 103 MJ and 23 × 103 MJ, respectively. Energy demands, including fossil and biomass, are attributable to plantation operations, including the usage of fertilisers. Plantations of multiple crops use more energy than plantations of oil palm alone because they require more fertilisers. It is not suggested to produce multi-feedstock biodiesel from sunflower, canola, and soybean since its energy balance is not better than biodiesel from palm oil.


Introduction
The majority of the world's transportation industry still utilises petroleum-based fuels such as diesel.Continuous usage of diesel will inevitably lead to scarcity and depletion (Mirhashemi and Sadrnia 2020).Diesel combustion also creates greenhouse gases, which may contribute to global warming and climate change (Rehfeldt et al. 2020;Osman et al. 2020).To satisfy the world's energy demands, a sustainable and environmentally friendly alternative energy source is required (Yesilyurt and Aydin 2020).
Biodiesel is a renewable energy that may be used in place of diesel.The possible environmental effect and energy balance are two factors to consider in the life cycle of biodiesel production.Although biodiesel is a sustainable energy source, its production method still relies on fossil fuels, which is a non-renewable energy source (Gheewala et al. 2022;Wahyono, Hadiyanto, and Budihardjo 2019).The usage of fossil energy in the production of biodiesel has a significant impact on the environment, particularly in the production of biodiesel from palm oil.Fossil energy is commonly employed in the production of fertiliser, methanol, and transportation (Gheewala et al. 2022;Silalertruksa and Gheewala 2012;Wahyono et al. 2020).Therefore, it is crucial to evaluate the energy demands and energy balance of the production of biodiesel from palm oil in Indonesia in order to determine which activities along the biodiesel production life cycle utilise the most fossil energy.Thus, it is possible to manage the process that uses the most fossil energy in an effort to restrict consumption of fossil energy and replace it with renewable energy sources that are less detrimental to the environment, such as biomass, water, wind, and solar.
The previous studies have investigated the energy balance of the production of biodiesel from palm oil in Indonesia.The studies investigate the net energy ratio (NER) and net energy value (NEV) in the production of palm oil biodiesel.NER is the ratio between net energy outputs and net energy inputs.NEV is the difference in energy content between biodiesel (and its coproducts) and net energy input (Susanto, Santoso, and Suwedi 2017;Wahyono, Hadiyanto, and Budihardjo 2019).However, it is not a complete energy balance since it ignores the criteria of net renewable energy values (NRnEV) and renewability.The NRnEV is the difference in energy content between biodiesel (and its co-products) and fossil energy inputs.The definition of renewability is the ratio between net energy outputs to net fossil energy inputs.In the study of energy balance in palm oil biodiesel production, at least four factors must be calculated: NEV, NRnEV, NER, and renewability (Silalertruksa and Gheewala 2012).There has been no prior study that has examined the energy balance of the production of biodiesel from palm oil in Indonesia by including the calculation of these four factors in the life cycle evaluation.
Additionally to biodiesel developed from single feedstocks, such as palm oil, there is biodiesel developed from several feedstocks (Hadiyanto et al. 2020).Because single feedstock biodiesel such as bovine tallow, corn, castor, pongamia, peanut, sunflower, and jatropha demonstrated poor quality, multi-feedstock biodiesel was created (Gomes Souza et al. 2021).Cold filter clogging (12°C), pour point (15°C), and cloud point (16°C) are all low for palm oil biodiesel (Atabani et al. 2012).Utilising feedstock of blended oil lowers the cost of multiple additives used to increase the cold flow qualities and oxidation stability of the produced biodiesel (Kumar, Singhal, and Sharma 2021).As a result, preparing a combination of diverse oils derived from rich resources, for instance, palm oil, sunflower oil, canola oil, soybean oil combined with low-quality inexpensive oil, for instance, wasted cooking oil may aid in the production of optimal blended oil with better fuel qualities.The use of waste cooking oil in biodiesel manufacturing adheres to circular economy principles (Al-Muhtaseb et al. 2021).Circular economy involves the resource-efficient valorisation of biomass in integrated, multioutput production chains, as well as the use of leftovers and wastes and the optimisation of biomass's value through time (Al-Mawali et al. 2021).
Prior researchers have successfully produced multi-feedstock biodiesel on a laboratory scale (Widayat et al. 2015;Flood et al. 2016;Hadiyanto et al. 2020).The production of biodiesel from multiple feedstocks has the potential to be a large-scale industrial process (Kumar, Singhal, and Sharma 2021).It is critical to understand the energy balance of the production of biodiesel from multiple feedstocks.It is to find out whether the biodiesel multi-feedstock plant is feasible to operate.Osman et al. (2021) have reported that there are many methods of converting biomass into biodiesel that have been developed to date, including homogeneous catalytic transesterification, heterogeneous catalytic transesterification, microwaveassisted transesterification, ultrasonic irradiation transesterification, non-catalytic supercritical methanol transesterification, and enzymatic catalytic transesterification.Compared to biological routes, these thermochemical reactions result in less greenhouse gas emissions.However, these procedures often need a large amount of energy and the addition of solvents or catalysts.Energy balance studies on biodiesel production using conventional to advanced methodologies and single feedstock have been previously carried out by Mohammadshirazi et al. (2014); homogeneous catalytic (KOH) and waste cooking oil, Sánchez-Bayo et al. (2020); heterogeneous catalytic (CT-269 resin) and Isochrysis galbana, Krishnan et al. (2020); microwaveassisted transesterification and algae, Martinez-Guerra and Gude (2016); ultrasonic irradiation transesterification and algae, Mariano et al. (2018); non-catalytic supercritical methanol transesterification and soybean, and Xie et al. (2022); enzymatic catalytic transesterification and algae.No previous studies have evaluated the energy balance of the production of multi-feedstock biodiesel from palm oil, sunflower oil, canola oil, soybean oil, and used cooking oil.Therefore, this study used LCA to assess the energy balance of industrial biodiesel production from multiple feedstocks.The findings of this research are juxtaposed to the life cycle of production of biodiesel from palm oil, that is now Indonesia's principal biodiesel source.

