Cradle to Gate
Identity ID
01d08e87-daed-478d-904c-d6ee92283cc4
Waste treatment
Associated ID
1b1d66d9-6f07-4ae6-a408-0df9e2b4d67e
Included activities starts
Included activities ends
Description
The process flow of anaerobic fermentation is "pre-treatment -> dry anaerobic digestion -> biogas electricity generation + digestate treatment". After manual sorting, crushing, magnetic separation, and biomass separation during the pre-treatment phase, inorganic impurities affecting fermentation are removed, and the degradable organic matter is crushed into slurry to meet the requirements for anaerobic digestion. The resulting slurry undergoes anaerobic fermentation, going through hydrolysis, acidogenesis, and methanogenesis stages, producing biogas primarily composed of methane. After desulfurization and purification, the biogas is sent to an internal combustion generator set for electricity generation, achieving an electricity output of 1. 8 kWh/m³. The anaerobic digestate is sent to a centrifugal dewatering machine for solid-liquid separation; the dewatered supernatant is directed to wastewater treatment, while the digestate is processed in subsequent steps. Odorous gases such as NH₃ and H₂S generated during the fermentation process are treated in an odor control system, with emissions complying with the requirements of the National Standard for Emission of Malodorous Pollutants (GB 14554-93). The digestate after anaerobic fermentation and dewatering contains abundant organic matter. The facility has established a composting workshop in later stages to mix the digestate with crushed straw, recycled compost, and other bulking agents for composting fermentation. The fermentation period generally lasts at least 7 days, and once the temperature drops below 40°C, the composting process is considered complete. The fermented compost is screened through a screening machine, and the material passing through the screen is the final fertilizer product, with a production capacity of 19.14 t/d. The fertilizer complies with the Organic Fertilizer Standard {NY525-2012} and the Bio-organic Fertilizer Standard {NY884-2012}.
Activity Description
Anaerobic fermentation technology converts kitchen waste into energy and fertilizer. First, the waste undergoes pretreatment, including sorting, crushing, and removal of inorganic impurities, to produce an organic slurry suitable for fermentation. The slurry is then fermented under anaerobic conditions to generate biogas, which is purified and used for power generation. The resulting digestate and digestate residue undergo solid-liquid separation and subsequent treatment. The generated odorous gases are treated through a deodorization system to meet environmental standards. The dewatered digestate residue is mixed with straw and other materials, composted through fermentation, and processed into organic fertilizer that complies with national standards, achieving resource utilization.
Process Description
kitchen waste on a dry basis: average organic matter content of 80–100%, crude protein 14–30%, and crude fat 15–30%; on a wet basis: moisture content 70–90%, oil content 3%, and salt content 1%.
Time period
2022
2026
Geography
China
Macroeconomic value
Business-as-Usual
Data validation
Yes
Technology
Current Technology
Technology comment
Anaerobic fermentation. Anaerobic fermentation is a process that utilizes anaerobic microorganisms to metabolize and degrade the organic matter in kitchen waste into inorganic substances under oxygen-free conditions, ultimately producing biogas primarily composed of methane. The solid content of kitchen waste ranges from 15% to 20%, with a carbon-to-nitrogen ratio between 10 and 25, meeting the requirements for the anaerobic fermentation treatment of organic waste. During the fermentation process, kitchen waste mainly undergoes three stages: hydrolysis, acidification, and methanogenesis. In these stages, elements such as carbon, hydrogen, and oxygen are converted into biogas composed of CH4 and CO2, while elements like nitrogen, phosphorus, and potassium remain in the digestate. Since digestate is rich in organic matter, it can be disposed of through various methods such as incineration, composting, or landfilling, and no well-established technology has been formed yet. Anaerobic digestion of kitchen waste occupies relatively small land area, causes less secondary pollution, and can convert waste into biogas for energy recovery, making it highly environmentally friendly and energy-efficient. This technology has attracted significant attention for kitchen waste treatment and resource utilization; however, it faces challenges such as complex pretreatment, high investment costs, and a relatively long overall process chain.