Decarbonisation Technology February 2026 Issue

a transport fuel, stopping carbon accounting at combustion and overlooking its industrial decarbonisation value. This article uses the DBCOM to evaluate the integration of fuel-cycle emissions with physically measurable refinery utility displacement. By capturing this dual effect, DBCOM reveals why refinery-integrated 2G ethanol delivers substantially greater decarbonisation impact than conventional fuel-centric assessments suggest, positioning it as a practical, near-term refinery decarbonisation instrument rather than a marginal biofuel upgrade. 1G and 2G ethanol: two distinct carbon logics 1G and 2G ethanol deliver the same molecule, but they operate under fundamentally different carbon logics. 1G ethanol reduces emissions primarily through biogenic substitution in transport fuels. While commercially mature, it faces structural constraints related to land, water, fertiliser use, and indirect land-use change, resulting in a practical decarbonisation ceiling typically around 35-45 g CO₂e/MJ. 2G ethanol represents a categorical shift rather than a technological extension. Produced from lignocellulosic residues, it avoids food-system trade-offs and achieves lower standalone lifecycle carbon intensity, typically 18-25 g CO₂e/MJ. Carbon intensity ranges and residue allocation treatment, including associated agronomic emissions, are pathway dependent and synthesised from publicly available lifecycle assessment frameworks such as GREET, EU RED II/III, and IEA Bioenergy Task 39, reflecting variation in feedstock type, ethanol production pathway, allocation methodology, and regional conditions ( Argonne National Lab, 2025 ) ( European Commission, 2024 ) ( IEA Bioenergy, 2024 ). These lifecycle values reflect established regulatory treatment of lignocellulosic residues, where upstream agronomic emissions are allocated primarily to the main agricultural product rather than the residue itself. Agricultural residues are therefore not treated as burden-free, but carry limited upstream emissions associated mainly with collection, processing, and transport ( IEA, 2023 ). The carbon intensity ranges already incorporate

upstream residue-related emissions as treated under prevailing lifecycle accounting conventions. Crucially, 2G ethanol generates renewable steam and electricity from its lignin fraction, enabling active displacement of fossil industrial energy – an attribute absent in 1G pathways. Why systems-level economics matter: beyond the silo 2G ethanol has been consistently undervalued, not because of technical limitations, but due to analytical boundary choice. Conventional techno-economic and lifecycle assessments evaluate ethanol largely within the biorefinery fence line, overlooking its interaction with energy-intensive industrial systems. In most medium-to-large refineries, 15-25% of direct CO₂ emissions originate from fossil-fired utility generation, making steam displacement a first- order decarbonisation lever. When 2G ethanol is co-located with refineries, lignin-derived steam and power directly displace these fossil utilities, reducing fuel consumption, operating cost, and carbon exposure. Capturing this interaction requires expanding evaluation beyond transport fuels to include industrial energy systems, revealing why refinery-integrated 2G ethanol functions not as a marginal biofuel upgrade, but as a dual-purpose industrial decarbonisation lever. Mass and energy dynamics: the technical foundation of 2G integration The lignin stream is the hidden engine of refinery-integrated decarbonisation. During 2G ethanol processing, lignin-rich residues are combusted in high-efficiency boilers, generating export-grade energy. A typical 100 m³/day plant produces ~40 MWth of thermal energy, 10-18 t/h of renewable steam, and 1.5-2.5 MW of electricity, closely matching refinery utility demand. Although CO₂ is released during fermentation and lignin combustion, these biogenic emissions originate from atmospheric carbon. Their high purity also enables low- cost capture, creating pathways toward net- negative fuels. Biomass supply and logistics: from constraint to strategic enabler Modern biomass supply chains have evolved