The costs of not Pyrolyzing

 Pyrolysis is a method for turning a whole range of waste streams into petroleum products such as cooking gas, gasoline, diesel fuel, airline fuel and all the way up to tars.  It is done by heating the material in question in an enclosed retort up to, typically, 5000C.  In a petroleum refinery, this would be called cracking.  If you heat heavy crude (long chain molecules) up to a high temperature it cracks the long chains and produced more of the more valuable short chain molecules.

It seems only right and logical that a pyrolysis unit/business should be credited with the costs it avoids.  In other words, we must take externalities into account.  Some of the worst abuses of people and the natural world occur because we don't take the true cost of our actions into account.

There are costs of not treating your waste streams by pyrolysis.  Some of them are general to all waste streams.  Some applying to specific wastes.  First the general ones.

General Costs of Not Pyrolyzing

Sending waste to land fill

First, a waste dump charges money per ton for waste that they store.  For specific wastes they often charge more.  Secondly, a waste dump typically fills up a formerly beautiful valley with garbage, removing it from public use and thirdly if not managed very carefully, water leaches out of the waste dump and pollutes the water down steam from the dump

Sending waste overseas

Hard to believe that this is actually a thing.  We used to send our waste plastic to China before they became a tad sensitive to being the garbage disposal country.  It hurt their pride.  Now, at least here in New Zealand, we send it to another country.  I won't say which one.  I don't want to hurt their feelings.  They don't dispose of this plastic in an acceptable way (pyrolysis for instance) and it blows into their streams, lakes and rivers and is carried to the ocean.  I don't think I have to detail the damage that plastic does in the ocean.  It has been covered again and again in article after article.

Costs for Specific Waste Streams

Used Tires

Leave a tire outside in any orientation you like.  After the first rain look inside.  No matter which way you oriented the tire, there is now a little pool of water inside.  As we all know, the weather is warming and various organisms are moving poleward.  One such class of organism are the mosquitoes.  A particularly noxious group are the Culex mosquitoes and A aegypti   They transmit a particularly noxious range of diseases.  Aegypti can breed in an upturned bottle cap. A massive  pile of tires is a huge mosquito breeding farm.

Of course then there is a fire danger with some really toxic smoke being produced and a leaching danger with some chemicals being leached by rain into the ground. 

Wood 

Starting at lumber mills, they produce great quantities of off cuts with no value and saw dust.  The saw dust has some value to horticulture and the off cuts can be sold as fire wood.  However, if you pyrolyze this waste, you produce completely green petroleum products and charcoal.  The charcoal can be incorporated into agricultural soils where it serves the same function as humus and last for a very long time, sequestering carbon in the process.  This lowers the financial obligation of a country under the Koyota protocol. 

 

If you build quality buildings from engineered wood, you, of course, sequester even more carbon for significant periods.

Treated wood is another problem all together.  Tannelized wood has been pressure treated with a mix of Chrome Copper and Arsenic salts.  There are many off cuts during the building process and over time, buildings will be demolished and this wood burnt.  The ash is toxic and you don't want it incorporated into your soils or sent to a land fill.  If pyrolyzed, the ash can be sent to a refinery and the metals recovered and kept out of the environment.  Otherwise, over time we are polluting our soils.

Electronic Equipment 

Electronic equipment is mostly plastic these days.  In addition it contains a wide variety of valuable metals.  All can be recovered by pyrolyzing the equipment and sending the ash to a refinery

Plastic  

When plastic is burnt in a normal 'bonfire', it releases dioxides.  The formula is C₆H₃O₂.  It is a liquid at room temperature and is used in transformers to suppress sparking.  Heated in a properly designed pyrolysis unit, dioxides are broken down into harmless compounds.  If left in nature, they accumulate in the fat and concentrate as they go up the food chain.  They are carcinogenic.  Eliminating dioxides from the environment reduced health costs. 

Charcoal Production

   Abstract
Traditional methods of charcoal production are messy, often operate in batches,  produce variable yields and  only use the volatile fraction of the pyrolysis process  to create the heat to char the wood.  A higher yield, continuous system is suggested which utilizes the combustion of the volatile fraction of the pyrolysis process to protect already pyrolyzed wood (charcoal)  from further oxidation.  In a commercial operation based on this system, considerable heat energy will be available for drying the feed stock or for whatever other purpose is required.  Continuous production should be easily to mechanize.  

