How To Use A Compost Thermometer

While compost thermometers are not necessary for a successful hot compost heap, they can be incredibly useful if you’re trying to increase the heat of your pile. For instance, if you build two heaps that are identical except for the presence of an activator, it can be difficult to determine whether the activator made a difference. However, a compost thermometer can easily help you monitor and compare the temperature of each pile.

Moreover, having a compost thermometer is also helpful when it comes to involving children in composting. Children are often fascinated by the high heat of a compost heap and may need to measure the temperature precisely for a school project or just for fun. So, even though it’s not necessary for successful composting, having a compost thermometer can definitely be advantageous in a variety of ways.

A compost thermometer

How To Use A Compost Thermometer

A compost thermometer typically measures between 12 – 20 inches in length and features a meter on one end. To use it, hold the metered end and insert the pointed tip into the center of the compost heap. Keep it in place until the meter stops moving, and then take note of the temperature reading on the meter.

However, relying on a single temperature reading can sometimes lead to inaccurate results if you hit a pocket of low activity in the pile. That’s why I prefer to take three temperature readings at a time. By reinserting the thermometer into the pile in a slightly different spot for each reading, I can get a more accurate temperature reading for the entire compost heap.

If there are no low-activity pockets in the pile, the temperature readings should be within a few degrees of each other. Taking multiple readings can help you identify any potential issues with your compost heap and ensure that it is functioning optimally.

Verifying that a hot compost heap has been constructed correctly

After constructing a hot compost pile, it should reach a temperature of 60°C (140°F) or higher within the first 24-48 hours. To ensure that your pile is heating up properly, use a thermometer to check the temperature starting 24 hours after construction. If the temperature hasn’t reached the desired level after 48 hours, it’s time to start troubleshooting.

Monitoring the temperature of your compost heap is crucial for its success. If the temperature is too low, it may indicate that the pile lacks sufficient nitrogen or needs more moisture. On the other hand, if the temperature is too high, it may mean that the pile needs more carbon-rich materials or more frequent turning to allow for proper aeration.

By regularly checking the temperature of your compost pile, you can quickly identify any potential issues and take corrective action to ensure that your pile is functioning optimally.

Compost-Thermometer in use
Compost thermometer in use.

Determine when to turn your compost heap with a compost thermometer

As long as a compost heap provides a favourable environment for bacteria, its heat will continue to rise. However, once the air and moisture become depleted, the bacteria population will decrease and the heap’s temperature will drop. If you take the temperature once a day, you will notice a significant decrease on the 4th or 5th day. At this point, it’s time to turn the pile and water each layer 4-6 inches to introduce additional air and moisture.

Continue to monitor the temperature daily until you notice another drop, then turn the pile again. This cycle may repeat 4 or 5 times if you turn the pile every time the temperature drops. After that point, the temperature will stabilize and won’t increase dramatically, and you can turn the pile once a week or so.

Regularly turning the compost heap helps to aerate the pile, allowing for proper decomposition and preventing the formation of anaerobic pockets that can slow down the process.

Other uses for a compost thermometer

A compost thermometer can serve several other purposes beyond checking the temperature of your compost heap. Here are some examples:

  • It allows you to ensure that your compost pile is functioning properly without having to get your hands dirty.
  • You can conduct experiments to test different composting methods or materials and measure their impact on temperature.
  • By measuring the temperature at different points in the pile, you can determine the size of the “sweet spot” or the hottest area in the heap where decomposition is most active.
  • You can also use the thermometer to compare the temperature at different depths or locations within the pile, such as the top vs. the bottom or the center vs. the outer edges.
  • The thermometer can help you determine if a sudden drop in ambient temperature affects your compost heap and adjust your management accordingly.
  • You can even find out if a small compost pile has enough mass to generate sufficient heat for proper decomposition.