Evaluation of crop residues and manure production and their geographical distribution in China

The amount of organic residue and waste in China and their uncertainties have not been quantitatively analysed, due to the lack of reliable data and proper quantification tools. Here we quantified the changes of crop residue and livestock manure in Chinese agriculture from 1978 to 2014, using coefficients collected from literature and a large statistical dataset. The uncertainties were tested using Monte Carlo model. The results showed that 819 megatons (Mt) of crop residue and 551 Mt of manure (dry weight base) were generated in 2014, which contained 25.3, 5.2 and 19.4 Mt of nitrogen (N), phosphorus (P) and potassium (K), respectively. Of these total amounts, 179.7 Mt of manure (32.9% of the total manure) and 212.9 Mt of crop residue (26.0% of the total residue) could be possibly used as composting feedstock. Our scenario analysis showed that up to 38% of manure from pig and dairy farm could be directly recycled to the field in 2020. Meanwhile, 85% of crop residue would be recycled to use, which implied that the proportion of agricultural organic residue and waste as compost feedstock could decline. Future recycling for organic waste through composting industry should be strengthened in the regions with high manure load, together with commercial regulation to redistribute compost product, with the sustainable and environmental aims.