Background
Over the last few years biochar/charcoal has become a hot new research topic. A number of factors, some old and some new have led to this situation.

Archaeologists have long known that Charcoal is refractory (doesn't break down easily) since they often find charcoal in ancient sites where fire has been used.  This is fortunate for them since at a push, charcoal can be used for carbon dating extending back 50,000 years.

Global warming has come upon us with the villain in the piece being our burning of sequestered carbon in the form of coal and oil and gas.  The resulting CO2 is the main suspect.

Some countries, Notably New Zealand, have rushed to sign up to Kyoto and take on a financial obligation for her production of green house gases.  This will cost the tax payers of New Zealand considerable money for no gain what so ever.  If we can use biochar to sequester carbon, this will reduce this hemorrhage of money.


All of the above were necessary but not sufficient reasons to spark the present interest in biochar.  The critical final factor was the discovery of Terra Preta in jungle locations.  In an area of  very poor soils, these charcoal rich soils are very productive.

Research efforts are underway all over the world to understand biochar.  The efforts are concentrating on the effect of different production methods (mainly the temperature at which the charcoal is produced) on its value as a soil enhancer and on its longevity in the soil.  In the Appendix, some information is given on the questions being asked.

However, the use of biochar as a soil enhancer will never become commercial if it is expensive to produce.  A commercial system should be inexpensive enough to establish at each source of raw material such as lumber mills with their offcuts and sawdust,  at forests with large supplies of prunings and forest litter or at an abattoir with a supply of bones.  It should be a continuous system rather than a batch system and it should effectively char a wide variety of material from fine sawdust and leaves to large pieces of wood and bark.The advantage of producing biochar on site is that it is reduced in volume and weight and hence is less expensive to transport.

The Learning Curve
As soon as Terra Preta was heard of, we started experiments  to produce charcoal.  It was thought that if charcoal is a valuable addition to tropical soils which are too warm to retain humus, it couldn't hurt to add it to temperate soils, many of which are humus poor.  The hope is that biochar will have the same water retaining and ion exchange properties as humus. In addition it is likely to supply surfaces and internal nitches (charcoal is porous) for microfauna films.

Charcoal Mark 1 consisted of simply making a fire, using material from the branch pile (about 2 meters high) and covering it with dirt once the flames had died down.  Anywhere a smoker showed through the dirt, more dirt was added.  After a dozen tries, discouragement set in.  The morning after the charcoal making exercise, the fire would more often than not still be hot and there were sections of ash where the charcoal had been consumed.  The system was laborious, dirty, batch rather than continuous and ineffective.  A huge quantity of branches resulted in very little charcoal.

Carcoal Mark 2 consisted of stuffing a 45gal drum with prunings from the branch pile and lighting it.  When the flames had died down, the barrel was gently tipped on its side and then upended, open side down.   Some dirt was kicked around the rim to seal it.  Next morning (many next mornings) we had some charcoal, the material was cold but there was much unburnt material from the bottom of the barrel.  However this led to Mark 3.

Charcoal Mark 3 used the same 45 gal drum but this time, a flame was lit in the bottom of the barrel using shavings from the woodwork shop and then branches were fed in to the barrel from the ever growing branch pile.   Branches were added until the drum was about half full of charcoal and then for a few minutes, only very fine material was added to to give lots of flame which died down quickly but kept the barrel very hot.  This was done to ensure that any large pieces at the top of the charcoal were fully charred.  The fine material gave out gasses rapidly which combined with the oxygen and protected the charcoal.  The barrel was then upended as described above.

During the production of one batch, large branches were pushed down into the charcoal layer to avoid them toppling  the drum.  When the Charcoal was examined next morning, uncharred wood was  found.  The butts of the branches had been protected from the heat of the fire and from oxygen.   It is critical that  new material is introduced on or above the surface of the growing layer of charcoal.

In most batches, the next morning the charcoal was cool, no ash was to be seen and everything from leaves to 5cm diameter branches were charred. The only batch with uncharred material was the above one where the branches were pushed into the charcoal layer.  An easily identified gum leaf, placed in the palm and rubbed with the thumb disintegrated into powdered charcoal while large chunks of wood, rapped on the edge of the drum to break them were completely charred all the way through.  A modest supply of branches gave a good yield of charcoal.  An added step was to wet down the charcoal next morning to ensure no live coals were present.

