Techno-Economic Analysis of a Biorefinery Utilizing Geothermal Energy for Biomass Drying and Auxilliary Power Generation

A techno-economic study of a biorefinery based on biomass gasification is conducted using Aspen Plus and corresponding economic analysis tools for three different scenarios.  In the first scenario, a 2,000 metric tonne per day biorefinery is modeled utilizing corn stover as the feedstock.  The gasification scenario modeled produces a synthesis gas that is upgraded to liquid transportation fuels, with excess hydrogen and electricity produced as co-products.  In an effort to reduce the overall greenhouse gas emissions associated with this process, the second scenario replaces steam utilized in the plant originally produced by the combustion of fossil fuels with steam derived from geothermal resources.  Finally, an additional power generating step based on the Organic Rankine Cycle is implemented in the third scenario which generates electricity from the low-temperature steam remaining from various processes that is normally exhausted to the atmosphere.  Results show that the lowest price of transportation fuels results from scenario one.  Despite the modest price increases, scenario two can reduce the overall greenhouse gas emissions resulting from the biorefinery, while the addition of the Organic Rankine Cycle increases the overall plant efficiency.