You really can make your own charcoal at home - even if you live in the suburbs! If you use the indirect method, which burns the gasses, and use a clean burning fuel (such as natural or LP gas) the emissions are mostly water vapor with very little smoke. It is not difficult to do and, even when burning waste wood to provide the carbonizing heat , the process requires less time and attention than barbecuing a rack of ribs in a wood burning smoker.
Introduction
Why would anyone want to make their own charcoal? For one thing, good hardwood lump burns hotter
and cleaner (but faster) than briquettes and is much easier to light.
You also know where it came from, what it contains and what was done to
it en route. There are endeavors other than barbecue which require high
quality natural charcoal: It is still the preferred fuel for forges and
blacksmithing. Folks who make their own fireworks and black powder need
specialty charcoals with specific burning properties such as that made
from willow or grapevine. When grilling or even barbecuing in most pits
with charcoal and wood, the quality of the charcoal is really not that
critical. There is enough airflow to dilute impurities. Now that I have
a Weber Smoky Mountain, though, charcoal quality, impurities and
additives become very important. It is a great little cooker and will do
everything folks say it will, BUT there is precious little airflow and
the meat is bathed in smoke for hours. What you burn, you eat! I have
read how briquettes are made by the major manufacturers. That leaves me
either burning to coals, which is impractical for the small amount of
coals needed by the WSM, or making my own lump, which is just a way to
burn to coals and store them for use as needed. Being somewhat of a
skinflint, I would rather utilize the resources at hand and make my own
lump as opposed to buying it. My objective in this endeavor was to use
existing technology to design a simple, cheap, reliable and efficient
method for the small scale production of charcoal for home use utilizing
readily available materials and minimizing the release of pollutants.
How to make Charcoal:
Timing is important. Plan to start your burn on the hottest, muggiest day of the year with a comfort index of at least 105 and air quality just above the minimum to sustain life. These conditions won't affect the charcoal process at all but will ensure that the experience is memorable.
There are two basic methods of making charcoal: direct and indirect:
For my first tests, I decided to try the
indirect method. There had been some posts on a pyrotechnics newsgroup
describing a procedure for making small quantities of willow or
grapevine charcoal in a cookie tin or five gallon bucket. For the
furnace, I used a 55 gal oil drum with the top cut out and a 12" wide X
10" high hole cut in the lower side for maintaining the fire. I used two
iron rods stuck through the sides about 8" from the bottom to support
the retort. I also kept the top which had been cut out. After the fire
was well established , the top was placed on the drum and supported by
rods to help hold the heat in yet allow a good draft. The retort was a
16 gal. steel drum with lid and I cut about six 3/8" holes in the bottom
with an acetylene torch. I burned it out well in the furnace to
eliminate petroleum residues. These drums are used for lubricants such
as transmission fluid and gear grease and are readily available.
After the retort was loaded with air
dried hickory the top was sealed and the drum was placed in the furnace
or burn barrel. Wood scraps and bark were placed under the retort and
around the sides and lit with newspaper assisted by a little burnt motor
oil to get things off to a fast start. There was right much smoke for
the first hour, but as things heated up and the moisture was driven off,
it burned so clean that all you could see were heat waves. With the vent
holes located in the bottom of the retort, the vapors and gasses were
discharged into the hottest part of the fire and burned.
I stopped the first test too soon and
only had about 1/3 charcoal. The rest was charred chunks of wood. The
second test burned for about 3 hours, until the gasses had just stopped
burning around the holes in the bottom. Results: 56# of wood yielded 17
1/2# charcoal or 32% by wet weight. Assuming an EMC (equilibrium
moisture content) of 12%, The yield exceeds 35% on a dry matter basis.
This is very good as most direct burns result in 20 to 25% at the best.
I got over 2 1/2 five gallon buckets of good lump and only one large
(4"X6") chunk showed signs of incomplete conversion with some brown in
the center.
I was going to run a series of trials to
compare the indirect method with direct (bottom lit) and direct (top
lit). After several burns using the retort, I decided that there were
such obvious advantages to the indirect method that I abandoned studies
of direct burns. The retort method is easy, reliable, and does not
require the skill and attention of direct burns. The equipment and
materials which I used are readily available worldwide. As the gasses
and volatiles are discharged into a hot bed of coals, I believe that
most of the pollutants are burned, adding to the furnace heat. I also
suspect that yield and quality are better. From what I have read, 35% by
dry weight is excellent; the resulting charcoal burns hot and clean; you
can almost light it with a match.
The direct method also appears to be more
compatible with heat recovery and waste wood utilization systems. I live
on a farm in Virginia and my wife operates a small sawmill. Disposing of
slabs and wood waste is a serious problem. I can burn a lot of the
hardwood slabs in my
indoor masonry heater/cooker. We have not found an economical use
for pine slabs (we can't give them away) and have started burning them
in a field. This is obviously a wasteful and polluting practice. My
ultimate goal is to build a small masonry furnace that would hold
several 55 gallon drum retorts and recover heat for domestic space
heating during the winter. Charcoal could be a marketable by-product. I
would burn pine slabs and waste wood in the furnace and make charcoal
from hardwoods in 55 gallon drums. This approach appears to be very
energy efficient as the gasses released by destructive distillation are
utilized.
