How can we reduce the climate impact of plastic?

This article is the second part of a two-part series on plastic and climate change. Read the first article, ‘What are the climate costs of plastic?’ here.

It is difficult to imagine a world without plastic. An incredibly useful material, its cheapness and physical qualities have revolutionized the way we eat, play, work, buy goods and even dress ourselves.

But, given the sheer abundance of this material that came to be within the short span of a few decades, scientists and communities are increasingly wary of the potential environmental impacts that the world’s overconsumption of plastic can bring. And with the climate crisis already upon us, the role of plastic – responsible for roughly 4.5 percent of global greenhouse gas emissions in 2015 – cannot be overlooked.

In the first article of this series, we looked at the greenhouse gas emissions connected to the creation and disposal of plastic. But its journey doesn’t always stop there. In this article, we’ll explore what happens to plastic that ends up in the ocean, emerging ideas about what this could mean for climate change and what we can do to stop greenhouse gas emissions from plastic.

Plastic at sea

The waste left unmanaged on land eventually finds its way into the ocean, where immense currents circulate it to all corners of the Earth.

Yet even as it gradually degrades in the ocean, plastic waste continues to have a climate impact. A study published in 2018 found that plastic on the ocean’s surface continues to emit methane and other greenhouse gases, with these emissions increasing as the plastic breaks down. Although the emissions from this appeared to be small compared with emissions during other stages of the plastic lifecycle, they are expected to grow as more and more plastic is consumed, released and then degrades in the environment. 

Even more unsettling are the implications that plastic pollution could have on the ocean’s biological pump, the part of the ocean’s carbon cycle in which microscopic organisms trap atmospheric carbon into the marine food chain and sequester it into deeper waters. The ocean captures more than 25 percent of human-derived carbon emissions, and without the ocean’s carbon cycle, the world’s climate would have already warmed substantially more than it has already.

However, ocean plastic could hinder the workings of this biological pump. As plastic degrades, it breaks into smaller pieces, eventually becoming ‘microplastics,’ which are smaller than 5 millimeters in length. And it is these mini bits that could possibly change the workings of the organisms that keep the pump going. 

“Microplastics are this prolific contaminant. Wherever we look in the oceans, we’re likely to find microplastics,” says Matthew Cole, a senior marine ecologist at Plymouth Marine Laboratory in the U.K. “I have colleagues and students across the globe who are taking samples from the equator to the poles, and they’re all finding plastics in their samples. Even in waters that are thousands of miles from places where plastics are produced, they are finding their way there.”

These pieces of microplastic might affect phytoplankton – the tiny plants that make up the base of the marine food chain – possibly by inhibiting their feeding or reproduction. The same might happen to zooplankton, which can ingest plastic by mistaking it for food. In a 2015 study, Cole and colleagues studied the effects of microplastics on the feeding of Calanus helgolandicus, a copepod, and found that the presence of microplastics in the water meant the copepods consumed 11 percent less algae and 40 percent less carbon biomass.

“Just like every other animal, including humans, we need food for energy,” says Cole. “And when these animals didn’t have enough energy because microplastics were getting in the way, there were consequences for their ability to reproduce. And in other species there is also evidence that there are impacts on growth and survival as well.”

Whatever zooplankton or creatures higher up on the food chain eat eventually becomes poop. This then sinks to the bottom and is a crucial way that carbon is sent to the seafloor within the biological pump. In a 2016 study, Cole and other researchers fed polystyrene microplastic pieces to zooplankton and discovered that their poop sunk at less than half the speed as the poop of zooplankton without microplastic. Thus, plastic may directly slow this part of the biological pump.

Research on the effects of microplastic on phytoplankton or zooplankton has mainly been conducted in laboratory conditions so far, so there could be differences in the real world. However, existing studies illustrate an alarming picture of how plastic waste could potentially harm the marine creatures that make up the foundation of the biological pump and the entire marine ecosystem. 

And it’s not just at the ocean surface where microplastics are found. A study published in January of this year found microplastic pieces within deep-sea squid species – including the vampire squid, which lives 800 meters below the surface. Guilherme Ferreira, a researcher at the Rural Federal University of Pernambuco in Brazil and an author of the study, suspects that the high number of plastic pieces found in the vampire squid could have been because they mainly feed on marine snow, which is the feces or dead bodies of creatures nearer to the ocean’s surface.

“Most of the plastics should be floating on the surface of the ocean, but the biological pump apparently has a role on the vertical transportation of microplastics,” said Ferreira, who added that plastic’s accumulation, then breaking into smaller pieces due to solar radiation and being ingested to become marine snow could make plastic more likely to sink.

Ultimately, the effects of ocean plastic on the carbon cycle remain unclear. But according to Ferreira, it could have major implications, because marine species can suffer sub-lethal effects from eating plastics – including a decreased predatory rate, oxidative stress and a lower capability to reproduce. This could come to affect the daily migration of some deep-sea marine species to surface waters to feed at night, called the “diel vertical migration,” which is an important part of the biological pump of the carbon cycle.

“For those species that perform the vertical migration, those sub-lethal effects should have a major impact, because they spend a lot of energy to swim, sometimes even 1,000 meters a day, to feed in the surface layers,” said Ferreira.

