BiocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More has gained significant attention for its potential to improve soil quality and combat climate change by acting as a long-term carbon sink. This versatile material also offers benefits such as enhanced nutrient and water retention in soil, increased soil microbial activity, and various industrial applications like air filtration and energy storage. As biochar is produced through the valorization of organic waste, it also aligns with circular economy strategies, enhancing the value of by-products.

A recent study by Goldaraz, Baima, Moles, Sierra-Pérez, Martínez, Murillo, Brun, and Blanc, published in Bioresource Technology (2025), addresses a critical gap in research by comprehensively evaluating the environmental and economic feasibility of biochar production via sorption-enhanced gasificationGasification is a high-temperature, thermochemical process that converts carbon-based materials into a gaseous fuel called syngas and solid by-products. It takes place in an oxygen-deficient environment at temperatures typically above 750°C. Unlike combustion, which fully burns material to produce heat and carbon dioxide (CO2​), gasification More (SEG). The researchers focused on two distinct feedstocks: sewage sludge and grape seeds, representing nutrient-rich municipal waste and lignocellulosic agricultural residues, respectively. Spain, being the country with the largest vineyard surface globally, produces a substantial amount of grape by-products suitable for biochar production. While sewage sludge is currently used as an agricultural fertilizer, its direct application carries risks of soil contamination from hazardous substances like viruses and heavy metals; converting it into biochar eliminates these contaminants, resulting in a safer material for soil improvement.

The study employed a rigorous methodology, utilizing both Life Cycle Assessment (LCA) to evaluate environmental impacts and Life Cycle Costing (LCC) to assess economic viability. The analysis was conducted on a pilot-scale SEG plant, a promising technology that not only converts organic biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More into biochar but also produces synthesis gas (syngasSyngas, or synthesis gas, is a fuel gas mixture consisting primarily of hydrogen and carbon monoxide. It is produced during gasification and can be used as a fuel source or as a feedstock for producing other chemicals and fuels.   More) that can be used as fuel. SEG utilizes a CO2 sorbent, typically calcined limestone, which reacts with the CO2 produced during gasification, driving the process towards hydrogen production and improving biochar quality by increasing its carbon content.

The results unequivocally demonstrate that grape seeds are a more favorable feedstockFeedstock refers to the raw organic material used to produce biochar. This can include a wide range of materials, such as wood chips, agricultural residues, and animal manure. More for biochar production than sewage sludge from both environmental and economic perspectives. For every kilogram of biochar produced, grape seeds yield lower environmental impacts across most categories. Specifically, biochar from grape seeds results in global warming potential (GWP) emissions of 11.0 kg CO2 equivalent, significantly less than the 17.8 kg CO2 equivalent from sewage sludge. The majority of these impacts, for both feedstocks, are attributed to the substantial energy consumption required by the gasification process. The higher energy intensity of the sewage sludge biochar production leads to greater environmental impacts. Although syngas production from grape seeds has a higher impact due to its larger yield, the increased displacement benefits from this syngas help offset more of the overall impacts. Additionally, the carbon sequestration achieved by the biochar further mitigates carbon emissions.

Economically, grape seeds also prove to be more advantageous, yielding a higher profit of €0.94 per kilogram of biochar compared to €0.82 per kilogram for sewage sludge. This is largely due to the significantly higher yield of biochar from grape seeds. The Break-Even Point (BEP) analysis further supported this, showing that grape seeds achieved cost/revenue equivalence with slightly lower quantities of biochar (24,517 kg of biochar and 116,456 m³ of syngas for grape seeds versus 33,733 kg of biochar and 63,082 m³ of syngas for sewage sludge).

The study also delved into the sensitivity of profitability to energy price fluctuations. While both systems are affected by energy costs, the analysis revealed that the profitability of biochar production from sewage sludge is more volatile and susceptible to these fluctuations than that from grape seeds. The elasticity of biochar profit with respect to electricity price for sewage sludge ranged from 0.06 to 0.19, while for grape seeds, it ranged from 0.03 to 0.09, indicating greater resilience for grape seed-based production.

Despite the promising outcomes, the study acknowledges that the current biochar industry faces challenges related to scalability and market demand, with a volatile market and fluctuating prices. However, the valorization of waste products within a circular economy framework is expected to drive growth in this sector by reducing raw material costs. Future research should focus on optimizing energy consumption, exploring alternative feedstocks, and thoroughly assessing the long-term benefits of biochar.

Source: Goldaraz, N., Baima, L., Moles, S., Sierra-Pérez, J., Martínez, I., Murillo, R., Brun, F., & Blanc, S. (2025). Opportunities for biomass valorisation through sorption-enhanced gasification: assessing environmental and economic aspects on biochar production. Bioresource Technology.