Plastic waste could be used as a valuable soil additive

A team of researchers from the University of California, Riverside (UCR) has moved a step closer to finding a sustainable use for the hundreds of millions of tons of plastic waste produced annually which frequently ends up clogging streams and rivers, and polluting the world’s oceans. The experts discovered a method to convert this waste into a highly porous form of charcoal or char that can capture carbon and could potentially be added to soils to improve water retention and aeration of farmlands, as well as to fertilize the soils as it breaks down.

The scientists mixed polystyrene (the type of plastic used for Styrofoam packaging) or polyethylene terephthalate (PET – the material often used to make water and soda bottles) with corn stover (the leftover stalks, husks, leaves, and cobs). This mixture was then cooked with highly compressed hot water, in a process called hydrothermal carbonization.

This study followed an earlier successful effort to use corn stover alone to produce activated charcoal that could help filter pollutants from drinking water. The researchers initially wanted to test whether activated charcoal produced from a combination of corn stover and plastic could also be an effective water treatment medium. Although this charcoal absorbed only about 45 percent of vanillin in test water samples – thus making it a rather ineffective medium for water cleanup – its potential use as a valuable soil additive remains an important discovery.

“It could be a very useful biochar because it is a very high surface area material,” said study senior author Kandis Leslie Abdul-Aziz. “So, if we just stop at the char and not make it in that turn into activated carbon, I think there are a lot of useful ways that we can utilize it.”

“I feel like we have more of an agnostic approach to plastic recycling when you can throw it in (with biomass) and use the char to better the soil. That’s what we’re thinking,” she concluded.

The study is published in the journal ACS Omega.  

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By Andrei Ionescu, Earth.com Staff Writer

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