The carbon cycle is a crucial method for achieving carbon neutrality. Researches show that methane emissions in rice fields account for 30% of total methane emissions from global agricultural sources. Methane emissions are one of the main factors contributing to global climate change and the greenhouse effect. Straw incorporation is an effective path to use agricultural waste resources. To reduce methane emissions in rice fields and utilize agricultural waste resources more efficiently, this research examines the impact of straw biochar returned to the fields on methane reduction. The research systematically reviews the fundamental characteristics and preparation methods of straw biochar, discusses the ways in which straw biochar application to the soil alters the soil condition, its impact on soil structure, and the mechanism of reducing methane emissions. This article aims to provide scientific evidence for the carbon cycle regulation method of promoting methane emission reduction through the application of straw biochar in the field, in order to facilitate the achievement of carbon neutrality.

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Anaerobic fermentation of food waste for methane production can help realize waste resource utilization and the "dual carbon" targets. We examine biochemical process and technology development of this method in full detail, covering how reaction happens at each stage and how equipment has changed over time. Also, we look at how key parameters affect methane production. It is worth noting that carbon-nitrogen ratio and temperature, together with external additives, can change efficiency in different ways. The results show that co-fermentation substrate adjustment and carbon-based material addition can avoid system acidification, and directional control of microbial community is expected to improve gas production stability. Current studies focus on single factor control and verification in laboratory scale, which makes it hard to apply in practice. Future work should examine multi-factor coupling mechanisms. Also, we should push results from lab to actual engineering applications. This review tries to build systematic knowledge framework for this field. In fact, results can be used as reference for large-scale application and process optimization of food waste anaerobic fermentation technology.

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Soil pollution by heavy metals has become an urgent problem, and we should develop some efficient methods for remediation. Phytoremediation is an environmentally friendly and gentle remediation technology, which uses plants to remove or stabilise pollutants in soil. However, it also has some disadvantages, such as low biomass production and poor heavy metal uptake. Moreover, plants themselves are very sensitive to heavy metal pollution, which affects their growth. Biochar, which is produced by the pyrolysis of biomass under low oxygen conditions, has a strong ability to adsorb heavy metals through physical adsorption and other mechanisms. It also has a positive effect on improving soil properties and enhancing the efficiency of phytoremediation. This essay hopes to summarise the current research on the interaction mechanisms between biochar and heavy metals, the effects of biochar on the improvement of phytoremediation, and provide a future research guideline for the sustainable use of biochar in the remediation of heavy metal-contaminated soil.

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The development of the digital industry and the growing embrace of green development have driven the advancement of high-performance, low-cost green batteries. As an electrode material, biochar boasts diverse raw sources, excellent stability and low cost, endowing it with significant application value in both electric double-layer and pseudocapacitive energy storage systems. Oxygen-containing functional groups in biochar serve as a key factor in tuning the chemical properties, safety and cycling stability of capacitors. Their content, type and distribution directly determine the performance of the devices. This paper systematically reviews the origin, regulation strategies and structure-activity relationships of oxygen-containing functional groups in biochar, with a focus on the effects of inherent feedstock components, pyrolysis conditions and oxidative modification on such groups. It clarifies the dual regulation and critical points of oxygen-containing functional groups in capacitors. By comparing the impacts of various oxygen-containing functional groups (OFGs), the mechanism and contradictory effects governing capacitor performance are revealed. The conflict between capacitance enhancement and compromised cycling stability is addressed through a B/N/P ternary co-doping strategy, aiming to explore future development pathways and achieve a balanced progress toward high capacity, high efficiency and long cycle life.This work systematically summarizes the origin, regulatory mechanisms and dual-regulation behavior of oxygen-containing functional groups, and outlines future development directions consistent with the green development philosophy. It holds important research significance for realizing low-cost, high-performance energy storage.

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