Woody biomass is widely utilised as feedstock for heat, electricity and cogeneration plants. In future it could also be sought by developers of biofuel processing plants, biorefineries and hydrogen production plants, but will compete with other biomass sources (OECD, 2004). Wood process residues are usually free on site (or even have a negative disposal cost) and are often readily utilised for heat and power, but residues from pruning, thinning and harvesting are often left in the forest. It is difficult to determine the delivered costs ($/GJ or $/t) of this fuelwood feedstock at a bioenergy conversion plant gate since there are many variables of plant location, transport distance, and methods and machinery used in the entire supply chain. Bioenergy conversion facilities also often operate with uncertain fuel supplies because the low value fuelwood currently available could become more valuable feedstock for newly developing markets.
The efficiency of conversion in bioenergy plants tends to be lower than for similar fossil fuel plants due to variations in feedstock quality, especially moisture content, and the typical smaller plant capacities since they are often constrained by feedstock availability (although the world’s largest bioenergy plant in Finland generates 265MW electricity, 100MW steam and 60 MW of district heat). The market potential for woody biomass is also constrained by the challenges for plant developers to obtain long term feedstock supply contracts and resource consents for plant construction. Hence less plants have been built than had been earlier envisaged. This paper examines how these issues relate to the carbon mitigation potential of using fuelwood for bioenergy.

By: R. E. H. Sims (Centre of Energy Research, Massey University)

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