A team of scientists from University of California, Berkeley, has developed a new method for breaking plastics down into their original building blocks. This could unlock a new highly-efficient recycling industry that produces valuable plastics and reduces the need to derive them from fossil fuels.

The problem with recycling methods today is that they collect and combine plastics with different chemical architectures to create weaker, less useful plastics. "The biggest problem is that there are hundreds of different types of these plastics with different lengths of [carbon atom] chains and distribution of lengths of the chains, etc.," said John Hartwig, professor of chemistry at UC Berkeley who led the new study, in an interview with Interesting Engineering.

"Each of these is made for specific purposes, like a yogurt container or the inside of a car door, from the same monomer but with a different chemical architecture to give different properties," he continued. "When those are mixed and melted and used to reform a new object, it does not have the properties of either the yogurt container or the car door."

Plastic waste is a well-known problem all over the globe. According to a United Nations Environment Programme (UNEP) report, approximately 430 million tons of plastic is produced yearly. Nearly half of that ends up in a landfill, while 22% is mismanaged and ends up in the natural environment. This is largely down to the fact the world reached Plastic Overshoot Day on September 5. That is, the day in the year when plastic waste surpasses the capability of waste management systems to handle the massive amounts produced.

"Plastics are fantastic materials," Hartwig told IE. "They are much lighter than glass or metal but can have enough strength. They are more pliable than glass. One would not wrap food to preserve it in glass and ship and store the food in glass, for example. It even uses less energy and water to produce than paper."

The issue with plastic is that it lasts a long time and is difficult to recycle. "Paper, glass and aluminum are easier to recycle, although this recycling, particularly of glass, uses a lot of energy."

Hartwig and his team set out to develop a method that would conserve the original value of virgin plastics such as polyethylene and polypropylene, which are widely used for plastic bags and hard plastic packaging, respectively. They devised a catalytic process that essentially vaporizes these plastics, converting them into hydrocarbon gases.

The new method solves a key problems of traditional recycling: the diminishing returns related to the quality of plastic produced. Typically, plastics created via recycling won't be reused for the same plastic packaging and containers found in supermarkets--such as for yogurts, milk cartons, and plastic bags.

"Plastics are currently recycled by mechanical recycling," Hartwig said. "By this method, plastics of a similar type are combined and reprocessed to make something new. However, the properties are deteriorated by mechanical recycling, so the value of the material produced is much lower."

The method, called chemical recycling, breaks the chemical bonds in polymer chains to allow for the creation of new virgin plastics. "In the best-case scenario, polymer chains are broken to recreate the monomer from which the polymer was made," Hartwig explained. "In our work, we found a way to cleave carbon-carbon bonds to form a single product that can be used to make new plastics. Thus, one can envision chemically recycling polyethylene and polypropylene to make the monomers from which new plastics with the original properties could be made."

"In non-chemical terms, I like to compare it to deconstructing a metal chain," he said. "First, we cleave the chain in the middle with a catalyst and leave at the ends a reactive unit--a carbon-carbon double bond. Then a catalyst will remove that open link by attaching it to a new one. By doing so, the next chain link is left open. The catalyst can then attach that open chain link at the end to a new chain."

Ultimately, Hartwig and his team's new process could lead to a massive reduction in the amount of new plastics produced. Over time, this would reduce the vast amount of fossil fuels used to create new plastics. It would also prevent a lot of plastics from ending up in landfills and a lot of chemical waste--produced by traditional recycling methods--from going into the atmosphere. Although, it may be a while before the new method starts operating on an industrial scale.

According to Hartwig, "one could envision being able to increase the scale of the reaction by improvements in the catalyst and in the engineering of reactors. However, the timescale and probability of it becoming commercialized is too hard to predict."