Harnessing plant agriculture to mitigate climate change: A framework to evaluate synthetic biology (and other) interventions.

Plant agriculture contributes substantially to global greenhouse gas emissions, yet it also offers powerful opportunities for climate change mitigation. Here, we focus on how to identify and prioritize synthetic biology strategies to reduce emissions and sequester carbon through plant-based interventions. Effective solutions must process large volumes of carbon, be scalable, yield a positive life-cycle balance, and be economically viable, technically feasible, and deployable in field conditions without undue damage to what remains of nature on Earth. Using Fermi estimation, we quantify the per-hectare, annual, and 100-year CO2-equivalent (CO2e) drawdown potential of emerging synthetic biology strategies-including improved CO2 fixation, reduced yield losses, root-deposited biopolymers, engineered nitrogen fixation, and methane reduction-and benchmark them against nonengineered approaches such as biochar, forestation, and fast-growing biomass crops. We used a 100-year horizon to allow for both development and implementation of high-risk but high-impact synthetic biology strategies. We integrate factors such as per-hectare effectiveness, year-on-year sequestration, deployment area, and storage durability. We demonstrate that while per-hectare impacts vary by orders of magnitude (<1 to >30 t CO2e/ha/year), deployment scale is the dominant factor determining total impact. Targeted synthetic biology strategies implemented across existing agricultural systems could deliver ∼120 Gt CO2e drawdown over a century and contribute to an additional ∼140 Gt CO2e drawdown. Decreasing synthetic nitrogen fertilizer use and biochar implementation have the biggest CO2e impact potential. Early-stage quantitative evaluation is critical to guide R&D toward climate-relevant solutions and deliver a prioritized portfolio of near- and long-term strategies. A transdisciplinary approach-linking synthetic biology, agronomy, engineering, and social systems-is essential to realize impact. This work offers a framework for evaluating plant agriculture-based climate mitigation strategies and highlights a key role for synthetic biology in mitigation pathways. Regular re-evaluation of strategies should be performed to ensure that they are meaningful for climate change mitigation as other factors evolve.