Blue sky thinking: bacteria have an appetite for recycling

The world is awash in plastic. Some 400mn tonnes are produced each year. Most is not recycled and ends up in landfills or the ocean. As it degrades, plastic also accumulates in the food chain. Microplastics are widespread in fish.

Yet plastic production is accelerating It is expected to grow 50 per cent by 2050 to almost 600mn tonnes a year, says the International Energy Agency. Recycling is expensive. Researchers think plastic-munching microbes offer an alternative solution.

Microbes are nature’s recyclers. They can create enzymes — or proteins — that break down organic matter into soil. In 2016, researchers in Japan discovered a bacteria that produced enzymes able to break down polyethylene terephthalate (PET), a substance used to make plastic bottles and polyester clothing.

Enzymes are an appealing choice. Although industrial chemicals can break down plastics, enzymes require less energy, making them a potentially greener option. Their use also allows easier recycling of plastic from mixed garbage.

The problem is that even the best enzymes tend to work relatively slowly, making them economically inefficient and hard to scale up to handle commercial volumes. Any naturally occurring plastic-gobbling bacteria would require serious bioengineering if they are to degrade plastic hundreds, or thousands, of times faster.

The main hurdle is an economic one. New plastic is cheaper than recycled versions. Without subsidies, plastic-eating bacteria and their enzymes will continue to compete with cheaper virgin plastics sourced from petroleum.

Start-ups are raising funds to speed up biorecycling. In the UK, Epoch Biodesign, which is targeting plastics that cannot currently be recycled, raised $11mn this summer. Across the channel, French company Carbios announced in 2019 that it had successfully produced new plastic bottles from PET with a process that makes them infinitely recyclable.

The goal is for bacteria to break down old plastic and create components used for new plastic. Eventually, plastic could become an enzyme-enabled circular economy.