[Terrapreta] energy balance and emissions

[Ron Larson]

Mariska (cc Terrapeta list)

You said in reply to two earlier messages today:



Thanks Ron
Going back to working it out from calorific values is useful.
I guess I was thinking about some external energy source that might be needed
initially, but of course the biomass can be used for this, which will just result in lower energy (or char) that can be harvested in the end.  RWL:  The larger commercial operations will certainly require something like you show below - but much char will be produced in the developing world (better growth conditions and lower labor costs) and I'll bet the numbers below are on the high side.

This confusion was probably fueled by a remark I found in Ullrichs' Industrial Chemistry Encyclopedia:

"For the production of 100 kg of charcoal, including the drying of the wood, 250 MJ of heat
and 27 MJ of electrical power are needed, as well as 5m3 of water"

    RWL:  Since 1 kWh = 3.6 MJ, this means 7.5 kWh ($.50 here) or $5.00 for a tonne - sounds OK.  But the 250 MJ for heat isn't clear - especially as there is no statement about the starting weight of biomass or the quality of charcoal produced (higher temperature being more costly and not necessarily better for terrapreta purposes).  I am greatly surprised at the water volume statement - but can't refute it.

Which suggests that this energy comes from an external source.  RWL:  Yup.  I hope you will look at the use of solar for some/all of that.  The advantage in some cases will be that the Nitrogen content of the exhaust gases can go towards zero.  Not much literature on solar for pyrolysis, but it should have some advantages.

Mariska

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