秸秆改土产能时空一体化处理的意义及局限性

The significance and application limitation of Space-time Integration of Soil Improvement and Energy Production bY Using Straw

  • 摘要: 我国每年生产大量的作物秸秆, 不加处理或处理不当, 会严重威胁水体或大气环境质量。秸秆还田是当前解决作物秸秆田间焚烧或无序堆放威胁环境质量的最主要方法。秸秆还田按目的可分为两种方式: 以处置秸秆为目的处置化原位还田和以消除作物生长障碍因素为目的的消障化异地还田。无论何种秸秆还田方式均未利用秸秆生物能, 虽在一定程度上可以提高土壤有机质含量, 但作用有限, 且无显著的时间累积效应。秸秆沼气化利用了秸秆生物能, 但因产气不稳定, 沼渣、沼液处理难等因素, 推广应用难度大。笔者提出了一种在同一时间和空间, 实现秸秆改土和产能等多重目标的秸秆处理方式, 称作“秸秆改土产能时空一体化处理”方法(Space-time Integration of Soil improvement and Energy production by using Straw, ISES), 即就近集中秸秆于需要改良的土壤, 使秸秆施用量达到5%土重以上, 与土壤充分混匀, 在淹水条件下, 密封培养, 收集厌氧发酵产生的沼气用作家庭燃料或作它用。ISES处理可跨肥力等级幅度提升土壤有机质含量, 产气量及气体中CH4浓度与沼气发酵相当, 且不需要处理沼液和沼渣, 可服务于改土、产能和固碳多重目标。加强IESE系统中碳转化和CH4产生过程及其产气率和CH4浓度影响因素的研究, 评估ISES处理过程及处理后的环境效应, 对于优化处理工艺, 明确可采用ISES处理的土壤类型、适宜的处理时间, 降低ISES处理的环境效应, 制订安全生产措施, 预测经济可行性都是十分必要的。

     

    Abstract: China produces a substantial amount of crop straw annually, and improper disposal, management, and burning in fields poses significant threats to water and atmospheric environmental quality. Straw return to the field is currently the primary way for addressing the environmental risks posed by crop straw. Based on its purpose, straw return can be categorized into two types: direct in-situ return, aimed at on-site straw disposal, and crop growth barrier-eliminating relocated return, designed to mitigate crop growth constraints. However, neither approach utilizes the bioenergy potential of straw. While they may enhance soil organic matter content to some extent, their effects are limited and lack significant cumulative benefits over time. The bioenergy of straw is utilized if straw is transferred into biogas through anaerobic fermentation in biogas digester, but its implementation is challenging due to factors such as unstable gas production and difficulties in treating the residue and liquid byproducts. This study proposes a novel straw management way, termed the "Space-time Integration of Soil Improvement and Energy Production by Using Straw" (ISES), which simultaneously achieves soil improvement and energy production within the same time and spatial framework. Specifically, ISES involves applying crop straw collected around to the soils requiring remediation at a rate exceeding 5% of the soil weight, thoroughly mixing it with soil, and conducting sealed anaerobic fermentation under flooded conditions. The biogas generated from this process can be collected for household fuel or other applications. The ISES method can significantly enhance soil organic matter across fertility gradients. Its gas production and methane (CH4) concentration are comparable to traditional biogas fermentation, without the need to handle biogas residues or slurry. It serves multiple objectives: soil improvement, bioenergy production, and carbon sequestration. Thus, further research is needed to: 1) investigate carbon transformation and methane production processes in the ISES system; 2) examine factors influencing gas yield and CH4 concentration; 3) assess the environmental effects during and after ISES treatment. Such studies are also essential for optimizing the treatment process, identifying suitable soil types and treatment timings for ISES, mitigating environmental impacts, establishing safety measures, and evaluating economic feasibility.

     

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