Burning Crops to Capture Carbon? Good Luck Finding Water

Mother Nature saved us from ourselves. Plants on land and in the sea absorb CO 2 as they grow. The oceans absorb more carbon dioxide than before, helping keep warming to 1.2 degrees Celsius above pre-industrial levels.

Our civilization is on track to reach 1.5 degrees warming in the early- to mid-2030s, which is the optimistic goal set by the Paris Agreement. The UN's Intergovernmental Panel on Climate Change stresses that it's not enough to dramatically reduce greenhouse gas emissions. Direct air capture machines that scrub the air of CO 2 could be used. Others are looking at ways to use plants to sequester carbon.

It is a huge challenge to decarbonize the entire energy sector in 20 to 30 years, which is what it would take to reach 1.5 degrees of warming.

One controversial idea is known as bioenergy with carbon capture and storage, or BECCS: You grow crops and burn them for energy, then capture emissions from the facility and pump them underground as gas. We already get bioenergy from plants by burning wood pellets or by producing ethanol from corn, but both are done without the carbon-capture-and-storage bit.

The only technology that removes carbon from the atmosphere isBECS, and it gives you a free energy source. Direct air capture is a type of capture that uses the air to absorb CO 2 from the air. On a planet with a ballooning human population that itself needs more food and water, BECCS requires lots of land and water. Climate change is already driving more intense droughts across the world.

Scientists wrote this week in the journal Science Advances about a scenario in which bioenergy crops were scaled up across the United States, and what that would mean for both carbon capture and water use. The good news is that large-scale BECCS would sequester a lot of carbon. The good news is that it would expose 130 million Americans to water stress because of the water required to grow all those crops and the extra fertilization that would cause rivers to be polluted with nitrogen.

Population growth, water and energy needs for people and agriculture, how land is used, and others are some of the variables that the researchers incorporated into socio-economic models. The models predicted where in the US it would be best to site bioenergy crops. The environmental consequences of changing the land to accommodate BECCS were projected in an Earth system model. The BECCS version included a little bit of reforestation.