Ethanol Production for Automotive Fuel Usage

The production of ethanol from potatoes, sugar beet, and wheat using geothermal resources at the Raft River area of idaho is being evaluated. The south central section of Idaho produces approximately 18 million bushels of wheat, 1.3 million tons of sugar beet and 24 million cwt potatoes annually. Based on these production figures, a 20 million gallon/yr ethanol facility has been selected as the largest scale plant that can be supported with the current agricultural resources. The plant will operate on all three feedstocks nominally processing potatoes for five months, sugar beet for four months and wheat for three months of the year. The process facility will use conventional alcohol technology utilizing geothermal fluid at a maximum of 280 F as an energy source. The process flow diagrams for all three feedstocks are currently being prepared. There will be basically three feedstock preparation sections, although the liquefaction and saccharification steps for potatoes and wheat will involve common equipment. The fermentation, distillation and by-product handling sections will be common to all three feedstocks. Three geothermal energy extraction systems were considered to accommodate the energy requirements of the ethanol facility (flashed steam, pressurized fluid and secondary heat transfer). Pressured geothermal fluid with direct heat transfer has been selected as the usage mode to minimize scale deposition. Tentatively, the geothermal supply wells will be laid out in square grids with 1/4 mile spacing. The number of wells required will be determined after the process heat load is calculated