Do net-zero plans add up? A framework and model to quantify risks of resource supply shortages in climate mitigation strategies

Abstract

Climate change is one of the greatest current threats to humanity and ecosystems. In response, governments and industries have developed net-zero plans to guide future investments and policy decisions, in which future demand for economic output is matched to the supply of emissions-free production. Most current plans assume that demand should grow without constraints, so depend primarily on technology innovations to substitute today’s activities with emissions-free alternatives, requiring little end-user involvement. However, the potential for such technologies is often overstated and disguised by burden-shifting. For example, plans may depend on synthetic fuels or biomass without accounting for their supply, or on use of negative emissions technologies without accounting for their land or energy requirements. The aggregated energy and resource demands of net-zero plans are not easily ascertained, and are often compared against overly optimistic projections of availability. Future supply expectations are biased by the dominant modelling approaches used today and by the limited consideration of the physical, social and political constraints on deployment rates. Without a comparison between aggregated resource demands and realistic supply availability, risks of supply shortages have not been clearly considered or articulated. This raises several critical questions:

How can independent net-zero plans from different industries be aggregated into a unified framework? Are current net-zero plans consistent with one another, or do their combined demands exceed probable availability? How can these plans be adjusted to reduce the risk of supply shortages?

This thesis addresses these questions by:

Developing a framework and model to aggregate the physical resource demands of net-zero plans; Comparing the aggregated demands of a broad selection of net-zero plans against probable future supply, based on credible deployment rates; and Providing a novel feasibility assessment, independent of potential biases in current modelling approaches.

Chapter 1 discusses the rationale behind existing net-zero plans, while chapter 2 reviews current modelling approaches. Chapters 3 and 4 introduce the novel framework and model developed in this thesis, which build on the realisation that all net-zero plans depend fundamentally on three Zero Emissions Resources (ZERs): emissions-free electricity, biomass and carbon storage. The model draws on a self-consistent dataset of resource flows of 170 processes - derived from an extensive literature search spanning academic reviews, lifecycle assessments, techno-economic analyses, policy documents and industry reports - documented in Appendix A. To provide a basis for comparison, evidenced expectations of probable future supply of the three ZERs are developed in Chapter 5, which consider historic data, industry projections, and current trends. Chapter 6 contrasts these trajectories of probable maximum supply against aggregated future demand to reveal significant risks of supply shortages. Dominant approaches to climate mitigation are shown to require an improbable expansion of the fundamental resources in the required timescales. These risks could lead to mitigation failure, shortages in vital services, such as heating and cooling, and increased global inequality. Applying the model in reverse, however, shows that alternative mitigation approaches, which focus on reducing overall demands, offer a plausible pathway for climate mitigation. This reveals many overlooked opportunities for innovations in policy, planning, service models, resource efficiency, service sufficiency and financing. The primary contribution of this thesis is the quantification of supply and demand of ‘Zero Emission Resources’ (ZERs) in net-zero plans. Key outputs include: • The ZERs model and framework; • A comprehensive dataset of resource flows for key net-zero (and conventional) technologies and processes; and • A demonstration of the model, which shows that existing net-zero plans would be at high risk of ZERs supply shortages. The model provides a strong foundation on which to base future analyses, including alternative model input assumptions and estimates of ZER supply.