Utilization of current pyrolysis technology to convert biomass and manure waste into biochar for soil remediation: A review

Biofuel production from waste residuals: comprehensive insights into biomass conversion technologies and engineered biochar applications

Biomass-derived residuals represent a vital renewable energy source, offering sustainable alternatives to mitigate fossil fuel dependency, address climate change, and manage waste. Although biomass generally has a lower calorific value (10-20 MJ kg-1) compared to fossil fuels (40-50 MJ kg-1), its energy recovery potential can be enhanced through advanced conversion technologies such as torrefaction, pyrolysis, and gasification. Additionally, biomass is considered carbon neutral when sourced sustainably, as the CO2 released during combustion is reabsorbed by plants during their regrowth cycle, maintaining a balanced carbon flux in the atmosphere. This review explores the diverse sources of biomass and examines their chemical compositions and inherent properties, emphasizing their transformation into valuable energy carriers and bio-products. It provides a comprehensive analysis of thermochemical, biochemical, and physicochemical conversion technologies, detailing their mechanisms, efficiencies and applications. Special attention is given to biochar, a product of biomass pyrolysis, highlighting its potential in pollution mitigation, carbon sequestration, and as a catalyst in industrial applications. The review delves into synthesis processes of biochar and performance-enhancing modifications, illustrating its significant role in sustainable environmental management. Additionally, the economic and ecological advantages of biomass-derived energy, including reduced greenhouse gas emissions and waste reutilization, are critically evaluated, underscoring its superiority over conventional fossil fuels. Challenges limiting the scalability of biomass energy, such as technology costs, process efficiency, and market dynamics, are addressed, alongside prospective solutions. By consolidating extensive research on biomass conversion technologies and engineered biochar applications, this review serves as a valuable resource for researchers and policymakers. It aims to guide advancements in biomass utilization, fostering a transition toward sustainable energy systems and addressing global energy and environmental challenges.

Sequential carbonization of pig manure biogas residue into engineered biochar for diethyl phthalate removal toward environmental sustainability

Manure biogas residue has attracted increasing attention in waste recycling but faces substantial challenges because of its low carbon content, high ash content, and high heavy metal content. A novel sequential carbonization approach was proposed for recycling biogas residue; this approach consisted of pre-pyrolysis, activation with Ca(OH)2, and then activation with KOH. Pig manure-derived biogas residue was upcycled into engineered biochar (EB) with a high yield (26 %) and showed excellent performance in removing a typical plasticizer, diethyl phthalate (DEP). The proportion of carbon content greatly increased from 18 % (biogas residue) to 67 % (EB); however, the ash content decreased from 50 % (biogas residue) to 24 % (EB). The concentration of heavy metals decreased, and Zn had the largest decrease from 713 mg kg-1 to 61 mg kg-1 (p < 0.001). The sorption of DEP onto EB was rapid and reached equilibrium within 20 h. The developed specific surface area of EB was 1247 m2/g and provided abundant sorption sites for DEP; additionally, the sorption quantity reached 309 mg/g. The sorption capacity was dominated by surface adsorption. The oxygen-containing functional groups, graphene structure, porous structure, and hydrophobicity of EB contributed to the pore filling, hydrogen bonding, π-π stacking, and partitioning processes. Furthermore, the EB showed excellent practical application potential and great cycling stability. A sequential carbonization strategy was proposed to upcycle manure biogas residue into the EB for DEP removal; moreover, this strategy can aid in the attainment of environmental sustainability, including sustainable waste management and environmental pollution mitigation.

Effect of black soldier fly larvae frass addition on humus content during low temperature co-composting

Initiating aerobic fermentation under low temperature is the main challenge for winter livestock manure composting. This study aims to address this issue by applying black soldier fly larvae (BSFL) frass as a co-composting additive to enhance the low-temperature composting process. Specifically, this work explored the effects of chicken manure and BSFL frass co-composting on the temperature, humus content, and microorganisms with fresh weight ratio of 2:1, 1:1, 1:2 (w/w) at 6 °C. The result showed frass could rapidly rise the temperature to 50 °C and significantly increased the humus content by 15.6 % ∼ 26.3 %. Moreover, microbial analysis revealed that Sphingobacteriaceae accelerated temperature rise via low-temperature reproduction, creating proper temperature for thermophilic bacteria (Truepera and Georgia). Additionally, Cellulomonas and other bacteria promoted organic matter degradation and participated in humus formation. This study presents a novel solution for low-temperature composting, providing practical insights for improving manure management in winter.

