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SE Texas | [Silvershoes wrote:]
>Biochar ... Anyone care to comment or educate some of the rest of us on this process?
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We've been doing it for a couple years (south-east Texas).
It started when we had land clearing (and cleaning up) that we wanted to do and wanted to recycle the biomass.
Long story short is that most people associate "charcoal" with being on par with biochar/agrichar/terra preta. This is pretty far off the mark. Charcoal is usually created during a process referred to as high-temperature pyrolysis (high heat, no or very little air). This process essentially destroys the resources/nutrients that us farmer/rancher types would hope to get out of the char.
HTP (high temperature pyrolysis) is definitely not the route that you want to take. While some folks will dump charcoal in their gardens and see some results, the HTP process wastes an extremely high percentage of what they could have otherwise had if they had used an alternative process like Low Temperature Pryolysis.
Low temperature pyrolysis for a limited duration of time is your best compromise for retaining nutrients while maximizing the internal surface area of the char. More internal surface area is beneficial to the microbial life that eventually decides to take up residence in the char. This is important because those are the microbes that will slowly be breaking down the char and releasing the items currently locked into the char. Think of it as a slow release system that doesn't impact your local water supply. :)
Current "biochar" methods revolve around taking a single source material (wood, peanut hulls, or whatever) which is kind of like trying to make a sandwhich with only 1 ingredient. Of course it can be done but as with most things in nature it helps to have a little diversity.
In regard to our operations we throw everything into the mix. We use solar heating (large diameter PVC cut lenthwise and mirrored with reflective mylar) to heat thermal oil that sits in a pipe running the lenth of the solar trough (very low tech but it works). The oil preheats and drys the materials. As everything is brough up to temperature the syngas/woodgasses produced by the biomass are used to to take the temperture up to roughly 425-450C (725-842F ... moisture content can make it difficult to stay consistent from one batch to the next) for about 50 minutes.
We've found that char granuals do retain moisture a lot better than the soil around them (we've weighed, crushed, baked, and then reweighed the field samples). Plants do try to get their root systems into any granual that they can. Whether to follow the water or to take advantage of the nutrients being slowly shed by the microbial process within the char I can't tell you. We are guessing it is a little bit of both. One thing is for certain and that is plant roots really latch onto the char.
Our char does take advantage of several different biomass sources. Local bycatch from fishermen, seaweed raked behind the pickup from a local beach, occassionaly bones from local sources (mainly wild hog from local game processors), and anything else that folks don't want that is natural and would degrade on it's own.
We also run what we call "seed" compost piles that are your basic run-of-the-mill compost piles ... after they mature a bit we mix in with the char to help establish a microbial foothold before it goes on the field. I don't think anyone else does this but we do it because it would make sense to kickstart the process. However, we didn't establish any baselines or greenhouse tests to see if there was a measurable benefit or not. So we mix it, lightly water it once, tarp it to let it sit for a couple weeks, then go put it in the field.
If you are interested in giving it a try you can go small scale and put some material in a pan and cover it (you don't want it to burn/ash and need to make sure it's not getting air as it's processed ... wrapping in tinfoil works). Throw it on in the BBQ for about a hour. Try to keep the temperature in that 725-842F range. You can even stick a small piece of small diameter copper tubing (or whatever) down into the material and run it outside the BBQ. As the material comes up to temperature you can experiment with flaring the syngas/woodgases that are vented during the process. We actually use those gases to help maintain temperature.
Anyway, it's all -very- low tech and scalable. Visually there is a big difference in the area's where we have started to build up the soil in this way. However, before anyone starts asking for soil numbers I don't have them yet. We take multiple soil samples of all areas at various depths before we start building them up, but we haven't processed any of them yet for an apples-to-apples comparison. We have even set aside some very small control areas where nothing is allowed to grow to see what the eventual differences might be between the breakdown of the char in those areas and the general field areas. Some of those areas are kept bare and some are under a thin mat of mulch. We wanted to give everything 5 years to get somewhat established. There is no hurry - there is no known timetable on total char breakdown except that it is probably measured in thousands of years. I guess it could be considered the ultimate slow release fertilizer :)
Texas A&M did a pretty good study a few years back where some student mapped out processing the biomass at various temperatures for various amounts of time to determine nutrient retention ratio to internalized surface area. It was that study that guided us in our early attempts to give it a try. For crops like Teff we've found that we don't need to add anything else but don't have lodging issues (which is very common if you put down too much nitrogen).
Personally speaking I think that this will continue to work well for us. We are still doing greenhouse tests where we added our version of biochar the first year and haven't done anything else with the soil since. I'm curious to see if the annual output is sustained or if it tapers off ... or if it increases. So far we've either matched or slightly exceeded the first year. We do use solar evaporation to keep the watering source constant because the mineral content of our water does vary from year to year and that would probably influence things. So we evaporate it and recondense it into glass holding tanks (old 5 gallon water bottles) and use that as our water source. From there it is measured out at regular amounts and intervals. It's probably not a perfect system but we did try to eliminate some of the variables.
It will be interesting to see what future years bring. If I had to do it all again from scratch I'd do it in a heartbeat. It's not a fast process but we think it's definitely worth continuing.
One other thing to note is that if I was buying char from somewhere I'd be extremely interested in what temperatures it was processed at and what types of biomass were going into it. You don't want charcoal, you want char. There is a big difference.
Hope this helps some.
H
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BioChar - we do it
