Snipped from NewScientist.com.

Here is something that I find very interesting. The very same thing that locked away all the carbon from our atmosphere millions of years ago is now being researched to lock it away again. Certain types of grasses (wheat and sorghum) have been found to store away extra minerals and scrape plant materials in little balls called phytoliths, also known as ‘plantstones’. These stones have been found to contain extra carbon that the plant did not use during its photosynthesis.

What makes these grasses different is, unlike just planting trees that put away tons of carbon, but release it when they die, these little plantstones are indestructible, so the carbon stays locked away thousands of years after the plant dies and decays. This new finding could be the next step in combating global warming.

Here is a small portion of the article (article is members only, sorry):

As phytoliths form, they also lock up carbon by trapping scraps of plant material. They are practically indestructible, so once the plant dies they enter the soil where they may sequester carbon for thousands of years, say Leigh Sullivan and Jeff Parr of Southern Cross University in Lismore, New South Wales.

They compared 200-year-old soils in Papua New Guinea with soils buried 400 to 4000 years ago by a layer of volcanic ash, which prevented the addition of any more organic matter. Sullivan and Parr found the longer a soil had been buried the greater the proportion of carbon contained in the phytoliths compared with the rest of the soil, suggesting other carbon sources, such as humus, release carbon dioxide more rapidly than the phytoliths. …

The next step is to assess how plants that are better at storing carbon in phytoliths fare in terms of crop yield and quality. “So far our studies of wheat and sorghum suggest that there is no trade-off between yield and carbon sequestration,” says Sullivan.

Strains could be bred with enhanced ability to produce phytoliths, or genetically modified to do so.