Can We Turn Plastic Waste Into Edible Protein?

A team of scientists, led by microbiologist Stephen Techtmann at Michigan Technological University, has developed a process to convert plastic waste into edible protein. The process uses technology that has been around for decades, pyrolysis and fermentation, combined with a proprietary bacteria population. Waste plastic is heated to high temperatures in the absence of oxygen to break it down into its individual components, or monomers. That’s the pyrolysis step. Then, the broken-down plastic (which has become an oil-like substance) is fed to a specialized population of bacteria that will ingest it and grow. That’s the fermentation step. The resulting bacterial cells are composed of around 55 percent protein, and this protein-rich biomass can be used as food.

The system currently focuses on common plastics like polyethylenes, polypropylenes, and PET (commonly used in soft drink bottles), but the team also plans to develop chemical processes that can break down other types of plastics. While pyrolysis does require energy to run, the end goal is to create a technique that is low energy and even potentially energy-generating, and the team is exploring options like solar power. “Sustainability is really at the center of what we’re trying to do here,” says Techtmann. “We’re trying to create a process that deals with plastic pollution and can potentially produce a valuable resource such as food.”

The process is several years away from widespread implementation, but Techtmann hopes in the next couple of years it can be executed on a smaller scale—as a portable system used to meet immediate food needs in disaster relief and other crisis scenarios. In the long run, Techtmann’s team seeks to scale the process to address pressing issues like food insecurity. Techtmann notes, “I don’t think this is going to be the silver bullet that solves everything, but it’s another opportunity because it’s going to take a lot of creative thinking to address these big problems.”

Food Insecurity Rising Worldwide

Food insecurity, the inability to acquire enough nutritious food, is a global problem fueled by the climate crisis and exacerbated by escalating incidents of climate shock, widening inequities in access to healthy and safe food sources, and economic slowdowns. Between 2014 and 2019, severe food insecurity increased everywhere in the world, except in North America and Europe. The COVID-19 pandemic may increase the total number of people experiencing food insecurity by 83 to 132 million. That’s in addition to the almost 750 million people who couldn’t get enough food to meet their needs in 2019. And these numbers will likely continue to go up. According to FAO projections, in 2030 the global population of undernourished people will exceed 840 million—a number that doesn’t yet fully account for the future effects of the pandemic.

In countries like the United States, where people consume high amounts of factory-farmed animal products, industrial agriculture contributes to food insecurity worldwide, as well as health epidemics like obesity, diabetes, and heart disease. Industrial agriculture displaces small farmers—according to the UN Environmental Program, large farms account for 1 percent of the world’s farms, but occupy 65 percent of the land—and rely on producing nutrient-poor food and ingredients for processed food products. Monocropping is practiced to meet industrial farms’ demand for cheap, low-quality feed, given to animals like cows and pigs held in miserable conditions. Frequent use of monocropping depletes the soil and causes erosion and environmental degradation, contributing overall to climate shocks and future climate change.

However, there’s a growing recognition of the ways in which industrial agriculture actively contributes to the factors leading to food insecurity. In the U.S., increasingly popular health and wellness trends have led to a demand for healthier, more sustainable sources of dietary protein. In addition to utilizing protein sources like soy, pea, chickpea, and other plants, the call for nutritious and appetizing protein alternatives has spurred the development of next-generation animal-free proteins. Like the protein from Techtmann’s food generator, these products are being developed with fermentation processes using microalgae, bacteria, and fungi.

An Innovative but Challenging Solution

Many of the next-generation proteins are geared toward markets like the U.S. and Europe with the aim of replacing animal protein in the diet with palatable, meat-like alternatives. Due to the regulatory requirements in place to approve new food products, some may risk ending up in animal feed—propping up an already unsustainable and inequitable system. But Techtmann insists his team’s goal has always been to feed people. He says, “Part of the reason we’ve aimed for this being something humans could consume is the fact that the farming of animals can have some very negative consequences…we’re hoping this system can provide an alternative to some other sources of protein.”

Implementing next-generation proteins on a wide scale is not without challenges. Jeremy Chignell, Senior Scientist and Fermentation Specialist at The Good Food Institute, says the use of fermentation to create new protein sources is an exciting application for one of humanity’s oldest biotechnologies, but there are several drawbacks. Among them, overcoming the regulatory hurdles to human consumption can be difficult and time-consuming, and marketing an edible product made from bacteria can be problematic—people may be hesitant to eat it.

There are also concerns about the purity of the plastics broken down in the generator—if they are mixed with other inputs then the system may not work, and any potentially toxic byproducts must be eliminated or minimized. And, of course, a big question is whether this process can be adopted on a large enough scale to address people’s nutritional needs and make a dent in the massive amounts of plastic waste choking the oceans and piling up in landfills. Chignell thinks there’s reason to be cautiously optimistic. “Pyrolysis is a very scalable process,” he says, “conceivably, you could get to the point where you’re processing a lot of plastic and turning it into bacterial protein.”

Techtmann sees his team’s system as filling a crucial gap in the field of next-generation proteins by using waste as the initial input, creating an opportunity to tackle the major problems of food insecurity and plastic pollution. And there’s no doubt that next-generation animal-free proteins like Techtmann’s have the potential to reduce human and animal suffering, address food insecurity, and mitigate environmental costs, but it will greatly depend on how the technology is applied and who it is used to feed.