Surplus forest biomass - The cost of utilisation through optimised logistics and fuel upgrading in northern Sweden

In order to achieve a net zero emission economy by 2045, Sweden's inland biomass resources are under examination. Large amounts of forest biomass in the north of the country are not utilised. In this study, resource mapping of surplus forest biomass, (logging residues, tree stumps and mill by-products) is carried out according to ecological harvesting restrictions to determine the annual potential of this resource. Using a network of terminals, optimised supply chains are used to determine the cost of feedstock supply and upgrading of biomass to value-added torrefied pellets. The results indicate that the total biomass surplus is 5.75 Mt (dry mass), representing a forested procurement area half the size of Sweden (224 500 km(2)). The surplus represents two per cent of Sweden's annual energy consumption and 60 % of its coal and coke use. Aggregation of the existing terminal network results in 274 to 1611 kt of biomass (dry mass) supplied to ten terminals. Supply and upgrading costs at the terminals reflect a tradeoff between the size of procurement area and the scale of upgrading; a large plant capacity corresponds to a low upgrading cost but a large supply cost and vice versa. The lowest supply cost is 79 (sic) t(-1) (dry mass) of feedstock and the upgrading capacity ranges from 86 to 1310 kt (dry mass). Utilisation of the surplus would require an effective energy cost range of 27-37 (sic) MWh(-1) exclusive of delivery cost to the end user and operational profits - corresponding to a minimum torrefied pellet price of 131 (sic) t(-1). Though much higher than other solid fuels, the energy price is comparable to that of natural gas. The results of this study have importance for legislation supporting EU and Swedish energy policy objectives. (C) 2020 Elsevier Ltd. All rights reserved.