Biochar Heat

(Click here for instructions for making ‘Biochar Multi Heater’ heaters).

This is the fun bit, thinking of the countless ways of capturing and using the heat produced by biochar pyrolisis stoves. Most people use heaters minimally because they can be environmentally detremental and expensive to run. Imagine the opposite; the more you run your heaters and cookers, the more biochar you produce, benefiting your garden, the atmosphere and your wallet.

Biochar producing cook stoves are an invention worth knowing about. They could well be the most important tool available to humans to reverse climate change, should they are taken up and widely used.

Just sitting round a biochar stove fire is a pleasure, the process of extracting the wood gas and mixing it with air at the point of combustion produces a very hot, smoke free, efficient fire.

The simplicity and scale makes them ammenable to anybody who wants one.

Pyrolisis stoves behave very differently from wood burning stoves and open fires. One important difference is that they produce a lot of heat in a relatively short amount of time. Very hot combustion for a shorter amount of time is more efficient and less polluting than a colder burn over longer periods of time; more particulates are burnt up.

Hot Water.

biochar hot water

A biochar rocket stove heating water. The vertical part of the flue is the water heater,

connected to a copper water cylinder.

The flue then runs horizontally in order to capture more heat in the room.

Pyrolisis stoves are well suited to heating hot water systems where hot water is then stored for example in a domestic hot water tank. The water is heated up quickly during pyrolisis and is available after the stove has been left to cool down.


Biochar rocket stoves are well suited to heating large ovens which are well insulated. They produce a lot of heat during pyrolisis which brings the oven up to temperature. They can then be run as a normal rocket stove at lower temperatures to keep the oven from cooling down.

These demonstrate very well the cycle of producing heat to cook food grown with biochar and producing more biochar as a result of cooking. Positive cycles such as this demonstrate ways by which people can break the destructive, fossil fuel dependent habits. The more food is grown, the more there is to cook. The more food is cooked, the more soil fertility can be mantained. The more fertile the soil,the more food can be grown.

The youtube video link below (under ‘Mobile Catering Units’) demonstrates such an oven.

Greenhouse and polytunnel heaters and soil warmers.

biochar polytunnel heater

I have always avoided using heaters to bring on earlier crops, they usually require burning fossil fuels.

However, wanting larger amounts of biochar for my 2 acre vegetable plot, I built a biochar rocker polytunnel heater using a 45 gallon drum and using a length of 10″ diameter pipe as the combustion elbow. This is surrounded with cob which acts as a thermal mass, heating the air in the polytunnel after the stove has gone out. The flue pipe goes under the soil, (in a raised bed) heating the soil. (I also decided to also add a stainless steel water tank and so have hot running water and a bath in the polytunnel for campers and voluntary workers!)

Mobile Catering Unit.

I made a mobile catering unit which I took to various festivals and events in spring and summer of 2011, demonstrating the principle of cooking baked potatoes and producing biochar. This consisted of a large oven, a bain marie for keeping sauces hot and a tea urn, all heated by biochar rocket stoves. This video was taken at the “Engineers Without Borders” festival;

Since this video was taken, I have modified the designs (for example by incorporating forced air.)

I believe it would not be difficult to modify a mobile catering trailer to burn wood gas. The opposite to fast junk food; small producers add value by cooking and selling their produce directly, and make a living which improves their soil and sequesters carbon.

(A lack of finances prevent me from that one at the moment.)


The Biochar Multi Heater

I have tried to maximise heat capture from biochar stoves by creating one simple device,

biochar multi heater

the biochar multi heater. This is an all in 1 oven, griddle, hot water system and room heater.