Boosting Plants to Close the CO2 Absorption Gap

Terrestrial plants (land based plants) are removing about 29 percent of our emissions that would otherwise contribute to growth of the atmospheric CO2 concentration. What Lucas Cernusak, ecoyphysiologist from James Cook University in Australia, model analysis showed is that the role of terrestrial photosynthesis in driving this land carbon sink is larger than estimated in most other models. Cernusak shows that photosynthesis has increased by 30 percent.

Humans add on average of 2 ppm of CO2 per year. The mass of the atmosphere is 5148 trillion tons. 2 ppm of CO2 is about 10.3 billion tons of CO2 per year. However, total human CO2 and global warming emissions is about 40 billion tons of CO2 per year. 75% gets absorbed by the land, plants and oceans.

Enzymes to Boost Plant Yields

Scientists from the University of Illinois and the Department of Agriculture have been experimenting with ways to genetically modify plants to store up even more carbon. An enzyme called rubisco is responsible for capturing CO2 for photosynthesis, and scientists want to make it more efficient.

Modified crops with increased rubisco boosts yields by about 40 percent, but using the modified plant enzyme on a large commercial scale could take more than a decade to implement. So far tests have only been done on common crops like tobacco, and it’s unclear how rubisco would alter trees, which capture the most carbon.

Best Trees for Absorbing CO2

The U.S. Department of Energy (DOE) has looked at tree species. Trees grow quickly and live long are ideal carbon sinks. Unfortunately, these two attributes are usually mutually exclusive. This would mean that the selection should be made for faster-growing trees that absorb more CO2 per year and then cut those trees down to store the CO2 as wood. The wood should then not be burned. Wood can be stacked up in dry locations where they will not rot.

Given the choice, foresters interested in maximizing the absorption and storage of CO2 (known as “carbon sequestration”) usually favor younger trees that grow more quickly than their older cohorts.

Dave Nowak, a researcher at the U.S. Forest Service’s Northern Research Station in Syracuse, New York, has studied the use of trees for carbon sequestration in urban settings across the United States. A 2002 study he co-authored lists the common horse-chestnut, black walnut, American sweetgum, ponderosa pine, red pine, white pine, London plane, Hispaniolan pine, Douglas fir, scarlet oak, red oak, Virginia live oak, and bald cypress as examples of trees especially good at absorbing and storing CO2. Nowak advises urban land managers to avoid trees that require a lot of maintenance, as the burning of fossil fuels to power equipment like trucks and chainsaws will erase the carbon absorption gains otherwise made.

Nextbigftuure notes that maintenance could be performed by electric vehicles using non-fossil fuel power generation.

SOURCES – DOE, National Geographic, Earth System Research Lab, NOAA Mauna Loa Observatory in Hawaii
Written by Brian Wang,