Due to the complex composition of food waste, on the one hand, it is not suitable for direct landfill and incineration because of its high moisture content and easy to cause environmental pollution; on the other hand, the infiltration of grease into the leachate system will affect the operation of the relevant treatment membrane system. Therefore, the kitchen waste must go through the pretreatment link, aiming at the material category produced after the pretreatment, and the kitchen waste treatment needs a combination of a variety of treatment processes.
|Solid waste||Organic solids, liquids||Other solid organic matter||Grease|
|Material||Mainly inorganic and synthetic substances||Less impurities, high volatile solid content||The solid content of organic matter is up to 20%, the volatile solid content is high, and the impurities are few||Oil contains water and can be used to produce biodiesel.|
|Proportion of kitchen waste||10%-35%||70%~80%||8%~12%||2%~3%|
|Handling method||Landfill or incineration||Anaerobic digestion (general)||Anaerobic digestion (common), biotransformation (rare)||Production of biodiesel|
Commonly used food waste treatment processes mainly include the following five: incineration, sanitary landfill, bioconversion, aerobic composting, anaerobic digestion. Anaerobic digestion is the most commonly used treatment process.
Incineration: Since the food waste contains high moisture and grease, and the calorific value is about 2000 + kJ/kg, direct incineration can not meet the calorific value requirements of the incinerator, but is likely to produce a large number of harmful gases such as dioxin due to insufficient combustion, and acid gases are easy to accelerate equipment corrosion, so direct incineration has been eliminated.After pretreatment, the solid waste produced can be co-burned with the waste incineration power generation project.
Landfill: The kitchen waste is pretreated and then landfilled, which has low cost and simple operation, but it will affect the surrounding environment, produce landfill odor, and cause soil and groundwater pollution.At present, the landfill rate of kitchen waste is gradually decreasing, and direct landfill of kitchen waste has been banned in some areas.
Biotransformation: The kitchen waste contains a large amount of protein and other substances, which can be used for biotransformation of insects such as black water fly, to transform the solid organic matter after three-phase separation of kitchen waste into humic piles, and to obtain specific organisms with economic value. This technology has low energy consumption and certain economic benefits. However, the processing cycle is relatively long, the cost of operating environment adjustment is high, and the product sales are difficult, so it is difficult to apply to large-scale projects.
Aerobic composting: organic substances in kitchen waste are biodegraded by aerobic microorganisms under aerobic conditions.The method has that advantage of low cost, simple process and good reduction effect, but occupy large land and is easy to cause air environmental pollution.
Anaerobic digestion: under anaerobic or anoxic conditions, the organic matter in kitchen waste is decomposed for many times through the synergistic effect of a variety of anaerobic microbial flora, and finally methane and carbon dioxide are produced. The biogas produced can be used for heating, power generation and purification of natural gas, and the biogas residue and biogas slurry produced can be used for bio-organic fertilizer. At present, due to the lack of downstream sales channels, a large amount of biogas residue can only be sent to the incinerator for treatment. The anaerobic digestion process is complex and the project investment is high, but the degree of recycling is high, and the biogas produced can be recycled, which can realize the harmless, reduction and recycling of kitchen waste treatment in general.
|Incineration||Imple operation and obvious decrement effect||Resource utilization is not effective enough|
|Landfill||Low cost and simple operation||Serious environmental pollution.|
|Biotransformation||Full utilization of resources||It requires high operating conditions and is difficult to promote on a large scale.|
|Aerobic composting||Imple operation and low cost||Land occupation and environmental pollution|
|Anaerobic digestion||High recycling degree and less pollution||Complex process and high investment cost|
According to the statistics of successful bidding of kitchen waste investment and operation projects in China from 2018 to 2021, anaerobic digestion is the main treatment process, accounting for 66%, and 16% of the projects adopt the co-treatment process of pressing and incineration. Household kitchen waste operation projects basically only use anaerobic digestion and aerobic fermentation processes, accounting for about 71% and 29% respectively.