死猪堆肥处理的通风率选择探讨

    Selection of ventilation rates on dead pig composting

    • 摘要: 针对生产中死猪难处理的问题,作者对死猪堆肥技术进行了试验研究。试验采用箱式堆肥方法,设定处理1、处理2、处理3的通风速率分别为300、200和100 L/(m3·min),每个处理设置4个重复;堆肥箱有效容积为0.95 m3,每个堆肥箱中间单层放入3头死猪(总质量30~32 kg),死猪上、下和四周是由玉米秸秆和猪粪混合的堆肥物料。在北京夏季条件下的运行结果表明,各处理堆肥箱内平均温度超过55℃的时间分别为19、19和34 d,处理间差异不显著;试验6周后,死猪仅剩下大部分骨骼,此时3种处理的死猪降解率分别达到(95.5±1.4)%、(94.7±1.7)%和(95.0±0.8)%,仅处理1与处理3的死猪质量(湿基)差异显著(P<0.05);试验14 d后粪大肠菌群数即能满足相关标准的无害化要求;各处理堆肥物料的同一特性参数的变化规律一致,且无显著差异,堆肥结束时物料的有机质(干基)质量分数在47%~48%,全氮和全磷(干基)的质量分数达5.7%~6.4%,超过《有机肥料》标准的总养分≥5%的技术指标要求。鉴于以上试验结果,综合考虑运行成本,建议死猪箱式堆肥的通风率不大于100 L/(m3·min)和堆肥时间不少于6周。死猪堆肥在无害化处理死猪的同时,将其转化成有机肥料,将为中国规模化猪场的死猪处理提供新的技术选择。

       

      Abstract: Routine mortality of animals is an inevitable consequence in animal production, the major disposal routes used in China are on-farm burial, incineration and rendering. None of these routes has been widely extended due to perceived environmental risks. On-farm burial poses a potential contamination threat to groundwater. A health risk from incineration arises from toxic emissions, such as dioxins and furans. The main environmental concerns associated with rendering relate to carcass collection and transport. The disposal of mortalities has become more of an issue for animal farming systems in recent years. Many countries are moving to alternative methods of carcass disposal. One alternative is composting, which has been proved to be a viable option for mortality disposal. However there is a lacking of information on dead pig composting in China. On-farm experiments of dead pig composting were conducted to investigate the much-needed alternative for intensive swine production, where dead pig disposal has become a serious problem. Twelve composting bins (1m L×1m W×1m H) were used, and three ventilation rates of 300, 200 and 100 L/m3.min were applied and designated as treatments 1 to 3, with each treatment containing 4 composting bins (as 4 replicates). Three dead pigs with a total weight of 30-32 kg were put together in the center of each bin. The lower and upper parts and surrounding of the dead pigs inside each bin were filled with a mixture of corn stalk and pig manure. The trial was conducted in a suburb of Beijing during the summer season. Both the mixture and dead pig residues were moved out of the composting bin every 2 weeks in order to measure the weights of dead pigs. Soon after measurement, the materials were put back with dead pig residue at a layer in the center. Results showed that: the average temperatures over 55℃ were 19、19 and 34d for the 3 treatments respectively, so that there was no significant difference among treatments. The degradation rates (in wet base) of a dead pig after 6w fermentation were 95.5±1.4%、94.7±1.7% and 95.0±0.8%, respectively. By then only the skeleton was left, and a significant difference (P<0.05) in the weights of dead pigs (wet base)between treatment 1 and treatment 3 was detected. The number of E. Coli could meet the demands of related national standards after 7 d, and all E. Coli were thoroughly killed after 2 w of composting. Each characteristic parameter of composting mixture from different treatments demonstrated the same trend,but no significant difference in each parameter among treatments was found. The contents of organic matter (dry base) in the composting mixture were 47%-48%, with a sum of total nitrogen and phosphorus (dry base) of 5.7%-6.4% at end of the trials, i.e. after 6w composting. Both values were higher than the corresponding indexes required by the Chinese Agricultural Standard of Organic Fertilizer. Composting was proved to be a viable and practical option for farmers to dispose of dead pigs. In view of the above results and the operational costs of aeration, the ventilation rate of no more than 100 L/m3.min and composting period of 6 w are recommended for dead pig composting in bins. Composting can dispose of dead pigs safely and practically, and turn mortalities into organic fertilizer, which offer a new and promising technology for on-farm dead pig disposal.

       

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