Getting the job done - Biochar on the modern farm

Getting the job done on the modern farm is a challenge that needs to be confronted on a capital sensitive basis. A good analysis of the problems facing us comes from Tom Miles over at the Terra Preta website in links. I have also posted one of his posts today and the reader can get a taste of the current debate by visiting the Terra preta link.

The rest of the world still relying on traditional agriculture can readily use the corn culture biochar stack that we believe created the Terra preta soils in the first place and have described earlier. This requires no capital investment whatsoever and likely achieves satisfactory results. It would be ironic if it turns out to be the best system which it reasonably could.

For the modern farm, I have proposed the application of a modified incinerator to produce Biochar. My first description came in my June post:

http://globalwarming-arclein.blogspot.com/2007/06/pushing-envelope-on-incineration.html

And you may wish to review that. What is becoming painfully clear, is that the secondary chamber will have to be fabricated inexpensively, eliminating its secondary usefulness as a incinerator and likely eliminating alternative recovery concepts. The machine needs to be basic and cheap because it cannot be operated year round to produce a premium byproduct.

Let us return to the concept of the modified shipping container. The original intent for this design concept was to deliver low impact incineration to a small municipality. This is achieved by the use of a two step burn. The first burn inside of the fire brick lined shipping container is held to just under 600 degrees by controlling the oxygen supply.

The flue gas, containing volatiles and other nasties (municipal waste, remember) is then vented into a separate much smaller chamber. Fresh air is injected, immediately jumping the temperature to 2000 degrees. This technique bypasses the production of intermediary combustion products that will be an emission problem. The high temperature flue gas can then be sent back into the first chamber as needed to increase the heat of its contents.

The system was extremely successful in largely eliminating emission problems surrounding the hospital waste that had driven the original development of this system.

This same system, built around a steel shipping container and perhaps a little simplification, can be used to produce a range of low temperature carbon based products ranging from biochar to possibly fully activated charcoal. The sizing is also right for agricultural use and the implied capital cost should come in at under $50,000 with any level of volume production. I anticipate that a manufacturer will simply supply the second chamber and the control system, while the buyer will acquire and line a shipping container. This will reduce costs even further and avoid shipping damage with the firebricks. A warning though, the second chamber, though comparatively small, must withstand very high temperatures and other stresses. The high performance and engineered municipal model of the secondary high temperature burner was costing out at a lot over $100,000 since it was cylindrical in shape and the bricks were over twice as thick and specially fabricated.

This system can be readily varied under operation in order to achieve the best possible yield of product including the option of not burning anything in the main chamber at all.

A typical charge of biomass will likely be less than ten tons for anything except wood for a twenty foot container. Something like straw could even be blown in.

As we have posted earlier, the one crop that can produce the most biomass per acre is corn. Corn will make ten plus tons of stover, while any grain crop will make at best one plus tons per acre. There is an order of magnitude difference. That also rather obviously implies an order of magnitude difference in haulage costs.

A farm producing enough corn stover to operate the carbonizer for say 40 days is not likely to have produced other types of waste that would need more than several days of additional operation. This means that the facility will be operated in the fall for a little over a month just after harvest. The produced carbon can be readily stored in preparation for been rebroadcast in combination with fertilizer onto the field originally cropped.

Our output is at least a ton of carbon for each acre of corn grown. We can then anticipate that the farm will be able to add a ton of carbon each year to every acre used for corn production. The increased fertility and the improved soil quality will also lead to an increase in corn production accelerating the process.

This new system now calls for a multi year field test aimed at defining costs and operating parameters and should be done soonest under an agricultural extension program. The visible payoff should come in the form of both sharply increased yields and a reduction in chemical inputs. In other words, the economic model is no different than the old traditional manure cycle of a mixed farm. It promises to just be a much better way.

It is clear that we will only achieve capital efficiency if we make the system a biochar only solution and integrate its use into farm operations in a way similar to the manure spreader. We may end up using the manure spreader to distribute the biochar unto the field. That would even clean the damn thing.