Sunday, May 12, 2013

HotBin Composting

I've just finished reading Jane Perrone's post on her experience with her HotBin and it reminded me I have been thinking of writing about my own experiences for a while, especially now that I've had it over 12 months so have seen it perform in all seasons.
Like Jane I was excited to take delivery because it meant I could compost all the things my wormery's and standard compost heaps couldn't, namely meat and cooked foods without the need for a Bokashi bin in the kitchen and the chance of it leaking and stinking the house out. Promised temperatures of 60C mean that even the problem of dogs mess can be eradicated because after half an hour or so at that temperature nothing nasty survives and it just becomes good old fashioned compost, saving me an awful lot of hassle (it sure beats bagging it in a plastic bag and putting straight into landfill).
Jane mentions that the bin is ugly but I disagree: It is a solidly built black polystyrene bin that slots in nicely down the side of the house in between my water butt and wormery's. I would even go as far as saying it is quite stylish looking, but you do have to bear in mind that I'm a bit strange when it comes to my composting set-up (touching on the fanatical when it comes to all things compost, even going as far as collecting banana skins and teabags from people at work and bringing them home to compost rather than let them go in landfill) ...
This is just after arriving and, untidy early Spring garden aside, I think it fits in quite neatly. When not over wintering in the greenhouse the wormery's live next to it so kitchen waste can easily be added rather than traipsing across to the lawn to the compost bins.
So how have things gone in the last 12 months?
First few months and emptying
I found it easy to get going and the compost-geek really kicks in when seeing the thermometer reading 60C and knowing that that means you are composting your waste at 32 times that of a normal compost bin (meaning usable compost in approximately 3 months!). However, Jane is right that it is a pig to empty. You remove the hatch and start forking out the finished compost only to find that the stuff above falls in its place before you get to the back, meaning not only is unfinished compost mixing with the good stuff but the compacted compost at the back stays there.
The "finished" compost is generally not the compost we are used to and will need ageing if it is going to be used as anything other than a rough mulch. You can either add it to a normal compost heap/bin for aging or add it to your wormery where the worms will go mad for it and turn it into even more beneficial vermicompost (more of a fertiliser than a compost). This is what I do now as I have 3 wormeries that were previously taking my kitchen waste but slowed down once the Hotbin arrived. They now take waste from the Hotbin every month or so and take another month or so to turn into vermicompsot for top dressing plants or adding round my vegetables as a mulch or feed.
Keeping the temperature up
The problem with emptying can cause problems with the air movement, which then results in the temperature dropping thereby slowing things down considerably. Once things get compacted the air vents in the bottom of the bin get blocked and the lack of air flow can cause the temperature to drop very quickly. I use a Compost mate that I bought from Wiggly Wigglers and currently costs £17.50 (worth every penny) for aerating the bin contents from above - you screw the tool into the compost and then pull out a plug of material creating a chimney that keeps the air flow working nicely (and the compost hot). However this can cause the newer stuff to fall deeper into the bin which means slightly longer before you can remove it.
In the summer keeping the bin hot is reasonably easy because you can add grass cuttings, though add too much and you get leachate leaking out of the bottom that attracts flies resulting in maggots and that silage-type pong oh so loved by ones wife (NOT!).
In the winter months however things are trickier and the bin maintenance becomes a weekly chore. I have found that adding LOTS of shredded paper helps in much the same way as it helps in a wormery; it keeps the air flow possible, dries out soggy compost (that can also restrict the airflow)and also keeps the temperature up as it composts quite quickly. I also add pelleted chicken manure to help keep the temperature up. So, the recipe is for each caddy of kitchen waste I add a handful of bark (supplied with the bin and also used for aerating the compost), a few handfuls of shredded paper and a cup full of chicken manure pellets. This keeps things working nicely as well as improve the quality of the finished product.
Conclusion
Much as I wouldn't swap it - when working well it works very well - and I'm turning kitchen waste round quickly for my plants at home and the allotment I don't think it is the single answer to all things compost. Much like my old composting set-up I think you need more than one bin, and at £149 that's unlikely because they are not what you would call cheap. With a second bin you would be able to have it composting nice and hot until it's full and then move onto the second bin. By the time the second was full the first should be done enough to be emptied completely and started again, thereby avoiding the emptying issues that make it so hard (and smelly) to use.
For more information and help Hotbin have a great Frequently asked questions section on their web site and are very good at answering queries both on Twitter and Facebook.