We live in a world of plastics. They have revolutionized medicine with life-saving devices, made space travel possible, lightened cars and planes (conserving fuel and lowering air pollution), and made all manner of consumer goods cheaper. However, their convenience and low cost have spawned a throw-away culture that has a dark side: Single-use plastics currently account for about 40% of the plastic produced every year.
Plastic waste is ubiquitous; we see it in bodies of water from creeks and rivers to oceans. The Great Pacific Garbage Patch is a colossal accumulation of marine debris, predominantly composed of nondegradable plastic, stretching across the North Pacific, twice the size of Texas. This litter, composed largely of single-use items such as water bottles, cups, plates, and food-storage bags, originates from various continents and is almost impossible to corral and remediate due to the small size of its pieces and the depth of the ocean.
The magnitude of this environmental problem extends beyond the Pacific; similar patches exist in the Atlantic and Indian oceans, the North Sea, and various other bodies of water, including creeks, rivers, and lakes. Current estimates are that more than 171 trillion plastic pieces are floating just in our oceans, a number expected to triple by 2040 if current trends persist. They disintegrate into smaller pieces, entangling animals and being mistaken for food by marine creatures, endangering the animals and leading to ecological damage.
Over time, these plastics degrade into microplastics, which are less than 5 millimeters long, and into even smaller nanoplastics. Both are pervasive across the planet and are even found in remote areas such as the North Pole and the Himalayas and within human bodies. The long-term environmental and health consequences of living with microplastics and nanoplastics are uncertain.
Tackling ocean plastic pollution has become a critical challenge, prompting innovative solutions from scientists. Recently, researchers at the University of Edinburgh engineered E. coli bacteria capable of digesting polyethylene terephthalate plastics, which are commonly used in bottles. This breakthrough involves a two-step process: The first strain of bacteria digests PET-containing plastics, and the second, engineered with CRISPR-Cas9 gene editing technology, converts the digestion products into valuable products such as adipic acid, which is used in the production of nylon, polyurethane, and other plastics.
The conventional production of adipic acid, a major industrial compound that is currently derived from fossil fuels, contributes to greenhouse gas emissions and ozone layer depletion. Thus, the new, genetically engineered bacterial strains show promise in converting plastic waste such as bottles into beneficial products, reducing net fossil fuel usage and, thus, greenhouse gas emissions.
Practical experiments using plastic bottles and industrial waste have demonstrated the effectiveness of the bacterial conversion process under ambient conditions and within a short time frame (hours), which implies that large-scale production is practical. French company Carbios plans to establish a commercial-scale facility by 2025, converting plastic bottle waste into other products, which would be a landmark in the real-world applicability of this technology.
Harnessing these bacteria for upcycling plastic waste into versatile, valuable compounds such as adipic acid is promising, but scaling this technology to address the vast amounts of plastic waste in oceanic deposits such as the Great Pacific Garbage Patch raises questions about not only logistics but also government regulation, especially concerning the use of genetically engineered organisms in international waters.
Regulatory hurdles, specifically those erected by the Environmental Protection Agency in the United States, pose challenges to deploying genetically engineered microorganisms in unconfined environments. The definition of "new" microorganisms, which are subject to stringent, expensive regulation under the Toxic Substances Control Act, can encompass even benign genetically modified microorganisms. ("New" microorganisms are defined by the EPA as those that contain genetic material from different genera, although that criterion is wholly irrelevant to risk.)
Despite these challenges, proponents believe that the transformative potential of this technology in reducing plastic pollution and greenhouse gas emissions could drive acceptance and demand. Overcoming regulatory barriers and successfully using genetically engineered bacteria to combat plastic waste would be a monumental achievement, but for now, it is a work in progress.
Henry I. Miller, a physician and molecular biologist, is the Glenn Swogger distinguished fellow at the American Council on Science and Health. He was the founding director of the FDA's Office of Biotechnology. Kathleen L. Hefferon is an instructor in microbiology at Cornell University.