[Gasification] A chemist who needs more education??

[Steve]

    Listers
    
    I think one point that Todd has not mentioned, is that gasification
produces a combustible gas, that can be used for Integrated Gasification
Combined Cycle operation.  This allows the gas to first pass through a
combustion turbine and then through a heat recovery boiler, to give 'two
bites of the cherry' in using the fuel.  IGCC therefore provides a greater
overall energy conversion efficiency.  For instance the (now defunct) ARBRE
Biomass IGCC plant near York, UK had an overall efficiency of 31 percent,
for that 8 MWe plant.  This would be hard to achieve using conventional
steam plants of this scale.
    
    Steve Schuck 
    
    Bioenergy Australia Manager
    c/o
    Stephen Schuck and Associates Pty Ltd
    Killara  NSW  2071
    Australia
    www.bioenergyaustralia.org
    
    
    -----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Phil Marsh
Sent: Wednesday, 23 April 2008 12:38 PM
To: 'Discussion of biomass pyrolysis and gasification'
Subject: [Gasification] A chemist who needs more education??
    
    This fellow has a Doctorate Degree, I do not, I'm just a dumb farmer,
but
    making a statement such as "gasifying coal generates more carbon dioxide
    than just burning it", has me very concerned about where he went to
school
    and what he might be teaching. It is my simplistic understanding that
fully
    oxidizing x moles of carbon will produce y moles of CO2 and that the
terms
    burning, combustion, gasification, etc just refer to the oxidation
route. 
    
    Comments anyone?
    
    Gasification flawed concept
    Prince George Citizen
    Monday, April 21, 2008
    Page 4
    By Todd Whitcombe 
    I teach a course at UNBC on Industrial Chemistry. 
    In it, we discuss the chemistry of sulfuric acid production and making
pulp,
    of refineries and brewing beer, and of a number of other important
    processes. We discuss the uses for their products and the effluents they
    produce. Then I have my students write reports about various industries.

    
    One of my students wrote her report on coal. In a moment of
synchronicity,
    she handed it in on the same day that there was an article on wood
    gasification in the paper. 
    
    I mention this because as she was handing it in, she said: "I don't know
    about wood but the stuff that I've read says that gasifying coal
generates
    more carbon dioxide than just burning it." 
    
    There it is. Gasification does not save carbon dioxide emissions. 
    All it takes is a little bit of reading, and a course in Industrial
    Chemistry, to actually find this out. Gasification is not a process that
is
    going to save on greenhouse gases. 
    
    The reason behind this is that wood, coal, or any other carbon
containing
    compound can be converted from a "solid" to a "gas" but it takes energy.

    
    A simple example of this process is a candle. Solid wax is melted to
make a
    liquid which flows up the wick where heat converts it to a gas. 
    
    It is the gaseous organic compounds that we actually see burn. This is
why
    the heart of a candle flame is brown. 
    Gasification essentially takes wood, heats it to the point where it
forms a
    gas, and then burns the gas. It takes a lot of energy to heat wood and
turn
    it into a gas. That is energy that doesn't go into the output from the
heat
    plant. 
    
    Why do this then? The answer is that gasified wood burns both hotter and
    cleaner than just burning the wood but at the expense of increased
carbon
    dioxide production. As I said last week, it's a trade off. 
    
    The amount of extra energy required, and emissions released, depends on
the
    water content of the wood. More water means extra energy and emissions. 
    
    So, when people start talking about all of the wood waste we have
available
    for burning, I have to wonder just what they mean and what it will truly
    cost to burn. 
    
    Sawdust and wood chips are not particularly dry. Just ask the guys at
    Pacific BioEnergy, where they have two massive kilns to dry the wood out
    before making pellets suitable for combustion. 
    
    Their clients need dry wood to make burning feasible. At 50 per cent
water,
    the net heating value of wood is only half of what one obtains at 10 per
    cent. Drying wood takes a lot of energy and generates emissions -- a
hidden
    cost of combustion. 
    
    On top of this, with recent developments in our local industries,
sawdust
    and wood chips are no longer waste, but valuable commodities. 
    
    Further, if we are talking about the waste wood that litters our forest,
    that isn't really waste. The branches and other detritus help to
maintain
    the forest ecosystem. They are also very wet. Burning wood doesn't seem,
to
    me, to make a lot of sense. 
    
    The irony of this discussion is that we are presently wasting methane --
at
    the sewage plant and landfills, from the refinery, and from agricultural
    waste -- which could be used to generate heat much more easily and with
way
    less impact. Indeed, since methane is a much more potent greenhouse gas
than
    carbon dioxide, burning it would actually lighten our carbon footprint.
And
    it gives twice as much energy per tonne of emissions compared to wood. 
    
    Maybe it is time to rethink the whole idea of a heat plant downtown. Or
    maybe it will have to wait until after the municipal elections. 
    
    Dr. Todd Whitcombe is a professor at UNBC and a politically active
member of
    the community. His column appears Mondays. E-mail: whitcomb at unbc.ca
    
     
    
    Phil Marsh
    
    Alterna Energy Inc.
    
    #102 3645-18th Ave
    
    Prince George, BC, V2N 1A8, Canada
    
    Main Office (250) 649-2460
    
    Dct Line (250) 569-2795
    
     
    
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