Estimate of the quantity of collectable straw resources and competitive utilization potential

Objectives Comprehensive utilization of straw is always one of the key issues should be addressed in sustainable agricultural development. Reliable assessment of the quantity and distribution of straw resources is the prerequisite for their profitable utilization. The uncertainties of the assessment are mainly induced by the variations of straw and grain ratio and collectible coefficients. The objectives of this study were to analyze the quantity and spatial distribution of straw resources in Jiangsu Province, quantify the uncertainty of the estimation, and assesse the greenhouse gas mitigation potential of various utilization patterns.

Methods The straw to grain ratio and straw collecting coefficient of a crop were calculated from the national scale of grain crop production. The uncertainty of the estimation was quantified based on the variations of straw to grain ratios and collecting coefficients, and the 95% confidence intervals of straw resource quantity were adopted for each item. Cluster and spatial analysis were employed to assess the spatial distribution of straw resources. The greenhouse gas (GHG) mitigation potentials of different competitive straw utilization were also assessed using the scenario analysis.

Results The straw to grain ratios and collecting coefficients of grain crops in Jiangsu Province presented large variations with the coefficients of variation of as high as 2.2%–16.73% and 5.43%–18.87%, respectively. The estimated total quantity of major crop straws was 39.74 million tons with the 95% confidence interval of 37.2–42.27 million tons, with collectible straw resources of as high as 30.62 million tons with the 95% confidence interval of 29.07–32.17 million tons. The straw quantities of rice, wheat, corn and soybean accounted for 53.2%, 36.7%, 7.9% and 2.2% of the total of the Province, respectively. The nutrient resources from the collectible straw were quantified as 255.8 kiloton N, 35.1 kiloton P₂O₅, and 462.2 kiloton K₂O, respectively. The nutrient resource quantity was found more in the North Jiangsu than in the South. The nutrient and energy contained in the unused straw were estimated to be 30.7 kiloton N, 19.32 kiloton P₂O₅, 157.64 kiloton K₂O and 1.7 million ton standard coal. The results of the scenario analysis showed that the GHG mitigation potentials of as high as 0.36, 2.3 and 3.8 million tons CO₂ equivalent could be achieved if unused straw could be returned to soil, be generated electricity, and be pyrolysis respectively, which accounted for 0.18%, 1.13% and 1.88% to total greenhouse gas emissions in Jiangsu province.

Conclusions There is a huge amount of straw resources in Jiangsu Province. Biomass pyrolysis preserves nutrients and organic matter and also has C sequestration and mitigation potential, which is a potential straw utilized technology that can be popularized.