A new analysis from the University of Sheffield and the Oxford Institute for Energy Studies warns that the UK’s residual municipal waste is becoming a contested climate resource, one that current policy frameworks risk allocating inefficiently.
The report finds that energy-from-waste with carbon capture and storage (EfW-CCS) delivers significantly higher and more durable climate benefits than producing sustainable aviation fuel (SAF) from the same waste streams.
Residual MSW, mostly biogenic material such as food, paper, and wood, can deliver up to −1,215 kg CO₂-eq per tone when processed through EfW-CCS, even without credits for displaced electricity or avoided landfill. The carbon benefit is driven by permanent geological storage of biogenic CO₂. Even in conservative scenarios, the pathway remains strongly net-negative.
By comparison, converting MSW into SAF achieves a best-case benefit of −700 kg CO₂-eq per tonne, the report shows, with most of the gains coming from avoided virgin plastic and metal production, plus displaced fossil Jet-A. Without landfill avoidance, the benefit falls to −334 kg CO₂-eq. SAF offers no carbon removal, and its performance depends heavily on avoided-burden credits that may shrink as the UK grid and materials supply chains decarbonize.
The divergence reflects the UK’s evolving policy landscape. EfW-CCS is supported through the £21.7 billion CCUS deployment program, with EfW projects shortlisted in the HyNet cluster. Meanwhile, the UK SAF mandate requires fuel suppliers to reach 22% SAF by 2040, increasing pressure on already limited waste-derived feedstocks.
Because the two pathways compete for the same finite waste resource, the authors argue that the UK lacks a coherent strategy for prioritizing waste allocation. While SAF supports transport decarbonization, its climate impact is fundamentally different from the durable negative emissions delivered by EfW-CCS, which the Climate Change Committee identifies as essential for net-zero pathways.
The study’s sensitivity analysis underscores the issue: EfW-CCS remains the climate-optimal use of waste at any biogenic carbon content above 5.1%, far below typical UK averages of 50–70%. This suggests EfW-CCS will remain the stronger mitigation option as recycling rates rise and waste streams become even more biogenic.
With both CCUS and SAF mandates accelerating simultaneously, the report warns that the UK may unintentionally divert waste from its highest-value climate use. Without integrated policy design, a resource intended to support long-term carbon removal could instead be absorbed into fuel supply chains offering only temporary emissions displacement.
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