In this guide we’ll take a look at the best compost thermometers for the UK market.
I’ve compared accuracy, lens quality, build quality and cost
to give you my top recommendations.
What is the Best Compost Thermometer?
In a rush? Here’s my top choice…
Everything I Recommend
More Detailed Compost Thermometer Reviews
Green Wash Compost Thermometer Review
This Green Wash Compost Thermometer is well made with a stainless-steel body and 40 cm long probe.
The 50 mm dial is clear and easy to read; however I did find that when left in the heap it misted up a little with condensation.
The measure does react quickly to changes in temperature, so you could just insert this compost thermometer when you needed to check the temperature and keep it in a dry place when not in use. The measurements are in Celsius only.
Overall this is an accurate and easy to use compost thermometer, and I consider it to be the best compost thermometer available in the UK.
ETI Ltd Stainless Steel Compost Thermometer Review
This ETI Ltd Stainless Steel Compost Thermometer has a 50mm dial and a 50 cm probe allowing you to read it easily and test the temperature deep within the pile.
The dial of this compost thermometer is clear and easy to read and has a colour coded scale that measures from 0 – 100°C and also indicates when the pile is warm, active or hot. The measurements are shown in Celsius only. The probe and dial are securely attached and well made. I left the unit in my compost bin over a week and found no problems with condensation.
This is a great value compost thermometer that works well, doesn’t mist up and is clear and easy to read.
Things to Know Before Buying a Compost Thermometer
Monitoring the temperature of your compost is the best way to ensure it achieves its optimum potential. By knowing when your compost is heating and cooling, you’ll be able to turn it at the appropriate time during its heating cycle for perfect results.
Compost thermometers can also indicate when your compost has reached certain stages of its development. You’ll know the exactly moment when your compost is ready for use!
So, let’s see if we can help find you the best compost thermometer to suit your needs. The following advice will help you make an informed decision, plus give some general tips on how to use these thermometers to improve your composting experience:
You might think that everything is going well with your compost – you’ve prepared the heap, got loads of material on it, and are patiently waiting for that quality compost yield to come soon.
The problem is, without using a thermometer, you can’t really know what’s going on with your compost and if it’s really working effectively.
There are several reasons why your compost might be too cool, so once you’ve identified that it’s not heating up, these steps should help you get it warm again in no time:
- Compost can fail to heat up if the compost pile isn’t large enough. If your compost thermometer shows that the core of the compost it too cool, consider the size of your compost heap. Hot composting heaps require a minimum biomass of 3 m³ – this can be achieved in a composting area that is 1 x 1 x 1 m. The aerobic bacteria in the compost heap will heat up the material, but without sufficient surrounding biomass to insulate this heat it will get lost quickly.
- Another thing to consider after getting a ‘too cool’ reading on a compost thermometer is if you are turning the heap frequently enough (or too frequently!). The heat is in the core of the heap, so it’s important to flip it regularly to make sure the ‘shell’ (outside) of the heap gets some time in the centre. Plus, turning the pile aerates it as well. This should be done approximately every 3 days.
- Your compost pile might be too dry, which will result in it being too cool to work properly. This might be something you can’t tell without a ‘cool’ temperature reading from a compost thermometer. Moisture is needed to help the microbes survive, and they create the heat. You can add water to your compost heap if it’s too dry, but you need to make sure it’s not soaking wet. A balance needs to be found between the compost getting enough oxygen and enough water (so you want to avoid filling all of the airways with water).
You can also use a compost thermometer to make sure your compost is correctly following through the different stages of composting. Which leads us onto the next section:
It’s really important to know what stage of composting your compost heap is at. This can dictate its needs and also let you know when it’s ready to use.
If all of the correct conditions are met (see above), compost should start warming up within a couple of days. Different microbes get to work at different temperatures, so at each heat stage different activity will be taking place in the pile.
When the pile reaches a temperature of over 60°C, this is the optimum temperature. It will stay at this temperature for a couple of days whilst the microbes get to work, then when this ‘hot temperature’ bacteria dies off, it will start to cool. If you manage to catch the temperature just as it’s starting to cool, and turn the pile, you should be able to persuade it to heat up again for a bit more bonus composting.
Eventually there comes a time when most the bacteria that works at the hottest temperature dies off, and the pile will cool down. When it cools down enough, the bacteria which work at lower temperatures will come back in and kick start the cycle again.
Compost thermometers are designed to be used in warm and moist environments, so it’s important that they have good durability. I recommend opting for a strong, rust-proof material such as stainless steel. A sealed dial will prevent water from seeping in.
The best compost thermometers have an IP55 rating which guarantees against moisture getting into the dial.
Thermometer Probe Length
The length of the probe is important, as you’ll need to take the temperature from as close to the middle of the pile as possible. While your measurements don’t need to be right at the centre, taking the temperature too close to the surface won’t give a good reading of what’s really going on at the core.
Most compost thermometers come with a probe around 50 cm long which is suitable even for large piles of compost.
Ideal Temperature Range
The temperature range is also worth looking out for. Most thermometers measure in 2 degree increments and the best models will have a range of 0 – 100°C. Cheaper models may have a smaller temperature range.
Some compost thermometers come with colour coded sections, so you can see whether the pile is warm, active or hot. This makes the thermometer even easier to use, as you’ll be able to see at a glance where your compost is in its heat cycle.
A Clear, Easy-Read Dial
You should ensure the dial is clear and easy to read, in your preferred units of measurement. Do be aware that some thermometers work exclusively in Celsius or Fahrenheit, whilst others allow you to choose between the two.
One problem with some dials is that they can mist up easily. Of course this makes sense because they’re being used around warm compost, but it can make taking a reading quite tricky. Some dials are treated with an anti-fog coatings which can be really useful.
Ultimately, you want to be able to read the temperature at a glance, so make sure the dial is also large enough to see easily!
Compost Thermometer FAQs
Simply insert the compost thermometer into the pile as far as it will go. Wait until the hand on the dial stops moving and make a note of the temperature. It is advisable to check the reading in several areas of the compost heap as there is not always a uniform temperature across the pile and you may occasionally find cold or hot spots.
Ideally, you should turn your compost after each burst of heat. When the temperature of your pile reaches 55-63°C this is the ideal time to turn. You should then leave it until the temperature rises again, which usually takes between 5 and 7 days.
To ensure that all diseases and weeds are killed you should monitor your compost pile carefully to ensure it has reached a temperature or between 60 – 65°C for three to four days. It is then safe to use. However, your compost will benefit from being left for a few days to cure and cool down before use. Do not allow your heap to remain at temperatures above 65°C for more than a few hours as this could cause beneficial microbes to begin to die off.