Assumptions for simulating the life cycle of production of biodiesel from multiple feedstocks
The largest biodiesel producer in Indonesia is located in the city of Dumai.The city of Dumai is the nationwide centre of the production of biodiesel due to its favourable expansive plantation land and coastal position (Budiman et al. 2017).Therefore, the city of Dumai is a suitable area for simulating the life cycle study of the production of biodiesel from multiple feedstocks.Figure 1 depicts a strategy of analysis of life cycle for production of biodiesel from multiple feedstocks.The following are the study's assumptions: (1) Plantations for soybeans, canola, sunflowers, and oil palm are all nearby.Each plantation is separated by 5 m wide empty land.
(2) The plantations are located around two kilometres from the multi-feedstock biodiesel refinery.
(3) Plants are irrigated with groundwater.(4) Three kilometres from the multi-feedstock biodiesel plant collect used cooking oil from restaurants.CO 2 emissions and the cost of transporting 1 tonne of used cooking oil for 3 km using a truck is 0.89 kg CO 2 and 173,400 Rupiah.(5) Deionised water is used for biodiesel washing.(6) The treating wastewater unit handles the leftover water, sodium hydroxide, and methanol, which are liquid inorganic and organic waste.

Simulation of the system boundaries of the life cycle of production of biodiesel from multiple feedstocks
This study aims to assess the energy balance of the production of biodiesel from several feedstocks.Using the LCA technique outlined in Principles and Framework for Environmental Management and Life Cycle Assessment, the energy balance of multifeedstock biodiesel is calculated (ISO 14040 2006).In this LCA analysis, the functional unit is 1 tonne of biodiesel generated from several feedstocks.The evaluation begins with feedstocks production on farms and in restaurants and concludes with completed goods (biodiesel from multiple feedstocks) production at the factory.Three stages comprise the cradle-to-gate of the life cycle of biodiesel production: the planting of multiple crops, the collection of UCO, the processing of oil, and the conversion of multi-feedstock biodiesel.Figure 2 depicts the system boundaries of biodiesel production from multiple feedstocks.Plantations of oil palm need fertilisers (dolomite, rock phosphate, urea) and herbicides (glyphosate).Plantations of canola need fertilisers (nitrogen fertiliser, phosphorous fertiliser, potassium fertiliser, calcium oxide) and pesticides.Fertilisers (phosphate fertiliser, nitrogen fertiliser) and insecticides are necessary for sunflower plantations.Plantations of soybean need fertilisers (limestone, nitrogen fertiliser, phosphorus fertiliser, potassium fertiliser) and pesticides (organophosphorus-compounds, thiocarbamate-compounds, benzimidazole-compounds, glyphosate).To the oil pretreatment step, sunflower, canola, and soybean seeds, including FFB, are conveyed using a dieselpowered vehicle.The agricultural phase produces soil emissions (pesticide), water emissions (phosphorus (P), phosphate (PO 3− 4 ), nitrate (NO − 3 ), and pesticides), and air emissions (carbon dioxide (CO 2 ), ammonia (NH 3 ), nitrogen dioxide (NO 2 ), and nitrous oxide (N 2 O)).
The restaurant contains storage space for UCO that has outlived its usefulness.UCO is delivered using a truck powered by diesel fuel, and the procedure is repeated daily at other eateries.The UCO is then transferred to the unit of pretreatment.The UCO collection results in emissions of air (carbon dioxide).
Energy and material inputs and emissions output at the stage of plantation of canola (Soraya et al. 2014;Bai et al. 2021), plantation of soybean (Bai et al. 2021), plantation of sunflower (Dekamin, Barmaki, and Kanooni 2018), plantation of oil palm (Ahmadi et al. 2021), and collection of UCO (Chung et al. 2019) were obtained from prior studies.