Why Does It Work
What is apparently happening is that as new material is put in the burning drum, it pyrolyzes and give out flammable gases.  Nothing new in that.  The burning gases use up the oxygen, protecting the charcoal from further combustion.  As long as there is a reasonable amount of visible flame, charcoal is produced rather than being consumed.  Important is to have a continual feed of new material.

A Comercial Unit
As a first pilot plant, one could start with a cast iron or steel cylinder with the same proportions as a 45 gal drum.  For ease of fabrication it could probably be octagonal, hexagonal or even square.  A conveyor belt would bring feed stock to a feed in trough sticking out of the side (like the old trash burners had).  The critical part, though, is to turn this into a continuous rather than a batch system.  This could be done by having an augur at the bottom to extract the charcoal.  The charcoal extraction system would have to be  air tight to ensure that air did not enter the charcoal bed.  The charcoal would be dumped into steel carts with air tight tops and left sealed overnight to ensure that the charcoal was extinguished.  Alternately the collecting carts could be sprayed with water.

Combustion air could come from the top as in the simple home system or could be introduced through vents in the side of the retort, above the surface of the charcoal.  Having these vents adjustable would give an added measure of control to the operator.  The extraction of charcoal from the bottom of the retort would ensure that the top of the charcoal bed was always below the vents.  The air could  be introduced tangentially to ensure a whirling, well mixed flame.

For the use of biochar to catch on, charcoal production must be inexpensive.  It is best if it can be carried out where the feed material is available since turning wood into charcoal greatly reduces its shipping weight and somewhat reduces its volume.  Any system which is continuous will be far more productive per retort than a batch system of the same configuration and size and hence more cost effective.  Having to cool and harvest a system takes considerable time and greatly reduces the production of a system of a given size.  Considerable heat will be produced which can be utilized for whatever purpose needed.

ps.  Just for the home charcoal maker, it helps if side branches are cut off large branches so that they don't hang up on the rim of the 45gal drum.  In this way, the branches self feed into the drum as the bottoms break off and you don't have to tend the drum all the time.  An occasional visit and top up is sufficient.

Biochar for Carbon Sequestration

Over the last few weeks there has been talk in the media on the need to increase the carbon content in our soil. The motivation mentioned is to reduce our liability under Kyoto. The reason we are not doing so is said to be the difficulty in measuring increases in Carbon.

Kyoto is all about the extent of change from the present situation and not about the  amount of carbon a country is currently sequestering.

A carbon rich soil, all else being equal, is a soil with more humus and other organic content such as the microfauna and miafauna. In other words a healthier more productive soil. I think there is a way of solving both the problem of increasing carbon and of having a reliable measurement which could be used to calculate our level of carbon sequestration and hence calculating our reduced liability under Kyoto.

How about if we incorporate charcoal into the soil. At first glance you might think that this is a scam. What good would it do to put charcoal into the soil. It is hardly worth doing it just to be able to say that the carbon content has increased. Have a look at this site for an explanation of the technical side of charcoal in soil.  Apparently charcoal fills at least some of the functions of Humus and is refractory at temperatures at which humus breaks down.



If charcoal is as refractory to breaking down as I have been led to believe, the amount we apply is the amount we can claim credited for.

What is needed first is a small research project in which charcoal is incorporated into soil. A random bunch of questions to be answered include:

1. Does charcoal actually hold nutrients and release them to the plants. In other words does it perform the function of humus. Recent work on Terra Preta suggests that it does.

2. Does the charcoal persist in the soil (probably) and if so, for how long.

3. If it does persist, does it's nutrient holding ability remain.

4. What is the effect of charcoal on the water retaining properties of soil

5. What is the effect of charcoal on the structure of the soil.

6. What is the effect of charcoal on the flora and fauna of the soil.

7. What is the effect of charcoal on the growth of plants which are rooted in the soil with respect to the amount of fertilizer needed, the persistence of nutrients in the soil and the leaching of nutrients out of the soil.

8. What is the effect on all of the above with respect to the particle size of the charcoal used.

There are many more questions that any agricultural scientist will come up with.

