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Biodiesel Basics

Biodiesel fuel is a cleaner burning, renewable alternative to diesel fuel made from any biologically based oil. While commercial Biodiesel is commonly made from virgin vegetable oils pressed from soybean, canola, peanut, or sunflower seeds, many small processing facilities around the world take advantage of waste fryer oil from restaurants.

"The use of plant oil as fuel may seem insignificant today, but such oil can, in time, become just as important as petroleum and these coal-tar-products of the present day." - Rudolf Diesel, 1912

Biodiesel is a renewable resource that is non-toxic, biodegradable, and energy efficient. It is the first alternative fuel to pass the heath effect tests of the Clean Air Amendments of 1990 and the only fuel that can directly replace petroleum based diesel in cars. Studies conducted by the US National Renewable Energy Lab found that tailpipe emissions in diesel engines using biodiesel have a significantly reduced amount of carbon dioxide, hydrocarbons, and particulate matter released into the atmosphere.

Small scale production is a growing trend on farms and at colleges around the country. The Biodiesel Project at Dickinson College began as a research project and continues to provide the campus with opportunities to study and explore biofuels, solar hot water, and other renewable energies.

Science Behind Biodiesel
Biodiesel Production

Biodiesel fuel is a cleaner burning, renewable fuel made from any biologically based oil. The oil of choice for the shop is Waste Vegetable Oil (WVO), which is collected from local restaurants and colleges. The WVO is put through a process called Tranesterification. During this process, WVO is mixed with a methanol and lye solution. The lye can be either KOH (potassium hydroxide) or NaOH (sodium hydroxide) and acts as a catalyst for the reaction. The ingredients are put into a reactor to be mixed and heated. Once the reaction is complete, there are two distinct layers present: biodiesel and a glycerin byproduct. Biodiesel made in the Dickinson shop is used to power several campus trucks, tractors, mowers, and even the President’s car! It is also used as a supplemental heat source for the greenhouse at the college farm during winter.

Since methanol, a toxic chemical, is still present in the fuel and glycerin at the end of the transesterification reaction, a process called methanol recovery is conducted on both layers separately to remove the harmful chemical. This methanol is later re-used in the next batch of fuel.

During Transesterification, a soapy substance forms in the fuel layer that must be washed out. The last stage of the process is to wash the fuel with water several times and then to let it dry allowing the water to evaporate. The biodiesel can be stored in the same holding tanks as petroleum based diesel. The two fuels can be mixed usually 1:4 biodiesel: petrodiesel in the fuel tank.

Glycerol Byproduct

Glycerol (or Glycerine) byproduct is a significant consideration for anyone undertaking biodiesel production. For every five gallons of biodiesel produced, approximately one gallon of crude glycerol byproduct results. This is inevitable, as the removal of glycerol from the original vegetable oil is the main goal of the biodiesel reaction. The glycerol that results from biodiesel production has several contaminants, and is costly to purify, thus the market value for the byproduct is very low. Increased commercial production of biodiesel in recent years has resulted in a worldwide glut of glycerol. All biodiesel producers regardless of scale should give ample consideration to how they will approach the glycerol question. Many "green-minded" small scale producers focus on fuel production yet fail to adequately handle their glycerol problem. Presently, there exists a great opportunity for innovators to convert this waste stream into a useful product.

Crude biodiesel glycerol (CBG) straight out of the biodiesel reactor contains significant quantities of methanol: approximately 20-25% by volume. The glycerol layer also contains residual catalyst (either KOH or NaOH), residual fatty acids, soaps, food particles, and other impurities. Due to its methanol content, CBG is considered a hazardous material (ignitable and toxic) by the Pennsylvania Department of Environmental Protection. As such, glycerol should be handled with the same care given to methanol. Contrary to popular belief, the methanol will not evaporate out of glycerol containers left open to the air. It takes significant heat, time, and agitation to remove enough methanol from the byproduct for it to be rendered non-hazardous.
Dickinson Biodiesel Research

In our shop, we make a concerted effort to only transfer methanol-laden glycerol through tubing between sealable containers, rather than splash pouring into open buckets (this reduces methanol vapors in the workspace). Our glycerol storage tank is vented to the outdoors during filling and emptying, but is kept sealed at all other times. We store glycerol in a sealable steel drum (rather than plastic), in order to reduce the likelihood of a fire-related tank meltdown that would add methanol-laden glycerol to the fire. When working with hoses or other glycerol containers, we wear gloves and goggles for personal protection. If a glycerol spill should occur, we ventilate the area using a fan and natural ventilation. All glycerol containers are labeled to indicate their contents. Buckets of glycerol are tagged to indicate the date of production, methanol content, and any other pertinent information such as catalyst type, water pre-wash, etc.

