Significance and application limitation of Space-time Integration of Soil Improvement and Energy Production by Using Straw

China produces a substantial amount of crop straw annually. Improper disposal, management, and burning pose significant threats to water and atmospheric quality. Straw return to the field is currently the primary method used to address 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 of these approaches utilizes the bioenergy potential of straw. Although 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 when it is converted into biogas through anaerobic fermentation in a biogas digester; however, its implementation is challenging because of factors such as unstable gas production and difficulties in treating the residue and liquid byproducts. This study proposed a novel straw management method, 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 from the surrounding area to the soils requiring remediation at a rate exceeding 5% of the soil weight, thoroughly mixing it with the soil, and conducting sealed anaerobic fermentation under flooded conditions. The biogas generated from this process can be collected for use as a household fuel or in other applications. The ISES method can significantly enhance soil organic matter across fertility gradients. Its gas production and methane concentration are comparable to those of traditional biogas fermentation, without the need to handle biogas residues or slurry. It has multiple objectives, including 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 methane concentration, and 3) assess the environmental effects during and after ISES treatment. Such studies are 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 of ISES.