Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production
Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production
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DOI：
10.1021/es071361i
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发表时间：
2008-06-01
影响因子：
11.4
通讯作者：
Lehmann, Johannes
中科院分区：
文献类型：
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作者：
Gaunt, John L.;Lehmann, Johannes
评估了优化用于生物炭和能源生产而不是仅用于能源生产的基于缓慢热解的生物能源系统对温室气体排放的影响。采用生命周期办法审查了原料生产的各种设想方案。我们考虑了目的种植的生物能源作物（BEC）和使用作物废料（CW）作为原料。生物能源效益情景涉及从种植冬小麦到种植芒草、柳枝稷和玉米作为生物能源作物的变化。CW情景考虑玉米秸秆和冬小麦秸秆作为原料。我们的研究结果表明，当生物炭应用于农业用地时，避免的排放量是仅用于化石能源抵消的2到5倍（2-19 Mg CO2 ha（-1）y（-1））。其中41-64%的减排量与生物炭中的碳保留有关，其余的减排量与抵消化石燃料的能源使用、肥料节省和避免土壤排放（CO2除外）有关。尽管在慢速热解技术被优化以生产用于土地应用的生物炭的情况下，能量输出减少了约30%，但每单位能量输入产生的2-7 MJ/MJ的能量大于可比技术（例如来自玉米的乙醇）的能量。每兆瓦时发电的碳排放量在91-360千克CO2兆瓦时（-1）之间，在考虑因使用生物炭而产生的碳抵消之前，远低于与化石燃料发电相关的生命周期排放量（600-900千克CO2兆瓦时（-1））。低温缓慢热解为生物能源生产提供了一种能量效率高的策略，生物炭的土地应用比生物炭用于抵消化石燃料排放时更大程度地减少温室气体排放。
The implications for greenhouse gas emissions of optimizing a slow pyrolysis-based bioenergy system for biochar and energy production rather than solely for energy production were assessed. Scenarios for feedstock production were examined using a life-cycle approach. We considered both purpose grown bioenergy crops (BEC) and the use of crop wastes (CW) as feedstocks. The BEC scenarios involved a change from growing winter wheat to purpose grown miscanthus, switchgrass, and corn as bioenergy crops. The CW scenarios consider both corn stover and winter wheat straw as feedstocks. Our findings show that the avoided emissions are between 2 and 5 times greater when biochar is applied to agricultural land (2-19 Mg CO2 ha(-1) y(-1)) than used solely for fossil energy offsets. 41-64% of these emission reductions are related to the retention of C in biochar, the rest to offsetting fossil fuel use for energy, fertilizer savings, and avoided soil emissions other than CO2. Despite a reduction in energy output of approximately 30% where the slow pyrolysis technology is optimized to produce biochar for land application, the energy produced per unit energy input at 2-7 MJ/MJ is greater than that of comparable technologies such as ethanol from corn. The C emissions per MWh of electricity production range from 91-360 kg CO2 MWh(-1), before accounting for C offset due to the use of biochar are considerably below the lifecycle emissions associated with fossil fuel use for electricity generation (600-900 kg CO2 MWh(-1)). Low-temperature slow pyrolysis offers an energetically efficient strategy for bioenergy production, and the land application of biochar reduces greenhouse emissions to a greater extent than when the biochar is used to offset fossil fuel emissions.