I have been experimenting with the production of charcoal over the past year. It is technically simple to obtain the benefit from the heat from burning the volatiles which are driven off during charcoal production while at the same time ensuring that there is a large yield of charcoal. Some feed stocks which can be used include the branches from putting lifts on trees, all off cuts and sawdust from lumber mills, all offcuts and sawdust from house and furniture manufacture, and even waste paper and cardboard. One can even include bones from abattoirs, thus incorporating some calcium and phosphorus in the resulting product. Using the method in the above link, even paper and cardboard can be turned into biochar.

If biochar turns out to be a valuable soil conditioner, New Zealand could end up in credit with respect to our net production of Carbon dioxide while at the same time improving our soils.

Making charcoal

For quite a while I have wanted to make charcoal. It is useful for the barbi, it can be used in a burner to keep the frost out of the green house and it can be dug into the soil to make Terra Preta. In the mean time my pile of branches has grown into a fire hazard. If one of my pyromaniac boys lite it, it will wipe out at least three peach trees and probably damage a nearby green house. My first efforts were pretty unsuccessful. I tried making a bonfire with some of the branches, feeding in new wood for a while and then when it had burnt down, shoveling soil over the pile and adding more soil where ever a wisp of smoke appeared. Usually when I opened the pile the next morning, there were still glowing coals inside, showing that air was still reaching the center and there were large areas of white ash with very little charcoal. It also involved shoveling a lot of soil. Yesterday, I tried something new.

I had a 45gallon (200l) steel drum available so a fire was started in the bottom of it. Branches were added from the pile, often sticking up well above the drum and as the bottoms burnt off, the tops were picked up from around the drum and stuffed back in. Branches were added until the drum was about a third filled with burnt material and then only twigs were tossed in from around the drum. They flared up, broke and died down pretty quickly. At this point there was very little flame. The drum was then gently tipped over on its side and then upended so that the open side was face down in the dirt. Virtually all the contents were still inside. A bit of dirt was kicked around the outside of the drum to exclude air and the drum was left over night

Next morning the drum was tipped back on its side and there was about a third of a drum of cool, extinguished charcoal of all sizes from the largest branches to the smallest twigs and leaves.We broke open some pieces to see what was inside. They were charcoal right into the middle. Even very fine material such as leaves crumbled in out hands, carbonized but not consumed. So what is happening here.

Wood consists of mainly hydrogen and carbon. When you pyrolyze (heat without oxygen) wood at about 500 degrees C, you drive off volatile material which is much like crude oil with all the various fractions found in crude oil and you are left with carbon (charcoal) and some mineral material which, if you burnt off the carbon would be the ash. The trick to making charcoal is to somehow burn the volatile fraction to create the heat to pyrolyze the wood without burning off the charcoal. The 45 gallon drum seems to fit the bill.

As you burn wood, the volatiles come off and make flame and of course some of the charcoal burns too. As you add more and more wood in the drum, a layer of charcoal starts to build up on the bottom of the drum but the oxygen coming down into the drum is used up by combining with the volatiles which are being driven off by the heat. There are no air holes in the bottom of the drum. You see the burning of the volatiles as flame. Very little oxygen gets to the charcoal and if the charcoal on the top is being burnt to some extent, it is excluding oxygen from deeper charcoal. In fact, twice now, when I tipped the barrel back over next morning, there was a layer of unburnt kindling that I had used to start the fire. A sure sign that Oxygen was not getting down to the bottom.

The experiment started with the drum sitting on its base in the vertical position. The burning was poor. The drum was then tilted by putting a piece of fire wood under one edge of the rim. That worked better. The drum was off-vertical by 20 or 30 degrees and what happened is that the hot gasses rose along the upper surface, drawing air down the lower surface. The burning worked really well once the drum was tilted.

In about the third batch it was noticed that if the branches were pushed down into the growing charcoal layer, the bottom of the branches didn't char. It is better to just let new branches to rest on the top of the building charcoal layer.

Just a warning. Charcoal is very easy to light. If an ember from the fire drops on the finished charcoal from a previous batch, it will light up. There will not be any flame and the only sign of burning, besides the heat, will be a white patch on the charcoal pile. Let this go for half an hour and the whole pile will be fully alight.

Happy charcoal making.