Land Use Pinch Analysis of Carbon Dioxide Removal Portfolios

Negative emissions technologies (NETs) will be needed to achieve net zero emissions by midcentury. NETs can deliver supplementary carbon dioxide removal (CDR) to offset residual greenhouse gas (GHG) emissions from economic sectors that are intrinsically difficult to decarbonize with existing technologies. NETs include nature-based techniques such as afforestation and soil carbon sequestration, as well as engineered solutions such as direct air capture and bioenergy with carbon capture and storage. Both classes of NETs have the potential to deliver large-scale CDR in the coming decades. However, deployment of NETs will be constrained by their own resource requirements. For example, many nature-based NETs require substantial land area, which may compete with other uses. Investment in NETs for climate change mitigation will thus require a careful analysis of the trade-offs between their costs and benefits. In this work, we propose a land use pinch analysis (LUPA) approach to determining NET portfolios when faced with land constraints. The work extends the time-tested pinch analysis technique from chemical engineering literature to a problem of contemporary interest. LUPA is then demonstrated using five representative scenarios which illustrate the practical implications of balancing CDR goals with land availability. If biochar requires dedicated land, direct air carbon capture and storage (DACCS) consistently has the lowest land footprint per unit of CDR, ranging from 0.000 to 0.077 ha/tCO2eq across all scenarios. If biochar land use is shared, it has the lowest footprint in the worst-case scenarios (0.035 ha/tCO2eq). However, in the base-case and best-case scenario with advanced technology, DACCS outperforms biochar, achieving a near-zero land footprint compared to biochar’s minimum of 0.010 ha/tCO2eq. These examples highlight the usefulness of LUPA as a tool for planning land-constrained commercial-scale CDR.