Decarbonisation Technology February 2026 Issue

Simplified DBCOM formulation

To express the dual-boundary effect in a practical form, DBCOM can be represented through a simplified carbon intensity adjustment: Carbon Intensity (adjusted) = Carbon Intensity (fuel) − Steam Benefit − Power Benefit Where: Carbon Intensity (fuel) represents the standalone lifecycle carbon intensity of 2G ethanol. Steam Benefit represents avoided refinery emissions from lignin-derived steam displacing fossil- fired boilers. Power Benefit represents avoided grid emissions from surplus electricity exported from the biorefinery.

Dual-Boundary Carbon Optimisation Model Conventional lifecycle carbon accounting evaluates ethanol primarily as a transport fuel, tracking emissions from production through final use and typically terminating the analysis at fuel combustion. While effective for comparing fuels, this approach excludes emissions dynamics within energy-intensive industrial systems, particularly refinery utilities, thereby capturing only fuel-side carbon intensity improvements while leaving system-level decarbonisation effects invisible. The DBCOM addresses this limitation by expanding the system boundary. It simultaneously accounts for (i) the lifecycle carbon intensity of 2G ethanol as a fuel and (ii) avoided refinery emissions achieved when lignin-derived steam and power displace fossil-based utilities. In addition to utility displacement, the expanded boundary also includes biogenic CO₂ released during ethanol fermentation and lignin combustion. Consistent with prevailing lifecycle accounting conventions, these biogenic emissions are treated as carbon-neutral at the system level due to prior atmospheric uptake during biomass growth and therefore do not contribute additional fossil carbon intensity. However, they represent physically measurable CO₂ streams. Fermentation CO₂ is typically high-purity and well-suited for low-cost capture, while lignin combustion CO₂ is more dilute but technically capturable using conventional post-combustion systems. Refineries that already operate, or are evaluating, pre- or post-combustion carbon capture could therefore realise incremental emissions reductions beyond those quantified in this study. While such carbon capture

opportunities are not required for DBCOM’s core conclusions, which focus on utility displacement within existing refinery configurations, they indicate a credible pathway toward further emissions reduction or net-negative outcomes where capture infrastructure is available. DBCOM therefore complements, rather than replaces, conventional lifecycle analysis. It retains established fuel-cycle metrics while adding an industrial boundary that reflects physically measurable emissions avoidance within refinery operations – an effect historically overlooked because it sits between fuel-centric lifecycle analysis and asset-level refinery decarbonisation studies. Illustrative numerical example A representative standalone lifecycle carbon intensity for 2G ethanol is approximately 22 g

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2G ethanol (Standalone)

CCS (Boilers/ SMR)

Electrofuels (PtL)

Green hydrogen (Renery use)

2G ethanol (DBCOM Integrated)

Decarbonisation pathways

Figure 1 Comparative cost of CO 2 abatement across major refinery decarbonisation pathways (Indicative cost ranges show that refinery integrated 2G ethanol under the DBCOM framework occupies the low-cost tier)