Biochar is a new word for a very old concept (see history for more on that topic). There is some confusion about whether biochar is the same thing as charcoal or activated carbon (also called activated charcoal) so I’ve created the Carbon Family Tree to try to explain some of the differences. All of these products start off with organic material that is baked in an oxygen limited environment – at varying temperatures with different equipment – to dewater and carbonize the biomass. The biggest differences are in the end use and the carbon footprint of producing them. Most of the time charcoal is used for producing heat either for grilling up delicious food (though perhaps questionable on the health-o-meter) or simply to keep us furless humans warm. So charcoal ends up turning into ash and then it is disposed of ….it may also end up in your compost or gardens but you don’t want too much of it there! Charcoal production has contributed to deforestation in some places and many forms of production are not all that eco-friendly. Activated carbon (AC) is heated at really high temps which helps to develop a high surface area that is useful for remediation, water filtration and odor control. The carbon footprint, like the price, for AC is pretty high though.
Biochar can be produced from a much broader range of organic materials. It is baked at temperatures ranging from 450 – 700C (generally), and the most common use for it at the moment is as a soil amendment although there are many areas of research going on right now to understand how it can be used as an AC substitute. The Carbon Footprint for biochar is the really cool story. In brief, during the carbonization process up to half of the CO2 absorbed during the plant’s life time is converted into a highly stable form of carbon. When char is buried in soil, the carbon is removed from the normal atmospheric carbon cycle for a long, long time, which is something we need to do asap! [see CHAR & CO2 Footprint page for more on that].
There is a big concern that once biochar ‘catches fire’, so to speak, we will shift to a mono-culture farming approach to maximize the amount of carbon which can be sequestered and absolve us of all our high carbon life-style sins. This would definitely be a bad thing and it is totally unnecessary as there is a huge supply of biomass out there that is finding its way to an early demise at a landfill where the nutrients are not only wasted but are the source of methane emissions!
The other main co-products from biochar production are heat (rather obvious that one!), syngas and bio-oil. Heat can be used for all manner of uses such as drying feedstock, heating green houses, warming cold hands, or it can be converted into electricity. The syngas really isn’t all that interesting from a small biochar production perspective (yet anyway). Some larger systems use the syngas to maintain the heat throughout the burn process.