The Process Design and Economic Analysis of a Farm-scale System for Producing Ethanol and Hydrocarbon (botryococcene) Fuels from a Lignocellulosic Substrate

Open Access
Hillery, Patrick Jefferson
Area of Honors:
Chemical Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Wayne Roger Curtis, Thesis Supervisor
  • Wayne Roger Curtis, Honors Advisor
  • Michael John Janik, Faculty Reader
  • Biofuels
  • Fermentation
  • Bioprocessing
  • Lignocellulose
  • Botryococcene
Within the broad effort to shift global energy sources away from fossil fuels and towards more sustainable resources, liquid biofuels represent one of the largest concrete steps away from complete reliance on petroleum to date, and represents a promising starting point for future progress. Currently, ethanol produced through the fermentation of either corn or sugarcane represents the overwhelming majority of current biofuel production worldwide. However, a large portion of current research into biofuels is focused on so-called “second generation” biofuels, which promise to provide fuels from lignocellulosic or cellulosic biomass. One method that has been proposed as a means to achieve this conversion is the use of a consortium of multiple organisms to enzymatically break down lignocellulosic material and convert the products into usable fuels. This study in particular examines a consortium of Clostridium phytofermentans and a genetically-engineered strain of Saccharomyces cerevisiae to carry out the fermentation of a lignocellulosic feedstock, yielding ethanol or a metabolically engineered advanced biofuel which is a triterpene hydrocarbon, botryococcene. The platform used to conduct this fermentation, as well as the equipment necessary to process the resulting fermentation mixture into marketable fuels, was considered on a scale that is appropriate for a typical farm (500 acres) and an economic analysis of the system was conducted. This approach represents a potentially major paradigm shift to very highly distributed production of fuel, in contrast to proposed large biorefineries. This analysis showed that the base case proposed system, which is based in part on data collected at a laboratory scale, is not economically feasible under current market conditions, but has the potential to become viable given either significant increase in crude oil prices (the proposed base case system is estimated to break even at approximately $122/bbl for West Texas Intermediate) or major improvements in yields of ethanol or botryococcenes from lignocellulose.