Feedstock and supply chain-oriented comparative cradle-to-gate life cycle assessment of torrefied pellets, case study: Finland.

Life cycle assessment (LCA) is used to compare global warming potential of torrefied pellets made of different feedstock materials, namely energy wood of birch and pulpwood of birch, pine and spruce. In addition, five different supply chain alternatives for each feedstock type are also evaluated. It is assumed that all of the biomass originates in the South Savo region of Finland and the pellets are used for co-firing with coal in a large-scale power plant in Helsinki, Finland. The results show that the torrefied pellets made of pulpwood of birch have the lowest global warming potential, whereas energy wood of birch impose the greatest environmental burden. Of the supply chain alternatives considered, biomass chipped with an electrical chipper in the torrefaction plant yard in South Savo has the lowest global warming potential. Consequently, torrefied pellets of birch chipped in an electric chipper in the torrefaction plant yard have the lowest environmental impact of all feedstock material and logistics alternatives. On the other hand, energy wood torrefied on-site in Helsinki results in the greatest environmental impact of all the raw material and logistics alternatives assessed. Furthermore, logistics with roadside mobile chipping generates 5-17% lower greenhouse gas (GHG) emissions than terminal crushing. Similarly, moving the torrefaction plant from South Savo to Helsinki would cause up to 6.5% additional GHG emissions depending on the raw material. Alternatively, chipping at the plant yard in a stationary electric chipper instead of crushing with a diesel-powered crusher would cause up to 18% fewer GHG emissions depending on the raw material. [ABSTRACT FROM AUTHOR]