Agricultural crop residues represent a significant part of the biomass potentially available for renewable energy systems. Sustaining soil organic carbon (C) is a common limiting factor applied to the biophysically available resource to determine crop residues potential for bioenergy. Studies quantifying this potential have so far largely considered crop biomass to produce renewable energy as being independent from the energy conversion pathway. However, the conversion method has great influence on how much C in crop residues can be returned back and retained in soils. Here, we applied the C‐TOOL soil C model for two extreme conversion pathways of agricultural straw management in terms of C returned back to soils, using Denmark as a case study. Those were anaerobic digestion, involving the return of recalcitrant C to fields, and combustion, involving no C returns to agricultural fields. Danish agriculture was represented by six different soil‐cropping schemes units on which our two extreme bioenergy pathways were modelled. We applied a premise that for a given geographical unit, the same long‐term soil C level needs to be achieved under these extreme bioenergy scenarios; therefore, we identified how much straw could be removed from agricultural fields in each case while maintaining equal soil organic carbon (SOC) levels. We found that at the scale of the whole country, only 26% of the straw potential can be harvested for use in combustion to maintain in average long‐term SOC at the same level as it would have been with the anaerobic digestion scenario. Thus, consideration for the biomass conversion pathway is important when identifying agricultural residue potentials for energy conversion while ensuring that SOC level is not compromised.

中文翻译：

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维持土壤碳的农业残留物生物能源潜力取决于能量转化途径

农作物残余物占可再生能源系统潜在生物质的很大一部分。维持土壤有机碳（C）是一种常见的限制因素，适用于生物物理上可利用的资源来确定作物残余物具有生物能源的潜力。迄今为止，量化这种潜力的研究很大程度上考虑到农作物生物质产生的可再生能源与能源转化途径无关。但是，转化方法对作物残渣中的多少碳可以返回并保留在土壤中有很大的影响。在这里，我们以丹麦的案例研究为基础，将C‐TOOL土壤C模型应用于返回秸秆的C方面的两种农作物秸秆极端转化途径。这些是厌氧消化，涉及顽固性C返回田间并燃烧，不涉及碳返回农田。丹麦农业以六个不同的土壤耕作计划单位为代表，在这些单位上模拟了我们的两个极端生物能源途径。我们采用的前提是，对于给定的地理单位，在这些极端生物能源情景下，需要达到相同的长期土壤碳水平；因此，我们确定了在保持相同土壤有机碳（SOC）水平的情况下，可以从农田中清除多少秸秆。我们发现，在整个国家范围内，只能收获秸秆潜力的26％用于燃烧，以将平均长期SOC保持在与厌氧消化方案相同的水平。从而，