Biomining the Future, Extracting Rare Earth Elements from Alaskan Coal

Abstract:

Rare earth elements (REEs) are used in computers, renewable energies, cell phones and are critical in the defense and healthcare industries. REEs are not currently mined in the U.S. due to the low yield in conventional extraction processes; however, acquiring a profitable domestic source of REEs is a critical national need. Coal has the potential to be a domestic source of REEs and microbes may offer a way to extract the REEs at circum-neutral pH. This project examined the process of bio-weathering to release REE from coal and compare the efficiency of different microbial species. Alaskan coal was incubated with Rhodoferax ferrireducens, Shewanella Oneidensis MR-1, or Acidophilum cryptum and cycled between oxic and anoxic conditions. Iron (II) liberation from the coal was initially used as a proxy for REE extraction. S. oneidensis produced the highest iron concentrations after an eight-week incubation. The leachate produced by S. oneidensis had a maximum recovery rate of 98.4% for total REE. Abiotic controls did not produce measurable levels of any REE. Furthermore, depending on the source of coal bio-weathering performed comparable to or better than acid leaching (1.2M H₂SO₄ at 75°C). Developing biomining technology is essential in order to meet the growing demand for renewable energy devices and microorganisms such as S. oneidensis may provide the means to get there.