Emma Goodwin, host at The Crossing, Forest Row, is fired up about Biochar. We asked her to share her thoughts and experiences…
We have just spent the first frosts of 2014 tending the fire of a biochar rocket stove; the invention of Ed Revill of Swansea Biochar, which ranks pretty highly in my estimation. It is a steam punk contraption, looking not unlike a Heath Robinson cartoon that has been handcrafted and lovingly created with the aim of allowing a household to exist in a carbon NEGATIVE, closed-loop energy system.
Home heating and hot water is provided by the biochar stove, which works on similar principles to a rocket stove, with an elbow-shaped combustion
chamber and mini flue, surrounded by a secondary chamber that is filled with fuel; it uses woodchip. The added bonus with a biochar stove is that with every burn you produce a bucket full of biochar.
The stove runs on kindling-sized sticks and ‘brash’ that’s two to three inches in diameter. The chamber surrounding this rocket-stove fire is filled with woodchip that has no access to oxygen. You need to feed the fire every ten minutes for a good hour and a half, to get enough heat to burn the woodchip. This is a good job for our kids as they are getting ready for school, and makes a cosy spot to get into their school uniforms. The fire tells you when it needs feeding as it roars when it’s hot enough to burn the wood gases in the woodchip. This is called pyrolysing the woodchip. It is effectively a mini charcoal-making kiln with a back boiler that heats water.
So what’s the big deal with biochar and should we be getting fired up about it? Oh yes. The Terra Preta of the Amazonian civilisations was built with biochar. This deep, dark, seemingly indestructible soil is eight feet deep in places and resists the incessant rains of rain forest, which mostly enjoy top-soils only inches deep. We enjoyed Ed Revill’s company for a Biochar Stove Workshop in October 2014, at The Crossing, when he extolled the virtues of incorporating activated Biochar into a no-dig growing system and brought some of his four year-old biochar soil to show us.
What is biochar exactly and what does adding biochar do to soil? Biochar is a term for charcoal that has been produced specifically to add to soil. A tiny spoonful of biochar has the surface area of a football pitch, and is electrically charged which enables it to hold on to elements and volatiles. Each tiny piece of biochar is like a high-rise apartment block for soil micro-organisms and mycelia (fungus), giving them a safe haven to multiply. Increased mycorrhizal fungal activity means increased glomalin, which acts like a glue sticking the aggregates in the soil together, improving soil quality, water retention and increasing fertility.
Ed’s Biochar soil has been made over four years by incorporating biochar into a no-dig growing system in his two acre vegetable plot in Swansea. An easy experiment to do to ascertain your soil aggregate quality (how well the soil holds together) is to take a lump of soil, dry it completely then drop it into a glass of water. Leave your soil sample in the water for as long as you like and observe. We did this experiment with a lump of field soil from The Crossing (clay, unimproved pasture) a lump of garden soil from The Crossing (clay base with two years improvement with municipal waste soil improver and well-rotted horse manure) and a lump of Ed’s biochar soil (sandy soil with years activated biochar and woodchip).
We dropped the soil samples into clear glasses at the beginning of our workshop and observed them at the end of the day. The results were quite jaw dropping. The unimproved pasture was like slurry; a flat layer at the bottom of the glass, disappearing in a cloud if you agitated the glass. The garden soil held together better, but still silted up the water. Ed’s biochar soil, on the other hand, sat undisturbed, in crystal clear water, maintaining its shape and distinction. Even when it was swilled around the soil remained intact, swimming in clear water.
I cannot tell you how excited I was by the results of this simple experiment. I have mourned the loss of top soil, seen cascading down the drain along the gutters of the lanes of Sussex where we live. I find it deeply disturbing to see the side of the road running with muddy slurry and have wished for a way to stop it. Wishes do come true. Biochar is a way of stabilising soil, though it seems wrong to mass-produce it to incorporate on an industrial scale. So let’s work on a human scale and produce biochar as a by-product of our home heating and hot water systems and it’s even better if you’re producing your own woodchip or coppiced wood to burn.
Have any of our other hosts and WWOOFers had experience with making or using biochar? Why not leave your experience or opinions as a comment below?
Emma and Stuart Goodwin recently moved onto their eight and half acre plot in Forest Row in East Sussex and are seeking a couple of dedicated wwoofers to spend the next season helping out with their newly established Community Supported Agriculture veg business. Search for hosts The Crossing on our website to get in touch with them.