Description of process scenario
Three simulated process scenarios for the plant of biodiesel from multiple feedstocks are shown in Figure 3(A-C).The process units of pretreatment, esterification, and transesterification are the focal point of scenarios 1, 2, and 3 (Figure 3(A-C)).Several raw materials of oil, such as crude sunflower oil (CSFO), crude canola oil (CCO), and crude soybean oil (CSO) have low levels of free fatty acids (FFA) ( < 2%) (Vicentini-Polette et al. 2021;Flood et al. 2016;Salmasi, Kazemeini, and Sadjadi 2020), while used cooking oil (UCO) and crude palm oil (CPO) have high levels of FFA ( > 2%), used to produce biodiesel from multiple feedstocks (Yusuff et al. 2018;Saksono et al. 2019).Before transesterification processes can be carried out, materials having a high FFA content requires a step of esterification (Litinas et al. 2020).
Scenario 1 involves the degumming of oil with low FFA (CSFO, CCO and CSO) in a single tank.Without gum, a combination of CSFO, CCO, and CSO is produced.UCO is filtered and CPO is degummed to eliminate contaminants during this time.Simultaneous esterification of filtered UCO and degummed CPO generates esterified oil.The blend of degummed CSFO, CCO, and CSO is then transesterified and filtered to form a product of biodiesel from multiple feedstocks (Figure 3(A)).
In scenario 2, the procedure of pretreatment is identical to scenario 1, which categorises materials according to their FFA contents.The distinction is that the degummed CSFO, CCO, and CSO combination will then undergo transesterification to generate biodiesel.The esterified oil generated from a blend of filtered UCO and degummed CPO will then undergo transesterification and purification to generate biodiesel.Next, biodiesel derived from CSFO, CCO, and CSO is blended with biodiesel derived from UCO and CPO to produce a product of biodiesel from multiple feedstocks (Figure 3(B)).
In scenario 3, every oil undergoes individual refining.CPO is treated by degumming, esterification, transesterification, and purification, while individually, CSFO, CCO, and CSO are handled by degumming and transesterification.Filtration, esterification, transesterification, and purification are used to refine UCO.Each oil's biodiesel is combined to create a product of biodiesel from multiple feedstocks (Figure 3(C)).The specifics of the simulation of process are shown in the multi-feedstock biodiesel plant's preliminary design for scenarios 1, 2, and 3, which is accessible in the Supplemental Information (Figures S1-S3).FFB, canola, soybean, and sunflower are stored at 30°C and 1 atm pressure in a warehouse before being delivered and dried to a 5% w/w moisture content using a belt conveyor dryer and then increased surface area by feeding them into the crusher.Elevators are then used to convey the dry seeds/fruit to the screw press machine, where they are processed into CPO, CSFO, CCO, and CSO, which are subsequently heated to 70°C utilising steam.The CPO, CSFO, CCO, and CSO are then diffused from the heater to the agitated degumming tank.Sunflower, canola, and soybean meal are produced by CSFO, CCO, and CSO, respectively.CPO byproducts include shell, kernel, fibre, palm oil mill effluent (POME), empty fruit bunches (EFB), and cake.Sunflower, canola, and soybean meal are used in the production of pellet feed as protein supplements in animal feed regimens (Lomascolo et al. 2012).This study's system boundary excludes the conversion of sunflower, canola, and soybean meal into derivative commodities.Mechanical processing of the kernels results in palm kernel oil (PKO) and palm kernel extract (PKE), while the partly separated shell serves as fuel for the boiler.The leftover shells could be utilised to generate activated carbon or sold as solid fuel.In multi-feedstock biodiesel facilities, fibre is further utilised for fuel of boiler to create steam and power.Cake is currently considered waste and has no environmental consequences because it has minimal utility and is routinely dumped in plantations (Silalertruksa and Gheewala 2012).To process EFB, co-composting with POME, inorganic and organic waste from CSFO, CCO, CSO, and pretreatment of UCO is employed.Before being co-composted with EFB and released to the environment as compost, inorganic, organic, and POME waste are processed to produce biogas.In scenarios 1, 2, and 3, the pretreatment technique for sunflower, canola, soybean, and FFB is identical (Supplemental Information (Figures S1-S3)).

Stage of oil pretreatment.
The gum content of the CSFO, CCO, and CSO mixture is coagulated in the tank of degumming at the oil flow rate 0.4% using a H 3 PO 4 solution of 20% v/v.The holding tank discharges H 3 PO 4 into a cylindrical storage vessel with a conical lid.The gum phosphate from the tank of degumming generates clods, utilising a centrifuge at 65°C and 1 atm pressure, they are extracted from the oil.The FFA and triglycerides in the oil blend should be completely purified from gum phosphate to ensure that none reaches the gum phosphate flow.From the oil, gum phosphate and water are separated as a result of the density differential.Scenarios 1 and 2 use the same degumming technique.In scenario 3, CSFO, CCO, and CSO are individually degummed in separate tanks of degumming (Supplemental Information (Figures S1-S3)).
Degumming CPO is performed in a separate tank of degumming, but the process is identical.In scenarios 1, 2, and 3, the CPO degumming procedure is identical.During the process of UCO pretreatment, the UCO inside the tank is delivered to a filtering machine, which removing contaminants.Prior to cocomposting with POME and EFB, inorganic and organic wastes from CSFO, CCO, CSO, and UCO are converted to biogas; this is identical for Scenarios 1, 2, and 3 (Supplemental Information (Figures S1-S3)).

The process of esterification. An oil blend composed
of UCO and CPO is injected into the reactor of esterification, where it mixes with H 2 SO 4 , methanol, and FFA after heating to 65°C at 1 atm.The FFA to methanol mole ratio is 1:15.FFA levels in utilised H 2 SO 4 are 0.5% by weight.The esterification process generates heat; therefore, water-based cooling medium is needed to keep a steady heat of 65°C.This esterification process has a conversion efficiency of 85%, and the esterification reactor products are triglycerides, biodiesel, unconverted reactants, and water.Then, these products are moved to a tank of neutralisation where CaO is used to eliminate the sulphuric acid catalyst.A screw conveyor transports CaO from the hopper to the neutralisation tank.The following is the reaction: Assuming the neutralisation process is complete, the decanter separation of the neutralisation tank's output product reveals the absence of H 2 SO 4 and CaO.The bottom product is a high-density compound consisting of methanol, H 2 O, and CaSO 4 that is stored in a holding tank.Meanwhile, biodiesel, triglycerides, and unreacted methanol with a lower density are sent to mixers of NaOH.In general, the technique of esterification for scenarios 1, 2, and 3 is identical.In both scenario 1 and scenario 2, UCO and CPO are esterified in a single reactor.In the third scenario, UCO and CPO are individually esterified using separate reactors (Supplemental Information (Figures S1-S3)).

