餐厨垃圾沼渣制备生物炭回用促进厌氧消化产沼气工艺的碳排放特征研究

Carbon emission characteristics of anaerobic digestion for biogas production enhanced by reusing biochar prepared from food waste anaerobic digestion residue

餐厨垃圾是一类重要的城市有机固废,厌氧消化是我国目前针对餐厨垃圾的主流处理工艺,而厌氧消化后沼渣的低碳处置是餐厨垃圾厌氧消化工艺的瓶颈之一.本研究以无锡市某餐厨垃圾厌氧消化处理工程为研究对象,提出了餐厨垃圾“厌氧消化-沼渣干化-热解-制备生物炭-回用”(工艺路线1)新型工艺路线,并以目前正运行的“厌氧消化-沼渣干化-焚烧”(工艺路线2)作为参考对照,采用联合国政府间气候变化专门委员会(Intergovernmental Panel on Climate Change,IPCC)提供的计算方法,计算并对比分析了两种工艺路线的碳排放特征.结果表明,两种工艺路线各阶段碳排放量与碳汇占比相似,碳排放主要来自于污水处理阶段、厌氧消化阶段和沼渣干化阶段,碳汇主要来自于油脂提取阶段和厌氧消化阶段.工艺路线1由于沼渣生物炭促进厌氧消化沼气产量的提升以及热解生物炭的碳固定,所得总碳汇比工艺路线2增加了14.19%,其总碳排放量比工艺路线2降低了2.63%.本研究结果表明餐厨沼渣热解制生物炭回用于厌氧消化促进产气的工艺路线实现了更高程度的资源化以及更少的碳排放,在当前碳中和的大背景下,该工艺可能成为未来餐厨垃圾处理技术的重要方向.

Food waste is a significant category of urban organic solid waste,and anaerobic digestion is currently the mainstream treatment process for food waste in China.One of the bottleneck technologies in the anaerobic digestion process of food waste is the low-carbon disposal of biogas residue.In this study,a food waste anaerobic digestion treatment project in Wuxi City was taken as the research object,and a novel process route of"anaerobic digestion-residue drying-pyrolysis-biochar preparation-reuse"(process route 1)was proposed.This was compared with the currently operating"anaerobic digestion-residue drying-incineration"(process route 2)as a reference.Using the calculation method provided by the IPCC,the carbon emission characteristics of the two process routes were calculated and compared.The results showed that the carbon emissions and carbon sequestration proportions at various stages of the two process routes were similar.Carbon emissions mainly came from the wastewater treatment stage,anaerobic digestion stage,and digestate drying stage,while carbon sequestration mainly came from the fat extraction stage and anaerobic digestion stage.Process route 1,due to the promotion of anaerobic digestion biogas production by biogas residue biochar and carbon fixation of pyrolysis biochar,increased the total carbon sink by 14.19%and it’s total carbon emission were 2.63%lower than that of process route2.The results of this study indicate that the process route of pyrolyzing biogas residue of food waste to produce biochar for reuse in anaerobic digestion to promote gas production has achieved a higher degree of resource utilization and reduced carbon emissions.In the context of current carbon neutrality,this process may become an important direction for future food waste treatment technology.