Life cycle inventory assessment and economic loss analysis for brown grease recycling in a food processing factory

Abstract

The environmental and economic viability of recycling brown grease (BG) in a Japanese food processing factory was assessed via oil and fat flow analysis, life cycle inventory analysis of oil-fat recovery equipment (OFRE), and economic loss evaluation. After installation in a food processing factory that discharges wastewater (oil and fat concentration: 2,100 mg/L; wastewater volume: 21.1 m³/d), the OFRE enabled biomass utilization of BG and increased the oil and fat resource rate from 0 % to 63.9 %. Additionally, using refined oil and fat from BG as an alternative to heavy oil A reduced CO_2eq emissions by 11.1 t-CO_2eq/year. Labor and odor control costs also decreased, resulting in a reduction of 51,387 JPY/(t year) in economic loss.

1. Introduction

Edible animal and vegetable oil and fat are typically used in restaurants and food processing factories, while waste oil and fat generated during food processing are often either collected and treated as waste or discharged together with wastewater. Waste oil and fat consisting of unused oil and fat and waste cooking oil from fryers are called “Yellow grease” (YG) (Ravikumar et al., 2017). Recently, there has been a growing movement to collect and recycle YG (Japan for Sustainability, 2008), and its use as a biomass resource has been promoted internationally.

An effective method of recycling YG is through sustainable aviation fuel (SAF). The International Civil Aviation Organization (ICAO) adopted the “Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA),” which requires airlines to reduce greenhouse gas emissions from international aviation starting in 2016 (ICAO, 2024). Therefore, the demand for SAF materials, including YG, will intensify in the future. In addition, YG can be recycled into livestock feed, industrial raw materials, biodiesel, and boiler fuel. Of note, approximately 95 % of YG is recycled in Japan (UCO Japan, 2022).

Since oil and fat used during cooking become attached to cookware, utensils, and tableware and then are discharged with wastewater, grease traps (GTs) must be installed to prevent these substances from polluting downstream wastewater treatment facilities. To maintain GTs, floating oil and fat are recovered by employees and treated as industrial waste. In addition, any oil and fat that leaked from the GT with wastewater is treated in downstream sewage treatment facilities or Johkasou. However, oil and fat that leak from GTs can clog sewage pipes and have a negative impact on biological treatment tanks. Moreover, if these substances discharged into public water bodies without being adequately treated, they can cause organic pollution, thereby adversely affecting aquatic organisms and causing foul odors (Iyo et al., 1997).

Floating oil and fat in GTs and associated food residue is called “brown grease (BG)” (Imai, 2024). The amount of BG generated annually in the United States is approximately 1.7 million t (Ryan et al., 2020). In Japan, the amount of BG generated in restaurants, school catering facilities, and food processing factories is estimated at approximately 700,000 t per year, and the potential availability of BG is estimated to exceed that of YG (ASTEM RI, 2023). However, few cases of BG being effectively utilized as a biomass resource have been reported; therefore, BG has been investigated as a new biomass resource, and expectations for its utilization should increase. Reports have indicated that directly burning BG as an alternative to heavy oil A has lower processing costs than converting it into SAF or biodiesel fuel, indicating that this application method is economically and environmentally rational and effective (Kobayashi, 2017). Noguchi et al. (2010) reported that oil and fat recovery from wastewater without energy consumption and subsequent use as a heating fuel in Japan would achieve a maximum heat energy of 9,070 TJ per year and reduce CO₂ emissions by 628,000 t-CO₂. The authors investigated the effectiveness of CO₂ reduction by using recovered oil and fat as energy at a food processing factory that had installed equipment to recover oil and fat from wastewater using the difference in specific gravity between water and oil. The results showed that the daily CO₂ emissions from the food processing factory were reduced by 659 kg-CO₂/d compared to the case where the equipment was not installed, demonstrating the effectiveness of using the recovered oil as energy (Otsuka et al., 2016).

Therefore, the environmental impacts of using recovered oil and fat as energy sources through direct combustion have been clarified. However, the environmental impact of reusing recovered oil and fat, including the life cycle of oil-fat recovery equipment (OFRE), and the economic impact of introducing OFRE have not been clarified.

Therefore, this study aimed to clarify the effectiveness of BG as a new biomass resource and the economic benefits of recovering BG based on oil and fat flow analysis, life cycle inventory analysis (LCIA) of the OFRE, and economic loss analysis of BG.

