A new Defense Advanced Research Projects Agency (DARPA) program— Environmental Microbes as a BioEngineering Resource (EMBER) (HR001121S0035)—seeks to develop novel, bio-based technologies to overcome key challenges facing domestic supply of Rare Earth Elements (REEs) critical to the US and Department of Defense (DoD).

Although the US has domestic REE resources, its supply chain is vulnerable due to dependence on foreign entities for separation and purification of these elements.

“Biomining,” an approach that uses microbes to extract or separate target metals such as gold or copper from a variety of sources is not yet useful for REEs because of poor specificity and selectivity of the microbes for REEs.

The EMBER program will leverage the diversity, specificity, and customizability of environmental microbiology to enable new biomining methods for the separation, purification, and conversion of REEs into manufacturing-ready forms. Microbes (and/or biomolecules), including those from extreme or metal-rich environments, can be biologically engineered or adapted to bind, assimilate, and manipulate individual REEs.

These biological components, once developed, may be assembled into an in-line separation, purification, and recovery workflow resulting in individual, purified REEs.

EMBER is targeting REEs from under-utilized domestic sources such as phosphate mine waste, acid mine drainage, and electronics recycling processes.

Scalability of EMBER’s approach will be demonstrated with proof-of-concept, pilot scale studies aligned with existing mining/waste treatment infrastructure.

The EMBER program will aim to fill a critical DoD supply chain gap. The program will target the development of bioengineered organisms/biomolecular approaches for REE purification, then translate these to practical biomining modules (e.g., biosorbent, biofiltration) that can be integrated with domestic REE sources.

—Dr. Linda Chrisey, EMBER program manager

The four-year program will address two Technical Areas (TAs) and be divided into three phases.

The goal of TA1, “Bioengineering for REE Utilization,” is to establish a platform for engineering organisms and/or biomolecules to enable the binding of REEs under harsh conditions. “Organisms” envisioned for this TA include microbes, fungi, or bacteriophage; use of photosynthetic organisms (cyanobacteria, microalgae) as chassis must include justification of the additional energy demands that these organisms require.

TA2, “REE Biomining” will focus on developing and testing a biomining workflow to purify individual REEs from actual source materials. Recovered REE materials may be in the form of salts (e.g., halides or nitrates), phosphates, oxides/hydroxides, or reduced metals, and should be devoid of biomass and impurities. Teams will develop and test a biomining workflow to purify individual REEs from complex source mixtures, likely using a combination of geological, chemical, and/or process engineering steps. Studies will progress from the laboratory bench scale to a pilot scale demonstration capable of generating at least 700 grams total REEs per week. It is anticipated that the pilot scale demo will need to be co-located with the REE source material site.

Teams must propose to both TAs to develop comprehensive, enduring solutions.

During Phase 1, efforts will focus on developing microorganisms and biomolecules suitable for use in REE separation—a challenging task due to the chemical similarity between REEs. In Phase 2, performers will work on improving the efficiency and scale of REE separation from actual source materials. Phase 3 will culminate in an aggressive, pilot-scale REE biomining demonstration. Throughout the program, the teams will work with an Independent Verification and Validation (IV&V) team established by DARPA.

EMBER aims to deliver multiple capabilities, such as the separation of REE mixtures into individual elements; inter-conversion of REE salts/oxides to facilitate production of manufacturing-ready forms; and new assays for high-throughput analysis of REE-containing cells and biomolecules.

—Linda Chrisey