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Biodiesel Apposed

Homebrew Open-Source Reactor Design

Maria "Mark" Alovert

©2005 Maria "Mark" Alovert

The author with the Appleseed, a community-designed biodiesel reactor.

A biodiesel reactor system can be built in as many ways as there are types of barrels, kegs, and tanks. This can be a blessing or a curse.

For a long time, biodiesel Web sites focused on chemistry more than on equipment. Limited details about reactor equipment left nonfabricator novices in the dark, especially when it came to recommendations for using salvaged materials. Then, along came some early vendors of homebrew "production" systems, selling an immature technology (see "Tank Talk" on the next page). Their advertising often exaggerated the difficulty of building homebrew equipment, quite possibly to justify their high prices for fairly unimpressive products.

open-source biodiesel

The homebrew community responded by embracing the "open-source" concept borrowed from software engineers. This community-based method of developing safer and higher-quality products is founded on completely disclosing plans, encouraging changes, and not limiting either the free or the commercial use of the resulting products. Open-source philosophy believes in the power of many poring over a design—"many eyes make problems shallow."

Appleseed Biodiesel Reactor

In our case with the Appleseed biodiesel reactor, it was a smashing success. We began publishing detailed plans on the Internet for standard systems that anyone could build, and then incorporated changes submitted by users. This eventually lowered the entry barrier for biodiesel homebrewing and has made the process safer, after much discussion of the safety "bugs" in homebrewing equipment. The would-be "Microsofts" of biodiesel equipment have recently adopted many of our safety improvements as well, and a couple of businesses have sprung up around sales of the open-source reactor.

The Appleseed—a pressure-resistant, insulated, no-fumes, no-weld, metal reactor—uses parts found at hardware stores or available through a few U.S. catalogs. Parts cost between US$150 and US$350. A full system based on this design can be built for between US$250 and US$600. These easy-to-build systems require no special skills. They take about a day to put together, and can make for a nice work party. Be sure to serve barbecue, and remember the party part.

Tank Talk

The flammable plastic tanks used by all of the ready-made biodiesel reactor vendors are an inferior material for reactors. Companies use them because they are the cheapest, lightest, conical-bottom tank available off-the-

Amber Crowley and Keiko Suda assemble their first water heater tank-based biodiesel reactor at an East Bay biodiesel internship class.

shelf. An early book on biodiesel suggested that these tanks made "ideal" reactors, leading biodiesel beginners to believe that white, plastic, and uninsulated are what a homebrew reactor should look like. In reality, you will never see plastic reactors in professional biodiesel plants, and they can be dangerous as home reactors.

Heating. As the photo below left demonstrates, directly heating the mixture to reaction temperatures in plastic tanks is unsafe. To avert the obvious dangers, some reactor vendors advise against heating at all. This significantly

Surrounded by a small orchard of Appleseeds, Rachel Nelson of Tucson, Arizona, puts the finishing touches on her reactor at a reactor-building work party.

When bad things happen to bad plastic—the remains of an early, ready-made reactor marketed in California. Luckily no one was hurt when this one leaked and caught fire. The Appleseed reactor offers an economical alternative.

open-source biodiesel

The vent assembly at the top of this tank is set up for methanol recovery using a condenser.

to clean it out. You should never open your reactor, because potentially dangerous methanol fumes are always present. No respirator or filter will stand up to methanol fumes for more than a few minutes without methanol breakthrough.

There's no need to clean the tank manually. If anything solidifies in your tank, heating will remelt it, so the tank can be drained normally. If your reactor doesn't contain a heater, you should be extra careful to prevent batches of "soap glop" or solidifying glycerol.

Water Heater Prep

The Appleseed reactor is one-half of an inexpensive biodiesel brewing system. It is designed for use with a no-weld wash tank built from an upside-down, 55-gallon (210 l) drum. With a heat exchange system, the reactor is easy to solar heat, and with a condenser, it can be converted to a methanol recovery still.

reduces biodiesel quality. An unheated reaction does produce some biodiesel and glycerol, but the emissions and long-term effects of burning that kind of poor-quality fuel are unknown. Heating ensures a more complete reaction and helps produce a high-quality fuel.

Insulation versus translucency. Many people like plastic tanks because, if left uninsulated, they are somewhat see-through. But because you'll want to insulate the tank, which lowers the energy required for heating, there's no point in buying a translucent tank. Without insulation, heating time is increased by many hours. An uninsulated tank can also lose heat during the reaction, which can result in a lower quality fuel. You don't need to see into the tank. You will see the contents as they drain through plastic tubing, so you will know when you have reached a different layer of the mixture.

Keep 'em sealed. Many people also make the incorrect assumption that they'll need a lid opening for their reactor

The lower plumbing manifold allows the single drain hole of a water heater to be used for multiple purposes— filling and draining the tank, and for mounting the sight tube and temperature gauge.

The lower plumbing manifold allows the single drain hole of a water heater to be used for multiple purposes— filling and draining the tank, and for mounting the sight tube and temperature gauge.

