Incorporating Co-Benefits into Enhanced Weathering LCA and TEAs — a Q&A with YSE Associate Professor Yuan Yao

Last month, YCNCC Scientific Leadership Team member and Yale School of the Environment (YSE) Associate Professor Yuan Yao authored a peer-reviewed article in Environmental Sustainability & Technology on “Analyzing Co-Benefits and Rock Sourcing in Life Cycle and Techno-Economic Assessment of Enhanced Rock Weathering.” Co-authors included YSE and Center for Industrial Ecology Graduate Researcher Jennifer Kroeger, Postdoctoral Associate Bingquan Zhang, and YCNCC Scientific Leadership Team member and Earth & Planetary Sciences Professor Noah Planavsky.  

YCNCC Science Communications Fellow Samantha Tracy sat down with Yao to discuss the rationale for this research and how it is important for the Center’s efforts to advance, implement, and scale natural solutions for climate mitigation.

YCNCC: To get us started, can you briefly explain the difference between life cycle assessment (LCA) and techno-economic assessment (TEA), and why they’re important to the implementation and scaling of carbon dioxide removal (CDR)?

YY:  LCA evaluates a product’s environmental performance, whereas TEA evaluates technical and economic performance. LCA is a quantitative method to analyze environmental impacts across a product or service’s life cycle. This includes all components of raw material extraction, manufacturing, transportation, use, and end-of-life . TEA is a different tool to evaluate the technical performance and economic feasibility of a new technology or project. LCA is important for CDR implementation and scaling as many monitoring, reporting, and verification (MRV) protocols rely on LCA methodology and data to perform carbon accounting and quantify GHG emissions.  We have published a study that provides detailed discussions of how LCA has been used in MRV protocols for CDR. LCA also provides helpful quantifications of other potential ecotoxicity or human health impacts that may be unintended consequences of CDR implementation.  TEA is particularly important for scaling as it can be used to improve the economical feasibility of CDR by allowing us to identify main cost drivers and understand the impacts of key process factors and locations at different scales prior to implementation. 

YCNCC: Enhanced weathering (EW) is a major research focus for the Center. What co-benefits does EW offer, and why is it important to factor them into LCA and TEAs? 

YY:  One of the potentially significant co-benefits of EW is reducing fertilizer usage. EW can also increase nitrogen use efficiency and can decrease land nitrous oxide (N₂O) emissions. Currently, there are limited quantitative methodologies to integrate  EW co-benefits into environmental and cost assessment. The lack of co-benefit assessment is a critical gap in previous LCA studies and MRV of land-based CDR. To fully assess EW and other CDR technologies it is critical that we assess and evaluate the role of co-benefits to determine their significance. Our analysis found that  incorporating co-benefits, specifically fertilizer and N₂O reduction, in our U.S. case study can make a significant impact on  the reduction of both environmental impacts and cost of EW. There is a continued need for field experiments and data collection to further evaluate and assess co-benefits. Our analysis can help identify future priorities. In our paper, we have also provided quantitative methods to aid in future co-benefit assessment.

YCNCC: How do you see this research being applied in carbon markets and public policy?

YY:  So far, the research tells us that co-benefits can play a significant role in environmental impact and cost for EW. This provides further evidence to motivate people to consider co-benefits when looking at CDR and offers a methodology to incorporate co-benefits into CDR project assessment, while also providing  a quantitative pathway for carbon markets and policies to incorporate co-benefits. We can see how different co-benefits may affect the costs and environmental performances of CDR, and can prioritize efforts that emphasize co-benefits with significant impacts on the overall CDR performances. Assessing and valuing co-benefits is also critical to draw policymakers and practitioners together to discuss other environmental benefits that may be related to CDR or EW projects.

YCNCC: Do you have plans to continue this work? Tell us about your next steps. 

YY: In our next paper, we are hoping to look more into the impacts on LCA and TEA of crop yield increases, another potential co-benefits of EW. We are also hoping to look more into how various CDR solutions can be integrated with existing industrial infrastructure –for example, assessing  different mineral sources or using waste minerals from retired mines, which could reduce both environmental impact and cost. In practice and training, I’m an industrial ecologist, which means I study energy and material flows, and associated environmental impacts, while considering  how social, political  and economic factors  influence material usage and transformation. In the future, I aim to combine these interests with CDR to assess how CDR scaling and implementation can persist within existing infrastructure, resulting in lower costs and potential co-benefits to those industries. 

YCNCC: Any last thoughts?

YY: This paper takes an interesting interdisciplinary angle, using combined knowledge from industrial ecologists and geochemists, and incorporating agronomic inputs. Fostering these collaborations is important as we continue to model additional impacts and assess future efforts to implement and scale CDR.