|  Biochar
is produced through the slow pyrolysis
of biomass. The process of converting biomass to char locks much of
the carbon into the char where, if added to soil, it remains stable
for hundreds, perhaps thousands of years, thereby making the process
carbon negative. Furthermore, adding biochar to soil increases its fertility.
Two huge benefits - so why isn’t this technology in wider use
?
The delay in commercialisation
largely comes down to economics – are the outputs of the process
worth more than the cost of producing them ? Below, we look at some
of the factors involved in the commercialisation process.
INPUTS
Feedstock.
Inputs could come from a range of sources – woodland waste, straw,
maize and rice husks, chicken litter, cattle slurry or paper waste,
much of which will either be free or may even have a negative cost.
A key driver will be to find sufficient supplies of feedstock at an
economically viable distance from the plant. for example, Dynamotive
in Canada use redundant building timber as feedstock. Other possibilities
include poultry farms and cattle lots.
Transport
This is could be the biggest obstacle. Transporting large quantities
of low value agricultural waste over long distances could render the
whole process uneconomic. In the UK, typical hire costs for a 15 tonne
truck are around £350 – £500 per day, perhaps a third
less if it’s owned and far less in other parts of the world. Loading/unloading
plant or manpower also needs to be accounted for. Assuming biomass availability
requires a 20km round trip from source to plant, which with loading
and unloading might allow four deliveries per day, the transport cost
per tonne would probably be well over £10 / tonne.
Pyrolysis plant
A pyrolysis
plant will consist of a kiln for the pyrolysis itself, driers, gas
cleaners, plus the pipework and control devices (up to 40 thermocouples
on a small test rig) needed to move the inputs and outputs safely. Typical
costs will range from a few hundred thousand Dollars for a pilot level
plant up to $16.5m for a plant capable of handling 200 tonnes /day(1).
Annual running costs will add several hundred thousand Dollars more.
Size is likely to be dictated by the availability of feedstock, potentially
limiting economies of scale
Outputs
Biochar
There is currently no market for char. Output is currently limited to
a small number of test rigs, limiting usage even for small scale trials.
Considerable work needs to be done on defining the types of biochar
produced. The feedstock used, presence of impurities (chicken litter
being a good example, or chrome copper and arsenic in preserved wood)
and the suitability for different soil types.
As with feedstocks,
freight costs to end users will be an issue.
Syngas
Syngas is a mixture
of hydrogen, carbon monoxide and carbon dioxide and can be sufficient
to fuel the pyrolysis process itself. The potential to sell surplus
syngas will be dependent on the price of oil and the proximity of customers.
Electricity
Heat generated from the pyrolysis process may be available to produce
electricity. This is unlikely to be a major output but could be sufficient
to support the process itself with any surplus available for sale to
the grid. As with syngas, energy prices will influence the potential
revenues available.
Carbon Credits
Despite its advantages both in carbon sequestration and soil improvement,
biochar has yet to be selected as a clean development mechanism (CDM)
by the IPCC. The value will also depend on the price of carbon –
currently around €25/tonne
Indirect
savings.
Adding biochar to soil will reduce the requirement for nitrogen based
fertilisers. The aromatic structure of char also retains nitrogen; nitrogen
runoff is becoming an increasing problem, causing deadzones in coastal
locations worldwide (see The
Economist 15 May 2008).
More Biochar
articles
Biochar:
An introduction
An
overview of the biochar process
Notes
(1)Dynamotive
bio oil plant in Guelph, Ontario. Figures from presentation by Desmond
Radlein COO, at International Biochar Initiative, Terrigal, May 2007
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