Feasibility of Sweet Sorghum to Ethanol and Value-added Products

Great Valley Energy, LLC assessed the feasibility of producing advanced biofuels and value‐ added co‐products in California using sweet sorghum as a feedstock. Great Valley Energy took part in three years of field trials using five varieties of commercially‐available sweet sorghum. Sweet sorghum agronomics were studied to estimate the delivered price of sweet sorghum billets to a production facility assuming displacement of current crops. An average cost of $46 per ton of sorghum stalks is estimated and 35 tons per acre is achievable.

Great Valley Energy constructed and operated a pilot demonstration plant using fractionation technology from KTC Tilby. The fractionation equipment was used to mechanically separate sweet sorghum stalks into component fractions. These stalk components were sampled and analyzed physically and chemically. Juice was expressed and biomass was dried and pelleted. Several process configurations were engineered to provide mass and energy balances. Equipment was sized, and capital and operating costs were estimated.

Three configurations of biofuel, biofuel intermediates, and value‐added co‐product manufacturing scenarios were further developed including:

Configuration 1 – Onsite production of denatured fuel ethanol, densified biomass (pellets), and nutraceutical extract powder;

Configuration 2 – Production of 20 percent sugar solution for over‐the‐fence fuel ethanol production, livestock forage/feed blend stock, and a tolling/offsite arrangement for extraction and upgrading of nutraceutical bioactive dermal layer; and

Configuration 3 – Production of 60 percent sugar syrup, construction product (oriented‐strand board), and a tolling/offsite arrangement for dermal layer bioactives extraction.

Funding requirements for configurations 1, 2, and 3 (including equipment, installation, site development, infrastructure, reserves and contingency) were estimated at $111 million, $41 million, and $119 million, respectively. These costs are expected to be within 30 percent of fully‐ engineered costs.

Internal rates of return for configurations 1, 2, and 3 were 19.2 percent, 25.4 percent and ‐2.7 percent, respectively, with more complex and capital intensive scenarios predicting lower returns.