8/13/2019 Charcoal Production Method

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Charcoal production method

The decision as to the method of charcoal production was the subject of much

research.

Traditionally charcoal in the UK was made in earth covered mounds (clamps)

which had a low conversion rate of approximately 2! and was very labour

intensive. " lar#e proportion of the wood in the clamp was burnt to fuel the

process.

The predominant method used in the UK now is the rin# $iln% usin# the same

basic method as the clamp% which has a conversion rate in the re#ion of &!

but has a number of drawbac$s includin# that it produces a 'dirty charcoal

contaminated with ash and earth from the #round below the $iln and it also

produces hi#h levels of emissions. The contamination is very undesirable for

many charcoal niche mar$ets .

etorts% which have been used since the *+thcentury% produce charcoal in a

fundamentally different process to the $iln or mound method they use an

external heat source to brin# the wood up to carbonisation temperature at

which point the #ases (syn#as) #enerated by carbonisation can then be burnt

to fuel the process. ,n effect the wood is 'coo$ed in an oven. This #ives very

#ood conversion rates ( in excess of -2!) and much #reater control over the

process allowin# very hi#h uality charcoal to be produced. "lso the burnin# of

the syn#as reduces air pollution to approx &! of that produced by rin# $ilns.

/e aim to tar#et niche mar$ets as they #ive hi#her returns for a much lowervolume of production than barbeue charcoal so producin# the hi#hest uality

is paramount therefore we selected the retort as our production method.

0mall scale retorts are prohibitively expensive costin# in excess of 1* for

the smallest units. This simply wouldn3t have been a reasonable choice for us

so after a period of research we built a small retort usin# a 'batch continuous

process. This uses metal drums containin# the wood to be carbonised placed

inside an 'oven which uses waste softwood unsuitable for other uses as fuel

to brin# the char#e up to carbonisation temperature whereupon the syn#as

#enerated by the char#e is burnt to maintain the carbonisation. 4y usin#multiple metal drums and sta##erin# their insertion into the retort the process

is lar#ely self maintainin# as lon# as the drums are removed and replaced at

the correct intervals. 5nce the drums are removed they are sealed so that the

charcoal can cool down with less ris$ of spontaneous combustion. The retort is

ban$ed with earth to act as both insulation and a residual heat store. /e are

also able to dry small batches of wood to produce $indlin# and the excess heat

could be used for other purposes includin# dryin# lo#s and sawn timber.