Soaking up the veterinary antibiotics through black C
‘Black carbon’ (i.e. char, charcoal, and soot) is a high C-rich material and has a significant influence on the mobility and retention of chemicals in soils.
Laboratory, field studies, and traditional farming practices suggest deliberately added black carbon (as charcoal, “biochar”) can impact on soil fertility, crop production, and availability of nutrients. Fundamental knowledge of how black carbon reacts with various compounds and with soil biological constituents is important to engineer black carbons that will best meet specific environmental applications, such as remediation of contaminated land.
Each year, New Zealand farmers use around 60 tonnes of veterinary antibiotics to prevent and treat diseases and to a lesser extent promote growth. But 80% of each dose passes straight through the animal and ends up in the environment. Soil- and water-dwelling microorganisms exposed to these antibiotics develop resistance, which in turn can be transferred back to both livestock and humans. Therefore researchers at Landcare Research have come up with a novel way to soak up these unwanted contaminants – and increase soil fertility at the same time. The solution may lie in biochar – obtained by burning biomass in the absence of air. Biochars can be made easily from green waste, sawdust, and even corncobs. Since biochar can contain 80% C and is resistant to decomposition, it is a form of C sequestration, thus also contributing to reducing greenhouse gases. Landcare Research scientist Dr Ajit Sarmah and PhD student Prakash Srinivasan tested the absorption properties of three different biochars, and their preliminary findings suggest biochar made from pine sawdust produced using the steam gasification process, is the most effective in sorbing contaminants.
Biochar made from pine sawdust absorbs 150 times more contaminants than soil alone because it has a very high surface area, high C content (~ 90%), and is more porous than other biochars. Its surface area is four times bigger than that of corncob and green waste biochars. It is envisaged that biochar applied at the rate of 10 tonnes per hectare could prove effective in slowing the release of contaminants. Biochar produced from pine sawdust was also found to be the most effective uptaker of antibiotics and hormones when amended with soil. Further work will be required to test these results under realistic field situations.
Ajit Sarmah & Prakash Srinivasan