The process of transesterification.
At a 1% w/w concentration of triglycerides, esterified oil from UCO and CPO, as well as CSFO, CCO, and CSO, is mixed with NaOH crystals.The solution is put into the transesterification reactor after being heated to 60°C.Methanol to triglycerides has a mole ratio of 6:1, resulting in a 95% reaction conversion.The reaction of transesterification takes place at 60°C and 1 atm of pressure.Owing to the exothermic nature of the process of transesterification, water is needed to keep a steady heat of 60°C.The reactor of transesterification generates the remaining untransformed reactants, glycerol, and biodiesel.
Using a decanter, standard-compliant biodiesel and glycerol byproducts are extracted from the transesterification reactor.Biodiesel may include up to total glycerol of 0.24% w/w, water of 0.05% v/v, and methanol of 0.05% w/w.The process of decantation yields primarily a biodiesel solution containing traces of triglyceride, methanol, and glycerol leftovers, thereafter transported to a tank of washing.If the NaOH has been entirely mixed in the glycerol, the product of bottom, mixture of glycerol and NaOH, is sent to the tank of neutralisation to neutralise the NaOH.The following is the neutralisation reaction: By reason of the neutralisation reaction is assumed to be complete, no H 2 SO 4 or NaOH is present in the product of the tank of neutralisation.As a result, the neutralisation tank generates Na 2 SO 4 liquid, using a decanter, is purified from glycerol.
The upper product, consisting of light components like methanol, is deposited in the tank of holding.Furthermore, the product at the bottom, glycerol, is decanted into a fresh decanter.The product at the top of the decanter is subsequently transferred to the washing tank of biodiesel, which is filled with water containing 25% w/w biodiesel.After that, the fluid is centrifuged to separate the biodiesel from the remaining pollutants.The centrifuge can produce biodiesel products of exceptional quality that comply with rules for sale and use as fuel.The solution is then deposited at 30°C and 1 atm pressure in a biodiesel storage tank shaped like a conical roof tank.The bottom product (H 2 O, methanol, triglycerides, and glycerol) is simultaneously fed to the tank of holding.
The product at the bottom of the centrifuge and decanter is temporarily stored in a holding tank before being sent to the column of distillation and converted into methanol.Before the mixture enters the column of distillation, it is heated in a preheater at 1 atm pressure to 80°C.As a consequence, the column of distillation yields a higher quality product: methanol of high purity with an H 2 O hint.The product at the top of the distillation column is returned to the cooler for additional blending, while the product at the bottom of the column of distillation is processed by the unit of treatment of wastewater.Next, glycerol in the decanter is purified of other pollutants, yielding pure glycerol as a byproduct.The system boundary of the study excludes the conversion of glycerol into its derivative products.
The process of transesterification is similar for scenarios 1, 2, and 3.In contrast, Scenario 1 differs in that, the transesterification process takes place in a single reactor.A blend of degummed CSFO, CCO, and CSO, as well as blend of UCO and CPO esterified oils are transesterified in a single reactor.Scenario 2 has two transesterification reactors, one for transesterifying the blend of degummed CSFO, CCO, and CSO, and the second for transesterifying the esterified oil from a blend of UCO and CPO.Scenario 3 has five reactors of transesterification, each of which transesterifies CSFO, CCO, CSO, UCO, and CPO individually (Supplemental Information (Figures S1-S3)).

Inventory of life cycle
SimaPro 9.0.0.49and the Ecoinvent 3 databases were utilised in this study (Pauer, Wohner, and Tacker 2020).Energy and material inputs, including emissions production throughout the UCO collection and plantation stage, based on prior studies (Table 1).In addition, calculations for the multiple-feedstock biodiesel plant's energy and material inputs and emission outputs were performed using Microsoft Excel and the concept of heat and mass balance.Table 2 and Supplemental Information (Tables S1-S3) provide the three preliminary design scenarios for the plant of biodiesel from multiple feedstocks.The LCI results for the transesterification procedure are based upon personal experiments.The environmental effect of producing biodiesel from multiple feedstocks is compared to biodiesel from palm oil.Table 3 displays inventory data for the production of biodiesel from palm oil in Indonesia.

Life cycle impact assessment (LCIA)
The cumulative energy demand (CED) was employed as the LCIA approach for the production process of biodiesel from multiple feedstocks in the current study.CED displays the energy demand outcomes in five energy sources categories: biomass renewable, nuclear non-renewable, fossils non-renewable, water renewable, wind, solar, and geothermal renewable (Wahyono, Hadiyanto, and Budihardjo 2019).Included in non-renewable fossil fuels include hard coal, coal mining of gas, lignite, crude oil, and natural gas.Non-renewable nuclear contains uranium.Water renewable comprises reservoir hydropower and river runoff hydropower.Biomass renewable consists of Note: Table 2 provides a summary of all information for the preliminary design of multi-feedstock biodiesel plant scenarios 1, 2, and 3. Additional details are accessible in the Supplemental Information (Tables S1-S3).