This approach allows us to assess the environmental and economic feasibility of BG utilization as a biomass resource in food processing factories.

By addressing these two aspects simultaneously, the study contributes to advancing the understanding of sustainable resource recovery from oil and fat in industrial wastewater treatment systems. In this research, BG is defined as floating oil and fat that can be recovered from the GT and sedimentation tank in the wastewater treatment facility of company M.

2. Materials and methods

2.1. Surveyed facilities and oil-fat recovery equipment

Maruzen Co., Ltd. Saitama facility (M company) (Japan) was selected as the surveyed facility. This facility produces stewed offal and sausage. Wastewater from stewed offal production contains oil and fat, and its inflow into the wastewater treatment facility was causing increased strain on and the equipment and foul odors. Therefore, company M introduced an OFRE (made by TBM Co., Ltd., Japan) into the GT to filter the wastewater from stewed offal production. A photo of the installed OFRE is shown in Fig. 1, and its specifications are shown in Table 1.

Fig. 1 Oil and fat recovery equipment at Company M

Table 1 Specifications of oil and fat recovery equipment

Item	Specification
Volume of recovery oil and fat refining unit (L)	1,000
Recovery performance of the recovery unit (L/min)	250
Refined oil and fat production volume (L/min)	5 to 30
Power consumption (kW)	Recovery unit: 0.75
	Recovery oil and fat refining unit: 3

The OFRE is made up of a “Recovery unit” and “Recovered oil and fat refining unit.” In the recovery unit, a recovery cup is placed on the wastewater surface of the GT and BG is recovered by suction using a pump. In the recovered oil and fat refining unit, oil and fat are extracted from the BG by heating and gravity separation and then filtered and refined. The refined oil and fat are transported and stored in containers and used as an alternative fuel to heavy oil A, such as in biomass boilers. Heavy oil A refers to heavy oil with a kinetic viscosity of 20 mm²/s or less according to Japan’s industrial standards, and it is mainly used as a boiler fuel (ENEOS, 2025).

2.2. Wastewater characteristics and wastewater treatment flow in surveyed facility

When installing the OFRE, the quality and volume of wastewater from Company M’s stewed offal and sausage production were investigated. The results are summarized in Table 2.

Table 2 Wastewater quality and amount at company M

Item		Stewed offal production	Sausage production
n-hexane extract (mg/L)	Minimum	9.6	16
	Maximum	7,800	390
	Average	2,100	140
Bio Oxygen Demand (mg/L)	Minimum	34.5	27.8
	Maximum	3,760	516
	Average	1,350	245
Wastewater amount (m3/d)		21.1	32.6

Before installing the OFRE, wastewater from the stewed offal production flowed into the GT, which separated the wastewater, oil, and fat by specific gravity. Spilled wastewater from the GT was merged with wastewater from sausage production and flowed into the wastewater treatment facility, which consisted of a law water tank, flow controller tank, sedimentation tank, and membrane bioreactor (MBR). BG from the GT and MBR was recovered by employees of Company M every day, stored in a freezer, and then treated as industrial waste.

After installing the OFRE in the GT, BG was recovered. The wastewater treatment flow after the GT did not change. Because BG recovery was performed using an OFRE, the employees did not perform BG recovery work.

2.3. Oil and fat flow analysis method

The amount of oil and fat from the three processes in company M was surveyed to understand the oil and fat flow. The three processes were stewed offal and sausage production, wastewater treatment, and waste. The survey was conducted in the form of interviews with personnel at company M on December 5, 2024. Since the OFRE was introduced in February 2024, operational data were collected from April 2024 to March 2025 after OFRE operations had stabilized. Data before the equipment’s introduction were obtained from January to December 2023.

The OFRE performance at company M was verified through the Environmental Technology Verification Program. Since the amount of BG in GT and the amount of oil and fat leaking from the GT were not available in the interview survey, these were estimated from the survey results of the Environmental Technology Demonstration Project (Ministry of Environment, 2025). The amount of oil and fat in the wastewater from stewed offal and sausage production was calculated based on the results of the field survey. The calculation method for each process is shown in Table 3.

