猪粪好氧发酵过程中挥发性有机物组分分析及致臭因子的确定

为了控制猪粪好氧发酵中产生的挥发性有机物(volatile organic compounds)及主要致臭物质,开展了猪粪好氧发酵试验,通过连续监测猪粪好氧发酵过程中所排放的挥发性气体,研究猪粪好氧发酵中产生的VOCs组分及其致臭因子。研究表明,在猪粪好氧发酵过程中共产生33种挥发性物质,除氨气和硫化氢外,共有31种VOCs,包括芳香烃12种,醛类8种,硫醇硫醚类4种,卤代烃4种,酮类2种,胺类1种;猪粪好氧发酵中主要致臭物质为:二甲二硫、甲硫醚、二甲三硫、乙醛和硫化氢,并建议将甲硫醚作为猪粪好氧发酵中产生的恶臭污染指示物。该研究可为猪粪堆肥过程中恶臭物质的监测、制定控制策略提供参考。

Component analysis of volatile organic compounds and determination of key odor in pig manure aerobic fermentation process

Pig manure aerobic fermentation will produce a trace of volatile organic compounds (VOCs), although the VOCs content is less, but the effect on human health cannot be neglected. VOCs are not a single substance, but a class of compounds. In order to control VOCs, investigation of odor-causing matters of pig manures in aerobic fermentation was carried out in August, 2014 at the Key Laboratory of Energy Resource Utilization From Agriculture Waste,Ministry of Agriculture,Chinese Academy of Agricultural Engineering, Beijing, China. We set up the aerobic fermentation of pig manure and straw mix with water content of 65%, and the ratio of carbon to nitrogen 25:1. In the aerobic fermentation process, in every 30 minutes, there was a five-minutes ventilation, and the ventilation rate was 1.0 m3/(min·m3). Aerobic fermentation period was one month. We conducted an experiment to monitor volatile gas emission from the aerobic fermentation process, and determined the pig aerobic fermentation of VOCs components and their emission patterns. Research results showed that high temperature aerobic fermentation period lasted more than 10 days. It produced 33 kinds of volatile substances. Most of them emitted at the stages of high temperature. Besides ammonia and hydrogen sulfide, there were 31 kinds of VOCs, including benzene, toluene, ethylbenzene, ortho xylene, meta xylene and p-xylene, styrene, cumene, phenylpropane, mesitylene, tert-butylbenzene, pseudocumene, naphthalene, formaldehyde, acetaldehyde, acrylic aldehyde, crotonaldehyde, benzaldehyde, pentanal, hexaldehyde, methyl phenyl aldehyde, methanthiol, methyl sulfide, dimethyl disulfide, dimethyl trisulfide, 1,1-dichloroethane, sym-dichloroethane, trichloromethane, carbon tetrachloride, acetone, butanone and trimethylamine. Of these 31 VOCs, there were 12 aromatic hydrocarbons, eight aldehydes, four Mercaptan sulfur ethers, four halogenated hydrocarbons, two ketones and one amine. The correlation analysis between importance to smelly gases and odor concentration showed that methyl sulfide, dimethyl disulfide and dimethyl trisulfide were significantly positively correlated with odor concentration (P<0.01). Hydrogen sulfide and acetaldehyde were significantly positively correlated with odor concentration (P<0.05). So the smelly and odor-causing matters of pig manures’ aerobic fermentation were mainly methyl disulfide, dimethyl sulfide, dimethyl trisulfide, acetaldehyde and hydrogen sulfide. In addition, dimethyl disulfide, dimethyl trisulfide, hydrogen sulfide and acetaldehyde were significantly positively correlated with methyl sulfide (P<0.05). In order to monitor the malodorous substances and provide reference for making control strategy in the aerobic fermentation of pig manure, we recommended methyl sulfide as a foul odor pollution indicator.