猪粪堆肥挥发性有机物的产生规律与影响因素

堆肥是畜禽粪便处理及资源化利用的有效途径,然而堆肥过程中极易产生挥发性有机物(VOCs,volatile organic compounds),引发恶臭问题,并对人体健康带来危害。该研究以猪粪和秸秆为原料,通过堆肥试验,研究了含水率、碳氮比和通风速率等工艺参数对猪粪堆肥过程中主要VOCs产生的影响。研究结果表明:堆肥过程中TVOCs的最高体积分数可达2 000×10~(-6)以上,主要在堆肥升温期产生。二甲二硫、二甲三硫是主要的致臭VOCs,其中,影响二甲二硫排放的主要因素为物料初始含水率,影响二甲三硫排放的主要因素为通风速率。极差及方差分析结果表明,堆肥过程中采用含水率65%,碳氮比30,通风速率0.1 m~3/(min·m~3)可以有效控制VOCs的排放。

Generation law and influencing factors of volatile organic compounds during pig manure composting

Abstract: As the main technology of waste recycling, composting is widely used for its easy operation and high efficiency. However, it is easy to produce VOCs (volatile organic compounds) emissions to the surrounding environment, and cause the odor problem. Odorous gases usually do not lead to serious health problems, but will make people mentally affected, make people lose appetite and feel nausea. Hydrogen sulfide, thiol, and so on can directly cause the harm to the respiratory system and endocrine system, and odorous gases have the duality of air pollution and harmful gas pollution. In recent years, the research shows that in the aerobic fermentation thioether is caused by stench in the air, and is one of the main pathogenic smelly factors. In order to comprehend the production regularity and influence factors of thioether in the aerobic fermentation of pig manure, an experiment was carried out in June, 2015 at Key Laboratory of Energy Resource Utilization from Agriculture Waste, Ministry of Agriculture, Chinese Academy of Agricultural Engineering, Beijing, China. This study took pig manure and straw as raw material, and through the orthogonal test investigated the effect of 3 parameters i.e. moisture content, C/N ratio and ventilation rate on the generation of VOCs in pig manure aerobic fermentation process. Experimental results showed that T4, T5, T7, T9 treatment (water content was 60%, 60%, 65% and 65%; C/N was 20, 25, 20 and 30; ventilation rate was 1.0, 2.0, 2.0 and 1.0 m3/(min·m3), respectively) reached the requirement of harmlessness, but T1, T2, T3, T6, T8 treatment (water content was 55%, 55%, 55%, 60% and 65%; C/N was 20, 25, 30, 30 and 25; ventilation rate was 0.5, 1.0, 2.0, 0.5 and 0.5 m3/(min·m3) respectively) did not reach. T2 and T3, did not reach the requirement of harmlessness because the moisture content was too low, T6 and T8 did not reach the requirement of harmlessness because the ventilation rate was too low, and T1 was because both moisture content and ventilation rate were too low. Therefore, in order to ensure the quality of fertilizer, it should try to avoid the low moisture content and low ventilation rate of composting. No matter what kind of compost parameters, total VOCs emissions were always concentrated in the early stages of aerobic fermentation, and the highest emission concentrations of all treatments were more than 2 000×10-6. As the moisture content increased from 55% to 65%, moisture content played the role of firstly promoting and then inhibiting for dimethyl disulfide, and firstly inhibiting and then promoting for dimethyl trisulfide. As the C/N ratio increased from 55% to 65%, dimethyl disulfide and dimethyl trisulfide were both firstly promoted and then inhibited. As the ventilation rate increased from 0.05 to 0.2 m3/(min·m3), dimethyl disulfide and dimethyl trisulfide were both firstly inhibited and then promoted. During pig manure aerobic fermentation, the order of the factors influencing dimethyl disulfide emission in turn was ventilation rate > moisture content > C/N ratio, and that for dimethyl trisulfide emission in turn was moisture content > ventilation rate > C/N ratio. The optimal parameters for reducing VOCs emissions were moisture content of 65%, ventilation rate of 0.1 m3/(min·m3) and C/N ratio of 30:1.