Every year on April 22, we celebrate Earth Day; promoting environmental enthusiasm and efforts to protect our planet’s precious natural resources. As part of ARPA-E’s authorizing authority that established the agency within the Department of Energy, we’re tasked to overcome long-term and high-risk technological barriers in the development of transformative science and technology solutions to address the energy and environmental missions of the Department. Because of this, our projects and programs focus on developing technologies that have the potential to radically improve U.S. economic prosperity, national security, and environmental wellbeing.

This year marks the 51st Earth Day, and looking back on the last few decades of Earth Day we’re reminded of what environmentalist and “Father of the National Parks” John Muir once said, “Of all the paths you take in life, make sure a few of them are dirt.” We’ve taken those words quite literally while exploring various technical paths at ARPA-E, and we’re looking back at a few of our “dirtiest” programs and projects this Earth Day focused on transformative soil-based and geothermal-focused energy technology development!

Starting with “dirt” itself, ARPA-E’s Rhizosphere Observations Optimizing Terrestrial Sequestration (ROOTS) program seeks mitigate the effects of climate change and improve soil health.  The ROOTS projects are developing advanced technologies, tools, and crop varieties that increase carbon accumulation in soil while reducing N2O emissions and increasing water productivity of plant systems themselves.  ROOTS utilizes America’s vast terrestrial resources as well as advances in energy and agricultural technologies to improve the ability of crops to store carbon below ground, seeking to turn soil into a more effective option for carbon storage and improve the energy efficiency of agriculture. ROOTS teams have developed a range of technologies to help remove CO2 from the atmosphere and store it in plant root systems, including monitoring devices that can be placed on plants themselves, imaging scanners to map root systems, and modeling tools to produce crops at scale that can greatly increase carbon uptake in soil.

These projects as well as others from ARPA-E’s new Systems for Monitoring and Analytics for Renewable Transportation Fuels from Agricultural Resources and Management (SMARTFARM) program can help to reduce greenhouse gases from the atmosphere, and connect agriculture to carbon offset markets.

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Continuing down the path of soil-based technologies, Energy Storage Systems Inc. from ARPA-E’s Grid-Scale Rampable Intermittent Dispatchable Storage (GRIDS) program is developing a new approach to long duration storage technology, utilizing soil and the earth in developing a low-cost iron-based flow battery for grid-level storage. Flow batteries are easily rechargeable systems that store electrolytes—the material that provides energy—as liquid in external tanks, which allows for separate optimization of the system energy and power. These batteries face challenges in development and deployment because of high system costs. ESS’ approach utilized cost-effective electrolytes based on iron and salt that’s abundantly found in earth and soil as opposed to expensive materials found in other current flow batteries to lower costs, size, and dramatically increase the energy density and storage time of their system.

Switching from soil to rocks, ARPA-E is supporting technologies that could transform the geothermal energy industry. While geothermal energy is a potentially vast source of clean baseload electricity, current drill bits used across the geothermal energy industry penetrate ultra-hard rock formations slowly and wear down quickly, making it geothermal resources difficult and expensive access. AltaRock Energy Inc., from ARPA-E’s OPEN 2018 program; is addressing this challenge by working to develop an alternative to conventional mechanical deep geothermal drilling technologies. Their project uses millimeter wave (MMW) directed energy technology to melt and vaporize rocks for removal, which could provide new pathways to utilizing efficient, clean geothermal energy by increasing drilling speeds and reducing costs for accessing higher temperatures and greater depths than the best current and proposed mechanical geothermal technologies.

While you might not typically think of long duration storage technologies when you think of soil and rocks, a team from ARPA-E’s  Duration Addition to electricitY Storage, or DAYS program, is working to develop a geomechanical pumped storage system that stores energy via pressurized water in underground confined rock. Quidnet Energy is developing a modified pumped hydro energy storage system that pumps water into underground rock, creating high pressures. When energy is needed, the system uses the pressure stored in the underground rock to force water back up and through a generator to produce electricity. Long duration energy storage systems like this work to address grid needs beyond those covered by daily cycling and have the potential to provide backup power to the grid for extended periods of time.

These programs and projects work to address a range of different technical spaces, but they all support the core mission of ARPA-E as an agency to reduce emissions, improve efficiency, and change the way that Americans get, use, and store energy. On Earth Day and every other day, ARPA-E continues to focus on developing the transformative technologies of the future that can radically improve U.S. economic prosperity, national security, and our earth’s environmental wellbeing. Visit our Program Search page to learn more about all of our active focused programs.