Key Takeaways & Executive Findings
- •• • Anaerobic digestion of each ton of food waste yields 70–80 Nm³ biogas, but simultaneously produces 69–80% liquid digestate and 2.7–3.6% solid digestate, creating a seasonal mismatch with land application that restricts resource utilization. • • Oil recovery from leachate via three-phase separation exceeds 98%, yet the remaining digestate streams still pose a management challenge due to high NH4+-N and continuous generation. • • Converting food waste to carbon source increases economic benefits by >203% compared to biogas route, but requires controlling SS and organic nitrogen to avoid adverse effects on activated sludge systems. • • Carbon source production via hydrolysis-acidification suffers from long fermentation periods and poor shock resistance, while pretreatment+membrane filtration retains SCOD but loses biodegradable particulate COD and retains some soluble organic nitrogen.
Abstract
Resource utilization of food waste is a key measure for implementing waste classification and constructing zero-waste cities in China. However, the technical route based on anaerobic digestion currently faces developmental bottlenecks. In this study, engineering-scale facilities located in Northeast, North, Northwest, and Southeast China were selected, and material flow analysis was employed to comprehensively assess the current status of anaerobic digestion of food waste. The results indicated that, during the pretreatment stage, both leachate and organic slurry from all surveyed regions exhibited high COD/TN ratios, and the leachate contained high concentrations of lipids. Following three-phase (oil-water-solid) separation, the oil recovery rate could reach over 98%. Anaerobic digestion of each ton of food waste from the four regions generated approximately 70 to 80 Nm³ of biogas, while simultaneously producing liquid digestate accounting for 69% to 80% of the total mass and solid digestate accounting for 2.7% to 3.6%. However, the annual continuous production of digestate was not aligned with the seasonal demand for land use, thereby restricting the pathway for resource utilization. Converting food waste into an external carbon source can significantly enhance its resource utilization efficiency, with the economic benefits increasing by more than 203% compared to the methanogenesis pathway. The selection of the carbon source production technology route should be comprehensively determined by taking into account factors such as the specific nitrogen removal requirements of the target wastewater treatment process, the quality requirements for the carbon source products, and the substitution rate of commercial carbon sources.
1. Introduction
China's food waste (FW) management has evolved from landfilling and incineration to a mainstream 'pretreatment + anaerobic digestion (AD) + product utilization' route. However, AD's primary outputs—biogas and digestate—face critical bottlenecks: digestate is produced continuously, whereas land application is seasonal, and its low economic value (organic fertilizer 100–500 RMB/t) combined with transport costs (0.5–0.8 RMB/(t·km)) makes long-distance disposal uneconomical. Moreover, land application limits for nitrogen and phosphorus further constrain digestate disposal. These factors undermine the sustainability of the AD route, necessitating alternative valorization pathways.
This study systematically evaluates four full-scale FW treatment facilities in Changchun, Rizhao, Changzhou, and Xi'an using material flow analysis. It quantifies the performance of pretreatment and AD, revealing high COD/TN ratios in leachate and organic slurry, and identifies the potential of converting FW into an external carbon source for wastewater treatment. The economic advantage of carbon source production over biogas (>203% increase) is demonstrated, but technical challenges such as controlling SS and organic nitrogen are highlighted. The findings provide a data-driven basis for selecting appropriate carbon source production technologies, considering the specific nitrogen removal requirements of target wastewater processes.
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ZHAO Zhenzhen, QIU Junjie, YI Yangmin, HUANG Huimin, JIANG Guihong, YANG Hujun, ZHANG Hongliang, HE Pinjing (2026). Current Status of Food Waste Anaerobic Digestion and Challenges in Carbon Source Production in China. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202607009
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Frequently Asked Questions
What are the main bottlenecks of the anaerobic digestion route for food waste treatment, and how does carbon source production address them?
The AD route generates 69–80% liquid digestate and 2.7–3.6% solid digestate per ton of FW, which are produced continuously but cannot be land-applied seasonally due to nutrient limits and transport costs. Carbon source production offers a higher-value alternative, increasing economic benefits by >203% compared to biogas, while avoiding digestate disposal issues.
What are the key quality parameters for food waste-derived carbon sources, and how do they affect downstream wastewater treatment?
Carbon sources must have low SS and organic nitrogen to prevent interference with activated sludge systems. High VFA and ammonification rates are required for denitrification. The study shows that pretreatment+membrane filtration retains SCOD but loses some biodegradable particulate COD and retains soluble organic nitrogen, which may impact nitrogen removal efficiency.
How does the choice of carbon source production technology depend on the target wastewater treatment process?
For municipal wastewater (COD 100–250 mg/L, NH4+-N 20–40 mg/L), higher VFA and ammonification rates are needed, favoring hydrolysis-acidification. For landfill leachate (COD 3000–10000 mg/L, NH4+-N 1500–3000 mg/L), lower organic nitrogen and SS are critical, favoring pretreatment+membrane filtration. The specific nitrogen removal requirements and effluent standards dictate the technology selection.
What are the limitations of hydrolysis-acidification and membrane filtration for carbon source production?
Hydrolysis-acidification suffers from long fermentation periods, slow production rates, and poor shock resistance. Membrane filtration can rapidly remove SS and non-soluble COD, but it also removes biodegradable particulate COD and retains some soluble organic nitrogen, potentially reducing the carbon source's bioavailability.
What future research directions are suggested to improve carbon source production from food waste?
Future work should investigate seasonal variations in FW composition and their impact on carbon source quality, and explore synergistic technologies combining acidogenic fermentation with membrane filtration to preferentially remove organic nitrogen while preserving carbon availability.
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