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Residential scale biochar converter
02 Jun '13

Convert biodegradable household waste into biochar to enrich/improve garden soil quality.


1. the biochar kiln can be an add-on to normal bbqs - fill kiln up with waste and bury in fire when having a bbq. At the end of the bbq, hopefully content will be turned into biochar. However, this seems a bit inconvenient and infrequent usage means impact would be smaller.

2. Dedicated fireplace with a extra compartment for converting waste to biochar. Could work in colder climate where fireplace is used for long part of the year. However, must avoid toxic fumes from entering living areas.

3. Integrate biochar kiln with stovetop. Greatest potential. However, ventilation and extract of fumes essential. 

Chris Mansell on Jun 03, 2013
Hi Lawrence,

I hadn't heard much about biochar before but it sounds really cool. Given the issues with ventilation and fumes, do you think it would be better if the biochar kiln was communal and/or run by the local government?

L Yu on Jun 03, 2013
Hi Chris,
Yes, that's definitely another option. The tradeoff in benefits is more tranportation costs vs potentially a safer and more efficient conversion process. The ideal scenario is to develop something that's simple and safe to use in the home.
Tim Tim on Jun 04, 2013
I remember coming across a company in New Zealand that had developed an industrial micro-wave for creating bio-char. They were called CarbonScape.


L Yu on Jun 04, 2013
Hi Tim,
That's interesting but i must admit it is out of my depth. At a high level, I'm guessing this method is more suited to large scale production as the power involved would be quite high. Also not sure how it will solve the off gassing issue - perhaps collected or flared?
Chris Mansell on Jun 05, 2013
Hi Lawrence,

Would this idea be limited to homes that have gardens? Homes without gardens would presumably have to transport the biochar they produce to an area with soil that could benefit from the biochar.

L Yu on Jun 05, 2013
I would say so. Without a use for the end product, i think there would be little incentive for the household to create the biochar (unless they are mad keen on sequestering carbon).
Nick Goddard (Judge) on Jun 11, 2013
There has been quite a lot of work on pyrolysis of household waste to produce a mixture of solid biochar, burnable organic liquids (with potential as a fuel if the water content is not too high) and combustible gases. The conventional approach uses thermal heating (either slow - as envisaged in this EarthHack post - or fast - by dropping the organic material into a heated fluidised bed) but microwave heating has also been explored. Key UK centres of excellence include the UK Biochar Research Centre (, the fast pyrolysis research group at Aston University and the microwave group in the Green Chemistry Centre of Excellence at York University. The liquid and gas products can be burned to power the pyrolysis unit. The residual biochar can be used as a soil improver which probably also sequesters the carbon (there is some debate about how permanently) or as a solid fuel briquette, which could be used locally (eg in a wood burning stove) or collected house-to-house for sale as a biofuel. Overall, I like the idea of a domestic or community scale biochar production unit as it would encourage a household or group of neighbours to take responsibility for their own waste disposal and recycling. Plus it is not just waste food which could be pyrolysed – in principle, green garden waste can be too. But what is desirable/technically possible is not necessarily commercially viable. It could be that the same feedstocks should be used for a domestic or community scale anaerobic digestion unit. So does anyone fancy doing some on-line research to find out the likely cost of a pyrolysis production unit and the economic value of the output……
L Yu on Jun 12, 2013
I have to wonder why community scale anaerobic digestion unit are not being done currently if it is cost feasible. Perhaps it has to do with the idea of having a big dirty plant in middle of suburban areas ... people won't mind as long as it is not near them; so it is politically infeasible?
To me domestic scale has the most going for it. The major barrier is one of DESIGN: how to make the process CONVENIENT because the technology itself easy and inexpensive. The design issues are:
1. Making it easy to collect the feedstock - not all household waste is suitable for conversion into biochar and most would need to be dried first. So ideally the device would have a compartment for storing and drying of feedstock.
2. Making is easy to load and unload the biochar kiln - currently the typical biochar kilns have rather inconvenient loading and unloading process; requiring lifting in and out of the biochar compartment from within a larger drum. The ideal process should be inline - feedstock goes in at one end and out the other.
3. Safety - as this is a off-gassing process, the recommended way is to do it outdoors. However, this greatly limits its potential as most people would rather use the heat indoors (cooking, space heating etc.). Is there a way to make it safe to have a biochar kiln indoors; is it just a matter of having a flue?
If we can solve the above, that would make creating our own biochar as easy as say composting then that would make it much easier for the public to uptake this.