Our Process
Pre Treatment
When using waste oil from restaurants we follow the standard procedures of filtration and water removal. However, we are not using heat in order to separate the grease as we are trying to use as little energy as possible. We fill an elevated 55 gallon drum through sieve filters at various microns (400, 300, 250, 100) and allow the solid waste and water to separate over time. This usually takes 1 to 3 days. After settling we pump oil off the top of the drum and into another stand-piped drum. This drum is elevated ~5ft off the ground and drains from the top (stand-pipe) and bottom (of the barrel). There is a ¾” coil of non-reinforced polyethylene tubing with small to large holes which drain into 7 different 5 micron filters. The filters are placed above an open top 55-gallon drum on wheels. This mobility allows us to move the drum across the lab for pumping into the reactor.
Treatment
Our reactor started as an overpriced, poorly constructed "do it all" kit from an online vendor. Do yourselves a favor and build one from scratch; it will save you a lot of money. The second reactor we built was a tank of 55 gallons, made of polyethylene, and could run 45-gallon batches at up to 140 degrees Fahrenheit. The tank and stand cost less than $200.
Most of the fittings were replaced with galvanized steel or black iron because the plastic parts continuously broke. At the bottom, we drained off glycerin and input methoxide. We used a small tank for our methoxide reservoir.
Currently we pour methanol (inefficient and unsafe, we know) into a 30 gallon polyethylene tank which has an agitator grounded and clamped to the inside of it. This serves to blend our methanol and potassium hydroxide (and is also fairly unsafe). The tank and reactor were designed together for minimal manual transfer. We use the reactor’s ½ horsepower pump, which drains and transfers methoxide into the reactor and completes the reaction itself.
We draw our oil directly out of the top of 55-gallon drums using either hand crank pumps or drill pumps. Water washing our biodiesel is our preferred method. We know Magnesol exists and currently want nothing to do with it. To conserve water we have an automated spray system, which has been piloted to determine the least amount of water necessary for washing the biodiesel. We use small fish tank bubblers for drying within those same wash tanks.
Our final product is filled into 55-gallon drums for storage. Being able to gravity feed our finished product into drums saves energy and a lot of human effort.