Ben Raskin - 07 April 2014

As bacteria rots organic matter down it produces heat. Trying to make use of this heat to help things grow in our cold Northern climate is nothing new. This is how the Victorians managed to produce pineapples in their walled gardens. However, there seems to be a renewed interest in harnessing this waste energy.

The Organic Growers Alliance organised a workshop at the recent Oxford Real Farming Conference in January on 'Appropriate Technology' for small scale food production. Amongst the plethora of innovative and traditional tools and technology mentioned, one of the things that caught the delegates imagination was that both the speakers Charles Dowding and Iain Tolhurst were experimenting with using heat from their compost piles to grow early crops.

By coincidence I also recently got my hands on a copy of an excellent book simply called 'Hot Beds' by an organic grower of longstanding: Jack First. I have experimented a little with this myself - mainly to aid germination in tunnels with no electricity - but with little success. Listening to Charles and Iain and reading Jack's book I can see why I failed.

The key as with most composting is getting the right materials in the right balance. Horse manure is the best apparently, though only if the horses are bedded on straw. However Jack gives information on a whole range of different materials and is even experimenting with using old clothes (form natural fibres of course). Size also matters, Jack recommends 6x6 feet minimum to ensure sufficient heat for a long enough period. Also you need to pack in the material to reduce the oxygen supply and slow down the process.

If getting early crops is not enough of a challenge then there are also ideas like embedding a water tank in the middle of the heap to give you free hot water. So this Spring I am going to try again with Hot Boxes, and hopefully with Jack’s bible to guide me I shall have a little more success.

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Ben Raskin
27 June 2014 15:11

Very interesting Valerie what you say about the snow. I guess the next step would be some low level renewable energy powered growing lights?Henry, glad to hear everything still well and that the tunnel is still up, will try to pop in and see you if I'm up your way.

Peter Mundy
23 April 2014 20:35

Ben - you've inspired me to sell the electric blanket and set up a heap under our mattress...! ;-) A fascinating read!

Valerie Muir
16 April 2014 20:35

I use loads of composted green waste, mainly to counteract the effects of high Ca soil. But adding it liberally to the unheated polytunnels keeps the temperature high enough to allow me to keep productive through winter with lettuce and various leaves. The main problem is lack of light, not temperature, so if there is a snowfall, with all the light there is a growth spurt.

henry hodgkinson
10 April 2014 18:29

hi Ben nice to see your still very busy. the farm is still organic and i am loving it. keep up the good work regards Henry ps the polly tunnel is still up

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