Biochar; the name geeks give charcoal

True to form, my attempts to focus on my academic work for more than two minutes during the working day have yet again failed, and I’ve found myself engrossed in another topic – Biochar. Well at least it’s not the cricket this time, and I can at least claim with a level of certainty that biochar at least has something to do with sustainability, though whether or not it can be done at home or not is open to interpretation!

First, the background: Biochar is just a nerdy and more scientific sounding way of saying charcoal, the ordinary substance that we’re all aware of from family barbeques. As its new name suggests, it is a charred bioorganic material, typically wood. Biochar is comprised of between 50 and 95% carbon and made by burning or baking organic matter in anaerobic conditions – as I’m sure many of you reading this blog are aware. However one of the aspects of biochar not considered until recently has been its ability to sink carbon.

Biochar is an incredibly stable material, and as opposed to your average bit of organic matter isn’t going to rot either aerobically or anaerobically, and therefore won’t create CO2 or methane as it does so. It therefore follows that if you create a kilo of biochar, then typically 800 grams of carbon will be sunk within it, breaking the carbon cycle and making safe from contributing to the greenhouse effect. This biochar will now keep the carbon locked within it for up to 5000 years! I repeat, 5000 years!

Of course as an average household creates around 6 tonnes of CO2 in a typical year, no one is suggesting that you might be able to burn the 8 tonnes plus of hedge clippings required to offset an entire households’ worth of material! But scaled up to provide a service for even a percentage of the 140 million tonnes of discarded organic waste produced in the UK each year, biochar could put a serious dint in offsetting carbon in the long term.

Of course, we then have to establish what we’re going to do with this charcoal, but again the answer is encouraging! Biochar has the added bonus of being very a very good addition to soils, particularly in the tropics where they improve soil structure and allow a soil to hold onto a greater number of nutrients. Biochar-slash and burn could be employed in rainforests where soil nutrient depletion currently drives farmers deeper and deeper into virgin forest. Indeed charcoal was been added to soils in the Amazon region hundreds of years ago for just this reason.

So can we make a difference at home? Well, probably not, but this shouldn’t stop us from trying in some small way! I’m sure lots of you out there are going to burn organic waste at some point this year so you may as well experiment while you do! Get a biscuit tin (or a number of), fill with bit of dry(ish) wood and stick it in your bonfire. The black stuff left in the tin is your very own biochar (being careful to remember to call it this, as it sounds more impressive than “charcoal”). Once it’s cooled, weight it and estimate that 80% of the weight is carbon. Hey presto, you’ve sunk that amount of carbon! Now dig it into your soil!