You may (or may not) be aware that biodiesel is usually made with vegetable oil, lye and methanol. You may also know (or not know) that there are other alternative ingredients that are in various stages of use, research and development.
The diesel engine, when it was unvieled by it’s inventor Rudolph Diesel at the World’s Fair in Paris in 1900, was running on peanut oil. Diesel designed it to run on mineral oil, but the French government, which had colonies in Africa where peanuts were grown, made the suggestion to test the engine on peanut oil.
(see this page for a brief intro to biodiesel)
One of the main arguments about biodiesel is that the use of food crops for vehicle fuel is unsustainable and contributes to global food shortages. This is true enough when the feedstock for biodiesel is vegetable oil. However, soy, canola, palm trees and other food crops are not the only things you can extract oil from. For the most part, the following alternatives involve feedstocks that don’t require the use of arable land. There are some emerging alternatives to canola and soy, such as camelina, and hemp, but they still require the use of arable land, so I have not included them here. To be fair, crops that are being grown for livestock feed can be pressed of their oil, then fed to livestock (and actually be easier for the livestock to digest), but I am not in favour of the livestock industry, and thus not considering alternatives that require or enable cattle ranching.
Feedstocks
Here are just a few examples of other feedstocks, some of which are currently being used for biodiesel production, some still being tested.
Algae
Algae is currently one of the most promising feedstocks being used for biodiesel, and has the potential of making a big contribution towards the replacement of fossil fuels. Currently the yield per acre of algae is much higher than any other known feedstock. Whereas canola can yield 147 gallons of oil per acre per year, algae can potentially yield 5000-20000 gallons per acre per year. What’s more, it doesn’t require arable land, and can be grown using waste water and carbon dioxide from coal plants. The main challenge so far, in terms of bringing the production cost down (as it is currently being produced around the world) is the process of seperating the algae from the water. Once that process happens, the algae can yield up to 50% of it’s weight in oil, and can be pressed like any seed.
Some links:
Is Algae the Biofuel of the Future?
Cultivating Algae for Liquid Fuel Production
Used Coffee Grounds
I just heard about this myself only recently. Apparently, used coffee grounds are 10% oil, which can be extracted using hexane. Not only that, but the grounds can still be used for compost after the oil is extracted.
While there is currently some discussion over on the homebrew biodiesel forum I frequent, I don’t know of any homebrewers doing this, although it is totally tested and proven, and is used in production of biodiesel in Brazil.
The downside is the amount of grounds used to make one gallon of oil. From what I can tell, it’s about 25 pounds per gallon.
Some links:
From coffee shop to biodiesel source in one step
Waste Coffee Grounds Make Great Bio-fuel
Biodiesel from Coffee Grounds
Used Tea Leaves
How fitting that both tea and coffee waste can be used for biodiesel. The bad news is that the energy required for this complicated high-tech nano-catalyst process is greater than the amount of energy the biodiesel provides.
A link:
Waste tea leaves could brew up biofuel
Pennycress
Not all cultivated biofuel feedstocks compete with food for arable land. It turns out the pennycress, long considered a weed, can be grown in the off-season, in between grain crops. Not only that, pennycress can be used for phtyoremediation, helping to cleanse soil of contaminants. To quote one of the below linked articles: ““The alternative is to dig and haul (the contaminated soil) and move it somewhere else…That cost is about $250,000 per acre. You can spend it there or you can phytoremediate, create jobs, clean it up, make biomass for power, and produce biodiesel.”
Some links:
Detroit’s vacant lots could boost Michigan biodiesel industry
Fungus
Researchers in Spain have been working on extracting oil from fungus. The good news is that it can easily grow in industrial vats and does not compete with food resources. The bad news is that it must be genetically engineered.
Some links:
Getting Bio Diesel With Molds and Fungus
Sewage Sludge
While waste water can be used to feed algae for use in biodiesel, this process uses the sludge itself (the solids left over after treatment of the water) to make biodiesel with. Apparently it can be done at a cost of $3.10 or so a gallon, which is cheaper than algae. However, there exists this idea that biofuel need be competitive in price to petrodiesel, which I find absurd. Sludge is almost there, though.
Some links:
Biodiesel from Sewage Sludge Within Pennies a Gallon of Being Competitive
Biodiesel Production from Municipal Sewage Sludges
Invasive Species
I’m having a hard time finding examples of invasive species being used for biodiesel. I yearn to see Scotch broom and other invasives that threaten biodiversity and traditional wild plant use eradicated from this area, and having a use for these plants I think would be a good motivator for getting people out there picking them.