The methanol content of the glycerol byproduct can be recovered via simple distillation, also known as "methanol recovery". Methanol recovery reduces the methanol content of the byproduct, greatly simplifying safe and legal handling of the final material. Methanol recovery also keeps this expensive, toxic material contained in the biodiesel shop, rather than releasing it into the environment.

Every batch of glycerol produced in the Dickinson College Biodiesel Shop goes through the methanol recovery process. We store the byproduct from several batches of fuel until we accumulate a 55 gallon load (approximately once each month). From one 55 gallon barrel of glycerol we typically recover between 10 and 15 gallons of methanol, which can be used again for making more biodiesel. Through DEP and independent laboratory testing, we have found that we need to bring the glycerol to 260 degrees F before the methanol content will be reduced to a level where it is no longer considered a hazardous material. For more information on methanol recovery, please visit our dedicated page on that topic.
Glycerol Options
The Dickinson College Biodiesel Project, as a member of the sustainable biodiesel producers' community, actively seeks to research and promote safe and responsible options for glycerol reuse or disposal. What follows is a summary of our current understanding of this topic. This page will be updated following further experimentation. Biodiesel producers are encouraged to contact their local environmental management office (such as the PA DEP) for the latest information regarding regulation of glycerol disposal in their area.

What NOT to do with glycerol:

  • Stockpiling of glycerol presents a health and fire risk, quickly becomes an eyesore, and may be illegal in some U.S. states. Glycerol stored in thin plastic fryer oil jugs ("cubies") will leak over time, creating a dangerous mess. The PA DEP prohibits accumulation of glycerol on site for more than one year. It is best to deal with glycerol as it is produced.
  • Dumping of glycerol into the environment is prohibited by law in many states. Glycerol dumped into streams and irrigation channels has resulted in fish kills on more than one occasion. Anything dumped into storm sewers may find its way into surface waterways. Land application is also regulated.generally speaking concentrated land application of glycerol is a bad idea. Dumping of glycerol into municipal (sanitary) sewers creates a safety and handling problem for the waste water treatment plant, and is most likely prohibited in local jurisdictions.
  • Burning glycerol may create acrolein gas, a highly toxic material. Acrolein has been used as a chemical weapon and is not something anyone wants floating around the home fireplace. While burning glycerol at a very high temperature (such as in a cement kiln or commercial boiler situation) may prevent harmful emissions, the fact remains that raw glycerol's status as a hazardous material results in very strict regulations for its combustion. Some small producers promote the practice of mixing glycerol with sawdust into "logs" for burning. We do not recommend this practice due to the combustion hazards, and the safety issues associated with excessive handling of glycerol.

What we do with glycerol at Dickinson College:

As stated previously, all byproduct goes through the methanol recovery process before moving on to its next use. Glycerol produced at the Dickinson College leaves the plant in one of the ways described on the following sections: Anaerobic Digestion of Glycerol into Biogas, Soap and Degreaser from Glycerol, or Glycerol Composting Research Project.

Anaerobic Digestion of Glycerol into Biogas

The Dickinson College Biodiesel Shop is indebted to the Innovation Transfer Network/ Keystone Innovation Zone program of Pennsylvania , for their generous support of our pilot study on anaerobic digestion of biodiesel glycerol.

Anaerobic digesters are commonly used by wastewater treatment plants and livestock farms for solid waste and manure processing. Digesters are living systems comparable to the gut of an animal or the bottom of a swampRichard Waybright, proprietor of Mason Dixon Farm near Gettysburg, PA, shares some seed material for the Dickinson College biogas experiments.: organic wastes are "fed" into a tank in an oxygen-free environment, where bacteria consume the wastes, breaking them down into simpler constituent molecules. Through the action of these bacteria, methane gas (or "biogas") is released, which can then be captured for use as fuel. Methane from commercial scale digesters is often used to power electric generators, while village scale systems commonly used in the developing world produce methane for cooking and home heating. These waste-to-energy systems create three solutions in one: waste removal, management of the environment, and production of clean, renewable energy. The most notable example of a methane digester in Pennsylvania is operated by Mason Dixon Farm near Gettysburg , where manure from a large dairy herd generates enough electricity to power the entire farm, while selling surplus energy into the utility grid. Many different types of waste can be converted to methane by anaerobic digesters, so long as a proper carbon to nitrogen balance and moisture content are maintained. Potential feedstock includes animal manures, human waste, foodscraps from restaurants and food processing Students visit with Mr. Waybright in the methane-powered generator room.  Mason Dixon Farm produces all of its own electricity from anaerobic digestion of cow manure.  The farm sells $200,000 worth of renewable electricity to the utility each year.plants, paper, cardboard, and yard wastes. In the first stage of digestion, acid-tolerant bacteria break down the wastes into glycerol, alcohols, and simple sugars. In the second stage, methanogenic bacteria convert these molecules to useful methane gas. The effluent of the digester is an organic slurry that can be used as liquid fertilizer or composted for further breakdown.

