(587ac) Optimization of Supply Chain Design With Two Production Options; Bio-Ethanol and Bio-Hydrogen From Switchgrass

This study focuses on the economic optimal design of supply chain for the infrastructure of two bio-products from switchgrass. Bio-ethanol and/or hydrogen are/is produced with different processing stage options. The basic processes are using steam explosions as a preprocessing, using fermentation as a main processing for bio-ethanol, and using steam reforming is needed as an option to get hydrogen from ethanol.

The switchgrass as a resource of the bio-ethanol is increasingly used and the produced bio-ethanol can be converted into the bio-hydrogen coming to the fore through the steam reforming process. The main process used for the bio-ethanol production is fermentation. Fermentation is a biological process in which sugars are converted into bio-ethanol. The fermentation of pre-treated biomass to ethanol is an attractive route to fuels that supplements fossil fuels. Before fermentation, biomass needs pre-processing to expose these sugars to an enzymatic attack. The highly complex lignocellulosic matrix consisting of cellulose, hemicellulose and lignin forms a barrier against enzymes in order to prevent degradation of the biomass into its individual components. Steam explosion is one man-made way to solve this problem by converting the recalcitrant property of biomass that is observed in nature. The major process used in producing bio-hydrogen from bio-ethanol is steam reforming. Steam reforming is the most useful process for the production of hydrogen-rich synthesis gas from light carbohydrates like ethanol. The ethanol is endothermically converted with water steam into synthesis gas including hydrogen in catalytic.

A relatively small difference between the two systems makes two types of bio-fuels; bio-ethanol and bio-hydrogen, with two different commercial values. The bio-ethanol production having the less stages and the production of bio-hydrogen with the higher commercial value needs to be compared. We built the two supply chain networks in a model to consider the two simultaneously.

The ultimate goal in this study is to choose the most benefit supply chain as an economical design. We maximize the overall profit, which is the revenues of each product subtracted by the sum of the total costs including the biomass acquisition cost, the operating cost, the capital cost, and the transportation cost based on the conversion ratios. The model sets the optimal number, location, and size of each plant and the amount of biomass, bio-ethanol, and bio-hydrogen to be transported between the plants of each stage. The model uses the industry data that contains the information of locations, costs for treatment and transportation of switchgrass, the proposed sites, the costs for the processing, transportation, establishment, fixing, operating, the yield of each plant, and the distance between the each plant and final market.

This network model covers Mississippi, which is located in the United States. We build the model using the mixed integer linear programming (MILP) and MILP is solved by using the computational program, GAMS.

This study can give useful information for the design of the optimal supply chain with two options: bio-hydrogen and bio-ethanol from switchgrass. The optimal design presents the economic comparing with the two type production systems and the infrastructure of the bio-ethanol and bio-hydrogen industries to be developed.