[Gasification] Biochar et al.

David Murphy djfmurphy at dodo.com.au
Mon Dec 9 06:29:47 CST 2013

Hi there Robert !

C:N of 30:1 is a good starting point for 
composting - you can't miss at that because once 
you have achieved 20:1 you don't need to work at 
it any longer.   It is said to be 'stabilised'.  
Some countries have a higher C:N for stabilisation 
- some states of the USA are actually as high as 
24 and I've even heard of 28  which is 
ridiculous.     Compost is all about the OM and 
bacterial population.  The higher the C:N ratio, 
the higher the bacterial count.   When you apply 
the compost to soil, you are adding the bacteria 
and the compost is their food.  This is the most 
efficient way to get N into the soil.  The 
bacteria eat their heads off, pro-create (by cell 
division, so they miss all the fun) and as they 
run out of food they die off.   Some just die of 
old age.   As they die they degrade rapidly into 
their main constituents, carbon (as CO2) and 
Nitrogen as N.  The N is converted into NO3 
(nitrate, in which form it can be absorbed by 
plants) by nitrifying bacteria in the soil.  Some 
of the CO2 is dissolved in the moisture of the 
soil to form carbonic acid, pH around 6.5 or so, 
which helps to regulate the soil pH.  The rest 
percolates up through the surface where some is 
trapped by the stomata on the underside of plant 
leaves and if there is NO3 present (and we know 
there is) photosynthesis occurs and the plant grows.

The food of soil benevolent bacteria is carbon so 
that the more C in the soil, the higher the 
population of bacteria and to maintain this 
population they will sequester as much of the 
available N as they can.   Therefore, restricted 
plant growth.


On 09/12/2013 8:49 PM, Robert Deutsch wrote:
> Dear DJM, I have never heard of 
> Hugelkultureither, but a Google search did turn 
> up a number of hits. Looks interesting, but I 
> have always heard that uncomposted woody 
> material put into the soil without adequate 
> nitrogenous materials will actually draw 
> nitrogen out of the surrounding soil as the 
> little microbes need both C and N to thrive.  A 
> balance of 20:1 to 30:1 is recommended for 
> successful composting.
> I just remembered the radio show I heard on rock 
> dust recommend igneous rock dust (ie Basalt or 
> Granite).
> *From:*Gasification 
> [mailto:gasification-bounces at lists.bioenergylists.org] 
> *On Behalf Of *David Murphy
> *Sent:* Monday, December 09, 2013 2:43 PM
> *To:* Discussion of biomass pyrolysis and 
> gasification
> *Subject:* Re: [Gasification] Biochar et al.
> Robert, I haven't got any thoughts on 
> Hugelkultur I'm sorry to say.   Actually, never 
> heard of it before !
> Clay won't get you any mileage.   You want 
> basalt dust.  The fines are an unwanted 
> by-product fromn a quarry.    You want it as 
> fine as possible, like talc actually and what 
> buy from a quarry will have some of this, but 
> only a small percentage.    The bulk will be 
> maybe 2 - 3mm, pretty small and it will work, 
> but the smaller the better.   Bacteria are 
> surface feeders and the smaller the particle, 
> the greater the surface area and therefore the 
> higher the pupulation of bacteria you can 
> support.   To get a good result from rock dust, 
> you should use it with compost.
> DJM.
> On 09/12/2013 4:22 PM, Robert Deutsch wrote:
>     Rock dust is a by-product of rock crushing
>     plants, I think granite is preferred dust
>     for Ag use (could be wrong on that point).
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