‘Crustivoltaics’ could restore vital ecosystems, benefit solar farms

By Nicholas Gerbis
Published: Friday, April 21, 2023 - 4:06pm

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Biodesign Institute/ASU
Biocrusts stabilize soil and contribute to nutrient cycling by fixing atmospheric nitrogen, a process in which nitrogen gas is converted into ammonia, making it available to plants.

A new proof-of-concept study in Nature Sustainability uses local solar farms to restore vital ecosystems called biocrusts.

The low-cost approach, which the authors dub “crustivoltaics,” can benefit solar farms by reducing dust on panels and potentially qualifying the farms for carbon credits.

For senior author Ferran Garcia-Pichel, director of ASU’s Biodesign Center for Fundamental & Applied Microbiomics, the research marks a milestone in a years-long journey.

“We started — in our lab, maybe 15 years ago or so — thinking, ‘Oh, we can make a difference. We know these microbes; we know what works; we should also start trying to work towards the solution,’” he said.

Biocrusts are thin, crumbly layers of soil and microbes. They protect looser particles from erosion, remove carbon from the air and help supply water and nitrogen to plants.

“When light has the opportunity to impinge directly on the surface of the soil, then that becomes habitat for cyanobacteria, algae, other photosynthetic, small organisms, and they make a habitat out of it,” said Garcia-Pichel.

But farming, construction and off-road vehicles tear them up, harming plants and kicking up dust.

“They’re brittle; they crumble like a cookie, and so they really cannot resist a lot of pressure,” said Garcia-Pichel.

Biodesign Institute/ASU
Ferran Garcia-Pichel is a Regents’ Professor in the ASU School of Life Science and the founding director of the Biodesign Center for Fundamental & Applied Microbiomics.

The three-year study shows the shade beneath solar panels can act as a protective nursery for growing biocrusts, which could potentially be transplanted elsewhere.

Garcia-Pichel said the idea grew out of another notion that’s been making the rounds for a while — that of using the shady acreage solar panels provide to grow heat-sensitive plants like tomatoes.

“I thought, ‘Well, if it works for plants, it will certainly work for or microbes,” he said.

The massive solar farms also answered another key question in biocrust restoration: How to scale up from growing samples in a lab to cultivating ecologies on huge swaths of land?

“It was not so much about the biology anymore; it was not about the microbiology, certainly, or the ecology. It was really about finding a different platform,” said Garcia-Pichel.

The authors estimate Maricopa County’s three largest solar farms could restore all fallow farmland in the county within five years. That’s about 70,000 hectares (nearly 173,000 acres or 270 square miles).

“I can see how we can do things now that we did not see possible a year ago, and things that are possible 1,000 times larger than we would have imagined,” said Garcia-Pichel.

Shireen Dooling
ASU researchers adapted a suburban solar farm as a breeding ground for biocrust. Photovoltaic panels promoted biocrust formation, doubling biocrust biomass and tripling biocrust cover compared to open areas with similar soil characteristics.

Science Sustainability