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Scientists from the United States, Kenya, Austria and Switzerland have confirmed in a new study, that figs can to absorb CO₂ and effectively store it in its own trunk and the soil around it.
Researchers have found, that figs form limestone-like deposits in the trunk and soil around them that provide a strong barrier to retain carbon. The results of the new study indicate, that some fig trees in Kenya absorb CO₂ and block it, forming calcium carbonate.
These trees were among the first fruit trees to use oxalate-carbonate process. They are not just absorb CO₂ and use it as a building material, like most trees, but store it in a solid mineral form, deep in the trunks and soil around them.
Some trees use CO₂ to form calcium oxalate. After some of these trees die and decompose, microbes and fungi convert the calcium oxalate into carbonate. It not only stores carbon longer, but also makes the soil around the tree more alkaline and rich in nutrients.
«We have known about the oxalate-carbonate pathway for a long time, but its potential for carbon sequestration has not been fully taken into account. If we are planting trees for agroforestry, given their ability to store CO₂ in the form of organic carbon while producing food, we could select trees that provide an additional benefit by also sequestering inorganic carbon in the form of calcium carbonate», — notes one of the study’s authors, Dr. Mike Rowley, Senior Lecturer at the University of Zurich.
Researchers from Zhejiang University, Nairobi Technical University of Kenya, Sadhan Forestry University, Lawrence Berkeley National Laboratory, University of California, Davis, and University of Nevshatel studied three types of fig trees growing in the district Samburu in Kenya.
They determined the distance from the tree at which calcium carbonate is formed and examined the colonies of microbes involved in this process. The results using synchrotron analysis on a device at Stanford University, they found that calcium carbonate is formed both on the outside of the tree trunk and in deeper wood layers.
«As calcium carbonate forms, the soil around the tree becomes more alkaline. Calcium carbonate forms both on the surface of the tree and within its structures, probably as microorganisms decompose the crystals on the surface and also penetrate deeper into the tree. This shows that inorganic carbon is stored deeper in wood than we previously thought», — adds Mike Rowley.
Of all the three types of figs studied by the researchers, Wakefield ficus was the most efficient at sequestering CO₂ in the form of calcium carbonate. Now the researchers plan to assess the prospects of this type of fig in agroforestry by quantifying its water requirements and yield. In addition, scientists want to conduct a more thorough analysis of how much CO₂ can be absorbed under different conditions.
Most of the research on the oxalate-carbonate pathway was conducted in the tropics and concerned trees that do not produce edible fruit. The first tree to be discovered to use the oxalate-carbonate method was iroko (Milicia excelsa). During its lifetime, this tree can bury up to a ton of calcium carbonate in the soil.
«Many tree species have already been identified that can produce calcium carbonate. But we believe there are many more. This means that the oxalate-carbonate pathway could be a significant, but as yet unexplored, opportunity to reduce CO₂ emissions from planting trees for forestry or fruit production», — Mike Rowley emphasized.
Source: SciTechDaily