There is a soap dish for sale in So Paolo, Brazil. There are millions of plastic soap dishes on sale in shops around the world. Some of the plastic in this dish was created by methane from a water treatment facility in California.

The methane in the bioreactor was transformed into a molecule called P3HB by ancientbacteria. P3HB is a kind of internal battery used by thebacteria. A California company called Mango Materials uses P3HB as a raw material to make lentil-sized pellets. The soap dish was made from the common currency of the plastic industry.

Scientists, non-governmental organizations and companies large and small are working together to make plastic more sustainable. Molly Morse is the chief executive of Mango Materials. 400 million tonnes of plastic is produced every year by the company. Food packaging, building materials, electronics, clothing, and a host of other things are made of plastic.

Non-renewable resources are important to the plastic industry. The majority of global plastic production is made from petroleum products. The reliance requires a lot of energy. The carbon budget needed to keep global warming below 1.5 C could be as much as 15% by the year 2050. It's 1

A huge waste management issue is created by the use of plastic. The sheer volume of waste that is created is unlike any other supply chain.

The majority of the plastic that has been produced have already been thrown away. Around 40% of plastic production is single-use plastic. Even after being thrown away, the most widely used plastic remains in the environment for decades or centuries.

Many plastic items can be recycled. Only a small percentage of the plastic that has been produced have been recycled twice. It's cheaper to make a new plastic product than to collect, recycle, or reuse it, according to a researcher at a university. It is a systemic problem.

Changing that picture will require action on many fronts, including scaling up established recycling technologies, rolling them out across the world, developing technologies to deal with hard-to-recycle plastics, and reining in the production of single-use plastic. The results may have benefits for the circular economy. Sarah King, a circular economy researcher at the Swinburne University of Technology, says that there is a lot that can be learned from the plastic space.

A better sort

To make plastics more sustainable, they need to be scaled up worldwide. The majority of the plastic that is recycled is mechanical. Plastic waste is collected, sorted, shredded, melted down, and formed into pellets to be sold to producers of recycled plastic products.

It is not simple in practice. Ed Cook, who studies waste plastics as part of the circular economy, says there is so many different types of plastic. Different types of plastic don't mix well when they are melted down and small amounts of the wrong type can degrade the quality of a whole batches

High-income countries usually use high-tech machines to sort their waste. Most of the time, these facilities target the most commonly used plastic types, such as polyethylene terephthalate (PET, used to make fizzy drink and water bottles), high-density polyethylene (HDPE, found in milk and shampoo bottles), and sometimes low- density polyethylene (LDPE,

You can sign up for Scientific American's newsletters.

Recycling plastic is usually lower quality than primary plastic. There are more than 10,000 different chemicals that can be used to make plastic. The recycled material from the same type of plastic often contains different combinations of Additives. The longer the chains that make up these materials, the shorter they become.

Plastic recycling usually amounts to downcycling because of these factors. A plastic beverage bottle can be used as a component for a park bench.

The market for recycled plastic is limited because manufacturers can't make many products with it. Most of the plastic collected for recycling in Switzerland will end up in recycled plastic products. She says it isn't enough if we only collect more. Secondary material can't be utilized without other changes to the plastic system.

Chemicals called compatibilizers are being developed to help different types of plastic mix together when they are melted down. Megan Robertson is a chemical engineer at the University of Houston and she says that the idea of applying it to recycling has gained a lot of traction. Robertson is trying to develop a more flexible compatibilizer that could be applied to diverse mixes of polymers, as several compatibilizers that can aid mixing of specific types of plastic are now commercially available.

Efforts are being made to improve the sorting of plastic in the recycling process. The HolyGrail 2.0 project is a collaboration between more than 160 companies and organizations involved in plastic packaging that is being piloted in Europe. These are codes embedded in plastic packaging that can be read by specialized cameras and contain information about the attributes of a piece of plastic waste. Another approach is called aligned design, which calls on plastic manufacturers to make products with less plastic and use the same set of Additives. Higher quality recycled plastic would be yielded by a larger volume of similar plastic. An easy win would be to make things simpler.

Companies are starting to listen to these ideas. The Coca-Cola Company has used green bottles for 60 years, but in August it began packaging its lemon-lime drink in clear plastic bottles. The company wants to help the recycling of its bottles back into bottles, rather than into other products that are harder to recycle. Coca-Cola will be able to increase the amount of recycled content in its packaging as a result of that. Increasing market demand for secondary plastics is one of the keys to increasing recycling rates. The problem of plastic waste could be solved if the people making the plastic needed the waste as a source of fuel. That makes me optimistic.

Global improvisation

Plastic is cheap to produce and can be used by people living in informal settlements with little access to food and water. It is less energy intensive to transport than other packaging materials. Even in the remotest places, these products are found all around the world.

There isn't an economic incentive to collect waste plastic from those isolated locations. Many low- and middle-income countries don't have formal recycling programs. Two billion people don't have access to regular waste management services. The majority of the 13 million tonnes of plastic that enters the oceans each year comes from areas with inadequate waste management.

A prototype sorting unit.
A worker sorts plastic bottles in Surabaya, Indonesia.
Bird trapped in discarded plastic netting.
A prototype sorting unit tested by the smart-packaging initiative HolyGrail 2.0 could improve the separation of plastic waste (top). A worker sorts plastic bottles in Surabaya, Indonesia (middle). Birds can be easily trapped in discarded plastic netting (middle). Birds can be easily trapped in discarded plastic netting (bottom). Credit: Digital Watermarks Initiative HolyGrail 2.0 (top); Juni Kriswanto/Getty (middle); tsvibrav/Getty(bottom)

Low- and middle-income countries recycle a lot of plastic. The informal economy tends to include recycling. The pickers collect plastic from the environment. The research shows that the waste pickers are behind more plastic recycling than the formal industry.