Table 3 Calculation items and methods for each process

Item	Calculation method
Amount of oil and fat in wastewater at stewed offal production	Amount of pig offal × Oil and fat discharge rate (15.0 %)
Amount of oil and fat in wastewater at sausage production	Amount of sausage × Oil and fat discharge rate (0.03 %)
Amount of organic matter in wastewater at stewed offal and sausage production	Bio oxyegen dimand concentration × Annual wastewater volume before and after OFRE installation (Table 2)
BG amount in grease trap	Oil and fat from stewed offal × Oil and fat trap rate in grease trap (16.5 %)
Spilled oil and fat amount from grease trap	Oil and fat from stewed offal × Oil and fat discharge rate from grease trap (83.5 %)
Amount of organic matter in excess sludge at wastewater treatment facility	Amount of waste excess sludge *1 × moisture content of excess sludge (80 %) *2

^*1 Amount of waste excess sludge: 98.0 t/year (Before OFRE installation), 154.0 t/year (After OFRE installation).

^*2 Reference: Wan et al., 2014.

2.4. Life cycle inventory analysis method

The LCIA boundary conditions included mining process, manufacturing process, use process, and waste and recycling process. The LCIA system boundary of this study is shown in Fig. 2.

Fig. 2 System boundary of this study

The transportation of iron ore in the mining process was assumed to be by ship from Australia, which was the world’s largest iron ore producer in 2023 (GLOBAL NOTE, 2025). The installation of the OFRE required only simple on-site piping work, and the unit was transported to the installation site by a company vehicle. Since the installation process did not involve any construction work or electricity use, its energy consumption was negligible. As a supplementary estimation, the CO_2eq emissions from transporting the OFRE (weight: 0.325 t) about 40 km by a company vehicle were calculated using the emission factor from the IDEA Ver. 3.5 database.

The resulting emissions were approximately 3.38 kg-CO_2eq, which were negligible compared with those of other life cycle stages. Therefore, the installation stage was excluded from the life cycle inventory analysis.

The electricity consumption of the OFRE system was measured to be 4,265.22 kWh per year, while the treated wastewater volume was 113,430 m³ per year. Accordingly, the specific electricity consumption of the OFRE was estimated at approximately 0.038 kWh/m³. Although detailed data on the electricity consumption of the wastewater treatment process at Company M are not available, a typical energy intensity of 0.304 kWh/m³ for wastewater treatment in Japan has been reported (Tsalas et al., 2024).

Thus, the electricity consumption of the OFRE represents less than 15 % of the typical energy demand for wastewater treatment, and the installation of the OFRE did not cause any noticeable change in the overall electricity consumption or aeration conditions at the treatment facility. Therefore, CO₂ emissions from the wastewater treatment process were excluded from this analysis.

A list of CO_2eq emission intensities is presented in Table 4. In the LCIA, the CO_2eq emissions in each process were calculated by multiplying the CO_2eq emission intensity (Table 4) by the input amount of each process. The CO_2eq emissions in each process (C_i) were calculated using the input amount for each process (I_i) and the CO_2eq emissions intensity in the database (D_i) according to the following equation.

Table 4 List of CO_2eq emission intensity

Process	Item	Reference *1
Mining	Iron Ore, 62.0 %Fe, Imported products, JPN	IDEA ver3.5.1 Database
	Iron ore shipping	IDEA ver3.5.1 Database
Manufacturing	Stainless Steel Semi-Finished Products, JPN	IDEA ver3.5.1 Database
Using	Electricity power	IDEA ver3.5.1 Database
Waste and recycling	Scrap metal (Recycling)	Green value chain platform, 2025 *2

^*1 In compliance with the IDEA data utilization rules, numerical values of emission intensity derived from IDEA are not disclosed in this table.

^*2 CO_2eq emission intensity for “Scrap metal (Recycling)” is 0.0122 t-CO_₂eq/t.

  

$$C_i=I_i\times D_i$$(1)

The input amounts (I_i) for the mining, manufacturing, and waste and recycling processes were calculated by dividing each amount by the useful life of the OFRE. The OFRE is food manufacturing equipment, and the statutory useful life of food manufacturing equipment is set to 10 years (Ministry of Finance, 2024). Therefore, 10 years was adopted as the useful life of the OFRE. The OFRE can refine BG so that it may be used as an alternative fuel to heavy oil A. Therefore, the CO_2eq emission reduction effect of the OFRE was verified using the amount of refined oil and fat of company M in one year as the basic unit of the LCIA. In the LCIA, the amount of BG was compared to the amount of heavy oil A because they can generate the same amount of heat when all of company M’s refined oil and fat are used as biomass boiler fuel.

