Safety in Small-Scale Biodiesel Production

Farm Energy June 14, 2016 Print Friendly and PDF


Although the biodiesel manufacturing process is fairly straightforward, there are several aspects of biodiesel production that need careful attention to detail for a productive, safe, and environmentally sound practice. First, some chemicals used could pose serious risks to the operator or to the environment, unless the proper precautions are taken for storage, process safety, handling, ventilation, and use. Second, disposal of glycerol by-product and waste water generated from biodiesel production could cause environmental harm, unless approved practices are used. Finally, operators need to pay close attention to the quality of the biodiesel produced and proper storage to avoid costly engine problems or excessive emissions during use.

Most enthusiastic newcomers to biodiesel production will find that successfully running a safe and responsible operation is not as easy as it looks. Production of biodiesel on a small scale carries inherent risks, and careless producers are likely to have mishaps. While the obvious goal of all producers should be to minimize mistakes, it is also important to know how to deal with these mistakes and respond appropriately. Knowledge, attention to safety, and advanced planning are the best approaches to preventing serious accidents.

Chemical Exposure and Safety

Methanol (a flammable, toxic alcohol) and lye (a corrosive, caustic base) are two hazardous chemicals required to convert vegetable oil into biodiesel. Overexposure to methanol can cause neurological damage and other health problems. Methanol also presents a serious fire risk.

Lye can cause skin and lung irritation. Both methanol and lye can cause eye damage or blindness. Rigorous precautions are necessary to avoid poisoning, fire, and contamination of soil and water resources. Before beginning a biodiesel project, please consider whether or not you can responsibly follow the safety protocols outlined in the sections below.

Handling of By-Products

Biodiesel processors generate substantial quantities of crude glycerol by-product (about one gallon of waste product containing glycerol for every five gallons of biodiesel produced). Most processors also use water for fuel purification, and may generate as much as three gallons of waste water for each gallon of fuel produced. Both glycerol and waste water require handling and disposal consideration (see Waste Management in Biodiesel Production for further information).

Responsibility for Vehicle/Equipment Failure

The moment that a small producer pours the first gallon of homemade fuel into a fuel tank, that producer takes responsibility for the future performance of the equipment in question. While there are thousands of examples worldwide of small producers successfully powering diesel equipment with homemade fuel, users should also understand that problems can and do occur.

Producers must pay careful attention to production chemistry, fuel-quality testing, and developing climate-specific winter blends. A basic understanding of the mechanics of diesel equipment and a readiness to address any fuel system problems that may arise are advisable. Small-scale producers are cautioned to develop their production skills while using their fuel in older, inexpensive equipment, before running their biodiesel in newer, more expensive, and essential equipment. Homemade biodiesel fuel that does not meet ASTM specifications should not be used in equipment that is under warranty if you expect the warranty to remain valid.

Process Hazards, Safety Precautions, and Handling Issues

Safety should be the top priority in any biodiesel operation, above all other goals. Accidents involving chemicals and/or large volumes of vegetable oil, biodiesel, or by-products can cause injury, loss of life, property damage, or environmental contamination. Those who hope to avoid future government prohibition of small-scale biodiesel production would do well to consider that regulation often follows accidents.

By following “best practices” for safety, small producers as a group will continue to remain in compliance with officials responsible for public and environmental health.

A comprehensive approach to safety begins with a whole-system consideration of all potential areas for risk, followed by thorough plans for accident prevention. As a backup, preparations should also be made for response to any accident that may occur.

As a general rule, users should obtain and read a copy of the Material Safety Data Sheets (MSDSs) for methanol and lye, and be familiar with the safety considerations for each chemical. A “best practice” is to create a clearly labeled “safety station” within the processing facility, where the MSDSs are kept readily accessible. This will allow workers and fire or emergency personnel to readily locate chemical safety information in case of an accident.

It is recommended that small-scale producers contact their local fire station to advise them of the processing and chemical storage that may be occurring on site. This will serve to warn safety personnel for their protection in case of a fire, as well as to give fire officials a chance to help small scale producers address any potential areas of concern.

Those who are unwilling to invite fire safety personnel to their facility would do well to consider their ability to responsibly produce biodiesel without incident.

