Litter to Glitter: Plastics to Fuel

Underserved communities are significantly impacted by plastic pollution. Many lack access to plastic processing facilities or simply have no viable options other than landfilling. Thus, plastics accumulate leading these communities to face environmental injustice problems. The Plastics to Fuel (PTF) project aims to give an opportunity for such communities to convert waste plastics into diesel-like product for their immediate use with a maximally simple pyrolysis reactor.

Out of the “Big 6” plastic types, only three are suitable for a pyrolysis reactor - High Density Polyethylene, Low Density Polyethylene and Polypropylene. Fortunately, many plastics such as milk jugs, syringes, straws, ocean plastics, irrigation tubing and drink cups are one of these types of plastics and can be pyrolyzed into diesel-like products. Plastic samples are categorized into the “Big 6” using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) shows the presence of additives in plastics. Milk jugs, for example, consist of High Density Polyethylene, as proved by DSC.

PTF has a bench scale reactor designed as a one-step batch pyrolysis candlestick reactor with an insulated kiln heating system. Heat is applied and breaks down longer, more structured carbon chains of plastics into liquid, shorter chains of diesel-like products. This reactor generally converts 1 kg feedstock to 1 L product. The product is then analyzed using methods such as Gas Chromatography Flame Ionization Detection (GC-FID) and Nuclear Magnetic Resonance (NMR). GC-FID determines the product’s relative carbon distribution while NMR shows chemical groups present.

A larger scale reactor for implementation in the community is under development. It is called the “Onionator” and is composed of 7 larger candlestick reactors in an oil drum which flow into one condenser. While the concept has been proven through testing the reactor, improvements and further investigation is needed to ensure it runs safely and consistently.