Life cycle energy and environmental performances of nine different biomass/coal co-firing pathways to power generation were compared. Agricultural residue (AR), forest residue (FR), and whole trees (WT) as feedstock were analyzed for direct (DC) and parallel co-firing (PC) in various forms (e.g., chip, bale and pellet). Biomass co-firing rate lies in the range of 7.53-20.45% (energy basis; rest of the energy comes from coal) for the co-firing pathways, depending on type of feedstock and densification. Net energy ratios (NER) for FR-, WT-, and AR-based co-firing pathways were 0.39-0.42, 0.39-0.41, and 0.37-0.38, greenhouse gas (GHG) emissions were 957-1004, 967-1014, and 1065-1083 kg CO2eq/MWh, acid rain precursor (ARP) emissions were 5.16-5.39, 5.18-5.41, and 5.77-5.93 kg SO2eq/MWh, and ground level ozone precursor (GOP) emissions were 1.79-1.89, 1.82-1.93, and 1.88-1.91 kg (NOx + VOC)/MWh, respectively. Biomass/coal co-firing life cycle results evaluated in this study are relevant for any jurisdiction around the world. (C) 2012 Elsevier Ltd. All rights reserved.