PE Liquid Hydrocarbon Production with the Electrobiome Platform
Abstract
Summary/Abstract. Fossil hydrocarbons meet the commercial and military demand for fuels and chemicals, but their continued use is risking the possibility of catastrophic climate change, which can lead to geopolitical disruption and insecurity. The U.S. Department of Defense has a unique and ever growing problem with carbon based fuels due to geopolitical problems and the economic and human cost in injuries and lost lives required to transport fuel to remote locations. For the Navy this jeopardizes the supply of fuels shipboard and at forward operating bases for the Marines. The applied research proposed here is aimed at the development of a system to convert CO2 into liquid biohydrocarbons that may be used as a drop in fuel, which is scalable and deployable to diverse geographies and/or climates to meet specific needs of the Navy. A two-stage bioreactor is proposed, one that microbially electrosynthesizes CO2 into acetate that is then used as a feedstock for liquid hydrocarbon production by algae with minimal or no light. The PI has established a microbial community growing on a graphite cathode, or a biocathode referred to here as an electrobiome. The electrobiome is dominated by species of acetogens (Acetobacterium sp.) and sulfur oxyanion reducing bacteria (Desulfovibrio sp. and Sulfurospirillum sp.), for which a metagenome has been sequenced. Hydrogen and acetate production by this electrobiome supplied with electricity and CO2 has reached 2.6 kg of H2 and 3.1 kg of acetate per m3 of catholyte volume per day. The goal of this proposal is to increase the production of acetate and feed it to a second stage bioreactor of a green microalga Botryococcus braunii that secretes C23-C35 hydrocarbons when fed with acetate. The electricity could come from any source and the CO2 from a waste stream or possibly ambient air. The first objective is to increase the electrosynthetic production of acetate and this will be achieved by the addition of inexpensive nutrients, functionalization of the cathode with biocatalyst-containing extracellular material (ECM) from the electrobiome, pH control, capture of excess biohydrogen with a hollow fiber membrane, and improvement of water oxidation catalysis at the anode with inexpensive catalysts. The second objective is to improve the growth rate and hydrocarbon yield by the algal culture, and the third objective is to test the best practices discovered in Objectives 1 and 2 in an integrated 2-stage bioreactor. While the concept of each stage of the proposed system has been proven, proof of concept of the integrated electrobiome/alga system remains to be done and is the goal of this proposal.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512219
Entities
People
- Harold D May
Organizations
- Medical University of South Carolina
- Office of Naval Research
- United States Navy