[Terrapreta] energy balance and emissions

[Ron Larson]

Mariska, etal

1,  I liked the IEA document at the Dynamotive site given below by Gary - 
and the idea of producing liquid fuels is certainly one that we can imagine 
being a winner, with some char output..  Fifteen percent is probably based 
on someone's study.  However,  as we hear from more producers, I can imagine 
that number going down.  Some fast pyrolysis plants are apparently using the 
charcoal (rather than incoming biomass) for heat - which seems like a 
terrible waste for those of us interested in getting charcoal into soil.

2.  Here's hoping we can hear from other companies where char is the desired 
output - and they are finding ways to use the co-product gases.

3.   Kevin's Excel spreadsheet and plot (last night's mail) are useful, but 
one has to assume the number (like 15%, but Kevin's default value is high) 
that you are looking for.  (Here's hoping that Kevin will provide a metric 
option as well.)

4.  But I think we are not answering your original energy question (given 
below), which was on "the benefits and draw backs of biochar production on a 
large scale."   I have heard skeptics say many times that it is better to 
NOT place the char in the ground if one is interested in atmospheric CO2 
levels.  I intuitively believe the opposite.  First, because of the 
increased soil productivity - and many years of biomass production to offset 
the initial investment of taking some useful energy (charcoal) out of use - 
with that increased later biomass available for fossil fuel displacement. 
But also there is the extra (double?) CO2 sequestered by the new soil 
bacteria and fungus fostered by the char.  I hope you are working on this 
problem - a small part of which is the 10%, 15%, 20% needed for the char 
production itself.  Doing everything parametrically is a fine first step - a 
(big) extension of Kevin's Excel spread sheet.  We on this list need this 
information to rebut the critics (who are on the energy - maybe also the 
climate - but definitely not on the soils side of this three-sided debate).

Good luck

Ron


----- Original Message ----- 
From: "Gary Rondeau" <grondeau at efn.org>
To: <terrapreta at bioenergylists.org>
Sent: Tuesday, November 13, 2007 9:54 PM
Subject: Re: [Terrapreta] energy balance and emissions


> Mariska,
>
> Ron's numbers don't answer how much energy is needed to bring the fuel
> up to the exothermic point (unless it was already subtracted in the
> 18MJ/kg number).   As an exercise I figured the energy required to bring
> 10% H2O in the feed stock up to pyrolysis temps and it turns out to be
> about 0.35MJ.  Not sure what the heat of vaporization of the pyrolysis
> products is - but total input heat load must be in the 1-2MJ/kg range to
> get the process started. I guess theoretically you could get some of
> that back if you were directly burning the pyrolysis products and
> directly using the heat, but would probably be lost if you were
> producing bio-oil.  Another one of those annoying 10% losses!
> This reference:
> http://www.dynamotive.com/assets/articles/2007/Task_34_Booklet.pdf
> claims that the pyrolysis process requires about 15% of the energy in
> the feed stock.
>
> Gary
>
>>Hello
>>
>>Sorry if this has come up before, I'm quite new on this list and haven't 
>>seen this discussed before.
>>
>>I'm doing some research into the benefits and draw backs of biochar 
>>production on a large scale,
>>which has led me into looking at the energy use and emissions of the 
>>production process.
>>
>>Has anyone found any publications or other information covering this, I 
>>have pretty much exhausted the www and available literature on pyrolysis - 
>>but they are all evading this issue.
>>
>>I'm assuming that the energy balance of the production is positive - ie 
>>some energy will be produced in the exothermic stage which will make up 
>>for the energy used to set the process off - but I want to find some hard 
>>numbers.
>>
>>
>>Any info is helpful
>>Thanks
>>Mariska
>>
>>
>>
>
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