New research published by the University of Bremen suggests enhanced weathering may in fact harm peat soils and fail to remove as much CO2 as it causes. The study led by Dr. Alexandra Klemme was published in the Communications Earth & Environment journal, part of the Nature Portfolio, on Sept. 17.
The research explores measurements taken over 10 years in rivers in Indonesia and Malaysia and the ocean coast of Sumatra.
Enhanced weathering is a geoengineering method of intentionally crushing rocks into powder to allow more surface area for carbon to bind to rock, thus accelerating the natural chemical process that traps CO2.
“Spreading pulverized rock over land – for example, agricultural land – is being discussed as a possible method for reducing atmospheric CO2,” Klemme said.
The method is considered promising, and peatlands are theoretically the optimal zones to successfully implement it, as tropical heat and humidity also speed up the natural weathering process. In Southeast Asia, which is the focus of the research, peatlands also protect against sea level rise and absorb high amounts of CO2. The land use loss to agriculture, though, impacts this process.
Enhanced weathering brings up the soil pH value and peatlands naturally have low pH. This is why scientists think the practice may improve crop yields while also trapping carbon. According to Klemme, however, raising the pH value of soils destabilizes them and this is not accurately taken into account when estimating how much CO2 can be sequestered using this method.
In fact, the University of Bremen study determined that enhanced weathering caused more CO2 to be released from peat soils, increasing carbon emissions from rivers and coastal waters.
The potential CO2 uptake that comes from enhanced weathering is reduced by 18 to 60% by re-emission, the researchers estimated. “Our findings suggest that in contrast to the desired impact, enhanced weathering may destabilize the natural carbon cycle in tropical peatlands that act as important carbon sinks and protect against coastal erosion,” the study said.
While Klemme and her team did not entirely rule out the benefits of enhanced weathering, they said more research is needed on how the method impacts different types of soils.