Agriculture and forestry residues are potential sources of sustainable energy that do not compete with food or demand land use changes. Small-scale biomass gasification could be used to generate decentralized renewable electricity where these biomass stocks are locally available, while co-producing biochar to sequester carbon. This study evaluated how the scale and the syngas-biochar trade-offs impact the economics and decarbonization potential of a gasification system. A small-scale downdraft gasifier fed with logging residues in Michigan was used as case study. A Life Cycle Assessment (LCA) approach was used to formulate Economic Benefit (EB) and Carbon Abatement (CA) objective functions that formed a Multi Criteria Decision Analysis (MCDA) problem. Feasible product mix and scale configurations were mapped, and a pareto frontier was identified. EB is maximized when the electricity generation and the scale are maximized, at expense of emitting 1.683 kg CO2eq/kWh. Conversely, CA is maximized to 0.348 kg CO2eq abated per kWh for the highest biochar production and the smallest scale. Results were found to be sensitive to external factors: EB optimum shifted to maximize biochar when the carbon price was increased from 5 $/ton CO2eq to match the social cost of carbon (50 $/ton CO2eq) and 2030 projections (100 $/ton CO2eq), CA increased 112.0% when grid electricity emissions were increased from 0.48 kg CO2eq/kWh (Michigan’s) to 0.87 kg CO2eq/kWh (West Virignia’s), and EB reached 0.147 $/kWh when a high electricity price of 33 ¢/kWh (Hawaii’s) is considered instead of Michigan’s 13 ¢/kWh. For different stakeholders and contexts, the maximization of positive impacts can require different technology configurations. The developed LCA-MCDA combined methodology provides an example of a framework that could inform decision-making in the deployment of biomass gasification to reconcile economic and climate change mitigation objectives.