1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 CHEC Research Centre, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark4 Risø National Laboratory for Sustainable Energy, Technical University of Denmark
A biorefinery concept based on alder tree plantations on degenerated soil is developed to comply with indicators of economic feasibility, fossil fuel depletion concerns, and long term sustainability issues. The potential performance of feedstock and biorefinery has been assessed through a literature study and by using a method developed during the study for first hand assessment and comparison of biorefinery system characteristics. The management of an average alder plantation in a 6-year coppicing system was found to fixate atmospheric nitrogen to the soil in yearly rates between 50 and 200 kg ha1 and produce a 6-year total dry biomass quantity around 33 Mg ha1 plus yearly leaf production. This production could facilitate a biorefinery to serve society with production of energy related and value added products to substitute the use of fossil fuels while at the same time replenishing degenerated soils. Integrating a biomass handling system, an LTCFB gasifier, a diarylheptanoids production chain, an anaerobic digestion facility, a slow pyrolysis unit, gas upgrading and various system integration units, the biorefinery could obtain the following production characteristics accounted on a yearly basis: Total system Energy Return on energy Invested 2.0, total system Exergy Return on exergy Invested 1.5, Net Energy Output 78 GJ ha1, Net Exergy Output 50 GJ ha1, Net carbon sequestration (as CO2 equivalents) 0.80 Mg ha1, Total product value 2030 V ha1 and Net Dry Matter Removal of approximately 90%.