In Europe and a handful of states in the U.S. , crude biodiesel glycerol is being fed to anaerobic digesters to boost biogas production. CBG may be an ideal digester feedstock for many reasons. Its high carbon levels can be used to balance more nitrogen rich manures, yet it offers carbon in a liquid state that will easily flow through digester tanks and pumps (most carbon rich wastes, like wood and leaves are fibrous, which can be problematic). CBG has a high pH, which can be used to buffer the negative tendency of digesters to acidify over time. Most interesting is the ability of microbes in digesters to biologically convert CBG's toxic methanol into useful methane. Methanol contamination is the principal challenge to CBG's safe disposal, so producers and regulators are very interested in environmentally benign methods for dealing with this material. The Waste Management bureau of the DEP has requested data to support the benefits of using CBG as a biodigester feedstock additive before this will be allowed as a regular practice in the Commonwealth.

Our research into glycerol digestions consists of two distinct projects. To determine the impact of glycerol additions to anaerobic digesters, we have designed and built a set of eight bench scale test digesters. These allow us to run simultaneous trials on mixtures of various feedstocks. At present (October, 2008), we have fine “Version 3.0” of the bench-scale research digester setuptuned and constructed a working system of mini digesters. While these allow us to make qualitative comparisons about the digestion of glycerol, our goal is hard data. To this end we are working with Robert Crosby of Biorealis Systems to fabricate a digital, data recording gas monitoring system.

This picture (left) depicts "Version 3.0" of the bench-scale research digester setup, housed in an insulated cooler for maximum efficiency. Four half-gallon Nalgene containers serve as the mini digestion units. The containers are floated in a warm water bath, kept at approximately 95 degrees F by a small aquarium heater (not pictured). The water is circulated among the digesters by the black pond pump shown at left, in order to maintain an even temperature between all containers. The PVC pipe configuration acts as a support structure for the digesters, as well as a means of moving the warm water throughout the water bath. Gas produced in the digesters exits to the gas scrubbing and collection vessels located outside of the water bath. Grey auto-shutoff quick-disconnect fittings (at top) facilitate easy separation of the digesters from the gas collection system.

Brass tee configuration

Gas exits the digesters through this brass tee configuration. The plug at the top of the tee (right) allows for easy insertion of a pH probe or pipette into the digester slurry without opening the large lid. It is vital to maintain a good seal on all components, and to prevent oxygen from entering the anaerobic environment of the digester, which would otherwise poison the methane forming bacteria.

This photo (left) shows the prototype of the initial design for the gas production recording system. This "tipping bucket" design used a weighted internal chamber, set on an off-center axis, designed to fill with gas as it was produced by the mini digesters. When sufficient gas filled the inner chamber, the change in buoyancy would cause the chamber to upset, which would then send a signal to a magnetic switch attached to the exterior of the unit. This design proved to be too cumbersome to replicate and was scrapped after initial trials.

Diagram of the updated design for the gas collection and monitoring system

Diagram (above) of the updated design for the gas collection and monitoring system (currently being debugged by Biorealis Systems). The water trap is a sealed container equipped with a pressure switch. As gas produced in the digester bubbles through the water trap, pressure builds within the air space above the water. When a pre-set pressure is reached, the PLR (programmable logic relay) opens the solenoid valve, releasing the gas to a secondary storage container. The PLR records a data point each time the solenoid valve opens due to pressure buildup. The pressure setpoint is calibrated to represent a known volume of gas. Each test digester feeds gas to its own dedicated water trap, and all water traps are monitored by a single PLR . By comparing the volume of gas produced between digesters, we can assess the effect of various feedstock blends on the gas production process.

layout of the gas monitoring electronics during the initial phase of constructionThis photo (left) shows the layout of the gas monitoring electronics during the initial phase of construction. These sensitive components are enclosed within a splash-proof box. The PLR, pictured at center, includes a digital readout for easy data downloads.

