Life cycle assessment of urban uses of biochar and case study in Uppsala, Sweden

Abstract

Biochar is a material derived from biomass pyrolysis that is used in urban applications. The environmental impacts of new biochar products have however not been assessed. Here, the life cycle assessments of 5 biochar products (tree planting, green roofs, landscaping soil, charcrete, and biofilm carrier) were performed for 7 biochar supply-chains in 2 energy contexts. The biochar products were benchmarked against reference products and oxidative use of biochar for steel production. Biochar demand was then estimated, using dynamic material flow analysis, for a new city district in Uppsala, Sweden. In a decarbonised energy system and with high biochar stability, all biochar products showed better climate performance than the reference products, and most applications outperformed biomass use for decarbonising steel production. The climate benefits of using biochar ranged from − 1.4 to − 0.11 tonne CO2-eq tonne−1 biochar in a decarbonised energy system. In other environmental impact categories, biochar products had either higher or lower impacts than the reference products, depending on biochar supply chain and material substituted, with trade-offs between sectors and impact categories. However, several use-phase effects of biochar were not included in the assessment due to knowledge limitations. In Uppsala’s new district, estimated biochar demand was around 1700 m3 year−1 during the 25 years of construction. By 2100, 23% of this biochar accumulated in landfill, raising questions about end-of-life management of biochar-containing products. Overall, in a post-fossil economy, biochar can be a carbon dioxide removal technology with benefits, but biochar applications must be designed to maximise co-benefits.

Biochar-biofertilizer combinations enhance growth and nutrient uptake in silver maple grown in an urban soil

“…Biochar, a charcoal soil amendment created by pyrolysis of organic material at low oxygen levels, has recently been promoted for use in urban forestry [ 10 , 11 ]. Biochar’s benefits include its resistance to decomposition, resulting in stable and long-lived carbon capture, provision and retention of plant nutrients, liming or stabilization of soil pH, increased soil microbial activity, enhanced moisture retention and availability, and immobilization of toxic substances such as heavy metals [ 12 , 13 ].…”

Life Cycle Assessment of a Wood Biomass Gasification Plant and Implications for Syngas and Biochar Utilization

“…Life cycle assessment (LCA) is among the most inclusive analytical techniques to analyze sustainability benefits and trade-offs resulting from complex systems [43]. Given that biomass gasification stands as a possible, promising strategy to increase the renewable energy fraction within national energy systems [44], LCA has been previously employed to evaluate the resulting environmental implications [45][46][47], including the valorization of biomass-derived syngas [48], the production of biochar and its UOL [49][50][51][52][53], and general biomass conversion [52,53]. Notwithstanding these research efforts, the number of studies addressing more complex systems involving biomass valorization through gasification for syngas production and its further combustion for the generation of electrical and thermal energy remain little investigated.…”

Synthesis optimization and adsorption modeling of biochar for pollutant removal via machine learning

“…Taking the raw material source, carbon content, oxygen concentration, process temperature and other variables related to synthesis process as the inputs of model training, the mapping relationship between the synthetic conditions and the physicochemical properties of biochar adsorbents can be quickly constructed. In addition, in the industrialization of biochar, life cycle and economy must be considered (Azzi et al 2022;Zhu et al 2022c). By employing machine learning, the life cycle and economic costs of different types of biochar can be effectively evaluated.…”