Plastic is a miracle of modern chemistry. From healthcare to food preservation to the automotive industry, these amazing polymers make modern life possible. Unfortunately, the properties that make plastic so valuable – low cost, endlessly formable, and chemically inert – have also created a global waste management crisis. Plastic does not naturally degrade in the environment, so once it has been produced, it persists in the ecosystem for decades or centuries. In fact, nearly every piece of plastic produced since 1950 is still around! And since much of the plastic products we use are single-use, like packaging, bottles, and shopping bags, the amount of waste generated is staggering.
Once plastic enters the environment it begins to break up into smaller and smaller pieces due to exposure to sunlight and weathering. These small particles are called microplastics – defined as plastic particles with a diameter of 5 microns or smaller. These microplastics and nearly impossible to recover and often end up in the ocean where they are consumed by marine organisms and begin migrating up the food chain. Recent research has found that nearly all humans on earth have microplastics in our bodies, and the long-term health impacts are largely unknown. Due to their small size, the only way to combat microplastics is to keep them out of the environment to begin with.
We often think of recycling as the answer, but the problem is that although plastic is in principle easily recyclable, the reality is much more complicated. Not only must plastic be sorted and transported to a recycling facility, but most plastic also contains additives that make recycling difficult. Compounds like dyes and colorants, fillers, UV light protectants, flame retardants, and plasticizers are added to virgin plastic resin to improve performance, but these additives greatly complicate the ability of recycled material from post-consumer plastic to be reused in a manufacturing process.
These issues are compounded in the developing world where lack of infrastructure make collection, sorting, and recycling nearly impossible. An improperly managed garbage dump is really not much better than dumping plastic waste into a ditch in terms of long-term sequestration. Wind and rain can sweep away lightweight plastic items, which end up in ditches and waterways. Unfortunately, there is often no other alternative for low-value plastic waste. Of course, long-term solutions require a dramatic reduction of the amount of single-use plastic imported into these countries, but there is also an immediate need to implement solutions to address the plastic collecting in garbage dumps right now.
Solutions that are low-cost, easy to operate and deploy, safe, and durable are needed right away.
One viable solution is the conversion of plastic waste into fuel oil for use in diesel engines or kerosene lamps and cookstoves. Once converted into fuel, the plastic is completely broken down and is permanently removed from the environment. The chemistry for this process has been well established for years, but creating a simple, low-cost process to carry it out in a developing world setting is a challenge. A research team at the University of Kentucky in collaboration with Makerere University in Uganda and the non-profit organization Engineers for Sustainable Energy Solutions (www.eses-plastic.org) have developed a processor that can meet these challenging requirements. Called the Trash-to-Tank processor, this low-cost, easy-to-operate unit can convert plastics into fuel oil. Specifically, plastics of Type 2 (High-Density Polyethylene), Type 4 (Low-Density Polyethylene), and Type 5 (Polypropylene) can be converted to fuel oil in this process. These plastics are commonly found in shopping bags, bottle caps, food storage containers, and plastic furniture. The Trash-to-Tank processor is an open-source design built from easy to acquire parts and is intended to be constructed in developing world communities.
Through the collaboration with Engineers for Sustainable Energy Solutions and other organizations around the world, the Trash-to-Tank processor has been deployed in Senegal, Uganda, and India with plans for additional processors in Nepal, the Dominican Republic, and Mongolia. A demonstration unit funded by a UK Sustainability Challenge Grant is in operation at Vaughn Warehouse in Lexington, where plastics collected by UK Recycling are being converted into diesel fuel.
Unmanaged plastic waste is a global crisis that is continuing to grow. Society’s appetite for plastic is increasing with no end in sight. The COVID-19 pandemic has exacerbated the problem due to the need for more disposable plastic items, like surgical masks, to protect public health. This research at UK is a small first step at combating the waste plastic crisis in developing communities around the world.