Efficient remediation of cadmium and lead contaminated soil in coal mining areas by MICP application in hydrothermal carbon-based bacterial agents: Nucleation pathways and mineralization mechanisms

The development of industrial mining has resulted in a large amount of Cd and Pb polluting the soil in mining areas, and leads to adverse health effects on the life of both plants and animals. Here, a soft template method was conducted to prepare hydrothermal carbon (HC) with regular morphology, which assisted with Bacillus pasteurii to induce calcite precipitation for decontamination of mining soil. Soil remediation experiments over 30 days of remediation with an HC microbial agent (HCMA) resulted in 89.4% and 87.8% decrease in the amount of leached Cd and Pb, respectively. The content of exchangeable Cd and Pb decreased by 76.1% and 81.0%, respectively. At the same time, soil fertility significantly improved. The electrostatic potential and surface charge distribution of extracellular polymeric substances (EPS) and sodium citrate (NaCit) were analyzed using DFT simulations, their nucleophilic and electrophilic regions were determined, and the nucleation mechanism was determined. The DFT results indicated that the oxygen-containing groups of EPS and NaCit had strong negative electrostatic potential and electronegativity, which could cause Cd2+, Pb2+, and Ca2+ to aggregate on their surfaces. They also combined with CO32- produced by urease during the decomposition of urea, resulting in Cd2+ and Pb2+ being encapsulated by calcium carbonate to form a coprecipitate. X-ray diffraction analyses revealed that the precipitate was mainly calcite calcium carbonate, which is more stable and less prone to secondary leaching of HMs. The gathered data prove the significant role of HCMA in remediation of mining soil contaminated with Cd and Pb.

Pyrolytic conversion of cattle manure into value-added products and application of biochar for adsorption of sulfamethoxazole

This study investigated the thermochemical conversion of cattle manure (CM) to propose a sustainable platform for its valorization, and explored the applicability of CM-derived biochar (CMB) as an environmental medium for the adsorptive removal of sulfamethoxazole (SMZ). CM pyrolysis was conducted under two atmospheric conditions (N2 and CO2), and the pyrogenic products were quantified and characterized. Real-time syngas monitoring revealed that CO2 enhanced CO generation from the CM, leading to the formation of a highly porous carbon structure in the produced biochar (CMBCO2). The adsorptive removal of SMZ by CMBCO2 was highly dependent on the pH conditions. The adsorption kinetics of SMZ onto CMBCO2 reached equilibrium within 540 min, following a pseudo-second-order model. The SMZ adsorption isotherms fit the Langmuir-Freundlich model, highlighting the importance of chemisorption in the adsorption process. X-ray photoelectron spectroscopy revealed that SMZ was adsorbed by non-electrostatic mechanisms, including hydrogen bonding, Lewis acid-base interactions, surface complexation, and π-π electron-donor acceptor interactions. This study presents an exemplary strategy for converting livestock waste into valuable resources, enabling the harvesting of energy resources and the production of treatment media for environmental remediation.

Valorization of Agriculture Residues into Value-Added Products: A Comprehensive Review of Recent Studies

Global agricultural by-products usually go to waste, especially in developing countries where agricultural products are usually exported as raw products. Such waste streams, once converted to "value-added" products could be an additional source of revenue while simultaneously having positive impacts on the socio-economic well-being of local people. We highlight the utilization of thermochemical techniques to activate and convert agricultural waste streams such as rice and straw husk, coconut fiber, coffee wastes, and okara power wastes commonly found in the world into porous activated carbons and biofuels. Such activated carbons are suitable for various applications in environmental remediation, climate mitigation, energy storage, and conversions such as batteries and supercapacitors, in improving crop productivity and producing useful biofuels.