In this study, the LCIA focused on CO_2eq emissions to evaluate the potential for greenhouse gas reduction through brown grease recycling. Other ecological impacts, such as eutrophication, acidification, or solid waste generation, were not quantitatively included in the LCIA boundary because they were considered relatively minor compared with the climate change impact and were outside the scope of the study objectives.

However, it is noteworthy that the reduction of oil discharge from wastewater effluents through OFRE installation could also mitigate ecological burdens such as odor generation caused by the degradation of residual oils and hypoxia-related impacts on aquatic ecosystems in receiving waters.

2.5. Economic loss analysis method

Five items related to BG that could cause losses to the company were selected: cost of odor control measures for the surrounding environment (O), cost of removing excess sludge from wastewater treatment facilities (S), wastewater treatment facility maintenance costs (M), losses due to eutrophication of public water bodies caused by discharged water (E_i), and cost of labor associated with employee BG recovery (W). Economic losses (B) were analyzed to determine the costs of these items and the amount of oil and fat from the stewed offal and sausage process (P) according to Eq. (2).

  

$$B=\frac{O+S+E_i+W}{P}$$(2)

The costs of implementing odor control measures for the surrounding environment (O) and removing excess sludge from wastewater treatment facilities (S) were recorded as actual costs for the survey period. The cost of odor control measures for the surrounding environment was set as the cost necessary for measures that would occur even if BG was recovered. The maintenance method of the wastewater treatment facility did not change after installation; thus, the maintenance costs were the same. Therefore, the wastewater treatment facility maintenance cost (M) was excluded from the economic loss analysis.

The loss due to the eutrophication of public water bodies caused by discharged water (E_i) was calculated using the annual pollution load (L_i) of water quality item i (chemical oxygen demand, T-nitrogen, T-phosphorus) discharged from company M and the integration factor (IF_i) (Itsubo et al., 2010) according to Eq. (3). The annual pollution load (L_i) was calculated by multiplying the average daily pollution load by the number of days the factory operated per year (250 days). The average daily pollution load and integration factors of water quality are listed in Table 5.

  

$$E_i=\sum _{}^{}{L}_i\times {IF}_i$$(3)

Table 5 Pollution load and integration factors of water quality

Water quality item	Pollution load (kg/d)		Integration factor (JPY/kg)	Reference
	Before installation	After installation
Total Nitrogen	0.495	0.412	82.5	LIME2, 2010
Total Phosphorus	0.089	0.088	973.9	LIME2, 2010
Chemical Oxygen Demand	0.475	0.512	0.64	LIME2, 2010

The labor costs associated with employee BG recovery (W) were calculated using the time required for each BG recovery (T), the number of people required for recovery (H), the number of recoveries per day (R), the Saitama prefecture minimum hourly wage for 2024, 1,078 JPY/h (Ministry of Health, Labour and Welfare, 2025), and the number of days the factory operates per year (250 days) according to Eq. (4). The items used to calculate the labor costs associated with employee BG recovery are shown in Table 6.

  

$$W=1,078\times T\times H\times R\times 250$$(4)

Table 6 Items used to calculate labor costs associated with employee BG recovery

Item	Before Installation	After Installation
Time required for each BG recovery, T (h/number of recovery)	4	0.5
Number of people required for recovery, H (people/number of recovery)	1	1
Number of recoveries per day, R (time/d)	1	1

3. Results and discussion

3.1. Oil and fat flow analysis result

The results of the oil and fat flow analysis for company M are shown in Figs. 3 and 4.

Fig. 3 Oil and fat flow before the introduction of oil-fat recovery equipment

The solid line indicates the oil and fat flow, and the dashed line indicates the flow of other substances.

Fig. 4 Oil and fat flow after introducing the oil-fat recovery equipment

The solid line indicates the oil and fat flow, and the dashed line indicates the flow of other substances.

Before installation, the amount of oil and fat flowing into the GT from the stewed offal production process was 34.5 t/year. For this oil and fat, 16.5 % (5.7 t/year) of BG was collected by employees and 83.5 % (28.8 t/year) flowed out from the GT to the wastewater treatment facility. Of the oil and fat that flowed into the wastewater treatment facility, 28.8 t/year was discharged from the GT and 0.1 t/year was obtained from the sausage production process. For this oil and fat, 60.7 % (21.0 t/year) of the BG was generated at the wastewater treatment facility and 22.8 % (7.9 t/year) of the oil and fat was treated at the wastewater treatment facility. The BG recovered from the GT and wastewater treatment facility was transported outside company M as industrial waste along with other industrial waste for incineration and melting. The biomass was not utilized.