Energy balance
Energy balance in the biodiesel production life cycle is often evaluated using four parameters: renewability, net energy ratio (NER), net renewable energy value (NRnEV), and net energy value (NEV) (Silalertruksa and Gheewala 2012).The method for calculating these four parameters is provided in Table 4.
The energy input value equals the cumulative energy demand value, i.e. biomass renewable, nuclear non-renewable, fossils non-renewable, water renewable, wind, solar, and geothermal renewable.The energy output figure corresponds to the energy content of biodiesel (and its co-products), including multi-feedstock biodiesel, glycerol, meal, biogas recovered from POME, shells, palm kernel, and EFB (Frischknecht et al. 2015;Silalertruksa and Gheewala 2012).

Results and discussion
The energy demands for the production of biodiesel from multiple feedstocks and biodiesel from palm oil are shown in Tables 5  and 6.There is discussion of the need for fossil, nuclear, water, biomass, wind, solar, and geothermal energy.The energy content of biodiesel derived from multiple feedstocks and biodiesel derived from palm oil is then addressed.Finally, the energy balances of biodiesel from multiple feedstocks and biodiesel from palm oil are compared (Table 8).MJ 20 × 10 3 20 × 10 3 20 × 10 3 674 674 782 14 × 10 3 16 × 10 3 21 × 10 3 35 × 10 3 38 × 10 3 42 × 10 3 a The energy demand is the same since scenarios 1, 2, and 3 need the same number of sunflower seeds, canola seeds, soybean seeds, FFB, and UCO as raw material inputs.
b The energy demand is identical as the oil pretreatment processes for scenarios 1 and 2 are the same process.

Fossil energy demand
The demand for fossil energy (FED) is measured in megajoules (MJ).FED is primarily supported by multiple crop cultivation and conversion of multi-feedstock biodiesel (Table 5).Diesel fuel, phosphate fertiliser, and urea production are the key roots of FED for the cultivating stage of various crops (Figure 4).Electricity and methanol production are the major sources of FED in the stage of conversion of biodiesel from multiple feedstocks, as they are in scenarios 1, 2, and 3 (Figures 6-8).This corroborates the results of Wahyono, Hadiyanto, and Budihardjo (2019).Production of urea necessitates a substantial quantity of hard coal (Adiansyah, Hadiyanto, and Ningrum 2021), phosphate fertiliser necessitates a large amount of hard coal (Peng et al. 2019), and methanol, electricity, and diesel necessitate a substantial quantity of hard coal (Wahyono, Hadiyanto, and Budihardjo 2019), all of which contribute significantly to FED biodiesel from multiple feedstocks.In scenarios 1, 2, and 3, the FED for biodiesel derived from several feedstocks is 32 × 10 3 , 35 × 10 3 , and 39 × 10 3 MJ, respectively (Table 5).The FED of biodiesel from multiple feedstocks scenario 3 is the highest since, at this conversion stage, the largest demands are for electricity for equipment and methanol for the transesterification process.Meanwhile, scenario 1 necessitates the least amount of electricity and methanol.The FED of biodiesel from multiple feedstocks is more than that of biodiesel from palm oil (20 × 10 3 MJ) (Table 6).This is owing to the greater use of urea and diesel on plantations of numerous crops than on plantations of oil palm, as a result of oil palm's higher yield (Soraya et al. 2014;Meijaard et al. 2020).When compared to other energy sources, FED is the highest (Tables 5 and 6).It means that the production of biodiesel from multiple feedstocks and biodiesel from palm oil continues to rely on fossil fuels as its primary source of energy (Figure 5).

Nuclear energy demand
Nuclear energy demand (NED) is measured in megajoules (MJ).
In scenarios 1, 2, and 3, the findings indicated that multiple crop cultivation and the stage of conversion of biodiesel from multiple feedstocks are the key contributors to NED (Table 5).Phosphate, urea, and potassium fertilisers production is the primary source of NED for multiple crop plantations (Figure 4).In the phosphate, urea, and potassium fertilisers production, uranium is utilised as a fuel (Frischknecht et al. 2015;Wahyono, Hadiyanto, and Budihardjo 2019).As in scenarios 1, 2, and 3, the key sources of NED in the stage of conversion of biodiesel from multiple feedstocks are electricity and methanol production (Figures 6-8).
Uranium is a fuel source in methanol and electricity production (Frischknecht et al. 2015;Wahyono, Hadiyanto, and Budihardjo 2019).For scenarios 1, 2, and 3, the NED for biodiesel from multiple feedstocks is 1,267, 1,388, and 1,836 MJ (Table 5), which is more than the palm oil biodiesel value of 1,190 MJ (Table 6).This is due to the fact that the total use of fertilisers on multi-crop plantations is 242 kg, but it is only 111 kg on oil palm plantations.

