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Most of the published biodiesel research is focused on using new vegetable oil (mostly from soybeans), or improving oil extraction techniques from algae. Both of these oil sources are usually too expensive for small producers, but potentially useful for large businesses.

Used vegetable oil is abundant in the United States. The figure quoted most often is about 3.5 billion gallons a year, and usually restaurants pay to have it picked up and treated as a waste product. Diesel fuel use in the U.S. is about 275 billion gallons per year. Government figures state that biodiesel could yield up to 7 percent of national diesel use if this waste oil resource was fully used.

Doing It

Homestead, Inc. is a farm-scale business in western Massachusetts, and has been making biodiesel commercially since 1999 as Yellow Brand Premium Biodiesel. Homestead is steadily growing with the help of friends and the work of the founder, Tom Leue. As far as I know, Homestead is the first and only commercial biodiesel producer in the northeastern U.S. Last summer as an intern at Homestead, I obtained firsthand knowledge of biodiesel production. The internship was funded by the Chelsea Center for Recycling and Economic Development.

Massachusetts is a great place for biodiesel because there are an increasing number of small farms. Usually with farming comes stinking, health-impairing, petroleum-fed diesel equipment. An equally great site for biodiesel is near a body of water where there are diesel boats.

Biodiesel spills are less harmful than petroleum diesel spills, since they are nontoxic and degrade much faster. However, biodiesel can coat and potentially suffocate marine life, just like petroleum. The nontoxic exhaust is easier on fragile marine ecosystems. Few people realize the value of biodiesel in the marine market, and it's not being pushed nearly enough. But, no matter where you decide to manufacture biodiesel, here's a model from Homestead, Inc.

The Factory

Homestead has made a commitment to follow the basic rules of responsible resource management: reduce, reuse, recycle. True to the spirit of recycling, much of

Homestead's equipment was previously used, and serves quite different purposes than in the past. Homestead's biodiesel factory is actually a converted maple sugar house.

A few of the parts from the maple syrup business were reused. The evaporator was made into a rendering pan to boil any water from the used vegetable oil before processing. The filter rig and storage tanks were also reused. Most of the remaining parts were salvaged from the junk pile in the back of the barn, or purchased from catalogs and local hardware stores as needed.

The space required is fairly modest—a heated garage, for example—and a small amount of land around it for storage. Making biodiesel might even fall between the cracks of local zoning rules. It is not easily put into any existing categories, so Homestead classifies it as a farming operation.

Keep in mind that there is no "correct" way to build a biodiesel factory. The description here will give you an idea of what can be done, and what works for Homestead. The processing system at Homestead has separate stages, as shown in the flow chart. Other small biodiesel producers do most of the work in a single drum processor, but are limited to one batch per day.

Finding the Raw Materials

Homestead, Inc. chooses to use recycled oil. In the northeastern U.S., virgin oils are hard to come by, while used fryer oil is abundant and very cheap. People who collect used oil are sometimes paid for collection services—up to US$1 per gallon in larger cities.

Homestead's biodiesel factory used to be home to a maple syrup business.

Homestead's biodiesel factory used to be home to a maple syrup business.

Depending on where you live, getting used vegetable oil may be the easiest part of the process. Homestead picks up used fryer oil in bulk from area restaurants, using a specially constructed tank. It is made from a salvaged pressure tank. The 250 gallon (950 l) tank uses a vacuum pump to create a strong vacuum in the tank. The tank's hose and suction wand have a filter to strain large food particles from the oil.

A standard 55 gallon (210 l) drum cannot support a strong vacuum, so a stronger steel container is needed. Homestead's tank and vacuum pump provide an effective suction system that sucks up hundreds of gallons of fryer oil in just a few minutes.

Homestead's biodiesel factory uses a lot of recycled equipment.

This suction rig can be easily rolled on and off the back of Homestead's pickup truck as needed. Bulk oil collection is much more efficient and easier than dealing with small, 5 gallon (19 l) containers of inevitably dirty fryer oil. Taking oil from the top of a bulk container (usually stored outside, behind a restaurant) avoids the water and other settled crud at the bottom.

Good oil is usually found at better restaurants—what you find out back of a restaurant tells you a lot about what's served inside. Fast food places often use palm oil, a naturally hydrogenated oil that is near solid at room temperature and difficult to work with. Best are family-owned restaurants that use canola or sunflower oils. Ask permission from the restaurant before taking their oil. Use the opportunity to tell them that you're going to make fuel from the stuff they're either throwing out or paying to have taken away.

Besides vegetable oil, only two chemicals are necessary for the reaction: methyl alcohol (also called methanol) and 100 percent pure, undiluted lye. They're both very strong chemicals and need to be handled carefully. Before buying the chemicals, make sure that you have proper storage and personal safety equipment, and that you know how to use it.