Some of these invasives, such as the chinese tallow tree, are being considered as possible fuel crops, which is a source of active debate, due to the invasiveness of these plants. If you do a websearch for biodiesel and invasive plants, you’ll read a lot about the threat of cultivated fuel plants escaping and becoming invasive.
However, I forsee a day when the potential for invasives as a fuel source will lead to their removal from fields and forests, something that many are already working on, for conservation and forestry purposes. I am guessing that using invasives as a feedstock is not considered commerically viable because once you clear an area, your supply is quickly exhausted. For this reason, production of biofuel from invasives is likely to be driven by conservationists and forestry companies.
Here’s a link:
Oregon teen scores with possible biofuel from Scotch broom
Chinese Tallow Trees a Potential Bioenergy Crop for Louisiana
Terpenes
Terpenes are widespread in nature, mainly in plants as constituents of essential oils. Conifers are the main source for the kind of terpenes sufficent for fuel. Termites and swallowtail butterflies also emit terpenes from their osmeterium, though I don’t even want to know whether they would be good for fuel. Using treesap for fuel is not very sustainable either, but the main source of terpenes for fuel (research stage) are synthetic (genetically-engineered). It’s reported that the production cost for this method is currently $6/gallon. This is a completely different process than the transesterification process that is currently used for biodiesel production.
Some links:
JBEI researchers discover bisabolane-to-diesel pathway
Bisabolane as a biosynthetic alernative to diesel
Feather Meal
Feather meal is made from poultry feathers by partially hydrolyzing under elevated heat and pressure and then grinding. Chicken feathers contain approximately 11% fat content. This byproduct of the poultry industry is used an an animal feed. Removal of fat content from feather meal (for biodiesel) results in both a higher-grade animal feed and a better nitrogen source for fertilizer applications.
Some links:
A Green Process for Producing Biodiesel from Feather Meal
Those are just a few possibilities, and no doubt we’ll continue to hear of more. (I’ll also add some more that I am reading about later.)
Catalysts
(Note: I’m more familiar with the ‘one stage’ process of making biodiesel, while many commercial producers use a two-stage acid/base process that utilizes sulfuric acid during the first stage to neutralize Free Fatty Acids (esterification, this is called). This first pre-treatment stage is not strictly necessary, except where a low grade oil with high Free Fatty Acid content is being used. Some of the processes below also eliminate the need for this pre-treatment.)
Catalysts are the chemicals used to provoke a reaction in the feedstock, turning it from oil to biodiesel. (Usually by seperating out the glycerine, a thick substance that will sink to the bottom of the reaction vessel).
Most homebrewers and commerical producers use a mixture of lye (sodium hydroxide) or caustic potash (potassium hydroxide, and alcohol (usually methanol, but sometimes ethanol), called Methoxide or Methylate, mixing that with the heated oil.
Previously all commercial producers used to mix the two ingredients themselves, but in the last few years most have switched to purchasing ready-to-use sodium methylate (or potassium methylate).
I’ve only ever used methanol, but would like to learn how to make and use ethanol, as methanol is a fossil fuel product, commonly produced from natural gas, and increasingly from coal, especially in China. This issue with this is that anhydrous (water-free/100%) ethanol is needed for waste veggie oil. This is apparently difficult with the average moonshine still.
Ethanol can be made using natural materials, including even waste newspapers and yard waste. Ethanol can also be used in gasoline engines with a few simple adjustments. So it’s worth learning how to make it (with waste materials of course).
An unfortunate fact for the biodiesel homebrewer is that sodium hydroxide is one of the main ingredients in a certain illegal street drug. As such, it is getting increasingly harder to find, and when you do find it, you often need to show photo ID and be reported to the meth-watch program (in the USA).
The newest processes in commercial production involves using high temperatures, high pressures and high alcohol ratio to elimate the catalyst completely. (Yet still requiring alcohol.) This is called the supercritical method. This method also allows for the use of lower quality feedstock, like used animal fats. The downside being the skills and equipment required are not available to the average homebrewer.
Some links:
Conceptual Design Study of Supercritical Transesterification
Supercritical Methanol for Biodiesel Production
The amount of research out there on different catalysts is surprisingly abundant:
Quicklime
Calcium Oxide, otherwise known as quicklime, is usually made by the thermal decomposition of materials such as limestone, that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. It is considered a heterogeneous, or solid catalyst. This class of catalysts are thought to be advantageous over sodium hydroxide and potassium hydroxide in that they can be easily seperated from the finished biodiesel (eliminating water washing) and reused (saving money and resources and waste). It is also safer than lye to handle.
