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Biofuel Blend Limits

  1. Sep 25, 2009 #1
    The US government is encouraging and limiting biofuel growth at the same time. My question is, why set the current cap of 10% on biofuels? Why is that cap there, and what would be the effects of removing it, assuming that the engine hardware is bioresistant material (i.e. no brass/copper)? Are engine deposits the only concern? The lower energy density? Thanks in advance.
  2. jcsd
  3. Sep 25, 2009 #2


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    I would guess that emissions and/or damage to exhaust components would be the biggest concern. I think biofuels tend to burn less cleanly due to less regulation, but I'm not sure about that.
  4. Sep 25, 2009 #3
    Hello. Biofuels have higher NOx emissions but generally lower carbon emissions to my knowledge so that wouldn't seem to be it. What damage exactly are you referring to?
  5. Sep 29, 2009 #4
    Noone's familiar enough with biofuels to give a response?
  6. Sep 30, 2009 #5


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    From what I understand, if you run biodiesel or vegetable oil in a diesel engine, it can result in damage the catalytic converter due to more exhaust particulates being burned. In addition, fuel filters clog up faster, and fuel lines can "gel" with biodeisel in cold environments.

    In engines that were not designed to run ethanol, the ethanol can eat through o-rings and seals that were designed for gasoline.

    I think the point is that not all cars on the road are 100% compatible with all the biofuels out there, and there are a lot of people that don't fully understand the fuels or if their car would be compatible with it or not.
  7. Sep 30, 2009 #6


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    That assumption is the main technical reason; incompatibility. There's also some political pressure from the fossil fuel refiners which most governments won't have the appetite to address in one fell swoop.
  8. Sep 30, 2009 #7
    Sounds like the confusion caused by the conversion to unleaded 20 odd years ago.
  9. Oct 1, 2009 #8
    from what I have heard, the new diesel engines have a particulate filter. to clean it a "shot" of raw fuel is allowed to go out the exhaust valve to burn it clean, and bio goos up the filter.
    I haven't taken a new one apart so don't know for sure
    but, I have to wonder if it has to do with big oil wanting to control it
    they can't be happy about the "bio-moonshine"

  10. Oct 3, 2009 #9
    Right but 'big oil' itself' has begun significant investment in biofuels on the scale of hundreds of millions in indiviual projects, as well as some of the big manufacturers like Rolls Royce.
    The filter does seem a major hurdle given the replacement of seals/rings with appropriate material. Thanks for the response.
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