Soil contamination by organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), pesticides, pharmaceuticals, and petroleum hydrocarbons has emerged as a global environmental concern due to their persistence, bioaccumulation, and potential health risks. Biochar, a carbon-rich material derived from the pyrolysis of biomass, has attracted increasing attention as an environmentally friendly and cost-effective amendment for remediating contaminated soils. This review systematically summarizes recent advances in the application of biochar for the remediation of organic pollutants in soils to guide the development of more effective biochar-based strategies for sustainable soil remediation. The physicochemical properties of biochar influencing pollutant interactions are discussed, including surface area, pore structure, functional groups, and aromaticity. Mechanisms such as adsorption, sequestration, microbial interaction enhancement, and catalytic degradation are elucidated. Moreover, this review highlights the influence of feedstock types, pyrolysis conditions, biochar modification strategies, and environmental factors on biochar performance. The analysis reveals that biochar performance is strongly dependent on feedstock selection, pyrolysis conditions, and post-modification strategies, which jointly determine pollutant immobilization efficiency and long-term stability. Current challenges, such as long-term stability, pollutant desorption, and ecological impacts, are critically examined. Finally, future perspectives on the design of engineered biochar and its integration with other remediation technologies are proposed. Rationally engineered biochar, particularly when integrated with biological or physicochemical remediation technologies, demonstrates strong potential for efficient and sustainable soil remediation.

Biomass torrefaction, a mild pyrolysis process at 200–300 °C under an inert atmosphere, has emerged as a pivotal pretreatment technology for solid biowaste conversion and functional carbon materials production. This process fundamentally transforms raw biomass through deoxygenation and aromatization, with improved material properties. The chemical composition and structural heterogeneity of the biomass feedstock significantly influences the deoxygenation and aromatization pathways during torrefaction, thereby tuning the pore structure, surface chemistry, and electrochemical performance of the resulting carbon materials. This engineered intermediate is highly amenable to subsequent activation and functionalization, enabling the synthesis of high-value carbon materials. Torrefaction-derived porous biochar exhibits exceptional performance as electrodes in supercapacitors, delivering high specific capacitance and cycling stability due to its hierarchical pore structure and tunable surface chemistry. Furthermore, these materials serve as highly efficient adsorbents for pollutants and, when doped with heteroatoms or metals, as potent catalysts for degrading organic contaminants via advanced oxidation processes. In the biomedical field, controlled carbonization yields biocompatible carbon quantum dots for bio-imaging and drug delivery. The current research frontier is shifting toward multifunctional composites, such as magnetically separable catalysts and 3D-printable conductive inks. By providing a versatile and sustainable platform for precursor engineering, biomass torrefaction effectively bridges the gap between abundant renewable resources and the pressing demand for high-performance, sustainable materials across energy, environmental, and biomedical sectors. This review comprehensively summarizes the current research progress and forecasts the future trend to contribute a potential solution with great practical significance.

Review Congyu Zhang *, Jin Fang, Yong Zhan, Xin Wang, Tao Chen, Kuifeng Hao, Jiaqi Ma and Yuting Wang School of Resources and Environment, Northeast Agricultural University, Harbin 150030, China * Correspondence: ztdw7727@163.com Received: 23 May 2024; Revised: 12 August 2024; Accepted: 5 September 2024; Published: 10 September 2024 Abstract: In the past decades, a series of phenomena such as global warming, glacier melting, sea level rise, and haze weather caused by the greenhouse effect have been reported, which seriously threaten the future of humans. To address this challenge, several countries have initiated interventions to prevent climate change, such as carbon neutralization. Given the current economic, social development and environmental protection requirements, microalgal carbon fixation appears to be a suitable approach to achieve carbon net zero emission while also promoting microalgal biofuel production. This promotes the realization of energy structure transformation and optimization of carbon neutralization. This article provides a comprehensive and state-of-the-art review of research progress on microalgal carbon capture and solid biofuel production via the torrefaction process, with focus on the efficiency and capacity of microalgal carbon fixation, as well as the principle and application of microalgal torrefaction. The detailed review includes the practical value and development prospect of microalgal torrefied biochar, fuel performance conversion, and mechanism in the torrefaction process. Furthermore, the environmental impact of microalgal carbon fixation and torrefaction process are discussed to evaluate the overall environmental benefits of microalgal utilization via life cycle assessment (LCA) method. The technical difficulties of microalgal carbon fixation and torrefaction process are also discussed. This review paper is beneficial to guide the scheme demonstration and specific implementation of microalgal carbon neutralization and thus lead to the efficient establishment of microalgal carbon reduction, biomass accumulation, and biofuel production techniques.