Novel Solid Base Catalysts for the Production of Biodiesel from Lipids
Slaked Lime
Slaked lime, (Calcium hydroxide) is made by when Calcium Oxide is mixed or ‘slaked’ with water. It is commonly used as an ingredient in the tortilla making process (technically it is used to nixtamalize corn, preventing niacin deficiency).
Some links:
Fungus
I mentioned above that fungus can be used as a feedstock, but it can also be used to replace lye in the transesterification process.
A link:
Fungi Make Biodiesel Efficiently at Room Temperature
Enzymes
A biofuels company in North Carolina recently announced that they’ve launched a new proprietary production process (say that three times fast) that uses enzymes instead of chemicals. I can’t say I understand how this works or where the enzymes come from, but they may or may not be genetically engineered.
This process is also known as lipase catalyzed transesterification or enzymatic transesterification, and has been the subject of a great deal of research for many years.
Here are some links:
Enzymes lead the way to sustainable biodiesel
Piedmont Biofuels successfully scales up commercial enzyme-based biodiesel production
A Novel Enzymatic Catalyst for Biodiesel Production
nickel on a porous support made of zeolite HBeta
Huh? What? Yeah, I know. We’re starting to get complicated here. This is one of the very new ones. Apparently this particlular catalyst is meant to address drawbacks in the processing of algae oil.
A link:
Biodiesel production method could reduce fuel’s drawbacks
DIY Lye from wood ash
One can make their own aqueous potassium hydroxide using wood ash. This is an old-time soap making skill.
A link:
Zinc Iodide
Zinc Iodide is a chemical compound of zinc and iodine. The anhydrous (dry) form is white and readily absorbs water from the atmosphere. It can be prepared by the direct reaction of zinc and iodine in refluxing ether or by reacting zinc with iodine in aqueous solution. A solid base catalyst, it is considered a safer, ‘greener’ alternative to sodium hydroxide and potassium hydroxide.
Transesterification of Soybean Oil to Biodiesel with Zn/I2 Catalyst
Metal Oxides
Metal Oxides are compounds formed by a metal and oxygen, in which the oxygen has an oxidation number –2. Many metal oxides have been studied for the transesterification process of oils; these include alkali earth metal oxides, transition metal oxides, mixed metal oxides and supported metal oxides. The use of solid metal oxides as catalysts in oil transesterification is well established, accordingly, researchers’ attempts are now focused on how to attain the highest catalyst activity.
Link:
Biodiesel production using solid metal oxide catalysts
Tripotassium phosphate
Tripotassium phosphate is a water-soluble ionic salt which has the chemical formula K3PO4. It is used as a food additive for its properties as an emulsifier, foaming agent and whipping agent.
Tri-potassium phosphate as a solid catalyst for biodiesel production
Hydrotalcites
Hydrotalcites are a class of anionic and basic clays known as layered double hydroxides. They are used a a solid base catalyst.
Source:
Biodiesel Production with Solid Catalysts (page 344)
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. It is one of the most abundant organic polymers on Earth, exceeded only by cellulose, employing 30% of non-fossil organic carbon, and constituting from a quarter to a third of the dry mass of wood.
The solid catalyst was prepared by subjecting the lignin to phosphoric acid treatment, followed by pyrolysis (oxygen-free heating) at 400 oC to produce a solid char, and then sulfonation by concentrated sulfuric acid.
Lignin-derived Solid Catalyst for Biodiesel Production from High-Acid-Value Jatropha Oil
Sugar
Sugar? Wow. What? Yes, it seems that as far back as 2005 (ancient days in terms of biodiesel innovation) the quest for a ‘green’ catalyst led a team of researchers in Japan to develop a method whereby they treat carbonized sugar with sulphuric acid (sulphonation) to create a solid acid catalyst. Three years later, a group of chemistry professors in North Carolina were working on improving the method to be able to use it simultaneously in acid and base stage reactions. According to some comments on the forums, the acid only process is very very slow and hard to reproduce.
Inexpensive, Efficient Organic Catalyst for Biodiesel Production from Carbonized Sugar
heteropoly acids
A heteropoly acid is a class of acid made up of a particular combination of hydrogen and oxygen with certain metals and non-metals. To qualify as a heteropoly acid, the compound must contain: a metal such as tungsten, molybdenum or vanadium, termed the addenda atom; oxygen; an element generally from the p-block of the periodic table, such as silicon, phosphorus or arsenic termed the hetero atom; acidic hydrogen atoms. Specifically the heteropoly acid Cs2.5H0.5PW12O40, has been used as a heterogeneous catalyst for the production of biodiesel from Arugula (Eruca sativa Gars.) oils. This seems to be another one-stage acid esterification process.
