Heat stone idea

[Rabbity]

I have an idea. Bear with me here...

To give a bit of background, I've had my Hotbin for a few months and am getting better at keeping it at temperature. At the moment I have an easy-to-maintain routine of taking my compost caddy out every day, putting in a couple of handfuls of shredded paper and one of bulking agent, shaking it all up and chucking it on the top. It's generally staying in the 40-60 zone, even now the temperatures outside are close to zero at night.

I've hit on another trick. Having put the hot water bottle in a few times when I've let the temperature get low (before I fed the bin every day) I noticed the temperature dropped off by 10 or so degrees when I took the bottle back out. So I tried leaving it in and found that didn't happen. The bottle seems to act as a heat reservoir, helping keep the temperature constant overnight and on chilly days. This got me thinking...

Why not add a heat stone? The bottle of water works really well, so a more conductive material would be even better. After a bit of research I've found that soapstone is supposed to have amazing heat retention properties and used to be used for bed warmers. So it seems to be ideal. A cube of it, maybe 10x10x10cm, would sit unobtrusively among my top layer of waste and I could move it up regularly.

So:

• has anyone found the same thing with the water bottle?
• has anyone else used a heat stone or another material, such as copper, this way?
• does anyone know somewhere I can get a good sized chunk of soapstone at a reasonable price?

Hotbin, if you're reading this, is this a good idea? Could you start supplying something like this as an accessory?

[EnlightenedElm]

Hi there Rabbity,

Thank you for your post and idea. We have to say, using a heat stone is not something which we have considered before as the HOTBINs can achieve and maintain hot composting temperatures well without any form of additional heat supply (bottle excluded) but we will definitely take a look at it.

You mention that your HOTBIN is generally staying between 40-60°C which is great news. It does however suggest that you do not need to use the kick start bottle on a regular basis as it only really helps the unit when the internal temperature is 15°C or lower. You should find that following a good feed (which includes a variety of waste types, shredded paper and bulking agent), the internal temperature naturally rises back to within the hot composting temperatures of 40-60°C without any further assistance as long as the bacteria are fed a minimum of 5kg (volume) of waste a week and if possible, added in two or three 'feeds'.

If you do try a heat stone in your HOTBIN though, please let us know how you get on!

[Rabbity]

Thanks EnlightenedElm. Neglect was part of my problem, but I also let the contents get really damp at one stage. Getting the temperature back up helped that clear, along with adding loads of dry material.

I suppose it was also greediness - I want to stay at 60 as much as possible and get that 30 day compost as often as possible. My wife's pet rabbits produce loads of waste hay (impregnated with a great starter - rabbit pee) and I can't keep up with them.

I will take your advice and try taking the bottle back out, and see if my daily feeds are enough to keep the temperature high.

I'll let you know if I find something suitable to work as a heat stone. I keep trawling the internet but haven't had any luck finding a large enough piece of unworked soapstone from a UK supplier. I think it would be particularly useful for when I go away for a few days and can't keep up the feeding routine.

[DaveK]

A question about "as long as the bacteria are fed a minimum of 5kg (volume) of waste a week". Could you translate this please?

kg measures mass and 5kg mass is almost a stone (11 lbs)
Volume isn't measured in kg - it's litres or cubic feet etc -

Could you please describe how big a compost bin would be (litres) to hold the 5kg you describe?

Thanks

[EnlightenedElm]

Hi DaveK - it equates to roughly 2 small kitchen caddies worth or 10 litres of waste.

[DaveK]

Enlightened you are!

1st: sorry for the delay in responding; life is frantic (too frantic)

2nd: Than k you for the info - it makes sense and fits in with how I've been managing the bin, but it's reassuring to know that I've not been screwing things up!