Sustainable value methodology to compare the performance of conversion technologies for the production of electricity and heat, energy vectors and biofuels from waste biomass

Abstract

The Sustainable Value methodology was used to compare and rank eight combinations of waste biomass types and conversion technologies on a common assessment basis to produce energy, energy vectors and advanced biofuels. The studied combinations included agricultural and agro-industrial residues, slurries and effluents, pulp and paper mill sludge, piggery effluents and organic fractions of municipal solid waste, to produce biodiesel by (trans)esterification, biogas by anaerobic digestion, ethanol by fermentation, hydrogen by dark fermentation, electricity and heat by combustion, biogas and synthesis gas by gasification, and bio-oils by pyrolysis or hydrothermal liquefaction. The numerator “Functional Performance” of the Sustainable Value indicator was estimated according to 14 criteria of process technology, material and energy inputs and outputs, and acceptance by the stakeholders. The performance of the technologies was classified based on the values of relative importance (φ) and level of satisfaction ( S ) attributed to each criterion. The gasification of residues from the olive-oil industry reached the highest “Functional Performance”, followed by anaerobic digestion of chestnut processing residues and pig-rearing effluents. The Sustainable Value denominator “Costs” depended mainly on the degree of maturity of the technologies, which penalised pyrolysis, hydrothermal liquefaction and dark fermentation. The final ranking of the Sustainable Value indicator was gasification > combustion > anaerobic digestion > (trans)esterification > pyrolysis and fermentation to ethanol > hydrothermal liquefaction > dark fermentation, respectively for the most adequate waste biomass types under study. Thermochemical conversions were mainly impacted by process and input criteria, while output and social acceptance criteria were more decisive for the biochemical conversions. • Sustainable Value (SV) analysis applies to waste biomass-to-energy (WBtoE) conversion • SV indicator enables the ranking of bio- and thermochemical WBtoE technologies • Costs uncertainty of low-maturity WBtoE technologies negatively impacts the SV score • Gasification of olive-oil industrial residues delivers the highest SV score of 4.09 • Biogas production by codigestion can further increase the SV score to 6.76