Accidents tend to occur when operators are tired, distracted, or hurried. Producers are advised to work slowly and thoughtfully, and to avoid juggling too many tasks at once in the biodiesel plant. Temporary rigging of equipment and shortcuts are high-risk behaviors that often lead to unforeseen consequences.

Chemical Handling


Methanol is toxic and must be handled and used in a well-ventilated area. Inhalation or ingestion of methanol can be very harmful at higher concentrations and can lead to death or blindness. It is especially damaging to the eyes; safety goggles, chemical-resistant clothing, and gloves must be worn whenever handling the material. If concentrations in the air exceed 200 ppm, air-supplied respirators are required, preferably with a full-face mask. (Canister respirators are not effective for regular use in methanol vapors).

The level at which the odor of methanol is perceptible is greater than 200 ppm. Thus, if one “smells” methanol in the processing facility, unhealthy personal exposure is already occurring. Producers are advised to alter any processing activity that results in perceptible methanol odors.

There have been many instances where methanol was ingested purposely because of its mildly intoxicating effect (much like ethanol). Ingestion has led to numerous cases of death or blindness, and precautions must be taken to keep this chemical away from children and animals.

Methanol ingestion, inhalation of high concentrations, and any contact with the eyes require immediate medical attention. Short-term exposure to methanol vapor can irritate the eyes, nose, and throat, and cause headache, nausea, vomiting, dizziness, and trouble breathing. Other common symptoms of drunkenness, such as lightheadedness, giddiness, blurred vision, and dilated pupils, might also appear. The symptoms depend on the level and length of exposure and can vary from person to person.

Methanol will readily dissolve into water and if released without proper treatment, can get into the water table. Methanol is flammable and presents a fire hazard. Its vapors are heavier than air and can travel a substantial distance to find an ignition source with subsequent flashback to the processing unit or methanol storage tank. Methanol’s flash point is a rather low 52 degrees Fahrenheit (11 degrees Celsius), which is the point whereby sufficient vapor is released to form a flammable mixture. At biodiesel processing temperatures (110 to 140 degrees Fahrenheit), there is enough methanol vapor generated to sustain a serious fire if air is allowed to mix with the methanol.

Sodium Hydroxide and Potassium Hydroxide

Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are corrosive and may be fatal if ingested. (These chemicals are both referred to as “lye” or “catalyst”). Skin contact can cause severe burns and the area affected should be thoroughly flushed with water or a dilute vinegar solution. Inhalation of the solid NaOH or KOH is possible if the material is reduced to dust-sized particles. Any of these situations is critical, requiring immediate medical attention. Sodium and potassium hydroxide must be stored away from water since water will inhibit the biodiesel reaction as well as cause heat release due to mixing, which can potentially cause a fire in adjacent material. NaOH, KOH, and concentrated solutions should never contact aluminum as they will create explosive hydrogen gas.

Proper safety gear for working with NaOH or KOH includes elbow-length gloves, chemical safety goggles, a dust mask or respirator, long pants, and shoes. An eyewash station and/or emergency shower within 25 feet of the workspace are also highly recommended. (A homemade eyewash station can be as simple as a dedicated garden hose or faucet that runs a constant, gentle stream of water up into the eyes. Design for “hands-free” operation so that an affected person can use the hands to keep eyes open while flushing.)

When measuring anything but very small quantities of NaOH or KOH, it is very important to wear a dust mask or cartridge respirator to prevent inhalation of caustic particles. A spray bottle of vinegar is handy for neutralizing any small residual catalyst spills in the workplace. Fine particles of NaOH or KOH will produce holes in clothing; thus a protective apron or jumpsuit is also advised. It is also helpful for each person working in the biodiesel shop to keep a spare change of clothes on hand, so that accidentally contaminated clothing can be quickly shed if needed.

Sodium methoxide is made by combining methanol and sodium hydroxide. Potassium methoxide is made by combining methanol with potassium hydroxide. These mixtures have many of the same corrosive and toxic characteristics as their components, and should be handled similarly. In solid form, sodium and potassium methoxides are not very stable and should be avoided. They can ignite on contact with water or moist air.