Informal workers are entrepreneurial and able to change jobs. According to a waste-management scientist at the University of Cape Coast in Ghana, door-to-door purchases of some of the most desirable plastic for recycling have begun. Some householders would not want to add plastic to the waste. The cleaner plastic will fetch a higher price than items that have been picked out of a landfill, he says.

In low- and middle-income countries, waste pickers and collector often come from marginalized communities and their activities are sometimes criminalized. They don't get value for money because they don't have the power to bargain That is starting to change. Efforts to include the waste pickers in waste management planning are being spurred by recognition of their contributions and concern for their working conditions.

Some of the plastic collected by waste pickers is recycled in larger countries like Brazil and Indonesia. Some is sent abroad to be recycled. Some is recycled by small-scale businesses. There is no environmental or public-health protection in these operations. There is a lot of variation in the global south.

Advanced breakdown

Despite efforts to boost established recycling approaches around the world, the past decade has seen increasing research attention turn to advanced recycling technologies. These methods have not been used widely on a commercial scale, but they could eventually allow recycling of plastic types that can't be recycled mechanically.

Pyrolysis is a method in which the plastic is heated to high temperatures without the use of oxygen. The chain breaks down into smaller components. Pyrolysis can be used to recycle mixed plastic waste.

The process of turning plastic into fuel is an energy intensive process that results in carbon being released into the atmosphere. In theory, the smaller molecules could be reassembled into plastic.

Another way to recycle is to break down the plastic into smaller pieces. The shortening chains and degradation of quality that happens with mechanical recycling can be circumvented. thermoset can't be recycled mechanically because they cannot be melted down These materials are used in wind turbine blades.

Upcycling is the process of making chemical products from the monomers that are more valuable than plastic and difficult to produce. 3-hydroxy--butyrolactone, which is used to produce cholesterol-lowering statin drugs, is one of the key roles that these chemicals have. Bardow says that the high value of these compounds could lead to a push to develop chemical recycling technology.

It takes a lot of energy to break plastic into smaller pieces because they are very stable. The researchers are looking for ways to reduce the amount of energy required. Robertson says that is where the game is right now.

Natural inspiration

In order to find the catalysts that could aid chemical recycling, we can visit places where they are already present in nature. Some of the approaches Mango Materials uses came out of work from Criddle's lab. Sometimes organisms can break down natural polymers, which can be used to disassemble human-created ones. Mealworms are the focus of Criddles research. The gut community of these Insturments can help them digest more than one plastic. Some researchers have found that certain types ofbacteria can break down multiple types of plastic into the same product.

The natural world is being looked at to make other parts of the plastics industry more sustainable. There has been an increase in interest in the production of plastic from renewable sources. If bioplastics were to scale up significantly, it could cause pressure on agricultural lands and water supplies. Methane is a potent greenhouse gas that is a product of wastewater treatment plants, landfill sites and agricultural facilities. Plastic is a more valuable material than other products that can be made from methane.

There are drawbacks to using bioplastics. Those made from fossil fuels are usually different from those made from polymers. They don't fit in with the recycling systems we have right now. The technology exists to recycle it, but the facilities don't because they don't produce enough of it. Another disposal solution is also provided by P3HB.

Beyond recycling

Global plastic demand is expected to triple by the year 2050. In an analysis released earlier this year, Bardow and his team found that scaling up recycling, relying more on renewable feedstocks and implementing other strategies could keep the current level of plastic production within "planetary boundaries". Even with all the tricks that chemists and chemical engineers can pull, there will be no sustainable solution if plastic production continues to grow.

There is a need to reduce the use of plastic. We haven't gotten very far if we just turn from making oil-based single-use plastic products to renewable-based single-use plastic products

There is no research that supports this transition. Most plastic research in Europe focuses on recycling and the waste phase of the material, with little attention to other parts of the product life cycle, according to an analysis of plastic research relevant to Europe. More than one-quarter of studies focused on recycling, but less than 10% focused on topics such as repair and reuse.

Efforts to improve plastic are continuing. An order of magnitude leap in capability is what Mango Materials is seeking for a facility that could produce up to 2,300 tonnes of P3HB per year. It is enjoyable to be a part of the solution. It is very difficult.

The article is part of Nature Outlook: Circular Economy.

  • Zibunas, C., Meys, R., Kätelhön, A. & Bardow, A. Comput. Chem. Eng. 162, 107798 (2022).
  • Geyer, R., Jambeck, J. R. & Law, K. L. Sci. Adv. 3, e1700782 (2017).
  • Lange, J.-P. ACS Sustainable Chem. Eng. 9, 15722–15738 (2021).
  • Tiso, T. et al. Metab. Eng. 71, 77–98 (2022).
  • Klotz, M., Haupt, M. & Hellweg, S. Waste Manag. 141, 251–270 (2022).
  • Wilson, D. C. & Velis, C. A. Waste Manag. Res. 33, 1049–1051 (2015).
  • Bardow, A. et al. Preprint at Research Square (2022).
  • Johansen, M. R., Christensen, T. B., Ramos, T. M. & Syberg, K. J. Environ. Manag. 302, 113975 (2022).
  • King, S. & Locock, K. E. S. J. Clean. Prod. 364, 132503 (2022)