Not to mention that it’s not just plastic that is being leaked into the ocean: “We’ve got land use – it’s intense. And we’re using lots of fertilizers and chemicals. There are tire particles. There are exhaust fumes. It all becomes a bit of a chemical cocktail,” says Cole. “There could be combined effects going on as well that we’re not even fully aware of at the moment.”

After plastic sinks into the depths of the ocean, its effects on the ecosystem and carbon cycle so far largely remain a mystery.

Can we move on from plastic?

There is growing awareness of the issue of plastic pollution around the world. Yet society’s dependence on it is unlikely to disappear anytime soon. The U.N. Environment Programme (UNEP) estimates that plastic waste could double by 2030, and it has been reported that fossil fuel companies plan to use plastic production to buffer their losses as countries increasingly switch to using renewable energy.

But there are ways to prevent this. Most experts interviewed in this article stated that the most direct and effective way to cut down on plastic-related greenhouse gas emissions was to use less plastic overall, especially single-use packaging. The caveat, though, is that this is often difficult and expensive, and in some cases alternative materials can actually have a higher environmental cost.

“A lot of people are working hard to reduce plastic in their own consumer purchases, but that’s really hard,” says Judith Enck, the president of Beyond Plastics. “I mean, I try to avoid plastic, and I can’t avoid it entirely. Any supermarket in the world is loaded with plastics.”

Thus, the circular economy was also often mentioned as crucial for limiting plastic waste. In contrast to the “take, make, waste” linear economic system that is currently in place, the circular economic model focuses on reusing, repairing and remaking products, minimizing the taking of new materials from the environment and the waste or pollution that comes from disposing used goods. 

Such a system would entail a rethinking of the way the current economic system works and still largely remains a theoretical concept. However, some industry initiatives are steps in this direction, including clothing rental programs, right-to-repair laws for appliances and take-back schemes in the furniture industry. 

Extended producer responsibility (EPR) schemes, in which manufacturers must also pay the costs of collecting, sorting and recycling the plastic, are also being introduced in more than 30 countries. In a 2020 briefing, the World Wildlife Fund (WWF) calculated that if companies paid a fee of around EUR 450 (USD 492) per tonne of plastic packaging within an EPR scheme, which is the rate under Germany’s EPR scheme, then China, Indonesia, Malaysia, the Philippines, Thailand and Vietnam could collectively raise over 13 billion USD. This could then be used to fund and enforce the waste management operations.

And just this month, almost 200 countries have agreed to set up a global treaty to tackle the plastic crisis, similar to the Paris Agreement for climate change. The world’s leaders have until 2024 to create the agreement, including its financing, legally binding stipulations and strength of standards.

The Brussels-based sustainability organization Zero Waste Europe is currently trying to have the European Parliament include waste-to-energy incineration within the EU Emissions Trading Scheme (ETS). An assessment by the group says that requiring waste companies to purchase credits for their emissions could result in lower emissions, a stronger financial incentive to recycle rather than discard waste, and job creation to fulfill the labor-intensive nature of recycling over incineration. 

A 2019 report from the Center for International Environmental Law notes that another important component of halting plastic-related greenhouse gas emissions is stopping the development of new gas, oil and petrochemical infrastructure. A main reason why plastic is so pervasive is because of its low cost, and increasing the supply of oil and gas on the market will continue to keep the price of plastic low to the point where creating more plastic is cheaper than reusing, refusing or recycling it. Such an action would also be critical for halting global climate change in general.

Livia Cabernard, a post-doctoral researcher at ETH Zürich and the author of a study that found that coal is making up an increasing share of plastic’s carbon footprint, says that an important way to reduce the carbon emissions of plastic production, other than reducing unnecessary plastic consumption, is to use clean energy to power the process. To fund the investment towards clean energy use, companies could transfer some of the cost to the consumer, although this would require transparency on the part of these businesses.

When reached for comment, Dow Chemical, one of the world’s largest chemical producers and a leading manufacturer of plastic, said that plastic helps prevent emissions by reducing food spoilage and waste. Jarrod Erpelding, the company’s global business communications director for carbon and circularity, said that Dow Chemical also plans to build the world’s first net-zero ethylene cracker in its Fort Saskatchewan facility – although the plan would triple the site’s ethylene and polyethylene capacity and depend on carbon-capture technology.

But, as Enck noted, any meaningful action toward tackling plastic pollution and its greenhouse gas emissions still depends on individual action: “Educate yourself. Vote. And become active in the legislative process to get important bills to become law.”

“I think this is solvable. There are alternatives to plastics, and we just have to mobilize a lot more people. We need an army, and right now we only have a platoon. So we need more people involved. This should be a grassroots effort from the bottom up.”

The actions of a single person can seem insignificant next to nearly 5 billion tonnes of plastic waste spread around the planet and a relentless economic machine that grinds out more. But every little bit of effort can make a difference, said Cole.

“A friend of mine once said, ‘Well, if you pick up [and properly dispose of] a plastic bottle, then that plastic bottle, if it had just gotten left over time, could become thousands, if not millions of bits of microplastics that could be eaten by animals.’ So taking that one piece of plastic away is reducing the load on the system. And that surely is only a positive thing.”