Phase Two of the glycerol to biogas project involves building a larger prototype production digester for use at the College Farm. This digester will be "fed" a mixture of ground food scraps from the College Dining Hall, mixed with glycerol from the biodiesel plant. After working with the pilot scale design to gain familiarity with the technology, the Farm hopes to build a larger digester to provide additional energy for use as a cooking and heating fuel.

Diagram (right) of the production scale digester under construction at the College Farm. From right to left, the three tanks represent 1: mixing tank, 2: main digester, and 3: gas collection tank. Note the coiled pipe within the main digester. This innovative design by Bob Crosby of Biorealis Systems allows digestion to occur in two phases within the same system. The acid phase of Diagram of the production scale digester under construction at the College Farminitial material breakdown occurs within the coil (a 4 inch sewer pipe), while the methanogenic phase of secondary breakdown occurs in the center of the drum. Organic wastes are mixed in the mixing tank, then pumped into the main digester through the coiled sewer pipe. As gas is produced, it exits the digester and is trapped underneath the inverted barrel of the gas collection vessel. When sufficient gas is collected within the inverted barrel, it is pumped to the point of use. For the initial system design, we will use the gas to power a water heater in the farm's greenhouse. This prototype design will handle approximately four to five gallons of food waste / glycerol slurry per day.

The glycerol to biogas project is a work in progress. While we have made significant advances toward completion, as of October of 2008 there are still several pieces of the puzzle which we are pulling together. Each trial and error experience results in an expansion of our understanding of this complex technology. This project is exciting in that it combines living organisms, simulated micro-ecosystems, and several interesting physical dynamics including digital monitoring and electronic controls. All of these factors need to line up in order for us to generate meaningful, reportable data. We are confident that the project will succeed, and encourage readers to visit this page again for updates in the coming months. (UPDATED 10/28/08).

Soap and Degreaser from Glycerol

One apparently viable option for re-use of the glycerol byproduct is refinement into a crude soap. Biodiesel Student Andrew Kamerosky demonstrates glycerol soap production at a farmers' workshop in North Carolina.glycerol soap has proven to be effective as a hand and body washing agent, as well as for industrial degreasing, floor cleaning, stain removal from clothing, and dish washing. Our project expended significant effort over the summer to refine recipes for liquid and bar soap, test market it to a variety of end users, and streamline the process for efficient soap production.

Student Andrew Kamerosky demonstrates glycerol soap production at a farmers' workshop in North Carolina. (Right)

Biodiesel is made using either sodium hydroxide (NaOH) or potassium hydroxide (KOH) as a catalyst. Glycerol byproduct from sodium catalyzed fuel will produce hard bars of soap (below, right), while glycerol from potassium catalyzed fuel will produce a liquid soap. In either case, the first step in responsible soap production is the recovery of any residual methanol in the glycerol. Following this process, the glycerol is allowed to cool to approximately 120 degrees (F), and then combined with additional sodium or potassium catalyst and water to initiate saponification. While the soap cools, essential oils are added to provide a pleasant fragrance. In our trials, CBG can be converted to an effective soap for a very low materials and labor cost. We found bar soap production to be far more troublesome than the more forgiving liquid soap. Glycerol based bars have a tendency to sweat in warm weather, and they tend to soften and melt prematurely when used in a shower.

The liquid glycerol soap (below), test marketed on the Dickinson College campus as "Green Devil Bio-Suds" (based on our school's sustainability program mascot), has earned a popular following. Several personnel from the college facilities management department use the soap for personal body care, and report it is most effective as a hand cleaner following greasy, dirty work. Its oil-cutting ability make it a good candidate for poison ivy treatment, yet it leaves hands moist and soft due to its high glycerol content. Free samples of the soap were also distributed to several area farmers and maintenance garages as a degreasing agent, and positive feedback has been received thus far.

Glycerol Composting Research Project

Alison DethoffComposting of biodiesel glycerol has long been promoted by members of the grassroots biodiesel community as a means of byproduct disposal. However, to our knowledge, little to no research has been done to document the effects of glycerol in a compost pile. Beginning in 2007, the Dickinson College Biodiesel Project carried out several composting research trials. These student-led projects were used as a teaching tool for upper-division biology students, while attempting to gather useful information for biodiesel producers seeking a responsible method for byproduct disposal. Students Alison Dethoff (left) and Jamie Panunzio (below) lead the successive research projects, assisted by Sarah Gold and Kelli Maurer. Ms. Dethoff and Ms. Panunzio's full reports from their research are linked at the bottom of this page. In all trials, methanol was recovered from the glycerol prior to composting.

