[Terrapreta] C02 Tree Capture - or miscanthus...

[Tom Miles]

Sean wrote:

"The value of the immediately harvested energy from the reaction could pay
for the process and leave the charcoal byproduct as a nearly free (or very
low cost) byproduct."

 

Let's examine that assumption using a farm scale system available in
Manitoba. As I suggested in August: 

"A farm scale charcoal system might include the same amount of equipment as
Vidir's Greenhouse Gas Displacement system which gasifies straw to replace
natural gas for heating heat poultry houses.
http://www.vidir.biz/index-biomass.htm Vidir's smallest system consumes 500
lb/hr (3 Million Btuh) of wheat straw. If built as a pyrolyzer it would
produce 100 lb charcoal and 1-2 million Btuh heat. The system cost is
$200,000. Annual operating cost with straw at $10/bale is estimated at
$16,000. Labor is figured at 3 hours per day $15/hr. Economics are based on
6 months operating time (in Manitoba) or 375 tonnes (752 x 500 kg
bales/year). At 20% yield that would produce 82 tons (75 tonnes) of charcoal
which could treat about 12 acres (at 7 tons/acre). In four years you would
produce enough charcoal for a 40 acre farm. At $200/ton the charcoal would
be worth about $16,400/year which would just offset the operating costs but
not capital. If you had a use for the heat (2 million btuh x 70% to hot
water = 1.4 MMBtuh, 33.6 MMBtu/day) in 30 days you would recover more than
$12,800 additional revenue to help pay for the plant. In six months you
would recover $16,400 in charcoal value and $76,800 in heat savings. So the
payback could be 4 years with heat recovery."

 

If you insisted on "nearly free" then you zero out revenues from charcoal
and extend the payback. Let's build one and heat your pig farm! 

 

Tom

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