The experts say that reducing emissions won’t be enough to reach international goals for limiting global warming. It will require the removal of billions of tons of carbon dioxide from the air each year. There are a growing number of startups working on the issue with dollars generated from the carbon credit market. Here are three examples. 

Seattle-based Lithos Carbon is spreading ground-up basalt on the soil. When rainwater mixes with the basalt, it traps CO2 as bicarbonate, which eventually flows to the ocean where it is stored for millions of years. Lithos buys basalt dust, a mining byproduct from quarries, and pays farmers to spread it instead of lime. Through this method, they expect to remove 20,000 tons of CO2 in 2023 while improving crop yields.

The nonprofit research organization Carbon to Sea Initiative is funding an experiment to see if modifying the ocean’s alkalinity could be an effective way to remove CO2. The team believes that increasing the alkalinity will convert CO2 already in the ocean into stable bicarbonate and carbonate molecules that sink to the bottom and, in turn, allow the water to absorb more CO2 from the air. Experiments are underway off the coast of Massachusetts. Much more work is needed to make it scalable and safe, as the alkalinity enhancement may pose risks to marine life.

Living Carbon, a California-based biotechnology company, has genetically modified poplar trees with pumpkin and green algae genes to make them grow faster. The trees absorb CO2 and turn it into wood at an increased rate. Pumpkins and green algae have genes that make the process of photosynthesis more efficient. In the greenhouse, the modified trees grew 53 percent faster than their natural counterparts. Trees have been planted outdoors to see if they produce similar results. Only female trees that don’t produce pollen are used to reduce the potential reproduction of trees with the altered genes.