Assessing biomass carbon dioxide removal supply chains: System modelling and economic assessment

Pyrolytic conversion of biomass is used to produce biochar—a stable form of solid carbon storage that is becoming an effective carbon dioxide removal method—and to produce sustainable liquid hydrocarbons that can contribute to sustainable shipping and aviation. This study aims to assess the economics of biochar carbon removal (BCR) across the entire supply chain. A mixed-integer nonlinear programming model is developed to determine the optimal carbon credit, a break-even carbon dioxide removal outcome at which a BCR system achieves a zero net present value. The model is applied to two case studies using available paper sludge and sewage sludge from 32 European countries, where biomass is converted into biochar and biofuel using the thermo-catalytic reforming process. Our results show that the necessary carbon credits are lowest under the partial aggregation of biomass and optimally located conversion plants, compared to fully centralized or decentralized approaches. The results of the optimization model for two case studies reveal that, with a carbon credit of 106 €/t-CO 2 , all plants utilizing paper sludge could operate cost-effectively, with most remaining economically viable even without carbon credit incentives. In contrast, BCR systems based on sewage sludge exhibit significantly lower profitability; over 90 % of plants require carbon credit to remain economically viable, and more than half need carbon credits at prices exceeding 150 €/t-CO 2 . • The economics of BCR are influenced by the costs of the biomass conversion process. • They also vary by the type of biomass, its abundance and geographic distribution. • Optimal location and scale of conversion plants allow for maximum cost efficiency. • With a carbon credit of 106 €/t-CO 2 , all paper sludge plants become cost-effective. • Over 90 % of sewage sludge plants need carbon credit above 150 €/t-CO 2 to stay viable.