Homestead gets chemicals from a chemical supply company, but there are other places to go. Methanol is a fuel for race cars, and is sold at racetracks and auto parts stores. Lye can be bought in a grocery or hardware store. Ethanol (which is created from renewable sources and is less toxic than methanol) can be substituted for methanol, but this decreases the reliability of the reaction and it is more difficult to obtain. Pay attention to biodiesel discussion groups on-line— new methods and ideas about raw materials are always coming up, and knowledgeable participants are willing to help.

Initial Filtration & Reaction

First you need a place to store the used vegetable oil. If the oil has been used heavily, it may be dirty and have a lot of water suspended in it (light brown and opaque appearance). A settling tank that allows dirty water to be drained from the bottom helps clear the oil over time. Or you can boil the water off in a flat rendering pan. If the vegetable oil is pretty clear and a decent, dark color, it can be used directly. The more storage capacity you have, the easier it is to deal with the various grades of oil you might pick up.

Nancy Leue stirs a new batch of veggie oil—soon to be biodiesel.

Nancy Leue stirs a new batch of veggie oil—soon to be biodiesel.

Used Cooking Oil In Coarse FMter

Oil/Water Settling Tank

Commercial Biodiesel

Oil/Water Settling Tank

Valves Pump

Valves Pump

Fine Filter:

20-50 microns

Fine Filter:

20-50 microns

Storage omestead's Yellow Brand Biodiese Factory

Storage

Methanol NaOH

Valve

Reaction Tank with Electric Mixer (heated to 125o F)

Methanol NaOH

Pumps

Reaction Tank with Electric Mixer (heated to 125o F)

Sodium Methoxide Mixing Tank with Electric Mixer

Sodium Methoxide Mixing Tank with Electric Mixer

Valve

Filter:

5 micron

Biodiesel Storage

Biodiesel Storage

Future Fuel Washing System

Waste The next step is to pump the oil through a filter into the reaction tank. Many types of filters can be used. A socktype, plastic mesh or a fine screen are effective, and don't need to be finer than 20 to 50 microns at this stage.

The reaction tank Homestead uses is a modified, open-top, propane water heater with a stirrer attached. A separate, small, deep tank for mixing the methanol and lye is necessary to produce the reactive chemical, sodium methoxide. A close-fitting cover for this tank is needed, along with a dedicated stirrer to avoid splashing. A chemical pump to transfer the chemicals will reduce potential exposure.

Compared to the insanely complex processes needed to refine petroleum into usable fuel, the chemistry of the reaction that makes biodiesel is very simple. The basic process involves mixing specific amounts of methanol and lye to make sodium methoxide. The sodium methoxide is added to the filtered oil, mixed for an hour, and allowed to settle overnight. Then, biodiesel is drawn

Valve off the top and filtered for direct use, and the glycerin by-product is drawn off the bottom.

Chemically speaking, the reaction is called transesterification. The reactants are transfatty acids, also called triglycerides (this is the vegetable oil), and a mixture of lye (sodium or potassium hydroxide) plus methanol, which forms methoxide. Methoxide is extremely reactive and dangerous—handle carefully! It breaks the transfatty acid/trigylceride molecule into two products—glycerin and methyl esters. Glycerin is the secondary product; the methyl esters are biodiesel.

The batch size is up to you. Homestead makes a relatively small batch (net 20 gallons; 76 l), and does two batches per day. The amount of chemicals used for the reaction is directly proportional to the batch size. The mathematical and chemical details are in From the Fryer to the Fuel Tank.

Ready for Sale

In Homestead's plant, the mix of glycerin and biodiesel goes into a commercial kettle, which is easy to clean and has a heating jacket to melt solidified glycerin in cold months. The last step is to transfer the top layer (biodiesel) to a dispensing tank for sale. Homestead pumps the biodiesel through a 5 micron filter and drains the glycerin from the bottom through a spigot.

Their tank is 275 gallons (1,040 l), with a dispensing pump like you'd find at a gas station—very convenient! If it has been properly filtered, biodiesel fuel straight out of the reactor can be used in a diesel engine. This fuel will not meet the standards for biodiesel, though; it still contains excess methyl alcohol and may also contain partially reacted oil.

A further refinement is a washing process to remove excess methanol and, to a lesser degree, other impurities. After the glycerin has been settled out, the biodiesel is moved to a tank that has a stratified layer of water at the bottom. Air is pumped through an aquarium stone in the bottom of the tank. The resulting very fine bubbles carry a thin layer of water on their outsides, which combines quite easily with methanol. Then as the bubbles reach the air at the top of the tank, they pop, leaving the water to work its way back to the bottom, picking up even more methanol on the way.

In addition to removing contaminants, washing also may reduce the energy value of the biodiesel slightly, but generally improves its overall quality. Homestead, Inc. expects to complete its fuel washing system in the summer of 2002, but so far has not had problems with the unwashed fuel.

You can use numerous pipes, valves, and pumps, depending on how mechanized you want to get or how much bucket-lugging you want to do. Homestead has tried several different types of pumps, but the gear pumps left over from the maple syrup business have

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