Plastic pollution in soil might not get the same attention as plastic in the ocean, but it is a big problem. The soil is being impoverished by agricultural practice involving polyethylene films. Researchers now have a solution. They have demonstrated that an alternative polymer biodegrades in agricultural soil, a welcome result. This research is published in Science Advances.

The polymer in the study is poly(butylene adipate-co-terephthalate) or PBAT for short. It had been previously shown that this material can be biodegraded, but the researchers wanted to demonstrate how to track the biodegradation in soils.

The researchers used a radioactive isotope of carbon in a version of PBAT so they could track how the material from the polymer was absorbed and utilized. The team was able to show that each part of the polymer was used by soil micro-organisms, including fungi. The species involved used the polymer as an energy source and managed to grow off it.

"This research directly demonstrates, for the first time, that soil microorganisms mineralise PBAT films in soils and transfer carbon from the polymer into their biomass," co-author Michael Sander, Senior Scientist in the Environmental Chemistry Group at ETH Zurich, said in a statement.

Polyethylene films are used in agriculture to cover soils. This is to keep weeds away, increase soil temperature, and maintain the soil's moisture. It is impossible for farmers to collect and dispose of all of the films. What's left behind gets incorporated into the soil. PBAT offers a realistic solution, although it is still early days. A few companies are producing the films, but since it is more expensive it is not widely used.  

"Unfortunately, there is no reason to cheer as of yet: we're still far from resolving the global environmental problem of plastic pollution," Sander explained, "but we've taken a very important first step in the direction of plastic biodegradability in soil."

Plastic pollution is a serious problem that can be tackled at every level of society. Individuals need to be conscious of the choices they are making, industries need to be proactive about using environmentally friendly products, and governments need to act with evidence rather than sentiment (e.g. the plastic straw bans). Biodegradable polymers are the sustainable way forward but more studies are necessary.

"As we have demonstrated, there is hope for our soils in the form of biodegradable polymers," added Sander. "The results from soils should, however, not be directly transferred to other natural environments. For instance, biodegradation of polymers in seawater might be considerably slower, because the conditions there are different and so are the microbial communities."