One of the shortages that everyone expects to occur in a power grid-down situation is a shortage of any type of fuel. For this reason, some people have at least one vehicle that runs off of diesel, and have put a system together to make their own bio-diesel. But now, there’s something new to add to the mix — making your own diesel and even gasoline out of scrap plastic.
Most plastics are petroleum products, so we shouldn’t be surprised that they can be converted back to fuels that we can burn. Basically, this can be done by the same method that petroleum is refined in the first place, factional distilling. Distilling is the process of separating mixed liquids by heating them to their evaporation point and then condensing them back down to a liquid. Fractional distilling is merely doing the same thing at several different temperatures, so that several different liquids can be drawn off.
The trick is in distilling it down to fuel, without it catching fire in the process. Many plastics burn readily and the diesel fuel and gasoline that we expect to distill out of those plastics are highly flammable. The secret to preventing it from burning is to remove one of the necessary ingredients for combustion from the equation. Since we can’t remove the fuel (the plastic) or the heat, we are left with removing the oxygen. This is done by performing the whole operation in nitrogen.
Nitrogen is a non-reactive gas that comprises the largest part of the air that we breathe. By melting and distilling the plastic in a nitrogen environment, we eliminate the ability of the hydrocarbons in the plastic to react with the oxygen, creating fire.
Not all plastics will work for this process, but only those with high levels of hydrocarbons, such as polyethylene and polypropylene. Of the two, polypropylene is better, as polyethylene has a high paraffin content. So distilling the diesel out of it requires a two-stage distillation.
Distilling the plastic requires making a distiller that will reach 570degrees to 750degrees Fahrenheit and maintain that temperature accurately. The petroleum products will distill out of the plastic at 570degrees Fahrenheit, but the overall process is much more efficient at 750degrees Fahrenheit. A simple feedback loop with a thermocouple and a temperature controller will make it possible to maintain the desired temperature if you are using electric heaters. For gas heaters, you will need to control the gas flow to control the heat. The distiller needs to be a sealed container, as all distillers are, and as I already mentioned, filled with nitrogen.
A tube needs to come out of the top of the distilling vat and run into a condenser. This is standard procedure for any distillation process. Copper tubing is usually used, as it has the best thermal coefficient available. In this case the copper tubing should be immersed in a cold water bath, as the faster the gases condense, the more thoroughly they convert back into fuel. If a cold water bath is not used, some burnable hydrocarbons will remain in a gaseous state.
The last stage is to let the output of the system vent through a water bubbler. This will capture the remaining petroleum hydrocarbons, which will then be able to be skimmed off the surface of the water. The remaining gas that bubbles out of the bubbler is flammable as well, and can be burned.
Shredding the plastic before beginning the process will make it more efficient, as the more plastic that is in the distiller, the better it will operate and the more fuel it will create before running dry. Once started, the process must continue without interruption until it is done. Should loss of temperature occur, the plastic will re-solidify in the distiller, making a solid mass that will be hard to melt again.
I mentioned that polyethylene has a high paraffin content. If allowed to sit, this paraffin will solidify, making it hard to use the fuel. The fuel can still be used, if the fuel tank is heated to about 86 degrees Fahrenheit, the paraffin will melt, allowing the fuel to be used as it is. If the fuel tank is not heated, then the paraffin will need to be removed. To do this, run the resulting fuel back through the distiller a second time. The resultant fuel from the second distillation will have much less paraffin content and will not solidify. The paraffin will be a high density paraffin, which is perfect for making long-life candles.
Please keep in mind that this whole process has to be tightly controlled. The temperature of the plastic when melting must be consistent and the whole process must stay as oxygen-free as possible. If oxygen were to get into the system, you would end up with a fire and no usable fuel.
Editor’s Note: Please use extreme caution when making your own fuel. Injury may result.