The design and costing of a continuous ethanol process using wheat and cell recycle fermentation

Abstract

The preliminary design and costing of a 100 million litres/year wheat-ethanol plant using continuous cell recycle fermentation, where the cells were separated after the fermentation using cross-flow membrane filters, were investigated. As part of the design, two other unconventional steps were required: the separation of suspended solids before saccharification and the hydrolysis of dextrins by immobilized enzymes. The total capital cost was estimated as $Can51.2 million (based on an exchange rate of $Can1.15 = $US1.00) and, based on a wheat price of $Can90/tonne, a total operating expenditure of $Can450 per 1000 litres of ethanol. Assuming an ethanol price of $Can460 per 1000 litres of ethanol, the total income (including by-products) was estimated at $Can630 per 1000 litres of ethanol, giving a net profit after sales, administrative overheads and taxes of $Can7 million/year. It should be noted, however, that the wheat cost makes up over 60% of the total operating expenditure and as such the profit would drop rapidly with increases in this cost.