Almost everyone has heard of bio-diesel and most of us know that it is fuel made from plant or animal material, usually plant material is grown specially for the purpose of making fuel.
Wiki describes it as follows:
On Wiki, I could find no definition for green diesel however I think there is an important distinction to be made here.
Biodiesel refers to a vegetable oil or animal fat based diesel fuel consisting of long-chain alkyl (methyl, propyl or ethyl) esters. Biodiesel is typically made by chemically-reacting lipids (e.g., vegetable oil, animal fat (tallow)) and alcohol.
Biodiesel is meant to be used in standard diesel engines and is thus distinct from the vegetable and waste oils used to fuel converted diesel engines.
Green diesel is chemically different than bio diesel, and it can be made from waste streams destined for landfill. It's green because it is preventing waste from going to landfill, and it's green because its "well to wheels" GHG footprint is the lowest of all fuels.
What is often overlooked in bio diesel is just how much fossil fuel is used to create it and just how much GHG are released from the time land is cleared and planted to the time the bio diesel is used in an engine. Following its life cycle, soy oil creates more than twice the green house gas emissions of green diesel made from biomass, according to a study by MIT researcher HM Wong.
The process to produce green diesel is very different from how bio diesel is made.
To make green diesel, waste and or biomass is first sorted to remove recyclables and other undesirable elements. It is then gasified at very high temperatures (10,000-12,000 degrees C.) where the molecular bonds are broken and then the syngas that is produced is passed over a catalyst at elevated temperatures. (More details of this process can be found at www.alternativefuelscorp.com )
The process was developed by two German scientists over 80 years ago, is well documented and is seen by many scientists and energy analysts as one of the most likely to succeed alternative fuel. In South Africa, 30% of the fuel is produced using this process.
Typically Fischer Tropsch, as the process is known, is used to convert coal and natural gas to liquid fuels, so the 1st generation process itself is not considered green because it is not sustainable, emits large amounts of CO2 and the raw materials are fossil based.
However using biomass or waste, 2nd generation Fischer Tropsch creates an ultra clean fuel from a sustainable source and can be set up to produce no emissions.
So what are the benefits of green diesel over bio diesel?
- There is no competition between crops and fuels over land use. In fact when using waste, land that would be used for landfill could be freed up to produce food crops or for other uses. It is estimated that if every acre of arable land in the USA was put to producing fuels, it would supply no more than 10% of what is needed every year.
- The other issue in the area of land use is one of soil cycles. How many times can you keep planting the same land with the same crops before the land becomes exhausted? Yes you can add fertilizer, but that again is mostly fossil derived and the run-off pollutes our rivers and lakes.
- The fuels produced by Fischer Tropsch also include a gasoline fraction and these fuels contain no sulphur, no particulates, no aromatics and no nitrous compounds, making them very clean burning and reducing the production of acid rain. Green diesel does not create the black smoke we all have experienced when driving behind trucks because it contains no particulates.
- Green diesel can be used in any diesel engine without modification. Other fractions can be used to run aircraft engines. This means that we can run cars, trucks, trains, boats, planes and generators on FT fuels without exacerbating GHG levels.
- Landfill waste is a problem for which there is no immediate solution. It costs north America about $80 billion dollars to bury a billion barrels of oil each year. As standards of living around the world improve, so does the volume of waste and at present waste seems inexhaustible. So this is truly a renewable fuel with far greater environmental benefits than bio-diesel. See my June 17th 2009 blog posting for details about recycling at the molecular level.
- Green diesel produced from BTL (biomass to liquids) or WTL (waste to liquids) doesn't smell like fossil diesel. In fact it has a pleasant kind of soap smell. So its not unpleasant either on the road or at the fuel pump. Bio diesel reputedly smells like french fries when used in engines, I'm not sure I want to be riding behind that first thing in the morning, but perhaps that's just me.
- In cold climates green diesel has a great advantage over bio-diesel. It doesn't cloud or gel until much lower temperatures (-40C) making it ideal for cool climates like Canada and the mid-west of the US. Imagine having to warm your fuel before starting out on a cold morning!
- Because it has exactly the same chemical properties as fossil based diesel, it can be blended with regular diesel, stored and distributed using the same infrastructure.
- Although chemically identical to fossil diesel, it has a higher cetane rating and on a gallon for gallon basis contains 22% more energy.
- It's cleaner
- It's greener
- It's sustainable