Salted crops seen as powerful tool to fight climate crisis

As emissions of greenhouse gases such as carbon dioxide continue to rise , and the climate feedback loops caused in part by those emissions accelerate, it is more important than ever to find ways to pull carbon out of the air. The problem is that direct air capture (DAC) technologies, such as the fast and efficient one developed last year by researchers at Tokyo Metropolitan University , are prohibitively expensive to build and maintain.

Also, the world's largest carbon capture plant , slated to open this year in Wyoming , will cost $600 to take a ton of carbon out of the air, though the project's developers hope to eventually bring the cost down to a hundred dollars. Even at $100 per ton, the cost would be enormous considering we need to remove nearly a billion tons of carbon from the atmosphere each year to meet current climate goals.

So scientists are working on finding other ways to remove carbon from the air in more cost-effective ways. Earlier this year, scientists at MIT proposed a relatively cheap way to remove carbon from the world's oceans so they can absorb more from the atmosphere, and last year chemists at UC Berkeley proposed using An inexpensive material called melamine captures carbon from chimneys and tailpipes.

Another affordable way to capture carbon from the air is through so-called agricultural sequestration. The technique works by growing crops that sequester carbon, such as certain grasses, and then burying those crops deep in the ground. The problem is that when the bacteria start breaking down these crops, the carbon will be released back into the atmosphere.

To overcome this obstacle, Berkeley scientists have come up with a simple solution: salt. By first drying the crops and then burying them in biomass pits covered with a two-millimeter-thick layer of polyethylene, and then adding salt, the crops can hold carbon stores in the ground for centuries.

"There are major questions about long-term storage of many of the recently popularized natural and agricultural techniques," said Harry Deckman, co-author of a new study on the method. "Our proposed agricultural sequestration method can stably store carbon in dry, saline biomass for thousands of years at a lower cost and more carbon-efficiently than other air capture technologies."

Unlike DAC technology, the researchers say their solution costs only about $60 per ton of carbon dioxide captured and stored. What's more, the process will be carbon negative, as two tons of carbon dioxide can be sequestered for every ton of dry biomass.

The team compiled a list of high-yielding plants and said most could be grown on marginal farmland, most of which are not currently being used to grow crops. They also say that a 1-hectare pit can hold 10,000 ha of biomass-based material Using these calculations, the researchers say that only one -fifteenth of the world's cropland, forests and pastures would be needed to sequester half of the world's greenhouse gas emissions.

"It would take a lot of farmland to remove all the carbon that's being produced, but that's the amount of farmland that's actually available," Yablonovitch said. "It will be a huge boon for farmers because there is currently underutilized farmland."

The research has been published in the journal PNAS .

Article source: University of California, Berkeley