Prioritization of alternative biomass pellets for heat production using multi-criteria ranking and greenhouse gas savings assessment

Alternative biomass pellets may expand the feedstock base for heat production, but their selection requires consideration of fuel quality, combustion performance, implementation constraints, and life-cycle greenhouse gas (GHG) savings. This study compares ten woody and non-wood pellet alternatives through parallel multi-criteria ranking and RED II/III-aligned GHG assessment. Fuel-quality, combustion, and life-cycle inventory data were obtained from the authors' previous studies and subsequently refined through additional testing and data validation. Socio-economic and socio-technical performance was assessed using context-specific expert input. The alternatives were ranked using WSM-AHP and MULTIMOORA-AHP, while pathway-specific GHG savings were calculated according to the RED II/III methodology and compared with the 80 % requirement for heat installations entering operation from 2026. Brewer's spent grain and wood pellets formed the leading group in the overall multi-criteria assessment. Buckwheat husk and sunflower husk pellets received the lowest consolidated MULTIMOORA-AHP scores. When only technical criteria were considered, wood pellets ranked above brewer's spent grain pellets, demonstrating the influence of deployment-related criteria on the complete assessment. All pathways except hemp pellets met the 80 % GHG savings requirement, while grass pellets remained closest to the threshold at 82 %. Processing-energy requirements and use-phase emissions were the principal sources of variation in pathway-specific GHG savings. By contrasting multi-criteria preference with GHG compliance, the proposed approach identifies alternatives that would be evaluated differently by either assessment alone and supports the assessment of pellet pathways lacking directly applicable RED II/III default values.