Bonding and Grounding

Static electricity can build up when fluid flows through a pipe or from an opening into a tank. Bonding and grounding prevents static electricity from causing a spark that could ignite vapors from a flammable liquid. Bonding physically connects two conductive objects together with a wire to eliminate the difference in static charge potential between them. A bond wire must be provided unless a metallic path between them is otherwise present.

A grounding wire eliminates a difference in static charge potential between conductive objects and the ground. Although bonding will eliminate a difference in potential between objects, it will not eliminate a difference in potential between these objects and earth unless one of the objects is connected to earth with a ground wire.

Plastic tanks are not recommended because they do not conduct electricity and cannot be properly grounded. These tanks can accumulate static electricity during fluid transfer that could start a fire.

General Fire Safety

No flames, smoking or sparks anywhere near the production area.

Spontaneous Combustion

Biodiesel production will routinely produce rags saturated with oil or biodiesel. It is also common (but not advised) for sawdust or other fibrous materials to be used as an absorbent for spilled biodiesel or vegetable oil. These materials present an inherent fire risk, as oily rags or sawdust can easily spontaneously combust. In 2007, a Pennsylvania barn burned to the ground when sawdust soaked with vegetable oil caught fire on a sunny day. These materials must not be allowed to accumulate in or around the workspace, including in open trash cans.

Oily rags should be kept in an air-tight metal container, a bucket of water, or sealed in evacuated plastic bags and properly disposed of in the trash. Free liquid should be squeezed into an appropriate container before disposal of saturated rags. When disposing of saturated sawdust in a dumpster, be sure to scatter the material to avoid any piles that may combust and cause a dumpster fire.

Electrical equipment should be rated for explosion-proof service and installed by qualified service personnel in accordance with the national electrical code and local regulations. Temporary rigging of electrical equipment is inherently dangerous and poses a serious fire risk. Heating elements used in processing fuel should be regulated by appropriate thermostats. Extension cords should not be used to connect electrical loads.

Fire extinguishers should be conveniently located throughout the biodiesel shop, and all users should be familiar with their operation. Avoid blocking access to extinguishers with clutter or equipment. Remember the acronym PASS: Pull the pin from the fire extinguisher. Aim the nozzle at the base of the fire. Squeeze the trigger device. Sweep from side to side of the flame as you extinguish the fire.

A twenty-pound ABC fire extinguisher is recommended. It is a good idea to run occasional “fire drills” in the biodiesel shop to be prepared in case of an actual emergency.

Safety Gear Summary

The following gear should be on hand each time you brew biodiesel:

  • Chemical-resistant gloves (butyl rubber is best for methanol and lye)
  • Chemistry goggles (indirect vented)
  • Face shield
  • Dust mask or cartridge respirator
  • Plumbed eyewash station
  • Small spray bottle with vinegar for neutralizing lye spills
  • Access to running water
  • Telephone in case of emergency and emergency telephone numbers
  • Fire extinguishers (20-lb ABC)
  • Absorbent material and spill-containment supplies

The Production Facility

An ideal space for biodiesel production will be well-ventilated yet protected from weather, and lockable to prevent untrained people from accessing chemicals and equipment. Adequate ventilation is an absolute must due to serious health hazards associated with methanol fumes and lye dust. Ventilation can be provided mechanically, via fans or chemical fume hoods, or by working outdoors in the open air. Storage space for vegetable oil, chemicals, and processing gear should be ample, and should not cramp the working space. Electrical and water service are also required for most processing systems. A secondary containment system is advisable in case of large spills of oil, biodiesel, wash water, etc.

A “best practice” is to have a separate space dedicated to biodiesel production, apart from other buildings that serve multiple purposes. Biodiesel processing in existing multi-use buildings risks the loss of assets in case of an unforeseen fire or other accident. Users are cautioned to absolutely avoid producing biodiesel in quantity inside their personal residences. Making biodiesel inside a production greenhouse or livestock barn is also not advised. Fires due to biodiesel production may not be covered by home or farm insurance policies.