For more details and
pictures, go to my
Charcoal Log and Results Page.
Further information and
links
The 'stoves' discussion group deals
mostly with small wood, charcoal or biomass burning stoves for
developing countries. There have been several interesting discussions
about charcoal making stoves but real information is hard to find. Start
with
Stoves Mailing List Archives for April 1997 The thread starts with a
discussion of the World Bank paper (which I have bookmarked below) and
resurfaces periodically in the archives up to present.
------------------------------------------------
Finnish research site Nice picture of a metal kiln but not much
info.
--------------------------------------------------
Step by step
direct method of making charcoal in a 55 gal drum. Simpler than
MsBelindas (quoted below) in that the barrel is not turned over in the
process.
----------------------------------------------------
World Bank paper on issues concerning charcoal in developing
countries.
------------------------------------------------------
Lots of links: the best ones are linked below in this document.
------------------------------------------------------
Making Charcoal: A startup business opportunity
for an Interesting 'quasi-scientific' look at charcoal check out "the
skinny on..... charcoal"
------------------------------------------------------------
Fuel for the Fires: Charcoal Making in the Nineteenth Century
Excellent description of the pile or clamp burning method.
------------------------------------------------------------
Brief description of a
small indirect retort.
------------------------------------------------------------
The old art of
charcoal making
------------------------------------------------------------
Excellent description of
charcoal making in England 1000 years ago.
MsBelinda's post to the Azstarnet BBQ
list:
Hello fellow smoker/bbq/grillers! Here is
the recipe, as requested, to make your own Lump Wood Charcoal (thereby
saving yourself tons of cash, and successfully robbing the "Kingsford
Mafia"..) To make 30-40 lb of charcoal, you will need:
-----------------------------------------------------------
Note: I found two discussions about
making charcoal by indirect methods. Both were on pyro newsgroups and
this is most informative:
After reading a note, I can see that this
was the weekend to make charcoal. A couple of weeks ago I went to a
local winery and picked up a load of fresh grape vine prunings which I
converted to charcoal on Sat. I used a very simple, yet effective,
method to make the charcoal which consisted of a 32 gal steel drum with
removable lid (furnace), a 5 gal steel bucket/lid (retort can) and a
welded steel grate.
I cut a 5x8 hole in the bottom-side of
the large drum which allows me to feed scrap wood into the fire burning
in the bottom of this drum. The grate sits in the bottom of the large
drum and allows the 5 gal can a solid resting spot with enough room for
a fire underneath (about 8"). The 5 gal can was first burned in the
furnace to remove any paint, asphalt roofing cement, plating or other
undesirable contaminants. Of course, the gasket in the lid also is
burned up in the process. A couple of 1/4" holes were drilled in the
bottom of the can and it was then loaded with grape vine. The lid was
held in place by using about 6 of the securing tabs.
The 5 gal can was placed on the grate and
the 32 gal lid was used as a damper and to help hold the heat in. More
wood was loaded into the fire. After about 45 min the grape starts
breaking down, in the absence of oxygen, and the steam and flammable
gases began to escape from the vent holes in the bottom of the can. This
gas jet is directed at the hot coals/flames and really adds to the
intensity of the fire with a very noticeable blow-torch sound which
lasts about 10 min. Flames are also present around the lid. After the
escaping gases/flames stop, I continued the cooking for another 5 min,
just to be sure all the wood was converted to charcoal.
The 5 gal can was removed, cooled down
and then opened. Perfect, black, hard grapevine sticks. These crush much
easier than mesquite. I weighed 3632 g of grapevine which yielded 709 g
of charcoal in one 5 gal bucket. The volume in the bucket decreased by
about 30%. After 5 loads I ended up with a 5 gal can of moderately
crushed grapevine charcoal. There were no traces of ash or uncarbonized
wood in any of the 5 batches.
I should mention that this is a joint
venture that X and I are working on. X supplied the drums, I did the
cutting/welding. We have a fellow pyro who is going to supply us with
some willow that we will convert that into charcoal soon. For most of my
pyro needs I am quite happy with the coconut shell charcoal supplied
through KSI, but it will be fun to experiment with grapevine, willow,
pine and any others that seem interesting. We already have mesquite
airfloat.
I suppose that some of you will think
that its a little whacky to be making your own charcoal, but I think
that charcoal is a larger variable in most pyro compositions than most
people think and that there is an uncertainty about what is the "real"
makeup in a bag of commercial charcoal. Its only after experimenting
with different charcoals that one notices that there really is a
difference in charcoals. This new "tool" will allow us a way to easily
make inexpensive charcoal from various types of wood. A smaller version
could be easily made by using 1 and 5 gal cans.
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