After OFRE installation, the amount of oil and fat flowing into the GT from the stewed offal production process was 43.8 t/year. For this oil and fat, 64.8 % (28.4 t/year) of BG was recovered by OFRE and 35.2 % (15.4 t/year) of oil and fat was spilled from GT to the wastewater treatment facility. The rates of spilled oil and fat decreased before and after installation of the OFRE, indicating that the OFRE had a reducing effect on spilled oil and fat.

For the BG recovered by the OFRE (28.4 t/year), 98.9 % (28.1 t/year) of oil and fat was refined and 1.1 % (0.3 t/year) was treated as industrial waste from OFRE. This indicates that the OFRE can efficiently convert BG into refined oil and fat.

A total of 15.6 t/year of oil and fat flowed into the wastewater treatment facility, and it consisted of oil and fat discharged from the GT (15.4 t/year) and oil and fat from the sausage production process (0.2 t/year). All the oil and fat were treated by the wastewater treatment facility. Although the amount of oil and fat treated in the wastewater treatment facility increased after installation of the OFRE, the separation membrane did not clog. A previous report indicated that when the amount of oil and fat in wastewater exceeds the appropriate range and the concentration becomes high, non-biodegradable oil and fat remain in the separation membrane, thus causing the membrane to become clogged, impairing the wastewater treatment function, and increasing the wastewater treatment costs (Kitanaka et al., 2012). Therefore, the increased amount of treated oil and fat was considered to be within the acceptable range for company M’s MBR.

The amount of refined oil and fat used as resources and disposed of as industrial waste was divided by the total amount of oil and fat discharged from the production process to calculate the oil and fat resource rate and waste rate (Table 7).

Table 7 Pollution load and integration factors of water quality

Item	Before Installation (%)	After Installation (%)
Oil and fat resource rate	0	63.9
Oil and fat waste rate	77.1	0.6

After installation, the oil and fat resource rate increased from 0 % to 63.9 % and waste rate decreased from 77.1 % to 0.6 %.

Because the ORFE recovers and refines BG trapped by the GT, the BG trap rate of the GT affects the amount of oil and fat refined by OFRE. The BG trapping rate of GTs has been reported to vary depending on the oil and fat concentrations in the inflowing wastewater. For example, if the oil and fat concentration in the inflow wastewater is 1,000 mg/L, then the BG trap rate will be close to 100 %; however, if it is 100 mg/L, then the BG trap rate will be approximately 25 % to 35 % (SHASE-S-217-2016, 2016). The average oil and fat concentration in the wastewater from company M’s stewed offal production was 2,100 mg/L, with a daily wastewater volume of 21.1 m³/d (Table 2). Most of the oil and fat discharged from the production process at company M were trapped by the GT. Thus, the OFRE has been effective in transforming BG into a biomass resource for company M. Therefore, the introduction of the OFRE to a food processing factory with a similar oil and fat concentration and wastewater volume as company M would enable a reduction in the amount of waste oil and fat and the refinement of biomass resources. Such changes have the potential to contribute to the creation of a circular society.

3.2. Life cycle inventory analysis result

The input amounts in each process are listed in Table 8, and the comparison of CO_2eq emissions from the OFRE and heavy oil A is shown in Fig. 5.

Table 8 Input amount for each process

Process	Item	Input amount	Unit
Mining	Iron Ore, 62.0 %Fe, Imported products, JPN	0.325	t
	Iron ore shipping *1	2,275	t km
Manufacturing	Stainless Steel Semi-Finished Products, JPN	0.325	t
Using	Recovery unit Electricity power *2	1,650	kWh/year
	Recovery oil and fat Refining unit Electricity power *3	2,610	kWh/year
	Transfer unit Electricity power *4	5.22	kWh/year
Waste and recycling	Scrap metal	0.325	t

^*1 Calculated based on the distance between Japan and Australia 7,000 km and the weight of the OFRE 0.325 t.

^*2 Calculated based on power consumption of 0.75 kW and uptime of 8.8 h/d.

^*3 Calculated based on power consumption of 3 kW, uptime of 10 h/time, and operation frequency: 61 times in peak season (August to January) and 26 times in off season (February to July).

^*4 Calculated based on power consumption of 0.2 kW, uptime of 0.3 h/time, and operation frequency: 61 times in peak season (August to January) and 26 times in off season (February to July).

