[Gasification] Got you calculators handy??

[Daniel Chisholm]

On Thu, 2007-22-03 at 20:40 -0600, Peter Singfield wrote:
> Maize flower = ground corn
> 
> Extracted from this url:
> 
> http://www.bioenergylists.org/en/compactbiogas
> 
> "Maize flour is an excellent feedstock for a biogas digester. One would get
> about 250 g of methane from 1 kg of maize flour. Methane would have a
> calorific value of about 11000kCal/kg. So the 250 g would have about 2750
> kilocalories"

Producing 250g of methane from 1000g of carbohydrate sounds to me a lot
like getting 25 cents for a dollar.

(OK, I'll admit that methane has a bit more than twice the energy per kg
than a carbohydrate does.  So it's not as bad as I blithely suggest,
you're actually getting about 58 cents for your dollar).

> What would be the equivelent net energy from 1 kg of corn converted to
> ethanol??

Before asking if ethanol is a better way to use corn, I think we should
ask whether corn is the right feedstock to use as an energy source.

Since this is the gasification list, we know that instead of letting
bugs turn it into methane, or enzymes and yeast turn it into alcohol
(each process being on the order of 50-60% efficient), we could instead
gasify it into CO and H2, at a net conversion efficiency of 70%-90%
(depending on the gasifier design and also whether you need a cold,
cleaned gas or if hot "dirty" gas is OK).

Putting aside for the moment the moral and other nontangible issues that
surround the burning of food, and focusing our money-grubbing coldly
rational economics selves on the narrowest of dollars-and-cents issues,
we see that food is expensive in comparison to energy commodities (be
they fossil or renewable).  And this is necessarily going to always be
the case, even from a thermodynamics basis (all food is energy, but not
all energy is food).  Eaters will always be able to outbid burners.

Assuming corn is (approximately) the same energy value as wood, you need
about 117 pounds of corn per mmBTU.  Since corn is 56 pounds per bushel
according to a quick Google search I just did, we can say (close enough
for engineering purposes) that two bushels of corn is about a million
BTUs.

So if corn is at $4/bushel, that's about $8/mmBTU.  This is a bit
cheaper than natural gas today, much more expensive than NG in The Good
Old Days, and roughly the same price as (perhaps a wee bit cheaper than)
#6 fuel oil today.  Coal is $2-$4/mmBTU, diesel oil or gasoline is about
$20/mmBTU, and 10c/kWh electricity is about $30/mmBTU.

And $50/wet-tonne(50%mc) hog fuel is $5/mmBTU.  A gasification list
member from British Columbia recently declared that he would personally
bury in mountain of hog fuel anyone willing to pay $50/tonne for the
privilege... ;-)


(Isn't it great that simple greed will keep our food supply safe from
being burnt?  Count the $/mmBTUs, and the grain will keep... ;-)


-- 
- Daniel
Fredericton, NB  Canada