Environmental footprint trade-offs in agricultural-residue biorefineries: hotspots, burden shifting and decision thresholds

Agricultural and agro-industrial residues are promising feedstocks for fuels, chemicals and materials, but their renewable origin does not guarantee lower environmental burdens. This review examines carbon, energy and water assessments of lignocellulosic-residue biorefineries. It compares product functions, system boundaries and coproduct accounting before interpreting reported hotspots and trade-offs. Across the reviewed pathways, burdens can arise from residue supply, pretreatment, enzyme production, product recovery and residual-stream management. Improving one stage may shift demands for heat, electricity, chemicals or water to another. Within-study comparisons report conditional changes in environmental rankings under different electricity mixes or residue-allocation rules. Such findings are scenario-specific; they do not establish universal decision thresholds. We propose a joint assessment procedure that separates physical burdens from avoided-product credits and tests coupled process parameters under local energy and water conditions. Few studies report directly comparable carbon, energy and water outcomes across competing routes. Decisions should therefore rely on transparent, balanced inventories and identify whether a crossover was reported in the source study or remains to be tested.