Winter crop and residue biomass potential in China

This paper estimates the potential biomass production from winter crops and summer crop residues in China. Rye is used to represent winter crop production, and straw from corn, wheat and rice is used to represent residue potential. Biomass totals are intended for use as energy feedstocks and are assessed in order to not compete with existing agricultural production. Accordingly, the analysis is performed in a spatially explicit manner by first calculating the amount of land suitable for the biomass production that excludes areas of competing interests. Existing corn areas are targeted as potential locations for supporting a winter crop of rye, and a global database of agricultural land use provides the spatial coverage of corn and other crops. To exclude areas that may already implement a winter crop, the corn land area is reduced by intersecting wheat and rice areas, which serve as proxies for all existing winter crops. To produce a less conservative estimate, corn land area north of 41 degrees latitude is not reduced by wheat and rice areas, assuming that such crops are not grown in the winter due to climatic constraints. The resulting land area suitable for supporting winter rye ranges from 6,564,620 to 16,776,000 ha. A rye growth model, RyeGro, is used to calculate a spatial distribution of yield as a function of total winter precipitation and average winter temperature. After excluding any areas with yields below 2 Mg/ha, the yield values are multiplied by the suitable land area to derive a range of production totals between 11,099,000 and 23,745,700 Mg of winter rye. Summer residues from corn, wheat and rice are calculated using land area and yield values from a global agricultural database and respective harvest indexes. Results indicate that 365,608,090 Mg of biomass are available from summer crop residues in China even after compensating for other uses for residue and harvesting logistics.