Vegetable Oil Vehicles

At Mission: Wolf, we have a vehicle that runs on vegetable oil. The fuel is free, carbon neutral (it would be hazardous waste otherwise), and less polluting than petroleum-based diesel.

When we started Mission: Wolf in 1986, we chose a location as far away from people as we could get. From our sanctuary, it’s a 45-minute drive to the nearest small town (Westcliffe, population 1150). To get some materials and supplies, we need to drive two hours to Pueblo or Colorado Springs. Unfortunately, that means that one of our big expenses and environmental impacts is fuel for our vehicles. In 2009, we began fueling our diesel vehicles on pure vegetable oil, cutting costs, reducing emissions, and re-purposing waste into fuel.

How can you run a car on vegetable oil?

Diesel engines were originally designed to be run on a wide range of fuels including kerosene and coal dust. Peanut oil was often a favorite due to its high energy density. Today, most people burn petroleum-based diesel fuel because it’s cheap and readily available. The design of the diesel engine still allows it to burn its original fuel: vegetable oil.

Our initial effort: Biodiesel

The Greasy Spoon, our fuel conversion building.

Our first adventure into non-petroleum fuels was with biodiesel in the early 2000’s. With scrap materials, we constructed a biodiesel processing building and began working with students from CU Boulder to produce biodiesel (vegetable oil combined with methanol). Biodiesel is a stable, effective way to fuel diesel engines, but the process turned out to be too risky for our remote, solar-powered facilities. Problems included inadequate storage facilities for flammable methanol, imprecise temperature control in our solar-heated buildings, and lack of chemistry expertise on our constantly rotating staff. During this whole process, we heard of people running straight waste vegetable oil through their engines with great success.

Pure vegetable oil and the dual fuel system

When comparing the performance of petroleum-based diesel and vegetable oil, there are two main differences. First, diesel gives more power to the engine. This means a little slower acceleration and lowered hill-climbing capability when running on vegetable oil. The second is that vegetable oil is viscous at normal temperatures. This means that we need to have a heat source to heat the oil before running it through the engine.

The solution: instead of putting vegetable oil into our gas tank, we have installed a second fuel system and a second fuel tank on our diesel vehicles. When the vehicle starts up, it runs on petroleum-based diesel until it reaches optimum running temperature. At this point, the driver can flip a switch and change over to the second fuel system. Vegetable oil is pre-heated with hot coolant before entering the engine. When we want to stop the vehicle, we need to flush petroleum-based diesel through for about 30 seconds to clean all the oil out (the engine can seize if vegetable oil cools down inside of it). The solution is simple!

Where does our oil come from?

We collect used vegetable oil (usually peanut oil) from local restaurants who would otherwise need to pay to have it disposed of as hazardous waste. It comes in the same 5-gallon plastic carboys that it was delivered to the restaurant in.

How do we process and filter our fuel?

With waste oil from french fry production, there are usually three impurities that we remove with our processing: water, solids (potato pieces), and waxy oil-based substances from being used repeatedly (we call that gunk). Our processing involves two methods:

1. Settling and passive heat:
When we first take in waste vegetable oil, it’s usually a mix of good oil, gunk (waxy solids), and solids. The easiest and more energy-efficient way to process the oil is to let it sit for a few weeks in a warm place. Our vegetable oil processing building was built for this purpose, and it acts like a giant greenhouse. Summertime temperatures in our heating room are in the 100°F range. Daytime temperatures in the winter are around 65°F, so we don’t process much in the winter.

During settling, solids and gunk settle to the bottom. Water evaporates out of the open container. In the end, we have nice, clear oil floating on top.

We do know people who use active heating to process their vegetable oil. This speeds things up and turns more of the gunk into usable fuel. At our solar-powered facility, this would consume all of our energy! Heating is extremely energy intensive, so we prefer to use passive solar heat to accomplish our processing, even if it’s a little slower.

Heating WVO oil carboys Vegetable oil drums

Below is our guide for new staff members learning how to work with carboys of oil.
Mission: Wolf WVO Carboys

2. Filtering:WVO filter
Our oil is run through two filters (one fuel filter and one water filter) before it’s ready to burn. This helps to remove any remaining impurities.

So, our whole process looks like this: we first settle our oil in 5-gallon plastic carboys in a hot room for a few weeks. We then pour all the good oil into a series of 55-gallon drum. We process about 55 gallons of oil per week, so oil spends about three weeks total in the drums. From the third drum, we pump oil through a fuel filter into the final evaporation tank in a hot room. After a week in the hot room, we do one final filtering, cycling the oil through a water filter for 40 minutes. From there, we open the valve and dump the oil into our fuel tank!

Below is a diagram of our processing system. This is an extensive system, using parts of our old biodiesel processor combined with some newer parts.
Mission: Wolf WVO Processor

Is all that processing really necessary?

Our processing is extremely thorough for a few reasons. First, we can’t afford to have sub-standard oil damage any of our vehicles. Since we run on donations, there are limited funds to repair vehicles. Second, we built our infrastructure to make biodiesel, so it’s a little overkill. It’s already there though, so we figure that it’s no extra work just to keep using it.

Some of our friends only process their fuel using our first step: settling and evaporation in plastic carboys. Make sure that if you do this, you’re careful! You can test for water content in your oil by heating a thin layer of oil past the boiling point of water and watching for bubbles to form. If any bubbles larger than 0.5mm form, you need to process your fuel more.

If you’re considering processing your own fuel, be thorough in your research!

What systems do we use in our vehicles? Our Dodge flatbed pickup truck has a Frybrid system installed. We had the system transferred from another identical vehicle after an accident, and it’s working great. The Mercedes station wagon has a system that one of our long-time staff members, Aaron Young, designed and built himself.

Is this a global solution to petroleum?

Unfortunately, there is not a large enough supply of waste vegetable oil (WVO) to power all the vehicles humans are using on this planet. It’s fun to think about french fries powering all our motorized transportation, but it just isn’t feasible. For us, it helps out our local businesses and gives us a way to reduce our impact on the world.

Interested in making your own conversion?

We recommend doing research into some of the larger companies that are making vegetable oil conversion kits:

WVO Designs (also see their guide on deciding on a system and making your own conversion)
Golden Fuel Systems (formerly Frybrid)

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