Silo Weak Weld Vent

Pros & Cons of the Appleseed Design


• Sealed, no-fumes design

• Ceramic-lined water heaters resist biodiesel chemical corrosion

• Thermostatic control of oil heating

• Threaded plumbing—no welding, safer and less leak-prone than plastic plumbing and gasketed bulkhead fittings

• Quick assembly

• Universal off-the-shelf parts

• One pump accomplishes several tasks

• Handles vacuum for methanol recovery and handles some pressure

• Inexpensive scalability of system (just keep adding more US$20 wash tanks to increase output)

• Open-source design, with a number of people adding improvements


• Brass, zinc, or iron plumbing may shorten biodiesel's shelf life

• Some plastic is used, which is a weak link in the system

• Many valves can lead to confusion

• Cheap centrifugal pump is fairly weak, and may mix only moderately well open-source biodiesel

Vent & Vacuum Breaker:

Piped to outdoors or condenser

Sight Tube:

Braided, clear PVC hose, 1/2 in.; shows level of oil in tank

Electric water heaters are commonplace scrap, and well suited for the Appleseed design. They resist high pressures, drain well, come already-insulated, and are thermostatically controlled.

First, remove the zinc or magnesium anode rod and the plastic dip tube from the top of the water heater. The anode is sometimes hidden below a knockout or plastic plug. You will need a 11/16-inch socket wrench to remove it. You'll find the dip tube underneath one of the nipples threaded into the tank. Flush out any mineral buildup with water or acetic acid, but don't worry excessively about cleaning the tank.

Be sure to rewire the water heater to bypass the upper heating element. Water heater elements will burn out if they are not submerged while energized.

Pipe Particulars

Homebrew reactor materials are usually a compromise among several factors—cost, availability, compatible materials, and safety. Obviously, safety trumps all other factors.

Use nongalvanized mild steel ("black pipe") or stainless steel—the ideal material if you can afford it. Try to stay away from zinc (galvanized pipe fittings), and definitely avoid copper. Zinc, copper, and iron can shorten the shelf life of your biodiesel by acting as catalysts for oxidation of the fuel. This is not a big problem for homebrewers, who do not usually store their fuel for a long time. The compromised shelf life will vary with the type of oil used for the feedstock.

I sometimes break the "no-zinc, no-iron" rule in favor of safety and cost. It's easy to avoid copper, but zinc in galvanizing or in brass valve bodies and cast iron fittings are harder to avoid if cost is the major consideration.

You also can use some types of plastic pipe. But heavy-duty, cross-linked polyethylene (PEX) is not available as fittings. And PVC has some limited problems withstanding the corrosive nature of biodiesel.

Using the Appleseed Reactor

Making biodiesel with the Appleseed reactor is a straightforward procedure. First, fill the reactor with vegetable oil. With some prodding, the Appleseed's pump will transfer oil from buckets (close the tank isolation valve first). Alternatively, you could transfer the oil with

The Appleseed Biodiesel Reactor

Top Ports: Old hot, cold (dip tube removed) & anode (anode removed)

Vent & Vacuum Breaker:

Piped to outdoors or condenser

Sight Tube:

Braided, clear PVC hose, 1/2 in.; shows level of oil in tank

Circulating Pump:

Chicago Electric Power Tools #1479, 1 in.

Note: This diagram is representational only and does not show all the minor fittings necessary to assemble the unit.

Circulating Pump:

Chicago Electric Power Tools #1479, 1 in.

Note: This diagram is representational only and does not show all the minor fittings necessary to assemble the unit.

an inexpensive, manual barrel pump plumbed into the reactor's drain tube. A sight tube will allow you to monitor the level of oil in the tank.

Next, heat the oil to 130°F (54°C) in the heater. Then mix methanol with a potassium hydroxide or sodium hydroxide catalyst to form a sodium or potassium methoxide. The simplest way is to add the catalyst to the methanol. I use 5-gallon (19 l) carboys (jugs) of heavy, high density polyethylene (HDPE) plastic as a passive mixer for methanol and the catalyst, providing no mechanical agitation beyond occasional rocking. Our supplier pumps the methanol directly into our carboys, which eliminates one methanol-handling step at home. The carboys have a convenient feature—the lids contain an optional, plugged set of 3/4-inch NPT threads. I buy an extra lid and use it to attach plumbing open-source biodiesel to the jugs. Rock the carboy every 10 minutes until the catalyst is completely dissolved.

Use the circulating pump to gradually mix the methoxide into the preheated oil for a couple of hours. The same pump can be used to draw oil from the storage tank, and to draw methoxide from a carboy. To provide more complete mixing, it also can be used to circulate the mixture from the bottom to the top of the tank.

After a 24-hour settling period, a glycerol/soap mixture will drop to the bottom of the reactor. Open the valve to drain off the glycerol. Tall, thin tanks are better than wider ones for reducing the amount of intermixed material from the junction between glycerol and biodiesel layers. The floor of a water heater tank isn't flat—it has an inverted dome shape with a drain at the pointed tip, which helps with separation of the layers.

Provide a system to water-wash the biodiesel, to remove the water-soluble impurities that are formed in the process. The Appleseed reactor has a fluid-transfer manifold, which is basically an inexpensive substitute for a three-way valve. This allows you to transfer biodiesel into a standpipe wash tank, where you can bubble-wash or mist-wash to your heart's content. The water carries the impurities to the bottom of the tank, and the clean biodiesel floats on top of the water and flows through the top of the standpipe into your container.

You will also need a filter, lab glassware for testing, and a means of collecting oil from restaurants (a pump or


Cost (US$)

Water pump, 1 in. clear


2 FortPak carboys

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