Re: Biogas

["BRENDAN MCEVOY" <bn@dna.bio.warwick.ac.uk>]

Hi Thomas,
                   I 've read about this system of biogas production 
and the main points against it are:
1) its hard to control the amount of  carbon dioxide  produced
2) you can get more than carbon dioxide produced such as hydrogen 
sulphide and ammonia as your yeast batch becomes exhauseted as well 
as various alcohols produced.

I suppose the way to overcome this would be to replace your yeast 
batch on a regular basis. You can also clean up your carbon dioxide 
to some extent by bubbling your carbon dioxide through another bottle 
of water before it goes into the tank, this I've read is supposed to 
improve it in terms of removing some of the unwanted gases etc.
 I think a careful eye though should be kept on your yeast batch 
especially if keeping sensitive fish such as apistos.

 While writing about this I thought of an old chemistry experiment 
from school that used marble chips and hydrochloric acid to produce 
carbon dioxide. This system could be adapted at home by using some 
form of calcium carbonate ie chalk, sea shells, marble chips or 
bicarbonate of soda (used for baking) with some form of weak 
acid such as vinegar (acetic acid) or citric acid (citric acid is 
available for cooking and from chemists- at least in the UK). You 
could then stick these into the same type of vessel as you would for 
the yeast and sugar and let the carbon dioxide bubble into the tank. 
You may have to watch the supply as the rate of production of carbon 
dioxide could be alot faster (depending on what ingredients you use 
and whether the chalk etc is powdered). 
  Both methods are cheap but the 2nd method avoids the production of 
unwanted gases etc.
 I would be interested to hear peoples thoughts on this and 
experiences of the 2nd method as i've tried neither.

Brendan
Brendan McEvoy
Dept Of Cell and Molecular Development
University Of Warwick
Gibbet Hill Rd
Coventry CV4 7Al
UK
Tel (01203) 522556