Location: Sustainable Biofuels and Co-Products
Title: Reduction in energy usage during dry grind ethanol production by enhanced enzymatic dewatering of whole stillage: plant trial, process model and economic analysis Authors
Submitted to: Industrial Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 5, 2011
Publication Date: August 1, 2011
Citation: Henriques, A., Johnston, D., Mcaloon, A.J., Dudukovic, M.P. 2011. Reduction in energy usage during dry grind ethanol production by enhanced enzymatic dewatering of whole stillage: plant trial, process model and economic analysis. Industrial Biotechnology . 7(4)288-297. Interpretive Summary: The production of fuel ethanol form corn requires the input of energy in the form of electricity, natural gas and steam, as well as the use of significant amounts of water for processing and cooling. The product contains more energy in the form of ethanol than is used in the production process; however, further reducing the energy required will improve the overall process and decrease greenhouse gas emissions. In order to reduce the energy and water required, an enzyme based process that aids in water removal was developed and tested at a commercial fuel ethanol facility. Data collected from the trial demonstrated the effectiveness of the enzyme and showed that natural gas could be reduced by as much as 12% and water could be reduced by as much as 14%. Process models developed from this data showed that there were tradeoffs between enzyme cost and natural gas savings. Sensitivity simulations show energy, water and economic benefits for a wide range of conditions. The results of this research will be useful to other research scientists, fuel ethanol producers, enzyme suppliers and ethanol plant design engineers who are interested in improving the overall fuel ethanol process.
Technical Abstract: A plant trial was conducted at a 54 MGPY dry grind fuel ethanol facility to evaluate the use of enhanced water removal from whole stillage by enzyme addition during fermentation. Laboratory data had previously shown significant improvements in water removal that could potentially result in significant energy and water savings during ethanol production. Plant baseline data was collected for normal operating conditions before and after the enzyme addition and statistically compared to the results collected during the enzyme treatment period. These results were also used to construct process and economic models. The results showed that the enzymes added during the trial proved to be effective. A significant increase in the amount of water removed during centrifugation was observed. The firing rate of the drier was decreased during the enzyme addition period, resulting in a 12% reduction in the amount of natural gas required to produce one gallon of ethanol. DDGS composition was unaffected. Process model simulations developed using the plant trial results showed a decrease in utility consumption for the enzymatic treatment model compared to the conventional model. Sensitivity analysis showed a tradeoff between the enzyme cost and drier’s natural gas savings. Additional sensitivity simulations with enzyme dosing show energy, water and economic benefits for a wide range of enzyme and natural gas costs. Water use was reduced by up to 14% for processing and 10% overall. Total energy reductions were calculated with the 40 MGPY process model and found to reduce greenhouse gas emissions by approximately 6.4 million kg of CO2 equivalents/yr.