[Stoves] Last? Alternative to Charcoal

[Crispin Pemberton-Pigott]

Dear Mike

 

>Great conversations on Charcoal verses everything else.  I can't understand
how percentages can be the same for all and less than charcoal?  What no one
seems to be speaking about is the inefficiency of making charcoal in the 1st
place?  

 

To cut straight to the heart of the matter, the fact that charcoal 'is
inefficient' is not a simple a statement as it first appears.

 

Turning any biomass (it does not have to be a tree) into charcoal changes
its properties a great deal. It first of all becomes dried completely which
takes a great deal of energy and it why the energy of fresh char is about
double (or more) the energy per kg of the biomass that was put into the
process. The 'total loss' is not a simple as trying to match the potential
fry fuel energy with some 'loss'. That is an overly simplistic view so the
get somewhere with the conversation it is important to view entire system
from the sources (a field or plantation of forest) to the heat inside the
pot at the far end.

 

Paul M mentioned that the transport for the equation he is putting together
he set at 3 times that of wood fuel because of the area needed to produce
the fuel. Well, that might be true in certain circumstances but it is not
generally true and not for agrifuels turned into charcoal. The value of an
agriwaste turned into char is greatly enhanced and as the transport is a
variable, I prefer not to fix an expense for transport until the local
circumstances.

 

Paul, thanks for replying to my queries. I am holding open the issue of the
transport value because as it is significant, I wouldn't like to see a final
outcome that was strongly affected by an assumption like triple the
transportation cost. 

 

Urban area produce a great deal of tree cuttings that is not exactly prized
cooking fuel. The value of a processed fuel is high for a reason, not just
production costs. Predictable fuels like char briquettes (especially little
ones that can be hopper fed) give much better performance than random tree
cuttings.

 

As it is true that a pelletized fuel (made from the same raw material as the
char) has more total energy, it is fair to compare them in terms of their
'as produced' energy per unit mass, however the cost of making pellets is a
heck of a lot higher per MJ than char. That matters in the overall energy
equation.

 

Although people routinely suggest that pellets are a great fuel, the energy
intensity is high. The Chinese machine that was mentioned recently on this
list has 2 x 60 kW electric motors. Consider the  GEK Power Pallet. It runs
on wood pellets. There is a positive return on the system, meaning the Power
Pallet can produce enough electricity to operate a machine that will make
enough pellets to run the gasifier and the Power Pallet. However it might
not also be able to produce the gasifier, the engine and the generator that
produces the electricity and the wood pelleting machine with its components
and motor. Do you see what I am getting at? Something has to power the
system. We can't take part of the system assuming that the energy needed to
run it comes free from somewhere else.

 

Char making (from biomass in general) is a low tech energy non-intensive
process that provides a net gain in energy, taking only biomass to begin
with and produce net energy for cooking. At present the use of diesel trucks
to move it has turned what used to be a biomass (draft animals) into an
extended supply chain that probably, ultimately, runs on oil. That could be
improved by using non-woody biomass as an input like the Sarai Stove fuel
from sugar cane leaves, but only applies to certain areas where the
distances are 'right'. 

 

To look for real, bankable alternatives, we have to keep an open mind think
of all the possible technologies that we could apply to the problems in the
production and consumption chain. Innovative changes to the charcoal market,
as were tried very successfully in Chad, can dramatically change the entire
market into a sustainable, profitable and effective system for provision of
non-fossil cooking fuels.

 

Regards

Crispin

 

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