VISIT TO THE EXETER BIOCHAR RETORT
For quite some time I have been fascinated by biochar – I thought it was some wonder material that could save our soils. Biochar is, in fact, a mixture of charcoal (carbon) and some form of biological material (nitrogen) for example compost or even donkey poo! And it does nutrify tired soils. The very high surface area of the charcoal provides habitat for all the creepy crawlies that keep soils alive and fertile.
Recently Robin Rawle and Geoff Self from the Carbon Compost Company hosted Making Local Woods Work for a demonstration of their 'Exeter retort'. Jim O'Shaunessy of Bristol Wood Bank gives us his take on the trip.
The burn was going well, with steam and methane coming out of a tall chimney with some gases being recycled back into the furnace area which was stacked with wood. The retort was made of stainless steel and was stacked with larger logs at the top. It also includes a trailer making the retort mobile and more shareable.
Exeter Biochar retort
The charcoal element can be produced in the traditional way with steel rings and a 24 hour burn time. The retort, however, is semi-automatic, much less polluting and has a dry wood burn time of a working day and a wet wood burn time of 14 hours.
The wood source for the charcoal can be varied; hard or soft woods, thinnings, reclaimed clean wood, bones and many other carbon sources. Making biochar is an ideal way to use up the finings from the charcoal burn, leaving the larger lumpy bits for the BBQ market.
Geoff and Robin are involved in the research and development of the retort and are selling retorts all over the world, including South Africa, the US and Australia. Big thanks to Geoff and Robin from Carbon Compost Company for a fun and informative visit. They are currently involved in research to connect the retort to a Combined Heat and Power System. More information can be found at http://www.carboncompost.co.uk/biochar.html
We finished off the day enjoying the hospitality of Alan Dyer of Axewoods Cooperative. He and his wife Denise opened their immaculate 'smallholding' to the MLWW gang for an afternoon of discussion and networking. They laid on an incredible feast including authentic woodfired pizza.
The group found it to be a productive day and luckily for us the sun was shining!