Permaculture writer Jonathon Engels walks us through the basics of using chicken manure and a compost pile to make an outdoor water heater.
With chickens comes manure, often in quantities and in places we’d rather not think about. But, make no mistake, chicken manure in the right—dare we say—hands is valuable stuff. Most of us know that it can be used to enhance garden fertility, but with a few design tweaks to your compost pile, chicken manure can also be the fuel that heats water.
Chicken Manure for High-Quality Compost
For composters and gardeners, chicken manure is a dream ingredient. Not only is it rich in nitrogen, which is one of the primary reasons all manures are popular for composting, but it’s also got plenty of phosphorus—common in bird manures—and potassium. All together, these three components make the familiar NPK blend we’re accustomed to seeing on fertilizer packages. They make for a fertile compost, too.
The challenge with chicken manure, however, is that it’s so high in nitrogen it’s prone to burning young plants. Therefore, it’s a bad idea to add chicken manure directly to a garden bed. Instead, it needs to be thoroughly composted first. The process of decomposition mellows the nutrients into usable, and much appreciated, amounts.
Composting Chicken Manure: Cold vs. Hot
There are two main methods for composting chicken manure (cold and hot), both of which will help with your gardening efforts and permaculture ambitions. However, only the hot method can be used to produce hot water. Here’s an outline of both methods so you can see the differences and decide what will work best for you.
Cold composting is the less labor-intensive of the two methods. A cold compost pile is a combination of nitrogen-rich elements, such as chicken manure or fresh grass clippings, and carbon-rich elements, including straw and leaves, that’s left to rot. These different elements are amassed and added as they become available over a period of time. Lots of people simply combine chicken manure with used chicken house bedding and call it a day. This can take a year or two to be viable for gardens, but in the end, it provides rich, lovely compost.
Hot composting requires a little more precision and labor, but it can produce usable compost much more quickly, not to mention the opportunity to harness heat. A hot compost pile gets up to 150 degrees Fahrenheit in just a few days. For hot compost, the nitrogen—say chicken manure—and carbon elements, straw or hay, are compiled all at once and layered carefully . Then, the pile is turned frequently to keep the temperature high. A Berkeley method hot compost pile can be ready to use in less than a month.
Not only is hot compost faster, but the elevated temperature also kills weed seeds and pathogens that might cause problems in the garden. Cold composts don’t usually reach sufficient temperatures for this. But, the real selling point for hot compost is the ability to make hot water without fire or electricity.
Using Hot Compost to Heat Water
A hot compost pile reaches temperatures in excess of 150 degrees, which is actually too hot to withstand for more than a second without serious burns. Hot water from a typical tap will max out at 120 degrees, which works well—obviously mixed to taste with cold water—for a shower. Hence, it becomes apparent that a hot compost pile might work, perhaps a little too glowingly, to supply hot water for shower or sink. And, in fact, this is something people are doing.
In order to do this, you just need to coil a long, black water hose between each pair of layers in the center of a hot compost pile. The coil moves from the bottom (where the water will enter) to the top (where it will exit). As water courses through the coils of hose, the heat from the compost pile warms it, sometimes to extreme temperatures. More advanced systems might even use coils of copper tubing to increase the speed with which the water heats up, as well as the longevity for which it stays heated.
Tips for Building a Compost Water Heater
Building a compost water heater is a little different than making a hot compost heap. In this case, we want the compost pile to heat up, but we don’t actually want it to break down too quickly. When the compost is done breaking down, the temperature drops, so the goal is to create a hot, but longstanding, compost pile. There are some methods to this madness.
- A compost water heater needs to be a large compost heap, something in the range of a cylinder with a 6-foot diameter and height, or a cube with 6-foot sides. While most compost piles are about 1 cubic yard, the primary goal here is to heat water, not produce compost. The swollen size helps the center of the pile heat up, insulates that center from outside temperature, and extends the life of the pile.
- The carbon material needs to be long-wearing. Nitrogen-rich materials intrinsically decompose quickly, but carbon takes its time. Still, in this situation, straw or hay would break down relatively quickly compared with wood chips, which are often available for free from tree trimmers. Using wood chips would make the compost water heater last for months.
- Sealing the in heat is also going to help. Rather than leaving the compost pile exposed to the elements, either wrap it in a tarp or plastic sheeting (repurposed billboard signs are great for this), or encase it in bales of hay or an outer layer of leaves. Essentially, this insulates the hot water heater, just as is done with the metal one in the house.
With these tips taken into account, building the actual compost pile is a bit like a recipe for a layer cake. It begins with a layer of twigs and sticks at the bottom for aeration, as all compost piles should. Then, there should be a 2-inch layer of wood chips topped with a 2-inch layer of chicken manure. The hose is coiled atop this, leaving a good foot of insulation at the sides. This arrangement is repeated until the pile is fully built and topped off with a thick carbon layer. Don’t forget to leave the hose ends out of the center of the pile, with the intake (female end) at the bottom and the outlet (male end) at the top.
Using Your Compost Hot Water Heater
For most of us, the reality is that we’re not likely to replace our home’s hot water setup with a compost-driven one, but that’s not to say that a compost hot water heater can’t be useful. They can work great for outdoor plumbing or, for example, a garage sink.
Outdoor showers are becoming more common these days, and they’re exhilarating on many levels. Admittedly, those of us who are bashful might feel a bit shy stripping au naturel in, well, au naturel, but with a couple of walls installed, outdoor showers can be private enough for anyone. They’re fun and liberating to use under normal circumstance, and they’re downright practical for those times when we’re too filthy—say after shoveling a heap of chicken shit—to go inside.
Similarly, many of us have outside sinks in a greenhouse or near a shed for cleaning up tools and whatnot. A hot compost water heater would be ideal for these situations, because the plumbing is usually basic and the risks of messing something up minimal. With confidence and experience, expanding the system to garage sinks or basement bathrooms might become more enticing. A washing machine might even be an interesting possibility.
Whatever the case, heating water is a big draw on energy, so there’s a lot to be said both ecologically and economically for producing it with a compost pile rather than electricity or gas. This hot water requires no fossil fuels and is completely renewable, with the bonus of several fertile cubic yards of compost being the ultimate output. For those with backyard chickens, the ingredient list is already half taken care of by the birds, and wood chips are inexpensive in bulk or free from tree trimmers.
Jonathon Engels is a traveler, writer, and vegan gardener. Born and raised in Louisiana, he’s lived as an expat for over a decade, worked in nearly a dozen countries, and visited dozens of others in between. His interests include permaculture, cooking, and music. More of his work can be found at Jonathon Engels: A Life About.