The energy return on investment of BECCS: is BECCS a threat to energy security?

Compliance with long term climate targets whilst maintaining energy security is understood to rely heavily on the large-scale deployment of negative emissions technologies (NETs). One option, Bioenergy with Carbon Capture and Storage (BECCS), is prominent in Integrated Assessment Models (IAMs), with projected annual contributions of 8-16.5 Gt CO 2 per year of atmospheric carbon dioxide removal whilst contributing 150-300 EJ per year, or 14 to 20% of global primary energy supply, in 2100. Implicit in these scenarios is the assumption that BECCS is a net producer of energy. However, relatively energy intensive biomass supply chains and low power generation efficiency could challenge this ubiquitous assumption. Deploying an energy negative technology at this scale could thus represent a threat to energy security. In this contribution, we evaluate the energy return on investment (EROI) of an archetypal BECCS facility. In order to highlight the importance of biomass sourcing, two feedstock scenarios are considered: use of domestic biomass pellets (UK) and import of biomass pellets from Louisiana, USA. We use the Modelling and Optimisation of Negative Emissions Technologies (MONET) framework to explicitly account for growing, pre-treating, transporting and converting the feedstock in a 500 MW BECCS facility. As an example, we illustrate how the net electricity balance (NE l B) of a UK-based BECCS facility can be either positive or negative, as a function of supply chain decisions. Power plant efficiency, fuel efficiency for transport, transport distance, moisture content, drying method, as well as yield were identified as key factors that need to be carefully managed to maximise BECCS net electricity balance. A key insight of this contribution is that, given an annual carbon removal target, increasing BECCS' power generation efficiency by using a more advanced biomass conversion and CO 2 capture technology could improve BECCS net electricity balance, but at the cost of increasing the amount of BECCS capacity required to meet this target. BECCS optimal deployment pathway is thus heavily dependent on which service provided by BECCS is most valued: carbon dioxide removal or power generation. Energy intensive supply chains and low power generation efficiency could challenge the ubiquitous assumption that BECCS is a net provider of electricity. Deploying a net negative energy technology at the EJ scale could represent a threat to energy security.