[Gasification] mycoremediation of tarry water

[Kevin]

Dear Stuart
  ----- Original Message ----- 
  From: stuart mather 
  To: Kevin C ; gasification at lists.bioenergylists.org 
  Sent: Saturday, February 02, 2013 8:17 PM
  Subject: Re: [Gasification] mycoremediation of tarry water







------------------------------------------------------------------------------
  From: Kevin C <kchisholm at ca.inter.net>
  To: stuart mather <kneebraceboy at yahoo.com.au>; Discussion of biomass pyrolysis and gasification <gasification at lists.bioenergylists.org> 
  Sent: Saturday, 2 February 2013 2:50 PM
  Subject: Re: [Gasification] mycoremediation of tarry water



  Kevin wrote:
   ....While I have not seen a report showing that blackwater disposal is harmful to the environment, I have not seen one that says it is not harmful either. However, a competent Gasifier Operator sent me pictures of his blackwater dump site a few years after he stopped dumping blackwater there, and the plants growing there seemed just as vigorous and healthy as nearby plants outside teh dump zone.
  > 
  > Best wishes,
  > 
  > Kevin
   
  That's intriguing Kevin,
  So I wonder why there seems to be a general consensus that dumping tarry water in a pond amounts to environmental vandalism. Not saying your gasifier correspondent was making it up. But you would think the President of Myanmar would have better things to do than declare black water gasification leach ponds toxic sites  Military juntas aren't well known for their environmental awareness. So why the concern about tar ponds people?
  Stuart.

  # A "Tar Pond" or "Blackwater Disposal Pond" is a highly concentrated "disposal situation". Too much of anything is almost certain to be a problem. One cannot grow carrots or wheat in a pond used to dispose of distilled water, and ethanol alcohol is a poison when taken in excess quantities at high concentrations, as an extreme examples. The issues here are one of both toxicity and concentration. A "Gasifier Tarpond" could indeed become qualified as a 'superfund site." However, the same chemicals, if spread in dilute form over say 1, or 10, or 100 square miles may present no significant hazard, and may even yiled a net benefit. 

  # I would say intuitively that there is a combination of "toxicity and concentration" above which, gasifire tar disposal is "bad", and that there are "toxicity and concentration" combinations below which gasifier tars are not hazardous, and may even be beneficial. I don't know all the compounds in gasifier tars, and the concentrations below which they can be "generally considered as safe." In my opinion, nobody can responsibly say for certain that "gasifier tars are toxic" unless one specifies both the components and concentration. Neither can anyone say for certain that  "gasifier tars are safe" unless one has a rational data base to support the statement. 

  # The process of smoking fish, meat, and other food products can be looked on as a way to dispose of "gasifier tars." :-) The fact that such "smoke tars" preserve foods proves that such tars are toxic to some life-forms. Some studies suggest that smoked foods are bad, while others suggest that while there may be some "cancer deaths" as a result of eating such smoked foods, the benefits from reducing deaths from pathogenic organisms that would otherwise be present greatly exceed the "smoking detriments."

  # "The way to eliminate the gasifier tar problem is to eliminate tar formation in the first place." This is not that difficult with properly designed and operated gasifiers. This can be done, as is evidenced by the many gasifiers in operation fueling IC engines, with no tar problems. Stratified downdraft gasifiers, and updraft gasifiers are well known as "tarry gas producers." In some applications, such gasifier systems can be very appropriate, because of their generally lower capital cost, and their ability to handle a wider range of fuel sizing and moisture content. Such gases can often be burned directly, without need for tar removal. TLUD stoves, which are basically "an updraft gasifier with a build-in burner to destroy the tars" are an excellent example of a gasification system where tarry gas is not a problem. If one wants to pipe such gas to a burner at a distance from the gasifier, then tar build-up in piping is likely to be a problem. Water quenching of such gas will remove many of the tars, ash and char that cause pipes to plug. Then one has the problem and cost of dealing with the "blackwater." If the problem, and cost of dealing with it are big enough, then it may be better to employ a different gasifier, and different fuel preparation techniques, to produce a gas with an acceptable tar level. 

  Best wishes,

  Kevin

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