A “plug-and-play” microbial technology enables the recovery of additional copper from low-grade ores when used alongside traditional sulfuric-acid heap-leach methods. Working synergistically within the existing heap-leach infrastructure, the unique microbial communities that have been cultivated by Endolith (Westminster, Colo.; www.endolithmining.com) are designed to thrive in sulfuric acid and break down minerals in the heap, including pyrite, chalcopyrite and chalcocite. “A lot of what the microbes can break down are really recalcitrant minerals that other technologies cannot. Within the heaps, the microbes find energy sources, and they are able to grow, and that is what effectively catalyzes the breakdown in a way that can outperform sulfuric-acid leaching alone,” explains Liz Dennett, founder and CEO of Endolith.
Endolith’s process recovers metals using microbes
Heap leaches are incredibly complex environments that can experience huge swings in temperature and pH, and many traditional copper technologies struggle with ores that contain components like arsenic, enargite or tennantite, or that have extremely dilute copper content.
“Every ore type is unique and where we really thrive are with those bizarre ores with many unique constituents, or those that are below 1% pyrite or chalcopyrite. In general, we’ve seen 30 to 80% greater recovery of copper than with sulfuric acid. By deploying these microbial ‘minions’ at scale, we’re really able to liberate copper, not just with faster kinetics, but ultimately with higher copper recovery,” says Dennett.
To ensure that the microbial consortia are up to these difficult tasks, Endolith’s team of scientists has designed what Dennett calls a “microbial Olympic training camp” where techniques like adaptive laboratory evolution help to optimize enzyme kinetics so that the microbes can thrive in conditions that may otherwise be inhospitable. Furthermore, she emphasizes that Endolith’s microbes are amended from naturally derived microbes and do not undergo any directed genetic engineering techniques.
In the field, Endolith’s microbes are grown onsite in fully automated “biohatchery” units that include analytical equipment and field instrumentation for remote monitoring and are set up so that the microbes can be pumped into the heap using existing raffinate systems. Endolith has demonstrated the technology at various laboratory scales with four different industrial customers, including through a collaboration with BHP’s Think & Act Differently (TAD) program, and has entered a partnership with the Alaska Critical Mineral Cooperative to pursue potential further development of the technology.