Biodiesel 101
|
| What is Biodiesel? Biodiesel is a fuel made from vegetable oil that runs in any unmodified diesel engine. Biodiesel can be made from any vegetable oil including oils pressed straight from the seed (virgin oils) such as soy, sunflower, canola, coconut and hemp. Biodiesel can also be made from recycled cooking oils from fast food restaurants. Even animal fats like beef tallow and fish oil can be used to make biodiesel fuel. While biodiesel may sound like something from the movie “Back to the Future,” its use dates back over 100 years to the invention of the diesel engine. |
| |
| |
Dr. Rudolf Diesel Dr. Rudolf Diesel actually invented the diesel engine to run on a myriad of fuels including coal dust suspended in water, heavy mineral oil, and, you guessed it, vegetable oil. Dr. Diesel’s first engine experiments were catastrophic failures. But by the time he showed his engine at the World Exhibition in Paris in 1900, his engine was running on 100% peanut oil. Dr. Diesel was visionary. In 1911 he stated “The diesel engine can be fed with vegetable oils and would help considerably in the development of agriculture of the countries which use it.” In 1912, Diesel said, “The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in course of time as important as petroleum and the coal tar products of the present time.” Since Dr. Diesel’s untimely death in 1913, his engine has been modified to run on the polluting petroleum fuel we now know as “diesel.” Nevertheless, his ideas on agriculture and his invention provide the foundation for a society fueled with clean, renewable, locally grown fuel. |
 | How Biodiesel Works Biodiesel runs in any unmodified diesel engine. There is no “engine conversion” typical of other alternative fuels. The diesel engine can run on biodiesel because it operates on the principle of compression ignition whereby air is compressed and then fuel is sprayed into the ultra-hot, ultra-pressured combustion chamber. Unlike gasoline engines, which use a spark to ignite the fuel/air mixture, diesel engines actually use fuel to ignite hot air. This simple process allows the diesel engine to run on thick fuels. Since biodiesel is chemically similar to petroleum diesel fuel, you can pour biodiesel right into the fuel tank of any diesel vehicle. Biodiesel has many advantages as a transport fuel. Biodiesel has lower emissions, it is made domestically (which increases national security), it does not affect engine performance and biodiesel is produced from plants. Since plants are a product of solar energy, biodiesel is “liquid solar fuel.” |
Biodiesel Benefits
1) Biodiesel runs in any conventional, unmodified diesel engine. No engine modifications are necessary to use biodiesel and there is no “engine conversion.” In other words, “you just pour it into the fuel tank.”
2) Biodiesel can be stored anywhere that petroleum diesel fuel is stored. All diesel fueling infrastructure including pumps, tanks and transport trucks can use biodiesel without modifications.
3) Biodiesel reduces Carbon Dioxide emissions, the primary cause of the Greenhouse Effect, by up to 100%. Since biodiesel comes from plants and plants breathe carbon dioxide, there is no net gain in carbon dioxide from using biodiesel.
4) Biodiesel can be used alone or mixed in any amount with petroleum diesel fuel. A 20% blend of biodiesel with diesel fuel is called “B20,” a 5% blend is called “B5” and so on.
5) Biodiesel is more lubricating than diesel fuel, it increases the engine life and it can be used to replace sulfur, a lubricating agent that, when burned, produces sulfur dioxide - the primary component in acid rain. Instead of sulfur, all diesel fuel sold in France contains 5% biodiesel.
6) Biodiesel is safe to handle because it is biodegradable and non-toxic. According to the National Biodiesel Board, “neat biodiesel is as biodegradable as sugar and less toxic than salt.”
7) Biodiesel is safe to transport. Biodiesel has a high flash point, or ignition temperature, of about 300 deg. F compared to petroleum diesel fuel, which has a flash point of 125 deg. F.
8) Engines running on biodiesel run normally and have similar fuel mileage to engines running on diesel fuel. Auto ignition, fuel consumption, power output, and engine torque are relatively unaffected by biodiesel.
9) Biodiesel has a pleasant aroma similar to popcorn popping in comparison to the all-too-familiar stench of petroleum diesel fuel.
Biodiesel Emissions
Overall biodiesel emissions are lower than gasoline or diesel fuel emissions (with the exception of NOx, which we discuss on the next page). Compared to diesel, biodiesel produces no sulfur, no net carbon dioxide, up to 20 times less carbon monoxide and more free oxygen. Biodiesel has the following emissions characteristics when compared with petroleum diesel fuel:
- Reduction of carbon dioxide emissions (CO2) by 100%
- Reduction of sulfur dioxide (SO2) emissions by 100%
- Reduction of soot emissions by 40-60%
- Reduction of carbon monoxide (CO) emissions by 10-50%
- Reduction of hydrocarbon (HC) emissions by 10-50%
- Reduction of all polycyclic aromatic hydrocarbons (PAHs) and specifically the reduction of the following carcinogenic PAHs:
- Reduction of phenanthren by 97%
- Reduction of benzofloroanthen by 56%
- Reduction of benzapyren by 71%
- Reduction of aldehydes and aromatic compounds by 13%
- Reduction or increase in nitrous oxide (NOx) emissions by 5-10% depending on the age and type of engine.
What is NOx?
