Charcoal is made by heating wood to break the chemical bonds that make up cellulose and to drive off the resulting gases and tars. The heating is done in an oxygen-deprived environment so that only the carbon in the wood remains. If you would like to view an interesting series of videos showing how charcoal was made up until the 1850s in Pennsylvania, click on these links: Part 1, Part 2, Part 3, and Part 4. This series of videos is from a 31 minute documentary made by Van Wagner and is a “historical re-enactment” of how charcoal was made in the “good old days” which were not all that great! It is an entertaining series of videos to watch but not something that would inspire me to go out and make charcoal that way!

There is a better way – a way that does not pollute the environment as badly as the traditional direct method of making charcoal does. This method is the indirect or “retort” method and involves “cooking” wood in a container with an outside energy source to drive off the gases and create charred wood. A retort is simply a sealed container of some kind that can withstand the heat of the external fire and allow the gases created by that heat to escape. For an overview of what is involved, I recommend looking at Daniel O’Connor’s site. There are improvements that can be made in the way he has created his retort, but they cost money. You will note that Daniel has used concrete blocks to build his enclosure. It has been my experience that concrete blocks don’t last very long when exposed to a wood fire – they crack and disintegrate. You will also notice, in one of the pictures, that the pipe that supports the drums has bent under the weight of the drums and the heat of the fire. A better method of constructing this kiln would be to use refractory brick and a thick steel plate to separate the drums from the fire underneath. But the principles that he is using are sound – the gas that is driven off by the heat of the external fire is carried via the pipe back down into the combustion area, where it is burned instead of escaping into the atmosphere where it would be a pollutant.

I think that a combination of the kiln-building expertise of wood-fired potters, the skills of a welder, and the enthusiasm of gardeners who want to use biochar in their gardens would result in a long-lasting retort that could produce biochar for an entire community.

As I wrote in the last post, it is quite possible to make charcoal in your own back yard. But does it make economic and environmental sense? After all, making charcoal in the traditional way produces a lot of toxic gases and smoke and it also does not capture the bio-oil and syngas that can be captured by industrial processes. I suppose this is a personal decision to make but my decision would be to buy charcoal rather than to make it myself.

So if biochar is identical to charcoal, why not go out and buy a couple of bags of charcoal briquettes, grind them up, and incorporate them into your garden soil? There are three reasons why I would advise against doing this. First, charcoal briquettes have more than charcoal in them – most also have coal as a secondary ingredient. I don’t know the percentages of each ingredient in the finished briquette, but this site says that 90% of the briquette is composed of charcoal and coal. The remaining 10% consists of an accelerant such as nitrate, starch to bind the grains of charcoal and coal together, and lime to let the back yard chef know when the fire is ready for the meat to be placed on the grill. Second, who are you supporting by buying briquettes? What company makes the briquettes? Who owns that company? What politicians are supported by that company? And what store are you buying the briquettes from? Wal-Mart? Third, do you really want the toxins contained in the briquettes to be mixed in with your garden soil?

A better choice, it seems to me, would be to buy a product known as “lump charcoal”. It is manufactured by many different companies, including Cowboy Charcoal, which I mentioned in a previous post. But there are many other companies out there to pick from and you may find the Naked Whiz’s Lump Charcoal Database a useful tool to help you make a decision about whom to buy your charcoal from.

If you are environmentally conscious (which I hope all of my readers are!), pay close attention to where the charcoal is manufactured and take into account the shipping costs involved. If at all possible, buy locally. Try to determine how environmentally sensitive the manufacturer of the charcoal is. Buying from a company in the United States is probably preferable to buying from a company that manufactures charcoal in a foreign country, simply because there are more environmental restrictions here, even after President Bush decimated environmental protections, than in foreign countries. I hope.

