Biogas energy potential for livestock manure and gross control of animal feeding in region level of China

Abstract: With the increasing demand for meat products, animal husbandry industry has developed rapidly in China in the past decade. Large amount of animal manure were produced, which would be an important sources of biogas energy production or serious pollutant sources to soil and water body, if discharged into the environment without appropriate processing. It is very meaningful to assess the impacts of animal manure on environment in China. Based on the pollutant excretion coefficient of livestock and poultry that was officially released by the Ministry of National Environmental Protection of China, and the latest statistical data from statistical year book of China in 2011 that was released by the National Bureau of Statistics and Ministry of Agriculture, the gross amount of animal manure and the biogas energy potential by animal manure in different regions of China were evaluated in this study. The whole country was divided into six regions and the major 10 species of livestock and poultry were selected. Meanwhile, according to EU's standard of limitation on nitrogen and phosphorus application, the loading capacity of agricultural land soil for nitrogen and phosphorus nutrients in 31 provinces of China were also assessed and the environmental capacity for livestock and poultry feeding were preliminary assessed as well. Comparing environmental capacity of animal feeding with the actual number of livestock and poultry raised, manure pollution risk on agricultural land in different provinces was analyzed. The results indicated that China produced 2.235 billion tons of animal manure in 2010, which would produce biogas 107.275 billion cubic meters, with the biogas by animal manure being about 60% equivalent energy potential of natural gas manure. The cattle manure was 982 million tons, amounted to 44% of the total, followed by pig manure, which was 465 million tons, amounted to 21% of the total. Shandong, Henan, Sichuan, Inner Mongolia, Hebei and Liaoning were the top 6 provinces produced more than 100 million tons and sum up to 916 million tons, amounted to 41% of the total. The average values of agricultural land soil loading of nitrogen and phosphorus nutrients were 43.73 kg/hm2 (TN) and 9.16 kg/hm2 (TP) in China. The loading values in Beijing, Tianjin, Hunan, Guangdong, Henan and Shandong were more than that in other provinces and have exceeded the EU's standard limitation. It can be considered that agricultural land soil in those provinces would be polluted if the animal manure were applied on the agricultural fields, because the number of livestock and poultry raised in those provinces has exceeded the environmental capacity of animal feeding. The environmental livestock feeding capacity in China are 12.956 billion pigs equivalent based on nitrogen and 15.974 billion pigs equivalent based on phosphorus. The actual total amount of livestock and poultry raised amounted to more than a quarter of the livestock feeding capacity, which was 3.473 billion pigs equivalent based on nitrogen and 4.519 billion pigs equivalent based on phosphorus in China. There were 20 provinces exceeded the 50% of environmental capacity animal feeding. Considering chemical fertilizer application, the agricultural land soil in those provinces is in high risk of pollution. The results of this study provided a refernce for decision-making on regional gross control of animal feeding and distribution of livestock farming.