The Dickinson glycerol composting studies have attempted to address physical, chemical, and biological impacts of the addition of glycerol to compost piles. While glycerol seems to "go away" when added to other organic materials, what really happens to the compost, and the living community of organisms within the compost piles? Is this really a legitmate practice, or just a sophisticated way of diluting our waste product into the environment? Are there any tangible benefits to adding glycerol to compost that might make this a marketable co-product (such as a "compost accelerant" or nutrient source)?

The verdict is still out, but our results can be summarized as follows:

  • Nutrients: Addition of glycerol derived from a potassium hydroxide catalyzed biodiesel reaction increases the presence of potassium in the finished compost piles. If the process is refined and controlled, this may allow compost managers to "spike" their composts with potassium if desired. It should also be noted that sodium hydroxide catalyzed glycerol will presumably result in a higher level of sodium in the resulting compost. While potassium is a major plant nutrient, sodium in excess can be harmful to soils, and thus composting of sodium based glycerol should be avoided.
  • pH: The pH of finished compost was elevated in correlation to the amount of glycerol added to the piles. It is not yet known whether this elevated pH could result in a "liming effect" which could be used to rectify acidic soils, or whether the high pH would be detrimental to plant growth.
  • Compost Temperature: Throughout successive trials, compost piles were found to reach higher temperatures in correlation with the amount of glycerol added. Initial tests used manually operated temperature probes, while a later trial verified the results with automatic temperature sensing data loggers. These findings are exciting in that it suggests glycerol may act as a compost accelerant, presumably by providing microbes with access to an easily metabolized carbon source (glycerol is a sugar alcohol). If the higher temperatures are able to provide more reliable mortality of weed seeds and pathogens in the composts, this would certainly be a potential benefit.
  • Bioassays: Two trials for phytotoxicity and inhibition of seedling germination were carried out, and results appear to suggest no toxicity at moderate concentrations of glycerol in the compost. In two separate trials, cucumber seedlings were grown in mixtures of test composts and potting media. A second type of bioassay was run using Berlese Funnels to assess the number and diversity of macroinvertebrates living in the finished composts. This trial showed a wide variety of insects, worms, and other invertebrates in all compost piles, regardless of glycerol concentration.
  • Increased presence of particular fungus: A conspicuous white fungus was observed to be prevalent in the more glycerol rich compost piles throughout all trials. While we have yet to identify the specific fungus, we suspect that it is a fungus favored by the increased presence of fatty acids in the glycerol composts. Ali Dethoff's study included a photographic assessment of the presence of fungal mycelia across the spectrum of glycerol concentration.
  • Soil Binding Effect: The more glycerol rich compost piles exhibited a caking effect, wherein the glycerol seemed to cause compost materials to stick together. This gives credibility to the often suggested use of glycerol as a dust control agent for dirt roads. While further research must be carried out to determine the soil and water chemistry impacts of glycerol applied to the land in any quantity, this observation suggests that glycerol may have potential as an erosion control agent for disturbed areas.

Those who have an interest in composting glycerol as a means of byproduct disposal are advised to consider the following:

  1. Biodiesel glycerol is not approved as an additive to composts for organic farms in Pennsylvania . Organic farmers should check with their local certifying agency before proceeding with glycerol composting.Jamie Panunzio
  2. Methanol must be recovered from the glycerol prior to composting, or the operator may violate regulations governing the disposal and handling of hazardous wastes (glycerol with methanol is a hazardous material due to flammability and toxicity).
  3. Prospective glycerol composters should consult with their local environmental regulators prior to proceeding with such a project. If questions or problems arise, the regulators may be directed to contact the Dickinson College Biodiesel project for further information. We are working with the Pa Department of Environmental Protection to determine legitmate protocols for glycerol composting.
  4. Never compost glycerol near a surface waterway or storm drain. Cover glycerol compost piles with "Compostex" fabric or other material to prevent rainwater saturation to the point of runoff (the goal is to avoid any runoff to surface waters or leaching into ground water). Add small amounts of glycerol to large amounts of absorbent compost base material, so that the glycerol will not run out of the piles.
Student Research Papers

Articles to be posted soon:

Ali Dethoff: Fall 2007/ Spring 2008 - Effects of Application of a By-Product of Biodiesel Production on Compost

Jamie Panunzio: Summer 2008 - Glycerin Compost Article

Links to be added soon
Dickinson College
Carlisle, PA 17013
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