Co-Generation of Fuels and Chemical in Mining Processes

We have developed an electrofuels method coupling an electrochemical reactor and a biological reactor containing chemolithoautrophic bacteria that have been engineered to produce chemicals or fuels [1,2].  Together, the two coupled reactors can use electricity generated from renewable sources to produce a chemical such as isobutyric acid or a fuel such as heptadecane from water and dilute CO₂ from air.    The process contains no other stoichiometric inputs, is scalable, and currently is undergoing improvements to the engineering of the bugs.  While such a process is feasible, the cost of the electrical energy and the equipment motivates the exploration of alternative approaches

An alternative is discussed here, where we explore the feasibility of using chemical energy released during bioleaching processes to co-produce chemicals.  Here the ore or mineral waste is the sole source of the energy required to convert CO₂ and water into the chemical.  The same chemolithoautrophic bacteria is exploited, since it is already used in the processing of between 10 and 25 % of the world’s copper from ore.  This organism grows under acidic conditions (pH of 2) using iron and/or sulfur as it energy source.  Its sole source of carbon is CO₂.  In theory, the organism can thus be used for co-generation of chemicals in a large variety of mining processes.

We explain the concept, present results for product formation obtained with simulated and real copper ores.  Furthermore, the economic feasibility is discussed in terms of techno-economic analysis.  Long term and short term possibilities for the technology are presented.

[1].  Xiaozheng Li, Roel Mercado, Sarah Berlinger, Scott Banta, and Alan C. West, ” Engineering Acidothiobacillus ferrooxidans Growth Media for Enhanced Electrochemical Processing,” AICHE Journal, accepted (September, 2014).

[2] Xiaozheng Li, Roel Mercado, Timothy Kernan, Alan C. West and Scott Banta, ”Addition of Citrate to Acidothiobacillus ferrooxidans Cultures Enables Precipitate-Free Growth at Elevated pH and Reduces Ferric Inhibition,” Biotechnology and Bioengineering, 111, 1940 (2014).