Paddy fields emit considerable amounts of methane (CH₄), which is a potent greenhouse gas (GHG) and, thereby, causes significant environmental impacts, even as they generate wealth and jobs directly in the agricultural sector, and indirectly in the food-processing sector. Application of biochar in rice production systems will not just help to truncate their carbon footprints, but also add to the bottom-line. In this work, the authors have reviewed the literature on climate change, human health, and economic impacts of using organic residues to make biochar for the addition to croplands especially to rice paddy fields. Biochar-bioenergy systems range in scale from small household cook-stoves to large industrial pyrolysis plants. Biochar can be purveyed in different forms—raw, mineral-enriched, or blended with compost. The review of published environmental life cycle assessment (E-LCA) studies showed biochar has the potential to mitigate the carbon footprint of farming systems through a range of mechanisms. The most important factors are the stabilization of the carbon in the biochar and the generation of recoverable energy from pyrolysis gases produced as co-products with biochar as well as decreased fertiliser requirement and enhanced crop productivity. The quantitative review of E-LCA studies concluded that the carbon footprint of rice produced in biochar-treated soil was estimated to range from −1.43 to 2.79 kg CO₂-eq per kg rice grain, implying a significant reduction relative to rice produced without a biochar soil amendment. The suppression of soil-methane emission due to the biochar addition is the dominant process with a negative contribution of 40–70% in the climate change mitigation of rice production. The review of the life cycle cost studies on biochar use as an additive in farmlands demonstrated that biochar application can be an economically-feasible approach in some conditions. Strategies like the subsidization of the initial biochar capital cost and assignment of a non-trivial price for carbon abatement in future pricing mechanisms will enhance the economic benefits for the rice farmers.

中文翻译：

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稻田生物炭应用进展与挑战的批判性综述：环境与生命周期成本分析

稻田排放大量甲烷（CH ₄），这是一种有力的温室气体（GHG），因此，即使它们直接在农业部门以及间接在食品加工部门创造财富和创造就业机会，也会对环境造成重大影响。生物炭在稻米生产系统中的应用不仅将有助于减少其碳足迹，而且还将增加底线。在这项工作中，作者回顾了有关气候变化，人类健康以及使用有机残留物制造生物炭以增加农田，特别是稻田的生物炭的经济影响的文献。生物炭-生物能源系统的规模范围从小型家用炊具到大型工业热解工厂。生物炭可以以不同的形式进行输送-原料，富含矿物质或与堆肥混合。对已发布的环境生命周期评估（E-LCA）研究的审查表明，生物炭具有通过多种机制减轻农业系统碳足迹的潜力。最重要的因素是生物炭中碳的稳定以及与生物炭一起作为副产品产生的热解气体的可回收能量的产生，以及化肥需求的减少和农作物生产力的提高。对E-LCA研究的定量审查得出的结论是，经生物炭处理过的土壤中生产的大米的碳足迹估计为-1.43至2.79 kg CO 最重要的因素是生物炭中碳的稳定以及与生物炭一起作为副产品产生的热解气体的可回收能量的产生，以及化肥需求的减少和农作物生产力的提高。对E-LCA研究的定量审查得出的结论是，经生物炭处理过的土壤中生产的大米的碳足迹估计为-1.43至2.79 kg CO 最重要的因素是生物炭中碳的稳定和与生物炭一起作为副产品产生的热解气体的可回收能量的产生，以及肥料需求的减少和农作物生产力的提高。对E-LCA研究的定量审查得出的结论是，经生物炭处理过的土壤中生产的大米的碳足迹估计为-1.43至2.79 kg CO每千克大米谷物₂当量，这意味着相对于未经生物炭土壤改良剂生产的大米而言，显着降低。由于添加生物炭而抑制土壤甲烷排放是主要过程，对缓解水稻生产的气候变化产生了40％至70％的负面影响。关于在农田中使用生物炭作为添加剂的生命周期成本研究的回顾表明，生物炭的应用在某些情况下可能是一种经济可行的方法。诸如对初始生物炭资本成本进行补贴以及在未来的定价机制中为碳减排分配不平凡的价格之类的策略，将为稻农增加经济利益。