Waste-to-energy and carbon footprint assessment in sugar manufacturing: A five-year analysis of cogeneration, eco-efficiency, and energy Price sensitivity

Energy-intensive agro-industrial sectors such as sugar manufacturing face substantial carbon footprints, particularly in fossil-fuel-dependent economies with subsidized, regulated energy markets. Using a five-year dataset (2021–2025) from an Iranian sugar factory, this study conducts a gate-to-gate operational carbon footprint assessment, with the resulting inventory characterized using the ReCiPe 2016 carbon footprint impact characterization method. The framework further integrates eco-efficiency and economic indicators. The average carbon footprint was 1701 kgCO 2 /ton (gate-to-gate, sugar stream), driven by natural gas (97%), with human health dominating the weighted endpoint impacts (0.0639 person-years/ton of sugar stream, unallocated, an indicative normalized estimate). On-site waste-steam cogeneration reduced emissions by 10.7% annually (13.0 million kgCO 2 /year avoided). We introduce the carbon intensity of energy spending (CIC), a cost-referenced carbon indicator with a five-year average of 177.9 kgCO 2 /US$. Because CIC is defined as emissions divided by expenditure, it responds inversely to energy price changes; this arithmetic property is illustrated through sensitivity analysis but should not be interpreted as a behavioral price response. CIC is therefore interpreted alongside the price-independent carbon intensity of energy (CIE) metric (57.9 kgCO 2 /GJ). A complementary decoupling elasticity analysis shows carbon emissions tracked production output proportionally in most years, with one notable exception. The novelty lies in the joint CIC and CIE indicator pair linking economic and physical carbon-efficiency dimensions, and the integration of decoupling elasticity with cost-based diagnostics at the facility level.