Having said all this, why not buy biochar directly from a company that makes it in an environmentally sensitive manner and captures the bio-oil and syngas that is also produced in the manufacturing process? In a word, availability. There just aren’t that many companies that make biochar for sale to the general public. There are companies out there that are making biochar, including BioChar and another company that makes an unrelated product, called Biochar Plus. However, I read that BioChar is only available in a minimum quantity of 4 tons at a price of .50 per pound, which works out to $2,000. That is a rather steep price and I don’t know of a home gardener who could use that much. Perhaps a group of gardeners could get together to buy it in bulk? The idea of using charcoal as a soil amendment is growing rapidly and there is a lot of research, development, and infrastructure building going on. In a few years, you will probably be able to buy smaller quantities of biochar quite easily. Until then, if you would like to experiment with biochar in your garden, your only realistic and environmentally sound choice seems to be to buy lump charcoal, grind it up, and mix it in with your soil.

If anyone has more information, I’d be pleased to learn of it!

Update 1/24/2010: I received a comment from a company in India which makes biochar for home consumption. The name of the company is Indochar and the name of the person to contact is Manju Thiagu. The contact information is indochar (at) gmail.com. I am not endorsing this company, merely adding it to a list of possibilities. Caveat Emptor.

The first question that I had was really basic: what is biochar? Well, it isn’t terra preta (terra preta is an Amazonian soil that has high levels of carbon of anthropogenic origin). Biochar is similar to charcoal in that it is produced by burning under the same oxygen-limited conditions that professional charcoal burners (known as colliers) have used for thousands of years. Biochar is essentially the same product that the Amazonian peoples used to create what became known as terra preta soils but modern production techniques yield more than biochar from organic feedstocks. The definition of biochar according to the International Biochar Initiative (IBI) also requires that it be used as a soil amendment for agricultural and environmental gain.

The biochar that is being produced today is different from charcoal in that it is a product of modern technology and industrial processes. Originally, the term biochar was applied to the material produced by a process called “slow pyrolysis” in which oxygen is limited, heating is slow, and the temperatures are from 450 to 650 degrees Centigrade. Two byproducts of this process are the production of synthetic gas, shortened in the literature to “syngas“, and “bio-oil.” Slow pyrolysis yields about 30% bio-oil, 35% biochar, and 35% syngas. The term “biochar” has since been extended to include the matter produced by the processes of fast pyrolysis, intermediate pyrolysis, and gasification. These other processes produce less biochar and varying percentages of bio-oil and syngas. The charcoal yield from traditional processes used by colliers might be as little as 10% with no syngas or bio-oil being produced whereas industrial techniques produce as much as 35% biochar plus syngas and bio-oil.

Can biochar be produced by the methods that colliers the world over have used for centuries? Yes. But industrial methods of producing biochar yield syngas and bio-oil in addition to charcoal. Traditional methods of charcoal production allow syngas and bio-oil to be wasted.

If you would like to read more about the technical details of how biochar is produced, please download this document, produced by Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO).

There is a lot more to biochar than the definition of what it is – that information will be the subject of future posts.

Fast forward two years: a big, big change. Suddenly, terra preta, now called “biochar”, is touted as the solution to global warming by some. Others are not so sure, so the truth likely lies somewhere in between. In its December 4, 2008 issue, Time Magazine had a piece that featured Josh Frye, of Wardensville, West Virginia, who was burning chicken litter to produce biochar. As usual with the mainstream press, there was more to the story than met the eye. Articles in The Mother Earth News and in BioCycle gave lots more information and revealed that biochar wasn’t something that the home gardener could easily produce in the quantity needed. The Gardening With BioChar wiki has a great deal of useful information about how to use biochar in the home garden and I intend to peruse this source in depth when I have the time. You can make your own biochar, but you can also buy regular charcoal from Cowboy Charcoal in 20 pound bags or you can buy a whole pallet of the stuff if you want to apply it to your entire garden. The TreeHugger site has an interesting article that documents up to a 17% increased yield by using biochar as compared to a control plot.

The International Biochar Initiative website also has a great deal of information on the subject. I’m not sure how I got to this particular page, but biochar is not a light topic. There is some very serious research taking place.

Here is a video that features Johannes Lehmann, of Cornell University, which offers an overview of this complex and fascinating subject. The truck spreading biochar and the pyrolysis unit are on Josh Frye’s farm:

Is anyone in Virginia or the Carolinas using biochar in their gardens? BioChar has “permaculture” stamped all over it – how many other folks out there are investigating its use?