A typical solution for small-scale producers would entail erecting an appropriately sized shed apart from other buildings on the property. Inexpensive modular metal buildings of various sizes (such as those sold as carports) are now commonly available throughout the country. Such buildings, when equipped with retractable walls and doors, would make an ideal site for small-scale biodiesel production. It is essential that the facility not be located immediately adjacent to waterways that could be impacted by spills of chemicals, oil, or biodiesel.

A good processing safety plan starts with a schematic flow chart for the proposed facility. Where and how will lye and methanol be stored and in what quantity? How will they be handled? Where will vegetable oil enter the building and where will it be stored? How will the materials involved in various processing steps move through the building? How will fuel and by-products exit the facility and where will they be stored? Be sure to note the location of safety gear. Once a schematic is made, it can be applied to the physical space under consideration for biodiesel production.

Processing Equipment

All of the problems associated with processing biodiesel can be handled with a properly engineered design. However, some Web sites suggest that you can build something with “what’s lying around the house.” This can be very dangerous and should be avoided. Please consult with experienced biodiesel producers or industrial personnel when designing your facility. While there are a wide variety of processor designs that will effectively convert vegetable oil into biodiesel, for safe and energy efficient production, a closed system that minimizes opportunities for escape of methanol vapors into the workspace or environment must be used. Although early books on biodiesel popularized the use of open top barrels for mixing oil with methanol and lye, these irresponsible designs result in increased fire risk, increased worker methanol exposure, and reduced fuel quality due to evaporation of methanol from the reaction tank.

Additionally, any pouring of large quantities of methanol or mixtures that contain methanol should be avoided in the process design. For this reason, a closed system, wherein oil, chemicals, and end products can be safely transferred using pumps, tubing, and valves, is ideal. Use of devices with sparking electric motors, such as drills or paint mixers, near open containers of methanol also presents a fire risk and must be avoided.

One widely used closed-system design is the water-heater-based processor (popularly known as the “Appleseed” reactor). Electric water heaters, whether purchased new or recovered from plumber’s salvage yards, have the following desirable features: they are sealable, factory insulated, and come equipped with electric heater elements, thermostats, a drain, and several inlet ports at the top of the tank. The water heater reactor uses a centrally located pump for recirculation of the reacting biodiesel. This eliminates the need for a mechanical mixer/stirrer, simplifying the system while improving overall safety.

A major concern with the Appleseed processor is the potential for explosion if the electric heaters are inadvertently left on after the reaction is complete and the contents of the water heater are evacuated. At this time, the water heater tank is filled with a potentially explosive mixture of air and methanol vapors, which could be ignited by the exposed heating element. Users of Appleseed processors are cautioned to never use the heating element after the methanol has been added to the system.

Sealed processors must be equipped with a temperature pressure-relief valve that is compatible with the tubing used to plumb the reactor (most water heaters are sold with 150- PSI valves, and these should be replaced with a 30-PSI valve if using any poly or plastic tubing). A manually operated vent valve, plumbed to the outdoors, is also essential, as described below. A sealed system based on a metal tank also allows for the recovery of excess methanol from biodiesel fuel and the glycerol by-product, which saves money and reduces handling and environmental complications after processing.

When plumbing a reactor of any design, stainless-steel or black iron tubing should be used wherever possible, as they are most compatible with the chemicals involved in processing. Galvanized fittings and any copper parts will reduce the oxidization stability (shelf life) of biodiesel, while standard PVC tends to break down over time.

Aluminum should also be avoided, as it will violently react with lye to form explosive hydrogen gas. Many systems use brass ball valves with no major ill effects. Wherever plastic, poly, or HDPE is used in biodiesel equipment, its proximity to heat sources should be considered. For example, early works on small-scale equipment popularized the use of conical-bottomed plastic tanks for the main reactor vessel. While they do possess some advantages, plastic vessels present an increased fire and spill risk in the event of an unforeseen overheating situation, structure fire, or other accident.

In the event of a fire in or near the processing space, any plastic tanks will likely rupture and release their contents, potentially adding fuel to the fire. Heating elements should never be installed in plastic tanks. Most conical-bottomed plastic tanks are not 100 percent airtight, and thus will result in some methanol release if used as a main reactor. These tanks also will not tolerate the high temperatures needed to use the reactor as a methanol recovery device.

