In recent weeks, a crew of staffers from a company called Charm Industrial have been working on the edge of Kansas corn fields, moving rolled bales of stalks, leaves, husks, and tassels up to a white semi-trailer. Inside, a contraption called a pyrolyzer uses high temperatures in the absence of oxygen to break down the plant material into a mix of biochar and bio-oil. The former will eventually go back into fields, adding carbon and nutrients to the soil.