The escalating climate crisis and unsustainable waste management practices necessitate integrated approaches that simultaneously address energy security and environmental degradation. Hydrogen, with its high energy density and zero-carbon combustion, is a key vector for decarbonization; however, conventional production methods are fossil-dependent and carbon-intensive. This systematic review explores biowaste-to-hydrogen (WtH) technologies as dual-purpose solutions, converting organic waste to clean hydrogen while reducing greenhouse gas emissions and landfill reliance. A comprehensive analysis of different conversion pathways, including thermochemical (gasification, pyrolysis, hydrothermal, and partial oxidation (POX)), biochemical (dark fermentation, photofermentation, and sequential fermentation), and electrochemical methods (MECs), is presented, assessing their hydrogen yields, feedstock compatibilities, environmental impacts, and technological readiness. Systematic literature review methods were employed using databases, such as Scopus and Web of Science, with strict inclusion criteria focused on recent peer-reviewed studies. This review highlights hydrothermal gasification and dark fermentation as particularly promising for wet biowaste streams, like food waste. Comparative environmental analyses reveal that bio-based hydrogen pathways offer significantly lower greenhouse gas emissions, energy use, and pollutant outputs than conventional methods. Future research directions emphasize process integration, catalyst development, and lifecycle assessment. The findings aim to inform technology selection, policymaking, and strategic investment in circular, low-carbon hydrogen production.

Environmental restoration and sustainable energy solutions require effective management and utilization of agricultural crop residues to reduce greenhouse gas emissions. Biowastes are a valuable resource that can be converted into biofuels and their byproducts, solving the energy crisis and reducing environmental impact. In this study, teff husk, primarily generated in Ethiopia during the production of teff within the agro-industrial sector, is used as a feedstock for slow pyrolysis. Ethiopia generates an estimated annual production of over 1.75 million tons of teff husk, a significant portion of which is incinerated, resulting in significant pollution of the environment. This study focuses on assessing teff husk as a potential material for slow pyrolysis, a crucial stage in biochar production, to tap into its biochar-producing potential. To identify the composition of biomass, the teff husk underwent an initial analysis using thermogravimetry. The significant presence of fixed carbon indicates that teff husk is a viable candidate for pyrolytic conversion into biochar particles. The process of slow pyrolysis took place at three temperatures—specifically, 400, 450, and 500 °C. The maximum biochar yield was achieved by optimizing slow pyrolysis parameters including reaction time, temperature, and heating rate. The optimized reaction time, temperature, and heating rate of 120 min, 400 °C, and 4.2 °C/min, respectively, resulted in the highest biochar yield of 43.4 wt.%. Furthermore, biochar’s physicochemical, SEM-EDX, FTIR, and TGA characterization were performed. As the temperature of biochar increases, its carbon content and thermal stability increases as well. Unlike fuel recovery, the results suggest that teff-husk can be used as a feedstock for biochar production.

In the drive towards environmental restoration and sustainable energy solutions, effective utilization and management of agricultural crop residues are vital to mitigate greenhouse gas (GHG) emissions and waste accumulation. Converting biogenic wastes into biofuels and bioproducts has the potential to tackle the energy crisis and contribute to environmental remediation. In this investigation, teff husk, primarily generated in Ethiopia during teff production within the agro-industrial sector, is used as the feedstock for the slow pyrolysis process. In Ethiopia, it is estimated that over 1.75 million tons of teff husk are generated annually, with a significant portion being incinerated in the fields, resulting in substantial environmental pollution. This study focuses on assessing teff husk as a potential material for slow pyrolysis, a crucial stage in biochar production, to tap into its biochar-producing potential. To determine the composition of the biomass, the teff-husk was initially analyzed by thermogravimetry. The significant presence of fixed carbon indicates that teff husk is a viable candidate for pyrolytic conversion into biochar particles. The process of slow pyrolysis took place at three varied temperatures—specifically, at 400, 450, and 500 °C. Process parameters of slow pyrolysis such as reaction time, temperature, and heating rate were enhanced to obtain maximum biochar yields. The highest biochar yield of 43.4 wt% was recorded at optimized reaction time, temperature, and heating rate of 120 min, 400 °C, and 4.2 °C/min, respectively. Furthermore, biochar's physicochemical, SEM-EDX, FTIR, and TGA characterization were performed. The thermal stability and carbon content of biochar were found to rise at higher temperatures. Unlike fuel recovery, the results suggest that teff-husk can be used as a feedstock for biochar production.

The rising demand for low-carbon hydrogen has intensified interest in biogas-reforming as a renewable, decentralized alternative to fossil-based production. However, published assessments of the competing reforming routes rely on inconsistent system boundaries and assumptions, which prevents a reliable comparison between them. This study addresses that gap by evaluating four biogas-reforming pathways, steam reforming (SR), dry reforming (DR), partial oxidation (POX), and autothermal reforming (ATR), within a single, consistent techno-economic and environmental assessment framework. Thermodynamic performance, life-cycle global warming potential, and the levelized cost of hydrogen (LCOH) are analyzed together, with cost uncertainty quantified through a 10,000-iteration Monte Carlo simulation and a six-parameter sensitivity analysis. The harmonized comparison shows that steam reforming is simultaneously the most favorable route for hydrogen yield, energy efficiency, levelized cost, and life-cycle carbon intensity, establishing it as the benchmark, whereas dry reforming, although it uniquely consumes CO₂, incurs the highest cost and the greatest catalyst-deactivation risk. Across all pathways, plant scale and capacity factor emerge as the dominant cost drivers, and biogas-derived hydrogen remains more expensive than conventional gray hydrogen, so its deployment depends on impurity-tolerant catalysts, improved heat integration, life-cycle-verified CO₂ management, and supportive low-carbon incentives. The novelty of this work lies in its unified, multi-criteria framework, which enables a like-for-like ranking of biogas-reforming routes and clarifies the conditions under which each becomes competitive.

The escalating global waste crisis necessitates sustainable valorization strategies, with biochar production emerging as a promising solution for converting organic residues into a carbon-rich material. This study evaluated biochar derived from corncob and khat waste pyrolyzed using allo-thermal and auto-thermal multi-purpose stoves. Biochar was fractionated into four particle sizes (>2 mm, 1–2 mm, 0.6–1 mm, and <0.6 mm) and characterized for ash content, pH, and electrical conductivity (EC). Results demonstrated that the auto-thermal stove, operating at higher temperatures (up to 800 °C), consistently produced biochar with greater ash content (khat: 12–19%; corncob: 11–14%), alkaline pH (9.2–10.0), and significantly higher EC compared to the allo-thermal stove (maximum 350 °C). EC values ranged from 0.38 mS/cm (coarse allo-thermal corncob) to 6.6 mS/cm (fine auto-thermal khat), with auto-thermal biochar exhibiting EC values 5–10 times higher than their allo-thermal counterparts. khat waste consistently yielded biochar with higher ash content, pH, and EC than corncob, reflecting its richer mineral composition. Particle size fractionation revealed that pH and EC increased progressively with decreasing particle size across all treatments, with the finest fraction (2 mm) to 6.6 mS/cm (<0.6 mm). This study demonstrates that decentralized biochar production using multi-purpose stoves can yield materials with tunable properties, and that khat waste—an underutilized regional resource—shows particular promise for producing high-ash, high-EC biochar suitable for acidic soil amendment.