Constraints on biomass energy deployment in mitigation pathways: the case of water scarcity

Abstract

To limit global warming to well below 2• most of the IPCC-WGIII future stringent mitigation pathways feature a massive global-scale deployment of negative emissions technologies (NETs) before the end of the century. The global-scale deployment of NETs like Biomass Energy with Carbon Capture and Storage (BECCS) can be hampered by climate constraints that are not taken into account by Integrated assessment models (IAMs) used to produce those pathways. Among the various climate constraints, water scarcity appears as a potential bottleneck for future land-based mitigation strategies and remains largely unexplored. Here, we assess climate constraints relative to water scarcity in response to the global deployment of BECCS. To this end, we confront results from an Earth system model (ESM) and an IAM under an array of 25 stringent mitigation pathways. These pathways are compatible with the Paris Agreement long-term temperature goal and with cumulative carbon emissions ranging from 230 Pg C and 300 Pg C from January 1st onwards. We show that all stylized mitigation pathways studied in this work limit warming below 2• C or even 1.5• C by 2100 but all exhibit a temperature overshoot exceeding 2• C after 2050. According to the IAM, a subset of 17 emission pathways are feasible when evaluated in terms of socio-economic and technological constraints. The ESM however shows that water scarcity would limit the deployment of BECCS in all the mitigation pathways assessed in this work. Our findings suggest that the evolution of the water resources under climate change can exert a significant constraint on BECCS deployment before 2050. In 2100, the BECCS water needs could represent more than 30% of the total precipitation in several regions like Europe or Asia.

The significance of biomass in a circular economy

“…This approach is helpful to recirculate nitrogen and phosphorus but also capture water for biomass production. The availability of water has been described as a "significant constraint" on supplying biomass for energy purposes (Séférian et al, 2018). Concerns about water use will only increase with growing demand for bio-based products and energy.…”

A Review of Criticisms of Integrated Assessment Models and Proposed Approaches to Address These, through the Lens of BECCS

“…IAMs could be "soft-linked" to other temporal and or/ spatially explicit approaches, e.g., for assessing water availability affecting biomass yields [105].…”

“…The final suggested approach ("supplement") would see IAMs used as part of a broader suite of approaches to understand the role of BECCS in low-carbon pathways. Such approaches include highly detailed regional and national land use models (building on [103]), expert elicitations and workshops to survey a range of views on the real-world feasibility and challenges of achieving different levels of BECCS [100] and earth system modelling to explore the planetary limits to BECCS [105,107]. This approach seems inherently more tractable than attempting to incorporate all nuances around BECCS into existing IAMs, given the computational and input assumption limitations already outlined.…”

Early Warning from Space for a Few Key Tipping Points in Physical, Biological, and Social-Ecological Systems

“…Biomass Energy with Carbon Capture and Storage (BECCS) may affect food production such as planting trees that compete for land and water resources with food production. In places where climate change causes water scarcity, it may limit the extent to which BECCS can be deployed to maintain carbon emission budgets (Séférian et al 2018). In turn, the water demand from BECCS is likely to cause declines in available water, thereby raising water scarcity and further constraining the deployment of BECCS-based mitigation (Séférian et al 2018).…”