Of the technologies and techniques available, the new report notes that four are basically ready for prime time. It recommends that reforestation, shifts in forest management and agriculture, and the biomass burning and carbon capture idea (dubbed BECCS) can be scaled up now safely and at a reasonable cost. But the ramp up would need to be massive, and it still wouldn’t capture enough carbon out of the air.
To sequester a single gigaton of carbon using BECCS would require up to 106 million acres—the equivalent of the area of California—of cropland being turned over to growing biofuels. The scale and payoffs of unproven techniques is even more staggering. Turning all 13,000 miles of hardened U.S. shoreline to wetlands and mangroves that could sequester carbon would only pull 0.001 gigatons of carbon out of the atmosphere annually. The science fictional idea of speeding up the weathering certain types of rocks that can capture carbon from the air is even more unproven, though it could potentially generate wild returns.