Fig. 5 Comparison of CO_2eq emissions with the use of OFRE and Heavy oil A

According to the LCIA results, the annual CO_2eq emissions from the OFRE were 2.69 t-CO_2eq/year. CO_2eq emissions from the combustion of refined oil and fat were not included because they can be regarded as essentially zero owing to carbon neutrality. The oil and fat flow analysis revealed that the annual amount of refined oil and fat was 28.1 t/year at company M. The CO_2eq emissions associated with the production of 1 t of refined oil and fat by the OFRE were calculated to be 0.095 t-CO_2eq/t. In comparison, the life-cycle CO_2eq emissions for producing 1 t of biodiesel from used cooking oil have been reported as 0.55 t-CO_2eq/t (Foteinis et al., 2020). Therefore, the refined oil and fat obtained using the OFRE show substantially lower life-cycle CO₂ emissions than those reported for used-cooking-oil biodiesel production, suggesting a clear environmental advantage of the OFRE.

Based on the unit calorific value of refined oil and fat of 36.9 GJ/t, the thermal energy obtained by the direct combustion of refined oil and fat at company M was 1,035 GJ/year. Because the calorific value of heavy oil A is 45.42 GJ/t (Agency for Natural Resources and Energy, 2025), 22.8 t/year of heavy oil A would need to be burned to obtain the same amount of heat as that obtained by directly burning refined oil and fat. The CO_2eq emissions from the combustion of heavy oil A are 13.8 t-CO_2eq/year based on a CO_2eq emission unit of 0.557 kg-CO_2eq/L (SuMPO, 2025), and the specific gravity of heavy oil A is 0.92 g/cc (Frances, 2017). Therefore, using refined oil and fat as an alternative fuel to heavy oil A will lead to a reduction in CO_2eq emissions of 11.1 t-CO_2eq/year. Therefore, utilizing the refined oil and fat obtained from the OFRE as an alternative fuel to heavy oil A results in an approximately 80 % reduction in CO_2eq emissions compared with the combustion of heavy oil A. Previous life-cycle assessment studies have reported that the combustion of biodiesel produced from used cooking oil achieves 40–86 % lower greenhouse gas (GHG) emissions than fossil diesel fuel (Xu et al., 2022). Consequently, the use of refined oil and fat as a substitute for heavy oil A demonstrates a comparable GHG reduction potential to those reported in previous studies on waste-oil-based fuels.

The CO_2eq emissions reduction effect of the OFRE changes depending on the amount of refined oil and fat. The amount of oil and fat refined by the OFRE was considered a variability factor, and its effect on the CO_2eq reduction effect was analyzed. The results are shown in Fig. 6.

Fig. 6 Reduction of CO₂ emissions with the use of refined oil and fat

For a food processing factory that discharges the same amount of wastewater as company M, the annual amount of oil refined using an OFRE would vary from 1 to 8 t/year. In addition, the CO_2eq emissions generated by burning a given amount of heavy oil A were compared with the annual CO₂q emissions from the OFRE. Food processing factories that produce 5.48 t/year or more of refined oil and fat were able to reduce CO_2eq emissions using the OFRE. In addition, the amount of refined oil and fat obtained using the OFRE were dependent on the amount of oil and fat in the wastewater discharged from food processing factory. The results of the oil and fat flow analysis (Fig. 4, oil and fat recovery rate of ORE: 68.4 %, refining efficiency: 98.9 %) showed that food processing factories that discharge more than 8.10 t/year of oil and fat can achieve a reduction in CO_2eq emissions by using an OFRE.

3.3. Economic loss analysis results

Table 9 and Fig. 7 show the results of the analysis of economic losses associated with BG per ton of oil and fat generated during the production process before and after the installation of the OFRE.

Table 9 Economic losses due to BG per 1 t of oil and fat from the production process

Item	Before Installation (JPY/(t year))	After Installation (JPY/(t year))	Change (JPY/(t year))
Odor measures costs	37,514	273	−37,242
Excess sludge extraction cost	42,124	56,311	14,187
Eutrophication of public water bodies	920	681	−239
Labor costs	31,156	3,063	−28,094

Fig. 7 Economic loss analysis by BG before and after OFRE introduction

The costs for odor control measures for the surrounding environment were decreased by 37,242 JPY/(t year) after the installation of the OFRE. The reason for this is the disappearance of BG in the GT and the lack of odor generated from the BG. In addition, the cleaning company cleaned the law water tank and flow controller tank twice a year as odor control measures before the installation. However, these tanks did not have to be cleaned after installation.