Comprehensive kinetic modeling and product distribution for pyrolysis of pulp and paper mill sludge

Pyrolysis holds immense potential for clean treatment of pulp and paper mill sludge (PPMS), enabling efficient energy and chemical recovery. However, current understanding of PPMS pyrolysis kinetics and product characteristics remains incomplete. This study conducted detailed modeling of pyrolysis kinetics for two typical PPMSs from a wastepaper pulp and paper mill, namely, deinking sludge (PPMS-DS) and sewage sludge (PPMS-SS), and analyzed comprehensively pyrolysis products. The results show that apparent activation energy of PPMS-DS (169.25-226.82 kJ/mol) and PPMS-SS (189.29-411.21 kJ/mol) pyrolysis undergoes significant change, with numerous parallel reactions present. A distributed activation energy model with dual logistic distributions proves to be suitable for modeling thermal decomposition kinetics of both PPMS-DS and PPMS-SS, with coefficient of determination >0.999 and relative root mean square error <1.99 %. High temperature promotes decomposition of solid organic materials in PPMS, and maximum tar yield for both PPMS-DS (53.90 wt%, daf) and PPMS-SS (56.48 wt%, daf) is achieved at around 500 °C. Higher levels of styrene (24.45 % for PPMS-DS and 14.71 % for PPMS-SS) and ethylbenzene (8.61 % for PPMS-DS and 8.33 % for PPMS-SS) are detected in tar and could be used as chemicals. This work shows great potential to propel development of PPMS pyrolysis technology, enabling green and sustainable production in pulp and paper industry.

Environment and agricultural practices regulate enhanced biochar-induced soil carbon pools and crop yield: A meta-analysis

Using biochar in agriculture to enhance soil carbon storage and productivity has been recognized as an effective means of carbon sequestration. However, the effects on crop yield and soil carbon and nitrogen can vary depending on environmental conditions, field management, and biochar conditions. Thus, we conducted a meta-analysis to identify the factors contributing to these inconsistencies. We found that biochar application significantly increased soil organic carbon (SOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidized carbon (EOC), particulate organic carbon (POC), total nitrogen (TN), and the C:N ratio in topsoil (0-20 cm) and crop yields. Biochar was most effective in tropical regions, increasing SOC, Soil TN, and crop yield the most, with relatively moderate pyrolysis temperatures (550-650 °C) more conducive to SOC accumulation and relatively low pyrolysis temperatures (<350 °C) more conducive to increasing soil carbon components and crop yields. Biochar made from manure effectively increased soil carbon components and TN. Soil with low fertility (original SOC < 5 g kg-1; original TN < 0.6 g kg-1), coarse texture, and acidity (pH < 5.5) showed more effective results. However, biochar application rates should not be too high and should be combined with appropriate nitrogen fertilizer. And biochar application had long-term positive effects on soil carbon storage and crop yield. Overall, we recommend using small amounts of biochar with lower pyrolysis temperatures in soils with low fertility, coarse texture, and tropical regions for optimal economic and environmental benefits.

Recent progress in the production and application of biochar and its composite in environmental biodegradation

Over the past few decades, extensive research has been conducted to develop cost-effective and high-quality biochar for environmental biodegradation purposes. Pyrolysis has emerged as a promising method for recovering biochar from biomass and waste materials. This study provides an overview of the current state-of-the-art biochar production technology, including the advancements and biochar applications in organic pollutants remediation, particularly wastewater treatment. Substantial progress has been made in biochar production through advanced thermochemical technologies. Moreover, the review underscores the importance of understanding the kinetics of pollutant degradation using biochar to maximize its synergies for potential environmental biodegradation. Finally, the study identifies the technological gaps and outlines future research advancements in biochar production and its applications for environmental biodegradation.

New insights into nitrogen control strategies in sewage sludge pyrolysis toward environmental and economic sustainability

Sewage sludge (SS) contains a certain amount of nitrogen (N), resulting in various content of N in the pyrolysis products. Investigates on how to control the generation of NH₃ and HCN (deleterious gas-N species) or convert it to N₂ and maximize transforming N in sewage sludge (SS-N) into potentially valuable N-containing products (such as char-N and/or liquid-N) are of great significance for SS management. Understanding the nitrogen migration and transformation (NMT) mechanisms in SS during the pyrolysis process is essential for investigating the aforementioned issues. Therefore, in this review, the N content and species in SS are summarized, and the influencing factors during the SS pyrolysis process (such as temperature, minerals, atmosphere, and heating rate) that affect NMT in char, gas, and liquid products are analyzed. Furthermore, N control strategies in SS pyrolysis products are proposed toward environmental and economic sustainability. Finally, the state-of-the-art of current research and future prospects are summarized, with a focus on the generation of value-added liquid-N and char-N products, while concurrently reducing NO_x emission.