Biomass energy demand
Biomass energy demand (BED) is commonly expressed in megajoules (MJ).BED is mostly caused by the cultivation of various crops (Table 5).The major source of BED for the growing stage of various crops is potassium fertilisers production (Figure 4).The production of potassium fertilisers necessitates the use of agricultural biomass as a fuel source (Frischknecht et al. 2015;Wahyono, Hadiyanto, and Budihardjo 2019).For scenarios 1, 2, and 3, the BED of biodiesel from multiple feedstocks is 1022, 1042, and 1115 MJ, respectively (Table 5).The BED of biodiesel from multiple feedstocks is significantly higher than that of biodiesel from palm oil, which is 340 MJ (Table 6).This is because agricultural biomass is used more extensively in multi-crop plantations than in oil palm plantations.Because of the oil palm's higher yield, multi-crop plantations require more potassium fertiliser than oil palm plantations (Soraya et al. 2014;Meijaard et al. 2020).Biomass is a possible renewable energy source, and its usage should be promoted since it is plentiful and can replace fossil fuels (Yana, Nizar, and Mulyati 2022;Wahyono et al. 2021).Optimising the utilisation of biomass energy is a positive step toward reducing reliance on non-renewable fossil energy.Biomass fuel made from wood waste is an inexpensive and efficient source of energy (Prasad et al. 2012;Liu et al. 2014).Shell and fibre are also excellent biomass energy sources (Silalertruksa and Gheewala 2012).

Wind, solar, and geothermal energy demands
Wind, solar, and geothermal energy demands (WSGED) are measured in megajoules (MJ).The findings revealed that the cultivation of numerous crops, as well as collection of UCO and conversion of biodiesel from multiple feedstocks, are the primary contributors to WSGED (Table 5).The principal roots of WGSED for the cultivating stage of various crops are phosphate fertiliser and urea production (Figure 4).Electricity production is the main source of WSGED in the stage of conversion of biodiesel from multiple feedstocks, as it is in scenarios 1, 2, and 3 (Figures 6-8).Wind, solar, and geothermal energy are used in very small amounts as power plant energy sources in urea and phosphate fertilisers production.Weather variations and climate change affect wind and solar resources (not weather proof).Meanwhile, geothermal resources are available around the clock, seven days a week (weather proof).However, geothermal energy is still mostly used to supply residential electrical demands (Østergaard et al. 2020;Li et al. 2015).As a result, WSGED has the lowest value when compared to FED, NED, BED, and WED.Wind, solar, and geothermal energy are primarily used  to satisfy the electrical requirements of multi-feedstock biodiesel plant.The electricity usage in scenarios 1 and 2 of the plant of biodiesel from multiple feedstocks is lower than in the plant of biodiesel from palm oil (Tables 2 and 3).As a result, WSGED biodiesel from multiple feedstocks scenarios 1 and 2 is lower than WED palm oil biodiesel, with 72 and 82 MJ for WSGED biodiesel from multiple feedstocks scenarios 1 and 2, and 91 MJ for WSGED palm oil biodiesel (Tables 5 and 6).

Water energy demand
Water energy demand (WED) is measured in megajoules (MJ).WED is mostly caused by multiple crop cultivation and conversion of multi-feedstock biodiesel (Table 5).The principal sources of WED during the cultivation stage of various crops are phosphate fertiliser and urea production (Figure 4).Electricity production is the main source of WED in the stage of conversion of multi-feedstock biodiesel, as it is in scenarios 1, 2, and 3 .Because of the climate change impact, the production of urea and phosphate fertiliser consumes relatively little water energy.Climate-related hazards affect hydropower productivity by altering the amount and timing of precipitation.Extreme weather occurrences, such as floods and droughts, make planning for hydropower development is tough.The river water flow is low throughout the summer, causing the hydroelectric capacity to diminish (IPCC 2014; Kim et al. 2017).As a result, the energy source for biodiesel production is independent of water energy.As a result, WED is lower than FED, NED, and BED.Water energy is primarily used to satisfy the electrical requirements of the plant of biodiesel from multiple feedstocks.The electricity demand in scenarios 1 and 2 of the plant of biodiesel from multiple feedstocks is lower than in the plant of biodiesel from palm oil.It is more likely to cause WED biodiesel from multiple feedstocks scenarios 1 and 2 than WED palm oil biodiesel.WED biodiesel from multiple feedstocks scenarios 1 and 2 have capacities of 434 and 484 MJ, respectively, whereas WED palm oil biodiesel has a capacity of 494 MJ (Tables 5 and 6).

Energy content
The average energy content of biodiesel from sunflower, canola, soybeans, palm oil, and UCO is used to calculate the energy content of biodiesel from multiple feedstocks.Biodiesel from multiple feedstocks has an energy content of 39,008 MJ, which is a little higher than the energy content of from palm oil, which is 38,070 MJ (Silalertruksa and Gheewala 2012;Efe, Ceviz, and Temur 2018;Mohammadshirazi et al. 2014).The energy content of co-product biodiesel from multiple feedstocks is significantly lower than that of co-product biodiesel from palm oil, at 70,033 MJ and 92,300 MJ, respectively.It lowers the overall energy content of multi-feedstock biodiesel (and its coproducts) below that of palm oil biodiesel (and its co-products), 109,041 MJ for multi-feedstock biodiesel and 130,370 MJ for palm oil biodiesel (Table 7).The value of biodiesel's energy content must be weighed against the amount of energy needed to generate it.Energy demand is equivalent to energy input and energy content is equivalent to energy output biodiesel, to calculate the energy balance, both are required.