Transesterification of Vegetable Oil to Biodiesel using a Heteropolyacid Solid Catalyst
Salt/Ionic Liquid
An ionic liquid (IL) is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below some arbitrary temperature, such as 100 °C (212 °F). While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ILs are largely made of ions and short-lived ion pairs. These substances are variously called liquid electrolytes, ionic melts, ionic fluids, fused salts, liquid salts, or ionic glasses.
Some links:
Use of Ionic Liquids in Biodiesel Production: A Review
Ionic Liquid Catalyst Simplifies Jatropha Biodiesel Production
Other methods
Supercritical Carbon Dioxide
According to an article in Phys.org (among other sources), Scientists at the Yale School of Forestry and Environment have discovered a ‘one-pot’ method for making biodiesel from algae that combines lipid extraction and conversion of those lipid into biodiesel, using supercritical co2.
“…similar approaches have been proposed for using supercritical methanol and ethanol, but the use of supercritical carbon dioxide requires lower temperatures, making it easier to work with and less energy-intensive. Another advantage, Zimmerman noted, is that the supercritical carbon dioxide, which acts as a solvent for oil, can be tuned to extract only specific components from algae oils, saving time and resources.”
Links:
Toward a more economical process for making biodiesel fuel from algae
One-Pot Algal Biodiesel Production in Supercritical Carbon Dioxide (original research paper – pdf)
Ultrasonic and Microwave
There are other methods which I’m not too familiar with and are sufficiently technical to be a bit over my head right now. They are the ultrasonic and microwave processes. Basically, as they names might infer, they use ultrasound and microwaves to assist in the process. Both of these process use the standard ingredients (lye, alcohol and oil) as far as I can tell, although research is being conducted on the use of the metals bismuth triflate and scandium triflate in a microwave process.
Some links:
Ultrasonic Biodiesel Processing
Microwave Technology and Continuous-Flow Production
Brown University Researchers Converted Waste Vegetable Oil to Biodiesel in a Single Reaction Vessel
Pyrolysis
It’s not technically considered a biodiesel process, but by burning biomass (dead trees for instance) without oxygen (a process called pyrolysis) you end up with a ‘bio-oil’ which can be blended with diesel.
Here are some links:
Thermal Depolymerization
As is the case with pyrolysis, it’s incorrect to call thermal depolymerization a biodiesel process, as the term biodiesel is technically reserved for fuels made using the transesterification process. For the purpose of this article, I’m including anything that involves turning a biological material into diesel fuel.
Thermal Depolymerization is one of the most exciting sounding processes, in that virtually anything can be used as a feedstock, including plastic bottles, medical waste and tires. The process is similar to pyrolysis, except that steam is somehow part of the process (hydrous pyrolysis this is called). This process is said to mimic the natural geological processes thought to be involved in the production of fossil fuels.
Here is a link:
Hydrotreating/Hydroprocessing
As mentioned in discussion of pyrolysis and thermal depolymerization, fuels made using the transesterification or catalytic process are known as biodiesel. Thermal depolymerization creates ‘renewable’ diesel and hydrotreating creates ‘green’ diesel or ‘Hydrogenation-Derived Renewable Diesel’ (HDRD). I’m still puzzling out what hydrotreating is, but it seems to involve hydrogen, as well as some specialized and expensive catalysts. It’s said to be chemically equivalent to petro-diesel and has a lower cloud point than biodiesel, which means it can be used in a broader range of temperatures.
Some links:
Biodiesel’s Nightmare: Renewable Diesel
Hydrogenation-Derived Renewable Diesel
There as yet does not seem to be any alternative to using alcohol in the biodiesel process, although if you know how to distill 100% (water-free) ethanol, you can use yard waste to make the ethanol. And while most methanol is made from fossil fuels, it can be made of a wide variety of organic materials. There exists even a direct process to make methanol using the waste gylcerine from the biodiesel process (using hydrogen as a catalyst).
New Process for Direct Conversion of Glycerol to Methanol
In the next chapter, I will talk about some new designs for homebrew biodiesel processors that may be a rival alternative to the standard Appleseed Processor that many of us homebrewers have grown used to.
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