Re: DIG-L: a note on "philosophical" vs. "technical" discussio

["Les. Gornall" <ae198@dial.pipex.com>]

>So, the answer to your discussion is: jump on the organic bandwagon.
>Persuade the "unwashed" of USA and UK that biogas generates that mystical
>something extra that will make organic farming even better.
I wish you could have seen the organic swards of grass at Portglenone 
Monastry fed off digest er effluent!  The unit has recently closed down 
after decades of operation due to the shortage of monks.  The few 
remaining are old and no longer farm.  We demonstrated on this plant that 
AD was the gateway to large scale organic farming in the UK.  Not that 
many listened. - We got BSE instead at a cost of 6,000,000,000 UK Pounds 
- (you can buy a number of good digesters for that!)


This organic growth factor is not mystical but actual.   There are very 
few long term experiments relating plant growth to the plant nutrients 
and micronutrients in digested vs undigested organic wastes.
- Have you ever tried to get a grant for a 20 year research project?

However, you should read :

MOAWAD H., ZOHDY L.I., BADR EL-DIN S.M.S, KHALAFALLAH M.A., ABDEL-MAKSOUD 
H.K., 1984, " Assessment of anaerobically digested slurry as a fertiliser 
and soil conditioner."  in
Halwagi ed. Proc.Int. Conf.State of the art on Biogas Technology Transfer 
and Diffusion, Cairo  Nov.17-24, Elsevier App.Sci. 499-519. 

Also Zohdy L.I. et al " 1984, repeated application of anaerobically 
digested slurry and its effect on the yield and NPK uptake of 
wheat,turnips and onion plants. (also in Halwagi ed. above.)

These workers found that whilst the annual difference in crop mass was 
greater for AD than UnD manures, the difference was not significant 
statistically - But the positive difference accumulated year on year for 
many years and so after 15 years you would expect almost 15% more crop 
mass.  

It seems to me that soils typically take 10,000 years to make and 100 
years to destroy.  The aim of using AD is that the decomposition of 
organic matter that would take place slowly in the soil is done quickly 
in the digester.  The AD effluent is then used to rebuild the soil 
structure faster and more efficiently than it is being destroyed by the 
agricultural activity which itself depletes soil organics 100 times 
faster than nature can repair the losses incurred by agriculture.  

If we put undigested sludge on the soil the soil first has to grow the 
bacteria for decompostion and typical growth rates of bacteria in soil 
(in Northern Ireland) are one doubling per year as determined by soil 
respiration experiments (see the work of prof. A. Mcfadden in the 
1970's).  There are also other losses from 'slurry spreading', nitrogen 
is lost, (bound up as microbial protein in AD effluent), clovers and 
nitrogen fixing plants are severely inhibited and earthworm populations 
fail reducing recycling.

It is a big subject and one that is severely underfunded academically.

On the other hand the chemical industry can prove that by adding several 
kg of ammonium nitrate onto the crop the mass will increase significantly 
in one year - the soil is depleted of humic materials until the polished 
sand grains and airless clays cannot hold simple chemical fertilser - it 
is washed into the groundwater, causes salinity but yes you have it - 
after a few years you need more chemical fertiliser to do the same job.  
Now that is what I call a profitable business (in the short term at 
least.).  After a while though the vegetables taste like blotting paper.









Best Regards




Les. Gornall
Director
Practically Green 
Environmental Services
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