Energy balance
Renewability, NER, NRnEV, and NEV are the four indicators usually utilised to measure the energy balance of biodiesel production.NEV and NRnEV values for biodiesel from multiple feedstocks and biodiesel from palm oil were positive, indicating that the production of biodiesel from multiple feedstocks and biodiesel from palm oil created an energy surplus.NER and renewability are similarly good for biodiesel from multiple feedstocks and biodiesel from palm oil, indicating that these fuels are viable for use (Wahyono, Hadiyanto, and Budihardjo 2019).
It demonstrates that the energy output of biodiesel is more than the energy input of the production of biodiesel.It is beneficial to the long-term viability of the production of biodiesel (Gheewala et al. 2022;Silalertruksa and Gheewala 2012).However, biodiesel from palm oil has a greater NER and renewability than multifeedstock biodiesel.The NER biodiesel from multiple feedstocks scenarios 1, 2, and 3 are 3.05, 2.86, and 2.55.Palm oil biodiesel has a NER of 5.66.Next, 3.31, 3.10, and 2.79 represent the renewability of biodiesel from multiple feedstocks scenarios 1, 2, and 3, respectively, while 6.23 represents the renewability of palm oil biodiesel (Table 8).The palm oil biodiesel energy balance is better to that of multi-feedstocks biodiesel.The reason biodiesel from palm oil has a better energy balance than biodiesel from multiple feedstocks is that the production of biodiesel from palm oil requires much less energy than the production of biodiesel from multiple feedstocks (Tables 5 and 6).
A comparison of the energy balance of multi-feedstock production in our study with that of previous studies is shown in Table 9.The biodiesel production that we conducted using the transesterification method with a homogeneous catalyst (NaOH) had the highest NER value in first place (3.05) compared to other advanced methods in biodiesel production, including homogeneous catalytic (KOH) transesterification (1.49), heterogeneous catalytic (CT-269 resin) transesterification (1.50), microwave-assisted transesterification (1.12), ultrasonic irradiation transesterification (0.85), non-catalytic methanol supercritical transesterification (0.84), and enzymatic catalytic transesterification (0.59).Ultrasonic and microwave are good candidates for lipid extraction from microalgae in an effort to reduce energy consumption and overall extraction time (Martinez-Guerra and Gude 2016; Krishnan et al. 2020).Production method of ultrasonic and microwave in the study of Martinez-Guerra and Gude (2016) and Krishnan et al. (2020) has low value of NER because it uses algae as raw materials, where the highest energy consumption is at the algae cultivation stage (Xie et al. 2022).Similarly, the enzymatic catalytic method can also reduce energy consumption, but the NER value is still low, because the raw materials used in the study by Xie et al. (2022) are algae that require high energy at the cultivation stage.Biodiesel production using the heterogeneous catalytic (CT-269 resin) transesterification

Best scenario chosen for the production of biodiesel from multiple feedstocks
The consumption of methanol and electricity are principal factors to the energy demand of the stage of conversion of multifeedstock biodiesel (Figures 6-8).This is due to the fact that coal is still used as a fuel source in the production of methanol and electricity (Wahyono, Hadiyanto, and Budihardjo 2019).The scenario with the least electricity and methanol input will have the least energy requirement.For scenarios 1, 2, and 3, the amount of electricity utilised during the stage of conversion of biodiesel from multiple feedstocks is 141.4,197.6, and 424.7 kWh.For scenarios 1, 2, and 3, the quantity of methanol utilised during the stage of conversion of biodiesel from multiple feedstocks is 339.2, 389.2, and 439.2 kg/hour (Table 2).Scenario 3 necessitates the most reactors of transesterification (five units) and reactors of esterification (two units) related to the process of transesterification being performed independently in each reactor for each feedstock.Meanwhile, in scenario 1, the process of transesterification is conducted out concurrently in one reactor for all five feedstock, need individual esterification and transesterification reactors.Based on the outcomes, scenario 1 exhibited the lowest for all energy demand categories when especially in comparison to scenarios 2 and 3 (Table 5).Thus, from an energy standpoint, scenario 1 is better than scenarios 2 and 3.
The energy balance study indicates that the biodiesel multifeedstock plant is feasible to operate.The overall energy consumption for the production of biodiesel from palm oil is approximately 30% less than that of multi-feedstock biodiesel.It improves the palm oil biodiesel energy balance over multifeedstock biodiesel.As a result, from an energy balance standpoint, biodiesel from palm oil is preferred for Indonesia.Nevertheless, there is still room for improvement in the technique of producing palm oil biodiesel.Hard coal continues to dominate the energy needs for palm oil biodiesel.Reduced usage of hard coal as a fuel can lead to improvements.Hard coal is a non-renewable energy source that will ultimately run out if utilised indefinitely.As an alternative to reducing hard coal consumption, higher use of shell, fibre, agricultural biomass, wood, straw, and other fuels can be made (Silalertruksa and Gheewala 2012;Liu et al. 2014).It is appropriate for Indonesia, which has an abundance of biomass resources, 146.7 million tonnes per year, that may be utilised as sustainable biomass fuel (Yana, Nizar, and Mulyati 2022;Wahyono et al. 2021).The usage of geothermal energy can then be expanded because Indonesia's geothermal energy potential is believed to represent around 40% of the world's geothermal energy potential (Nasruddin et al. 2016).Its purpose is to assist the Indonesian government's strategy, namely the national energy supply target of more than 17% renewable energy in 2025 (The President of the Republic of Indonesia 2014).In Indonesia, biodiesel used in transportation must still be blended with diesel.The Indonesian government has enacted a regulation requiring the use of B30 biodiesel, a blend of 30% biodiesel and 70% diesel (DGEBTKE 2019).Biodiesel-diesel blends have shown increased engine performance and lower smoke emissions (Hasan et al. 2021).Increasing the proportion of sunflower oil biodiesel in diesel from B0 to B50 enhances braking torque and braking power (Samani et al. 2020).This is a consequence of the greater oxygen concentration of biodiesel in the combustion region, which results in comparatively more complete combustion (Gharibian et al. 2022).Consequently, future research should also evaluate the performance of the combustion of multi-feedstock biodiesel and diesel blends.

