基于可收集的秸秆资源量估算及利用潜力分析

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

【目的】准确估算秸秆资源量及其分布是秸秆综合利用的重要基础,秸秆资源量估算的不确定性主要在于草谷比和可收集系数的变异性。本研究基于江苏省区县尺度粮食产量数据,定量分析了江苏省主要粮食作物秸秆资源量及其不确定性,进而探讨了不同秸秆利用方式的温室气体减排潜力。【方法】按草谷比和秸秆可收集系数估算区县尺度粮食作物秸秆资源量和可收集资源量,分析了草谷比和可收集系数的变异性,探讨了秸秆资源量估算的不确定性来源,采用置信区间计算方法给出了江苏省作物秸秆资源量95%的置信区间。通过聚类分析与空间分析对秸秆资源量空间分布进行评价;最后基于情景分析方法对不同秸秆利用方式可能带来的环境效益进行计量。【结果】江苏省主要粮食作物草谷比和可收集系数存在较大变异,其变异系数分别为2.2%~16.7%和5.4%~18.9%。江苏省2014年水稻、小麦、玉米和大豆秸秆资源总量平均为3974万t(95%置信区间为3720~4227万t),而可收集秸秆资源量平均为3062万t(95%置信区间为2907~3217万t);其中,水稻、小麦、玉米和大豆秸秆资源可收集量分别占全省的53.2%、36.7%、7.9%和2.2%。江苏省粮食作物秸秆氮、磷、钾养分资源量分别为25.58万t(以N计)、3.51万t(以P2O5计)、46.22万t(以K_2O计),在空间分布上各养分资源均呈现北高南低的特征。未被利用(焚烧和丢弃)的秸秆相当于3.07万t氮肥(以N计)、1.93万t磷肥(以P2O5计)、15.76万t钾肥(以K_2O计)以及170.12万t标准煤。情景分析结果表明,如将未被利用秸秆进行秸秆还田、秸秆发电或热裂解炭化,可分别带来约36.2万t、230.18万t或381.16万t二氧化碳当量的减排潜力,相当于江苏省温室气体排放量的0.18%、1.13%或1.88%。【结论】作物草谷比和可收集系数的变异性是秸秆资源量估算不确定性的主要来源,发展区域特征的草谷比和可收集系数是未来秸秆资源评价研究的重要内容。江苏省粮食作物可收集秸秆资源较为丰富,但不同作物间可收集资源量存在较大差异。与其他利用方式相比,生物质热裂解具有更高的固碳减排潜力,是农业可持续秸秆资源利用的潜在途径。

[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.