Are deep eutectic solvents biodegradable?

Recently, deep eutectic solvents (DESs) have gained immense attention and consideration as a “greener” alternative to conventional volatile organic compounds and even ionic liquids. They have been marketed as cost-effective, environmentally benign, non-toxic, and biodegradable. However, most of the studies carried out on DESs have been dedicated to their physicochemical properties and their numerous applications; the evaluation of their biodegradability and environmental impact is still limited. It has been shown that depending on the choice of individual constituents used to prepare a DES, some of them cannot be simply deemed biodegradable. With the lack of attention toward the biodegradability of DESs and their fate, a short communication is needed that sheds light on their current status and elaborates on the biosafety issue. Thus, this work highlights key research efforts to date concerning DES biodegradability with the purpose of providing insight into directions for improving the sustainability of DESs and lowering their environmental impact, an essential task that will open doors for their large-scale application in a variety of industries.