Local Food and Energy from Top Lit Up Draft Micro-Gasification Stoves, by Doug B.

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"Food and energy are the two keystones of any community economy anywhere on earth.   If we produce and distribute food and energy locally, we have the food, the energy and the money.   We establish the capacity to create and retain wealth in our community.   We put in place the two foundations of any human economy."  -David Yarrow.

More and easier food and energy production immediately raise standards of living. Less time worrying about essentials, leaves more time to do everything else.  Do not overlook this simple truth in preparedness and future planning. 

Top Lit Up Draft (TLUD) stove technology has many virtues: 

  • Less fuel required, less time spent gathering fuel
  • Works with small fuels, brush, twigs, bark, husks, hulls, cobs, cones, even stemmy grasses.
  • Little or no fire-tending necessary after lighting
  • Smoke free operation when done with skill
  • Easily controlled, reduced risk of spreading fire
  • Easy and reliable concealment of smoke and light during combustion (used in WWII resistance movement)

MAKES CHARCOAL 

Stove made charcoal has many uses:
 

  • Medicine, anti-diarrheal, poison control, burns poultice
  • Liquids filtration 
  • Low power explosives since the 9th century
  • Long term soils improvement  
  • NOT typically suitable for gas phase filtration  

The invention of Top Lit Up Draft heating and cooking appliances goes back at least to the WWII resistance movement, possibly much farther back.  Resistance fighters "burned smoke", a two stage combustion process, to conceal position while making heat.  The gas flare could be left open for visible light, or easily concealed with a shroud. Proper design of a shroud increases water boiling performance for a pot nestled into the shroud.  The trick to "burning smoke" is counterintuitive for experienced fire builders. Combustibles are loosely piled into a can with open air holes in the bottom, then

LIT ON TOP

Lighting on top creates an upward draft of warmed air, that pulls fresh air up through the pile to the flame front, technically termed a "pyrolysis" zone.   

The difference is similar to burning off a field of dry grass with the wind, or against the wind. A regular campfire burns "with the wind", a pyrolysis system burns "into the wind", a more easily controlled combustion process. 

The simplest example is an open can without a lid. 

  • Punch a few small holes in the bottom  
  • Loosely fill the can about 3/4 full of combustibles (small, dry paper wads for testing)  
  • Outdoors, on a still day, light it on top  
  • Observe how it makes smoke, and the smoke catches fire as it escapes the top rim of the can   

A lot of smoke will probably escape unburned during this test. If it eventually "goes to smoke", all smoke no flame, quickly try lighting the smoke. Note how easily the smoke ignites.  It may progress into a clean burn, or a smoky mess. 

The next advancement is concentrating the smoke and introducing the second shot of fresh air below the point of concentration.

  • Make a cap lid with a central hole about 1/4 the diameter of the can  
  • A slightly oversized lid with a deep downturned collar works best  
  • Make the hole by "pizza slicing" and folding the resulting tabs alternately upward and downward is fast with a pocket knife, and forward looking, but leaves sharp edges  
  • Just below the top rim of the can, punch an odd numbered ring of holes, evenly spaced, with a total face area about twice the total face area of the holes in the bottom  
  • be sure air can move freely through all holes  
  • Light the pile on top  
  • As the pile begins burning well, cap the can with the oversized lid   

You should see a ring of flares coming up through the concentrator hole, almost like a burner. The number of flares likely corresponds to the upper air intake holes and/or tabs.  If it goes to smoke, light the smoke.  The flare becomes more durable as the process continues, then fades near the end of the run.  When the flame disappears, the process has entered char burning mode. With enough oxygen, char burns to ash, emitting elevated levels of poisonous carbon monoxide in the process.  Stainless steel drink mugs, thermos bottles, and serving pots are a great way to experiment. 

With a little experience you will learn to tailor custom designs to balance heat output to runtime. You can also scale up or down to a size that suits the mission.    I carry a TLUD made from a small tapered thermos in my bugout bag.  While I have not tried any of the commercial units, I already know from design experience that what I have made suits me better than what I can buy. I can taper the flame from yellow to blue, use it as a light, conceal the light, and even snuff it at mid-process for long lasting catalytic style heat. 