Engines running on biodiesel sometimes register an increase in Nitrous Oxide (NOx) emissions. NOx is a low-level emission that contributes to the yellowish haze around cities. NOx emissions are produced when something is burned in Earth’s atmosphere, (which is about 80% nitrogen and 20% oxygen). The range of increase in NOx emissions resulting from biodiesel can be anywhere between 1-15% but is generally around 5%. The measurement varies widely according to engine type and the type of biodiesel fuel used. For example, Cummins engines generally register lower NOx emissions than Caterpillar engines and biodiesel made from rapeseed has often shown actual reductions in NOx emissions while biodiesel made from soy generally shows an increase in NOx emissions. Engine age also affects NOx. Older diesel engine may produce up to 12 grams of NOx per brake horsepower hour (bhp) whereas newer diesel engines typically produce as little as 1.4 grams of NOx per bhp - less NOx emissions than many gasoline engines.
Solutions to NOx Emissions
Regardless of engine make or biodiesel fuel type, there are two simple methods to reduce NOx emissions. NOx emissions are a function of temperature. In the case of biodiesel, NOx emissions are a function of combustion temperature. The higher the heat of combustion, the greater the NOx emissions. Because biodiesel contains more oxygen than diesel fuel, the heat of combustion is slightly higher. By retarding engine timing 1-3 degrees, combustion temperature will drop slightly and the NOx emissions of an engine running on biodiesel will drop to levels at or below those recorded when the engine was running on diesel fuel. NOx emissions will also decrease with the use of a catalytic converter, a device that uses rare earth metals to break apart emissions. While catalytic converters have been standard on gasoline vehicles for some time, they have only recently become standard on diesel vehicles in the United States. The complete lack of sulfur in biodiesel fuel allows the use of powerful NOx breaking catalysts that have been unusable until now.
Biodiesel & Cold Weather
When diesel fuel or biodiesel cools, wax crystals can form in the fuel. The crystals can plug fuel filters and stop the flow of fuel to the engine. Diesel fuel #2 can be used down to about -10 deg. F (-23 deg. C) and diesel fuel #1 (kerosene) can be used down to about -20 deg. F (-29 deg. C). In contrast, biodiesel made from rapeseed can be used down to (-9 deg. C), biodiesel from soy can be used down to (-1 deg. C) and biodiesel from used cooking oil or animal fat can be used down to roughly between (9-12 deg. C).
Cold Weather Solutions
There are many ways to keep a diesel vehicle’s fuel system warm in winter. In fact, some diesel vehicles come stock with cold weather equipment. There are six different ways to keep a diesel vehicle’s fuel system from gelling in winter. The use of a block heater at night and a tank heater during the day has allowed biodiesel to be used in Yellowstone national park down to -40 deg. F.
The six methods for keeping a diesel fuel system operational in winter are:
1) An engine block heater to keep the engine warm at night. This helps with starting on cold mornings.
2) A fuel tank heater, which circulates coolant through a pipe in the fuel tank.
3) An electric element fuel line heater, which heats the fuel at one point.
4) A coolant-operated fuel heater, which uses hot coolant and a heat exchanger to heat a section of the fuel line.
5) An electric fuel line heater. This is like an electric blanket for the fuel line, which extends from the fuel tank to the fuel filter.
6) Winterizing agents and additives.
Making Biodiesel
The process of converting vegetable oil into biodiesel fuel is called transesterification and is luckily less complex than it sounds. Chemically, transesterification means taking a triglyceride molecule, or a complex fatty acid, neutralizing the free fatty acids, removing the glycerin, and creating an alcohol ester. This is accomplished by mixing methanol (wood alcohol) with lye (sodium hydroxide) to make sodium methoxide. This dangerous liquid is then mixed into vegetable oil. The entire mixture then settles. Glycerin is left on the bottom and methyl esters, or biodiesel, is left on top. The glycerin can be used to make soap (or any one of 1,600 other products) and the methyl esters is washed and filtered. The resulting biodiesel fuel when used directly in a Diesel engine will burn up to 75% cleaner than petroleum diesel fuel.
Transesterification was conducted as early as 1853. One of the first uses of biodiesel (transesterified vegetable oil) was powering heavy vehicles in South Africa before World War II.
Why make biodiesel? Vegetable is a much more dense substance than diesel but biodiesel is very similar to diesel fuel. Biodiesel benefits from a viscosity that is twice that of diesel fuel and a molecular weight is roughly 1/3 of vegetable oil. Most Diesel engines were designed to use highly lubricating, high sulfur content fuel. Recent environmental legislature has forced diesel fuel to contain only a minimum amount of sulfur for lubricating purposes. Thus, the high viscosity of biodiesel makes it a perfect fuel of choice for diesel engines.
To learn more about making biodiesel read:
Joshua Tickell’s book, From the Fryer to the Fuel Tank (Now available as a 15meg, downloadable, printable and transferable PDF).
Fun Biodiesel Articles
Biodiesel from Fish Oil | Biodiesel from Fish Oil | Navy Producing Biodiesel |
| | | |
Veggie Car Article
The Athens News | Biodiesel from Algae | Biodiesel Life Cycle |
| | | |
Children's Exposure to Diesel Exhaust
on School Buses
Part 1 | Children's Exposure to Diesel Exhaust
on School Buses
Part 2 | Children's Exposure to Diesel Exhaust
on School Buses
Part 3 |
| | | |
From the Fryer to the Fuel Tank
by Joshua Tickell
Article | Indigo Girls Letter | Biodiesel Cleans Up
Mardi Gras Festivities |
| | | |
Recycled VW BioRabbit Project | Using Microalgae | |
| | | |
