[Bioconversion] Re: [Gasification] instead of ethanol -- make natural gas??

[andrew]

On Sunday 13 November 2005 23:06, Jeff Davis wrote:

>
> > AJH Following on from Kevin's concerns I worry that nutrient depletion
> > from short rotation crops, like grasses or young coppice, will not be
> > sustainable in comparison with a well managed timber stand where only
> > the main stem is removed.
>
> I have read that switchgrass will go for at least 10 years, some say a life
> time, if you take care of it. Never cut it short, below 8", when it is
> green. When brown, cut as low as you wish. If the yield is dropping one can
> burn a field and next year, it is said that it will return to it's high
> yield. Plants are plants, leave some tree stuff in the forest and leave
> some grass stuff behind in the field (fertilizer).

Jeff it doesn't alter the fact that grasses have high ash content compared 
with wood from the middle of a stem. If this ash or the flue gas is high in 
phosphates or potassium then you are depleting the soil with each crop. If 
you are loosing some, most likely phosphorus compounds but we hear a lot of 
alkali metals (potassium) causing problems with heat exchanger surfaces, this 
indicates they are leaving as volatised compounds and there is little chance 
of them being returned to the place where the crop came from.

AJH