CHARCOAL

Ancient charcoal makers, known as colliers, held guild status in their communities.  Upconverting wood was a combination of art and science, tuned by years of practical experience.  When using TLUD stoves, rather than burning charcoal which can generate dangerous levels of carbon monoxide (read the warnings on a bag of charcoal), it is best to save charcoal for uses outlined above.  To save charcoal, at the end of the run, using tools or gloves to protect from hot surfaces:  

  • Remove the run time cap and replace with a solid cap, preferably one that tightly seals the upper air holes 
  • Set the can on solid ground to block the holes in the bottom   

After sealing, the volatiles continue to "cook" from wood pores, until all oxygen in the can is consumed. This final conditioning opens up pores, elevating the charcoal into a more activated state. A nice low heat is produced during the process.  After cooling, the charcoal is poured into a second metal container and tightly sealed.   

A very common mistake of charcoal making newbies is believing that charcoal has cooled enough to pour into a plastic container.  If you wish to try plastic, try it outdoors, far away from anything that can ignite. Later, you will likely come back to a small ring of plastic goo.  Charcoal is highly reactive in certain states. It is an essential component of black powder.  TLUD char generally has different characteristics than retort char.  Technically TLUD char making is an oxic rather than an anoxic process.   In practice that means retort char generally retains more weight from the original biomass by holding more volatiles inside the pores.  That makes retort char generally better for cooking and selling by the pound.  Oxic char making is more prone to releasing the volatile elements, creating a lower weight per volume product with higher adsorption capabilities.  In practice that generally makes TLUD char better for filtration and as an emergency substitute for activated carbon.   The original feedstock and process temperatures also affect the adsorption properties of the finished char.

Google the works of Dr. Hugh McLaughlin for in depth discussion of the technical aspects.  The variations in some cases are quite significant.   A report published by Professor Kaneyuki Nakane from the University of Hiroshima reported that bamboo char had seven times the water holding capacity of hardwood char made for cooking. That is a very important characteristic when adding charcoal to soils for drought resistance when growing crops on rooftop gardens.  This author can vouch for the fact that crushed bamboo also works great for fuel, in a specially adapted TLUD. 

MICRO-GASIFICATION
Next steps toward micro-gasification, creating combustible vapor from biomass, include adding chimneys, insulation, dampers, fan power and alternate materials.  

  • Chimneys add draft to make air flow more reliable. An inside chimney diameter slightly greater than twice the concentrator hole diameter is magical. Chimney heights up to 20x concentrator hole diameter add draft. Taller chimneys begin to negatively impact draft.   
  • Insulation or shrouds maintain a high process temperature and ideally pre-heat the second shot of oxygen to reduce accidental "quenching" of the flare with cold air.  
  • Dampers rationing air to the top and/or bottom of the process, allow fine user adjustments during runtime. Dampers are also a huge convenience for shutdown.  
  • Fan power can further simplify control. Requires fans and power.  
  • Stoves can be made from pottery clay, bricks, 55 gallon drums, dug into a hillside, etc.   

The learning odyssey has practical forward applications. Skilled practitioners use these basic gasification concepts to create gas to power internal combustion engines.  Woodgas is simple, once you understand it.  Understanding the basics first, saves a lot of experimenting on bigger projects. 

BIOCHAR
Charcoal created from biomass, applied in the root zone, has improved crops production on many soil types.  A new term "biochar" was coined in 2007 as researchers study the effect.    Earlier crops, greater production, and enhanced drought resistance are nearly universal effects reported from TLUD char.  Improving downstream water quality, sequestering atmospheric carbon, and purifying soils prior to medicinal herb plantings are more ethereal use cases that make sense considering the physical properties of charcoal.  In my experience, and by many reports, very little TLUD charcoal is required to create a noticeable response in plant growth and crops improvement.  A handful under a fruit or nut tree planting, or a light sprinkling under mulch that the worms will work into the root zone of plants does wonders.  Feeding small quantities of char to poultry was studied at the University of Georgia with reports of better bird health and higher quality fertilizer droppings with less odor. 

ECON 101

Assured energy, food, and medicine at the most local scale possible is not only practical in short-term survival situations, it is 21st century thinking with deep historical roots that holds promise of great days ahead.  My favorite woodgas engine builder, Wayne Keith, is fond of saying "With woodgas, the buck stops here, in my pocket". Wealth creation cannot be much more local than that.  Plentiful food and energy are essential to a high standard of living. TLUD technology is more than a passing fad in stoves making, it is a key to long term better living at the smallest practical scale.  More info is available at resiliencemovement.com on the energy tab, including pictures and links.

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This page contains a single entry by Jim Rawles published on February 21, 2013 12:52 AM.

Letter Re: The Water Filter Quest was the previous entry in this blog.

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