The complaint I hear most from HOTBIN owners, especially in the first few weeks, is some version of: I've been feeding it for a fortnight and the temperature hasn't budged.
It's frustrating, particularly when you bought the thing precisely because it's meant to get hot. The good news is there's almost always a clear reason, and it's fixable. The slightly annoying news is it's rarely just one thing. Usually it's a few small issues stacking up together.
First, know what temperature you're aiming for
The Mini and 200L come with two thermometers, a lid one and an internal probe. The Mega has the lid thermometer, with a probe available separately. Where you've got both, use both.
The lid thermometer gives you a rough trend. It reads the heat escaping through the lid rather than the compost itself, so on a half-full bin it'll read low. The internal probe is the accurate one. Push it into the top 5 to 10cm and give it a couple of minutes. That's the reading you want sitting in the 40 to 60°C range. There's also a small valve on the lid that wants to be open by about 2mm in normal use.
The five most common reasons a HOTBIN isn't heating up
1. Not enough waste. This is far and away the most common one. The bin needs a minimum amount of active material to build and hold heat. Roughly 2.5kg a week for the Mini, 5kg for the 200L, 20kg for the Mega. Frequency matters too. Feed it two or three times a week rather than one big weekly dump. If you're regularly under those amounts, a smaller model would suit you better.
2. No woodchip, or not enough. Woodchip holds open the air gaps right through the material. Without it, oxygen can't get around and the bacteria doing the heating can't work. A good handful every time you feed it. If you've been skipping it, loosen the top layer and mix some in now. You should see a difference within a couple of days. Don't use sawdust, it's too fine.
3. Too much wet waste, not enough paper. Food waste and grass hold a lot of water. Without dry paper to soak it up, the bin gets waterlogged, slumps, and slows right down. For every caddy of food, add about half a caddy of shredded paper. If it feels heavy and wet, mix the top through with dry paper and woodchip and put it back.
4. The lid isn't shut properly. The bin relies on its insulation to hold the heat. If the lid isn't sitting flush or the straps aren't tight, the heat just escapes. Check the front hatch too, any gap there lets cold in and warmth out.
5. Cold weather and a new bin. Below about 15°C outside, it takes longer to get going. That's what the kick-start bottle is for. Fill it with hot water, wrap it in a layer of waste, and bury it in the top for 24 hours. You might need to do it two or three times in the first week. Only worth doing once the bin's at least half full.
What if it's wet and smelly rather than just cold?
That's a related problem, and it means the bin's gone airless. If it smells of rotten eggs, take off the top few centimetres, mix it well with dry shredded paper and woodchip, and put it back with some fresh easy stuff. If it smells of ammonia, you've got too many greens and not enough browns, so add cardboard, paper or dry leaves and mix through. Either way the smell should settle within a day or two.
A practical recovery checklist
- Take the temperature with the internal probe, not just the lid gauge.
- Check the lid valve is open by about 2mm.
- Check the lid's sealed and the straps are tight.
- Check you're hitting the minimum weekly waste for your model.
- Check you're feeding two or three times a week, not once.
- Check there's woodchip going in at every feed.
- Check the moisture. It should feel like a wrung-out sponge.
- Too wet? Mix in dry paper and woodchip and shut the lid firmly.
- Too dry? Add fresh moist waste. Only add a cup of hot water as a last resort.
- Cold snap? Use the kick-start bottle once the bin's at least half full.
A brand new bin won't hit 60°C on day three, and that's fine. You're looking for a gradual climb over the first week to ten days. If after two full weeks of decent feeding it still hasn't passed 30°C, work down the checklist. Something on it will be the cause.
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Adam
I'm Adam, the founder of Compost Guy. I'm passionate about empowering people to embrace composting! Whether you're a seasoned composter or just starting your journey, I'm here to help.
