Optimisation of biochar-based supply chains for negative emissions and resource savings in carbon management networks

Climate change is a global issue, and the main reason causing climate change is carbon dioxide (CO₂) emissions. Biochar, a stable form of carbon that can be obtained from pyrolysis of biomass, can potentially reduce CO₂ emissions. By applying biochar into soil, a stable form of carbon is stored under the soil. Biochar application is able to achieve negative emissions because the stored carbon was previously fixed from CO₂ via photosynthesis. Biochar application also brings additional benefits to soil as it helps to retain water and nutrients in soil. The benefits of biochar can be scaled up by developing biochar-based carbon management networks (CMNs). However, there are very limited decision support tools available for designing optimal biochar-based CMNs. This work presents a methodology to develop a decision support tool for biochar-based CMNs. Proposed methodology provides guidance on how a mixed-integer linear mathematical model can be formulated as a decision support tool to design biochar-based CMNs. The developed model has capabilities to determine the optimal network based on cost while considering several constraints. These constraints are CO₂ emission reduction, water and nutrient retention and several land constraints. The network costs considered are capital cost, operating cost, transportation cost and transport fuel consumption cost. The model also factors transport routes, hiring cost and truck capacity into the network. A case study based on the palm oil industry is solved to demonstrate the use of the model. Results from the case study show that total biochar production, water savings, nutrient savings, cost savings and total network costs were 307 t/day, 7.1 M m³ water/year, 6.0 k t nutrients/year, RM 25.6 M/year and RM 17.9 M/year, respectively. Besides that, a sensitivity analysis is done to analyse the impact of CO₂ emission reduction targets on the network costs. Aside from this, two alternative scenarios from the case study were investigated further.