Harness the power of your compost and build your very own compost shower. We show you how.
Whether you are a gardener with a passion for compost making, or a child who has felt the warmth of a pile of grass clippings, you will be familiar with the heat created by decomposing material. Our aim is to capture and use this heat to create a hot compost shower.
Since our original trial we have made about a dozen compost heaps to power showers, the best of which gave us five months of continuous hot water. It is joy to stand under a warm compost shower knowing you are benefitting from the energy and compost cycle, and watching the run-off flow onto the citrus.
The most important thing to remember when building a compost shower is that you need anaerobic compost – without air. The microorganisms in anaerobic compost work slowly and give off heat for many months.
This is different from the more common aerobic compost, which needs plenty of air, attracts microorganisms that need oxygen and works fast – although the heat generated is not useful for heating water.
In a compost-powered hot-water system we are looking for a constant heat, between 43 °C and 55 °C, over a long period.
You will need:
- a shower, including drainage (ours goes directly to a citrus orchard)
- a water supply with enough pressure for a shower (you’ll need cold water too, to adjust the temperature)
- 100 metres of 20mm poly-pipe
- a collection of 20mm fittings (eg. valves, joiners)
- a compost thermometer
- about six cubic metres of freshly mulched plant material.
Experiment with plant material you have. Freshly cut, small size woodchips are ideal, and we have used eucalypts, acacias and grasses.
Such material will have a good carbon/nitrogen ratio, and maximum surface area for holding moisture. Be careful to discard sharp material that could puncture the pipe.
Make a large anaerobic compost heap between your water supply and your shower. We have enough room to create two heaps, and as one heap cools, we use a valve to switch to the other.
You’ll need plenty of time to create the right conditions – a moist, compact environment – so set aside a couple of days and invite some friends over to help.
Build the heap slowly, add water constantly and tamp it down continually. When the heap is about 30cm high, add your first coil of pipe, and take care where you place it: keep it off the centre of the heap so that it doesn’t get spiked by the thermometer later; and don’t put it too close to the edge as it should be well insulated.
Take care not to kink or cross the pipe – when it is warm it will be much more flexible, and any twists can turn into kinks. Undoing the heap later to find and fix a problem is not desirable. Have the pipe full of water when you are building, and add another coil about every 20cm.
Continually walk or jump on, or tamp the heap as you are building it, including tamping the sides to create a compacted heap. But be gentle directly after laying pipe. Keep the heap wet during the building; put a sprinkler on it when you take a break.
When your heap in finished check the temperature in the middle with the thermometer. The temperature should rise slowly over the next week until it reaches an ideal shower supply temperature of 50 °C. Once the heap is made, we tend to cover it with black plastic, but this is just to protect it from outside conditions. No other maintenance is required.
Now simply enjoy your shower. Oh and did I mention that you get great compost at the end!