畜禽粪便生物炭固碳量、养分量的估算及田间施用潜在风险预测

Assessment of carbon sequestration and nutrient resources by turning animal manure into biochar and its potential environmental risk for field application

为了探讨畜禽粪便转化为生物炭后固碳量、养分量及田间施用潜在风险,选取了牛粪、猪粪和鸡粪为主要畜禽粪便原料制备生物炭,通过对其产率、碳含量、养分含量及重金属含量的分析,结合畜禽粪便产量数据,估算了畜禽粪便转化生物炭后固定碳的量和养分的量,并对其田间施用潜在的重金属污染风险进行预测。结果发现:我国2015年主要畜禽粪便总产量达到1.90×10^9 t,其全部转化为生物炭后,固碳量达到3.51×10^8 t,相当于我国约17.2%的碳排放量;此外,固定的总养分量为1.73×10^8 t,氮、磷(P2O5)和钾(K2O)分别占总养分的32.6%、46.8%和20.6%。然而,畜禽粪便生物炭中Cu、Zn和Cd的含量超标严重,特别是猪粪生物炭中Cd的含量高达34.36 mg·kg^-1,超标极其严重不能直接还田。研究表明,畜禽粪便转化为生物炭是一种有效固定碳和养分的方法,但也存在重金属污染的潜在环境风险,需对其作进一步评估。

Fresh dairy,swine,and chicken manure were collected and pyrolyzed at 500°C under an oxygen-limited condition for biochar production.The yield and total C,N,P,K,and heavy metal content of these manure-based biochars were investigated to estimate the potential environmental benefits and risks of these manures being converted to biochar followed by agricultural use.Based on the normal production of animal manure,the yield of biochar from these three manures,and the C content in the corresponding manure-based biochars the C sequestration amount increased to 3.51×10^8 t if all animal manures(1.90×10^9 t in total in 2015)were converted to biochar.This value was equivalent to about 17.2%of the national total C emissions.Moreover,these biochars exhibited high NPK nutrient content with 1.73×10^8 t in total,of which N,P(P2O5),and K(K2O)accounted for 32.6%,46.8%,and 20.6%,respectively.However,our analysis showed that the Cu,Zn,and Cd contents of manure biochars consistently increased during the pyrolysis process,exceeding the standard limits for direct field use.The Cd content in pig manure biochar reached up to 34.36 mg·kg^-1.These results show that converting animal manure to biochar followed by agricultural application may be viable for soil C sequestration,improvement of soil nutrient status,and efficient disposal of con?siderable amounts of animal manure;however,the soil contamination risk with heavy metals should be given greater attention.Long-term field studies are required that focus on the environmental performance of manure biochars,which are important to enable the development of more scalable biochar strategies.