Current carbon removal methods are proving to be inadequate and costly. But Berkeley researchers have a novel proposal: growing biomass crops to capture carbon from the air, then burying the harvested vegetation in engineered dry environmental chambers. This unique approach, called agro-sequestration, keeps the buried biomass dry to suppress microbial activity and stave off decomposition, enabling stable sequestration of all the biomass carbon.
“We’re claiming that proper engineering can solve 100% of the climate crisis, at manageable cost,” said Eli Yablonovitch, professor of electrical engineering and computer sciences. “If implemented on a global scale, this carbon-negative sequestration method has the potential to remove current annual carbon dioxide emissions — as well as historical emissions from the atmosphere.”
Ensuring the stability of the buried biomass is a challenge. While these storage environments are devoid of oxygen, anaerobic microorganisms can survive and cause the biomass to decompose into carbon dioxide and methane, rendering sequestration approaches carbon-neutral, at best. But living cells must be able to transfer water-solubilized nutrients and water-solubilized waste across their cell walls to survive. According to co-author Harry Deckman, decreasing the water activity — similar to relative humidity — below 60% stops these metabolic processes, which has been shown in research from both the U.S. Food and Drug Administration and NASA.
This approach, unlike prior efforts toward carbon neutrality, seeks not net carbon neutrality, but net carbon dioxide removal. According to the researchers’ analysis, for every metric tonne of dry biomass, it would be possible to sequester approximately 2 tonnes of carbon dioxide.
Agro-sequestration is also extremely cost effective. Together, the agriculture and sequestration costs total $60 per tonne of captured carbon dioxide, in comparison to some direct air capture and carbon dioxide gas sequestration strategies, which can equal or exceed more than $600 per tonne.
Learn more: To more effectively sequester biomass and carbon, just add salt (Berkeley News); Scalable, economical, and stable sequestration of agricultural fixed carbon (PNAS)