膨松剂对厨余垃圾堆肥CH_4、N_2O和NH_3排放的影响

Effect of bulking agent on CH_4 , N_2O and NH_3 emissions in kitchen waste composting

厨余垃圾有别于混合生活垃圾,具有高有机质含量和高含水率等特点,单独堆肥会产生大量CH_4、N_2O、NH_3和渗滤液,为减少厨余垃圾堆肥过程污染物的排放,该文以居民小区产生的经大类粗分后的厨余垃圾为研究对象,以菌糠为膨松剂,设置15%、25%、35%3个添加质量比(湿基)的堆肥处理,以纯厨余垃圾单独堆肥为对照处理,研究菌糠作为膨松剂对厨余垃圾堆肥过程中CH_4、N_2O、NH_3和渗滤液排放的影响及其最佳添加比例。结果表明,堆肥过程中,添加菌糠可以完全避免厨余垃圾堆肥过程中渗滤液的产生;堆肥结束时,添加15%和25%菌糠的处理堆肥达到腐熟标准,但添加35%的菌糠使堆肥高温期缩短,不利于有机质分解;与对照处理相比,添加15%、25%和35%比例的菌糠均可以减少堆肥过程中CH_4和NH_3的累计排放量,且减排量与添加比例正相关,但只有添加15%菌糠的堆肥处理明显降低了N_2O的排放量;添加质量比为15%和25%菌糠的堆肥处理,CH_4和N_2O排放总量比厨余垃圾单独堆肥分别减少45.8%、19.6%,而添加质量比为35%的菌糠使CH_4和N_2O排放总量为厨余垃圾单独堆肥的1.14倍(每t物料,干基)。综上,菌糠作为食用菌种植废弃物,可用作厨余垃圾堆肥膨松剂,在适宜的添加比例条件下,能够在避免堆肥过程中渗滤液产生的同时,减少CH_4、N_2O和NH_3的排放量。研究结果可为厨余垃圾堆肥过程温室气体减排、氮素损失控制和工艺改进提供理论依据和试验基础。

Composting is a biological process which can reduce the volume and mass of organic waste, as well as produce a safe, stabilized, and nutrient enriched soil amendment. In recent years, composting has been widely used in handling kitchen waste. However, kitchen waste is different from mixed municipal solid waste, which has the characteristics of high organic matter and moisture content. It would produce a large quantity of greenhouse gas （GHG）, ammonia, and leachate emitted to the environment, and the compost wouldn＇t reach the mature standard if composted alone. Bulking agent is a kind of compost amendment, which is usually used to create inter-particle voids to provide an air space in compost materials, meanwhile, to regulate the water content of the waste. Spent mushroom substrate is usually discarded after mushroom cultivation and is in need of processing, which has the appropriate characteristics of loose structure and small particle size as a bulking agent. In this study, the kitchen waste sorted from residential quarters was chosen as the research object, and the spent mushroom substrate was taken as the bulking agent. The added proportions （mass, wet basis） of spent mushroom substrate were set as 15%, 25%, and 35%, and a control treatment was conducted with kitchen waste without a bulking agent. The four aeration treatments were conducted over a 28-day period in 60 L reactors. The effects of spent mushroom substrate on greenhouse gas, NH3, and leachate emissions, as well as the optimal adding proportion in kitchen waste composting were investigated. During the experiment, maturity indexes such as temperature, pH, C/N, and germination index were determined. Meanwhile, continuous measurements of leachate and greenhouse gas emissions were carried out. The results showed that adding spent mushroom substrate could avoid leachate production in kitchen waste composting; compost from treatments with added proportions of 15% and 25% reached the mature standard of compost, however, the thermophilic phase in the 35% of spent mushroom substrate treatment was shorter （6 d） than that in the other treatments, which would decrease the degradation rate of organic matter. Adding spent mushroom substrate in kitchen waste composting could reduce the emissions of CH4 and NH3, and the emission reductions were positively correlated with the added proportions of spent mushroom substrate; while only the treatment with 15% of spent mushroom substrate decreased NeO emissions obviously. Adding 15% and 25% of spent mushroom substrate in kitchen waste composting could reduce the total GHG emissions by 45.8% and 19.6% respectively （per ton of dry matter）, but the GHG emissions from the 35% of spent mushroom substrate treatment was 1.14 times that of the control treatment. Spent mushroom substrate, waste of edible mushroom cultivation, can be added in kitchen waste composting as a bulking agent to reduce leachate and gaseous emissions, as well as to improve the nutrient content of compost.