Conclusions
The biodiesel multi-feedstock plant is feasible to operate based on the energy balance analysis.Multi-feedstock biodiesel have a lower energy content than palm oil biodiesel, 109,041 MJ for biodiesel from multiple feedstocks (and its co-products) and 130,370 MJ for biodiesel from palm oil (and its co-products), the palm oil biodiesel energy balance is better.It is due to the energy input required to produce biodiesel from palm oil is substantially lower than that required to produce multi-feedstock biodiesel from used cooking oil, palm oil, sunflower, canola, and soybean.The energy demands for the production of biodiesel from multiple feedstocks and biodiesel from palm oil are 35 × 10 3 MJ and 23 × 10 3 MJ, respectively.Thus, the renewability of palm oil biodiesel is 6.23, which is greater than the renewability of multifeedstock biodiesel, which is only 3.31.In terms of Indonesia's energy balance, palm oil biodiesel continues to be superior.Nevertheless, efforts must be made to enhance energy management procedures throughout the life cycle of production of biodiesel from palm oil.The most energy input used in the production of biodiesel from palm oil is fossil energy, which is derived from hard coal.The reliance on hard coal as a fuel source must be minimised since hard coal is a source of non-renewable energy that would ultimately run out if utilised constantly.The utilisation of agricultural biomass as a fuel can be expanded as a substitute for hard coal.The limitations of this study are the plantations of multiple crops are irrigated with groundwater, groundwater is not a sustainable source.Next, the simulation of multi-feedstock biodiesel production is still based on the traditional biodiesel industry process of transesterification employing a homogeneous catalyst.In the future, it will be important to undertake a life cycle evaluation of hydrocracking and hydroisomerisation of palm oil biodiesel production.The point of the study is to determine whether or whether this method is superior from an environmental and energy standpoint compared to palm oil biodiesel manufacturing in Indonesia, which still uses potassium hydroxide or sodium oxide as homogeneous catalysts.Future research is also required to evaluate the combustion performance of a biodiesel and multi-feedstock biodiesel blend.It is because the blend of new renewable energy and diesel may increase engine performance and minimise emissions of smoke.

Figure 1 .
Figure 1.Map of the life cycle of multi-feedstock biodiesel production simulation in Dumai City, Indonesia (Google Earth 2020).

Figure 2 .
Figure 2. The system boundary of simulation of the life cycle of biodiesel production from multiple feedstocks (Wahyono et al. 2022) with modified.

Figure 4 .
Figure 4.The same contributor to the energy demand of various crop plantations and UCO collection in scenarios 1, 2, and 3.

Figure 5 .
Figure5.Contributors to the energy demand for pretreatment of oil, the use of electricity and phosphoric acid being the primary contributors at this stage, are identical for scenarios 1, 2, and 3.

Figure 6 .
Figure 6.Contributors to the energy demand of scenario 1 for the conversion of multiple feedstocks to biodiesel.

Figure 7 .
Figure 7. Contributors to the energy demand of scenario 2 for the conversion of multiple feedstocks to biodiesel.

Figure 8 .
Figure 8. Contributors to the energy demand of scenario 3 for the conversion of multiple feedstocks to biodiesel.
fl o w e r o i l b i o d i e s e l d c o o k i n g o i l b i o d i e s e l M

Table 1 .
Multiple-crop plantation and UCO collection inventory data.
Notes: LCA investigations undertaken in Malaysia, Indonesia, Iran, and China yielded data of inventory.Inventories are compiled from nations whose practises of agriculture management are comparable to Indonesia's.The information is then extracted from the most current source.Thus, all data may be used as input for dependable data in the stages of UCO collecting and multiple crop plantations.a Soraya et al. (2014) → Indonesia is the location of the LCA study by Soraya et al. in 2014.b Ahmadi et al. (2021) → Indonesia is the location of the LCA study by Ahmadi et al. in 2021.c Bai et al. (2021) → China is the location of the LCA study by Bai et al. in 2021.d Dekamin, Barmaki, and Kanooni (2018) → Iran is the location of the LCA study by Dekamin et al. in 2018.e Chung et al. (2019) → Malaysia is the location of the LCA study by Chung et al. in 2019.

Table 2 .
Inventory data on the preliminary design of scenarios 1, 2, and 3 for a multi-feedstock biodiesel plant.

Table 3 .
Indonesian inventory data on production of palm oil biodiesel.

Table 4 .
The parameters of energy balance.

Table 5 .
Energy demand of 1 tonne of production of biodiesel from multiple feedstocks.

Table 6 .
Energy demand of production of 1 tonne of palm oil biodiesel.

Table 7 .
The energy content of multi-feedstock biodiesel and palm oil biodiesel.

Table 8 .
Energy balance of biodiesel from multiple feedstocks and biodiesel from palm oil.

Table 9 .
Net energy ratio of various methods of biodiesel production.