Beyond biomass? Alternative fuels from renewable electricity and carbon recycling
Lower carbon fuels can deliver emission reductions during the transition to electrification and in the longer-term for applications like aviation that are more difficult to transition away from liquid fuels. This paper reviews some of the pathways being considered for recycled carbon fuels (RCFs) and renewable fuels of non-biological origin (RFONBOs), two categories of alternative fuels incentivized by the European Union’s recast Renewable Energy Directive (RED II). Specifically, for RCFs, it analyzes the climate impact of bacterial fermentation of carbon monoxide in industrial off gases and liquid fuels from plastic waste. For RFONBO, it analyzes the synthetic fuel from renewable electricity pathway. For both fuel types, there is evidence that not all pathways will deliver net climate benefits.
When analyzing the climate impact producing fuel from waste plastics, the emission of carbon that would otherwise be semi-permanently sequestered in landfill affects the climate impact of this pathway. If the carbon combusted when RCFs are used would not otherwise have been emitted into the atmosphere, then there is little scope to deliver net climate benefits.
Where other energy recovery services are displaced by RCF production, the picture is more complicated – there may be opportunities to improve inefficient systems, or to replace lost power generation with low greenhouse gas (GHG) intensity renewables. Lifecycle analysis tools should be used to assess the net climate benefits of adopting these new fuel production systems. Under the RED II, both RCFs and RFONBOs may be granted support by European Union Member States to encourage production, but the Directive does not yet contain lifecycle analysis requirements for either family of technologies.
The RED II calls for the European Commission to establish a minimum GHG saving threshold for RCFs. If displacement emissions and combustion emissions are properly included in the assessment, there will be lower uncertainty about the emissions from RCFs than those of biofuels, and no major emissions terms outside the system boundary.
For RFONBOs, the most important question regarding regulatory treatment is to define the electricity consumed as fully renewable. If net climate benefits are to be ensured, additional renewable electricity capacity should be developed, rather than simply claiming renewable power that would have already been generated.