While homemade wooden stands are commonly used to support biodiesel equipment, these also present a weak link in overall plant fire safety. In the event of a fire in the plant, a wooden, oil-soaked stand will likely burn, dumping whatever liquid is in the tank it supports into the fire. An ideal fire-safe biodiesel plant will use metal tanks supported on secure metal stands.

Ventilation, Methanol Fumes, and “Make-up Air”

The main reactor and other processing equipment will be laden with methanol vapors at various times during biodiesel production. Whenever fluids are added or drained from a sealed reactor, make-up air must be allowed to flow into or out of the reactor to prevent pressure or vacuum buildup. Air leaving the reactor should be vented through tubing to the outdoors through a condenser, as it may contain toxic or flammable vapors. The condenser will collect the methanol vapors so they are not released into the environment.

Methanol fumes will also be present when glycerol is drained from the reactor, and when raw biodiesel is pumped from the reactor to wash tanks, especially if these fluids are drained while hot. Gas analysis in one Pennsylvania biodiesel facility found methanol concentrations in excess of the lower explosion limit (and personal exposure limit) when splash-pumping warm biodiesel into an open wash tank. Remember, if you can smell methanol in the workspace, there is a problem with your process design to be corrected. A best practice is to transfer all methanol-laden fluids via tubing into closed vessels, and to vent all vessels to the outdoors.

One innovative design drains glycerol into a sealed container, which has air-vent tubing temporarily plumbed to the main reactor, so that air pressures between the two vessels can stabilize without methanol release into the workspace or environment. Periodic venting of the reactor to the outdoors is still necessary due to thermal expansion and contraction associated with heating and cooling. However, if this occurs through a condenser, methanol release is minimized. Such a “fumeless” design is very attractive for air-quality considerations.

Operator’s Quick Reference

Basic processing equipment developed in the home or farm shop can become complicated with multiple valves and switches for various purposes. Even experienced operators can make mistakes, and opening (or failing to open) certain valves during processing stages may result in spills or accidental release of dangerous chemicals into the workspace. A best practice is to develop a well-thought-out process diagram, including step-by-step guidelines for the state of valves and switches during different stages of production. This diagram should be posted on or near fuel-making equipment, to serve as a reference for all trained operators.

Step-by-Step Process Protocol

In biodiesel shops where multiple operators use shared equipment (co-ops, educational facilities, etc.), it is helpful to print off and post a standard processing protocol. Such a document ensures that all personnel follow proper safety and fuel quality procedures during each step. In addition, a “batch step checklist” that follows a batch of fuel from tank to tank on a clipboard is a handy way for multiple plant operators to communicate exactly what is happening in each tank in the shop. Also, a batch record sheet that documents the inputs and processing of a specific batch should be maintained as part of the record-keeping system.

Other Topics on Biodiesel Safety


For Additional Information

  • Biodiesel Safety video A 10-minute video that helps home biodiesel producers to understand the safety precautions that must be taken when working with the chemicals used to produce biodiesel.



Contributors to this Article

This article was excerpted with permission from Biodiesel Safety and Best Management Practices for Small-Scale Noncommercial Use and Production, published in 2008 by the College of Agricultural Sciences at Pennsylvania State University.


  • Prepared by Matt Steiman, Wilson College and Dickinson College Biodiesel Education Programs; Craig Altemose, Centre County extension director; Dennis E. Buffington, professor of agricultural and biological engineering; Glen R. Cauffman, manager of farms and facilities; Michelle Ferguson, environmental protection specialist, Pennsylvania Department of Environmental Protection; Mary Carol Frier, department of crop and soil sciences; Lysa J. Holland, environmental compliance engineer; Wallis A. Lloyd, adjunct professor of chemical engineering; Kate Lumley-Sapanski, assistant director of environmental health and safety; Joseph M. Perez, adjunct professor of chemical engineering; Greg W. Roth, professor of crop and soil sciences and state program leader for renewable and alternative energy; and James Young, regional manager, Pennsylvania Department of Environmental Protection.

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.