Techno/economic and life cycle assessment of the production of high value chemicals: acetic acid case study

The production of intermediate high-value-chemicals provides a route to establish biorefineries that can be expanded to produce an array of fuels and chemicals.  A bioconversion facility using an acetogen fermentation pathway would first produce acetic acid which could then be converted downstream to ethanol, ethylene, and finally a drop-in fuel.  From a capital cost and risk perspective, it is best to initially construct a moderate scale biorefinery that produces the first intermediate, acetic acid. ASPEN chemical engineering software is used to simulate acetic acid production at a bioconversion biorefinery.  Acetic acid production follows the path of pretreatment, enzymatic hydrolysis, acetogen fermentation, and acid purification.  Separation of acetic acid from water is a major expense, and requires considerable energy, when producing pure acid starting with biomass. We have investigated different approaches to this separation, including distillation, liquid-liquid extraction using ethylacetate, and an extraction process using an organic phase containing trioctylphosphine oxide (TOPO).  Techno/economic analyses of biorefineries using each separation scheme will be presented.  Capital and operating expenses for each configuration and profitability using discounted cash flow analysis to establish minimum selling prices are used to assess economic viability.    Life cycle assessment is used to investigate environmental impact. The global warming potential (GWP) of acetic acid production with different conversion and recovery processes are assessed.  Acetic acid has many end uses, each having different long term carbon implications. Cradle to grave LCA results will be presented that illustrate the global warming potential for each of these end use scenarios.