08-10-2010 11:23 PM
Is it green? Depends where the feedstock comes from, ideally a waste or by product stream provides the best solution. Algae seems to be up and coming, especially if the algae is a byproduct of wastewater treatment.
There are success stories and miserable failures, most occured before a comprehensive standard for the refining, blending, storage and handling of biodiesel fuels and blends. Try www.biodiesel.org for some industry info. Not everyone conforms to the recently adopted standards, so occasionally there is still a horror story or two.
I had expereince early on, with CAT, Cummins, Generac and Mitsubishi engines, blends from B5 to B100. Overall best experience with B20 from reputable suppliers. B5 didn't really have very measurable impacts in the studies and tests I was involved in. B100 had challenges in some engines, mainly fuel system seals.
Storage was an ongoing problem, fuels turned fairly rapidly had no apparent problems, fuel stored for over 6 months in warm humid environments had issues with stability, oxidation and biological growth. Regular treatment with proper additives took care of most issues, but did require more care than diesel fuel. I have no direct experience with these fuels in cold weather applications.
Temperature issues did come into play in unit injected and high pressure common rail systems, problems included shortened injector life, ragged spray patterns resulting in poor combustion, smoke, elavated exhaust port temps. Mitigation included up sized fuel coolers and in a couple of cases fuel chillers. Most of those problems resulted in engines using batches of waste cooking grease derived fuels, not sure of the chemistry, but certainly worked thru a number of the results.
Use of bio fuels increases NOx while reducing PM, CO and UHC's in most cases, so "green" may or may not be the case depending on local restrictions.
In some places in Europe, feedstocks are derived from flaxseed oil, so if the fields are available, a suitable crop can be grown without displacing food stocks, and causing issues such as habitat and wildlands destruction then it's a good solution.
I think it has possiblities, it just isn't a complete solution for all cases, at least based on my experience so far.
Hope that helps, Mike L.
08-07-2010 07:12 PM
This is all very interesting ,but the query that is in the back of my mind when ever I read about or hear about bio fuel is,if this fuel type is so ecologically sound then why are the governing bodies in my country not making this fuel readily available to the public. I personally don't know of any bio fuel filling stations in Scotland, so it makes me wonder ,are the governing bodies trying to extract as much revenue from heavy oil as possible before these types of fuels become more readily available to the public and if so shame on them.
06-17-2009 11:03 AM
biofuels will most likely not "break down" une der high temperature and pressure conditions; they migh do the opposite though.
just think of a deep fryer. after a while at ca. 190 °C vegetable oil and animal fats do react with itself ( and air) and tend to polymerize. it forms that hard coating on the edge of the deep frier ( all cooks now about this). well when making biodiesel, the chemical characteristic that allows these fats to polymerize is not removed; thus biodiesel can polimerysze over time at high temperatures ( and this can be accelarated depending on the quality of the biodiesel tank; i.e. metal tanks can promote polimerization. )
We have used pure vegetable oil in a 3516 engine. there were no visible presence of polymrer coating on fuel line parts but we had a bizare abnormal valve and valve seat wear.
we are investigating this but is seems to be a difficult case
11-24-2008 05:43 PM
Green fuel is a wonderful debate - biodiesel is very green (ie environmentally friendly) if it is manufactured from existing feedstock (waste oils, oil crops grown on existing farmland, etc). Unfortunately these existing feedstocks are only capable of supplying around 5 to 10% of our current liquid fuel requirements and even then they put pressure on food production.
The EU push for bio fuels has resulted in the widespread destruction of rainforest in Indonesia to establish palm plantations to produce the oil for biodiesel. The net carbon dioxide and methane release into the environment from burning and decaying rainforests is, by some estimates, worse than simply using fossil fuels. Plus the habitat of various endangered species, eg orangutans, is further reduced.
Biodiesel is renewable, but it could only be considered sustainable if our liquid fuel requirements dropped to about 5% of current usage. In the end, I think biodiesel is a political solution rather than an engineering solution. Just my 2 cents worth!
10-22-2008 03:50 PM
10-21-2008 07:19 AM
Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.
We did a project a couple of years ago that used pure B100 Biodiesel and obtained a lot of information from the National Biodiesel Board website (http://www.biodiesel.org/resources/faqs/) which is where the above came from. I am not sure about the blended biodiesel fuels but if you design with B100 be very aware of the materials that cannot be used. We had a long list of materials that the contractor was not to use with this fuel type and that the generator manufacturer (Caterpillar) was to remove from the generator. Needless to say the contractor and manufacturer decided to install standard equipment with no modifications and then had to spend time in the field replacing parts and pieces later because the B100 is that corrosive to certain materials.
We did get LEED points for using B100 though, so if you are looking for extra LEED points....
Almost forgot. The primary reason we used B100 is because it is considered non-toxic and safe to the environment.
Hope this helps.