有机酸添加剂对低碳氮比条件堆肥氮素损失控制效果研究

Effects of organic acid additives on nitrogen loss in low C/N ratio during composting

为减少堆肥过程中的氨气挥发和氮素损失,以鸡粪、玉米秸秆和菌渣为发酵原料,采用强制通风静态堆肥罐进行41 d的好氧堆肥试验,研究低C/N(15)条件下两种有机酸(柠檬酸、草酸)对堆肥过程中氨气减排效果和氮素形态转化的规律。结果表明:添加5%(鲜质量)的柠檬酸、草酸增加了堆肥50℃以上高温天数和连续高温天数,降低了堆肥初始物料1.70个和1.88个pH值单位。草酸对堆肥主要发酵时期氨气减排有较好的效果,柠檬酸对氨气减排的影响主要集中在堆肥前10 d,随后减排效果减弱。与CK相比,柠檬酸、草酸分别降低堆肥过程中氨气累积挥发量44.15%和69.57%,氮素损失量分别降低了25.16%和48.54%。堆肥中氮素主要以有机氮的形态存在,与CK相比,添加柠檬酸、草酸处理有机氮含量分别提高了9.44%和23.13%,氨基酸态氮含量提高了11.23%和15.53%,酰胺态氮含量提高了18.43%和39.99%。柠檬酸、草酸提高了堆肥结束时无机氮含量,与CK相比,铵态氮含量分别提高了68.13%、408.48%,硝态氮含量提高了17.94%、45.75%。堆肥结束后CK、柠檬酸、草酸处理有机碳含量分别下降了31.44%、22.16%、15.70%。各处理温度、粪大肠菌群数、蛔虫卵死亡率均达到《畜禽粪便无害化处理技术规范》(GB/T 36195—2018)要求,但是草酸处理种子发芽指数未达到无毒害标准。试验结果表明,添加有机酸具有较好的氮素损失控制效果,且添加草酸效果优于柠檬酸,但是从堆肥产品无害化角度考虑,草酸添加量和添加方式还有待进一步研究。

Ammonia volatilization as a result of composting processes has raised public concern.The study of ammonia emission control technology in composting can provide a reference for effective control of nitrogen loss.Studies on this ammonia emission and its control can provide practical technology for efficient nitrogen loss control.To reduce ammonia volatilization and nitrogen loss in the process of composting,chicken manure,corn straw,and bacterial residue were composted aerobically for 41 days in static forced-aeration composting reactors.The effects of two organic acids(citric acid and oxalic acid)on ammonia emission reduction and nitrogen transformation in composting process under low C/N(15)conditions were investigated in this study. The results showed that 5%(fresh weight)citric acid and oxalic acid addition increased the number of days with a maximum temperature above 50 ℃ and the number of consecutive high temperature days as well as reduced the pH value of the initial compost by 1.70 and 1.88. Oxalic acid had a significant effect on ammonia emission reduction during the fermentation period of composting, while the reduction of ammonia volatilization by citric acid addition was primarily concentrated in the first 10 days of composting, and then the ammonia volatilization rate increased rapidly. Compared with the control treatment, citric acid and oxalic acid addition treatments reduced the cumulative ammonia volatilization by 44.15% and 69.57% and reduced total nitrogen loss by 25.16% and 48.54%, respectively. Nitrogen in compost mainly exists in the form of organic nitrogen. Compared with the control treatment, citric acid and oxalic acid addition also increased the organic nitrogen by 9.44% and 23.13% and increased the amino acid nitrogen by 11.23% and 15.53%, respectively. Furthermore, the amide nitrogen content increased by 18.43% and 39.99%, respectively. The addition of citric acid and oxalic acid increased the content of inorganic nitrogen at the end of composting, the ammonium nitrogen was raised by 68.13% and 408.48%, and nitrate nitrogen was raised by 17.94% and 45.75%, respectively. The contents of organic carbon decreased by 31.44%, 22.16%, and 15.70% in control, citric acid treatment and oxalic acid treatment, respectively. All treatments met the relevant requirements of composting maturity based on temperature, fecal coliform number, and ascaris egg mortality. However, the seed germination index of oxalic acid treatment did not meet the non-toxic standard. The results of the study indicates that adding organic acids has significant effects on nitrogen loss reduction, and oxalic acid is a better choice than citric acid. However, the addition amount and method of oxalic acid as harmless composting products needs to be further studied.