The labor costs associated with employee BG recovery were decreased by 28,094 JPY/(t year). The reason for this is that the BG recovery time by the employee was reduced by 1/8 owing to the lack of BG in the GT. Employees who recovered from BG could participate in the production process, which increased productivity.

The costs for removing excess sludge from the wastewater treatment facilities increased by 14,187 JPY/(t year). This is because the installation of the OFRE eliminated the need for employees to collect BG, thereby increasing the amount of oil and fat treated at the wastewater treatment facility and increasing the amount of excess sludge generated at the facility.

Although some expenses were increased, the economic losses due to BG per 1 t of oil and fat occurred from the production process were decreased by 51,387 JPY/(t year). Therefore, OFRE installation is expected to contribute to reducing BG-related costs and improving profit margins at food processing factories, thereby providing economic benefits for food processing factories that discharge oil and fat.

The authors reported that the popularization of similar OFRE could potentially eliminate cleaning-related jobs from GT and wastewater treatment facilities and generate new positions based on the new technology (Otsuka et al., 2024), such as in new wastewater treatment-related industries linked to OFRE.

In this study, the equipment investment cost of the OFRE was not included in the economic loss analysis because it was covered by the manufacturer under a demonstration agreement.

Nevertheless, since the annual reduction in the economic losses due to BG per 1 t of oil and fat is 51,387 JPY/(t year), the introduction cost (approximately 10 million JPY) is expected to be recovered within a few years of operation. Thus, the overall economic feasibility of OFRE installation would not change significantly even when the investment cost is considered.

4. Conclusions

This study advances the understanding of BG recycling by presenting a comprehensive evaluation framework that includes both environmental and economic perspectives. The findings suggest that installing OFRE can promote both environmental conservation and economic efficiency in food processing factories that discharge oil and fat. Furthermore, the framework proposed in this study can serve as a reference for future research and practice aimed at achieving carbon neutrality and circular economy goals in industrial wastewater management.

The following results were obtained.

1) The oil and fat flow analysis revealed that the oil and fat resource rate increased from 0 % to 63.9 % and waste rate decreased from 77.1 % to 0.6 % before and after OFRE installation. In addition, food processing factories that discharge highly concentrated oil and fat wastewater, where the GT has a high BG trap rate, can reduce the amount of waste oil and fat and refine biomass resources by installing an OFRE.

2) The LCIA revealed that 11.1 t-CO_2eq/year of CO_2eq emissions could be decreased using the refined oil and fat as an alternative fuel to heavy oil A.

3) he economic losses analysis revealed that the economic losses due to BG per 1 t of oil and fat generated via production processes decreased by 51,387 JPY/(t year) by installing the OFRE, which was based on actual data from April 2024 to March 2025. Therefore, OFRE installation has economic benefits for food processing factories that discharge wastewater, including oil and fat.

Acknowledgments

We would like to express our deepest gratitude to Mr. Hideyuki Hara of Maruzen Co., Ltd., Mr. Kunihiro Sahara of TBM Co., Ltd., and all their employees for their cooperation in this research.

Nomenclature

Item	Unit	Contents
Life cycle inventory analysis
Ci	t-CO2/year	CO2 emissions in each process
Di	t-CO2/unit	CO2 emissions intensity in the database
Ii	–	Input amount in each process
Economic loss analysis
B	JPY/year	Economic losses by BG
Ei	JPY/year	Losses due to eutrophication by water quality item
H	people/number for recovery	Number of people required for BG recovery
i	–	Water quality item “COD, Total Nitrogen, Total Phosphorus”
IFi	JPY/kg	Integration coefficient in LIME2
Li	kg/year	Annual pollution load of water quality item
M	JPY/year	Wastewater treatment facility maintenance cost
O	JPY/year	Cost for odor control measures for the surrounding environment
P	t/year	Amount of oil and fat occurred from stewed offal and sausage production
R	time/day	Number of BG recoveries per day
S	JPY/year	Cost for removing excess sludge from wastewater treatment facilities
T	h/number for recovery	Time required for each BG recovery
W	JPY/year	Labor costs associated with employee BG recovery

Declaration of conflicting interests

The authors declare that they have no conflicts of interest.

Notes

(URLs on references were accessed on 19 January 2026.)

References

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