Biomass usage for power and liquid fuels

The objective of this study is to evaluate alternative methods of utilizing biomass in western Canada to generate power and ethanol (for ultimate use as a transportation fuel), in order to identify the relative cost of alternatives. The study is a techno-economic evaluation that develops detailed discounted cash flow models. The results can help guide policy, research and development decisions in the implementation of greenhouse gas mitigation. The cost of power based on direct combustion of forest harvest residues (chips from limbs and tops of trees) and whole forest biomass (chips from whole tree) are US{dollar}63/MWh and US{dollar}47/MWh, respectively. Optimum plant size, which is tradeoff between per unit capital cost and transportation cost, is 137 MW for forest harvest residues and 900 MW for the whole forest. Whole forest biomass likely requires a remote location with dedicated transmission, but has low transportation cost due to the high biomass yield per gross hectare. Forest harvest residues have a very low yield per gross hectare because of the long rotation and low cutting density in the boreal forest. Power from forest biomass is not economic in western Canada, but may become so if a system of trading greenhouse gas credits emerges. At a fossil fuel based power price of US{dollar}30/MWh, forest harvest residues and whole forest based power would require a carbon credit of US{dollar}36.20 per tonne of CO2 and US{dollar}18.30 per tonne of CO 2, respectively. The study compares power cost from direct combustion and biomass integrated gasification combined cycle (BIGCC). BIGCC reduces the cost of biomass power for forest harvest residues by 13.7% compared to direct combustion and increases the power for whole forest biomass by 7.9%. Large-scale biomass processing couldn't rely on truck delivery of biomass due to road congestion; pipeline transport of biomass could be an alternative. Cost of pipeline transport of biomass is estimated and compared with truck transportation. Pipeline transport of truck delivered wood chips is only economic at large capacities and medium to long distances. For a one way pipeline, the minimum economic capacity is >0.5 M dry tonnes per year and for a two way pipeline, the minimum economic capacity is >1.25 M dry tonnes per year. Pipeline transport of corn stover costs less than trucking at 1.4 and 4.4 M dry tonnes per year for a one way and two way pipeline. Pipeline transport of biomass is limited by carrier fluid uptake. Boreal wood chips absorb water quickly when immersed and reach a moisture level in excess of 60%. The absorbed water reduces the lower heating value (LHV) of the wood chips, which in turn makes them not suitable for combustion or gasification applications. It could be used for fermentation processes, as the process itself is aqueous. If the carrier fluid is oil, it absorbs oil in excess of 25% in less than 20 hours of immersion. At this level of absorbed oil, more than 50% of the available LHV in the chip comes from oil. Large-scale ethanol production from low yield biomass like corn stover using pipeline transport is not economic as compared to small distributed units, while large-scale ethanol production from high yield biomass like wood chips is economic. A reduction in the cost of ethanol of more than 10% can be achieved for wood chips.