Compost Greenhouse Heat Source – Heating A Greenhouse With Compost

The concept of using compost to heat a greenhouse is not new. But it has been used only in few cases.

There are several reasons why this method was never widely adopted:

1) The cost involved; 2) The time required; 3) The difficulty of controlling the temperature; 4) Lack of understanding of the technology behind it; 5) No practical use case scenario for it.

Nowadays there are many people who have realized that compost can be used to heat a greenhouse. And they are trying to do it.

However, the problem is that most of them don’t understand what exactly is going on under the hood. They just want to get started and start heating their greenhouses with compost heap. So let’s see if we can explain all these things in simple terms so you will feel confident enough to try it out!

What Is Compost?

Compost is a type of organic matter which consists mostly of decaying plant material. It contains no nutrients or bacteria, but rather decomposes slowly over time into humus (a mixture of fine particles). Humus acts like a sponge to absorb water from the air and retain it inside the compost pile. This keeps your plants hydrated and healthy. If you add too much water, it evaporates off and causes mold growth in your greenhouse. (This is why it’s important to keep your pile balanced).

What is the Ideal Ratio for Compost?

There is no exact ratio for compost, but it’s important to keep in mind that the type of plants you’re growing will affect the ratio of nutrients inside the pile. Here is a list of all the main ingredients involved in any organic matter:

Carbon – this represents the “energy-providing” element found in a pile. When you have a lot of carbon, the pile will smolder and smoke a lot.

This type of pile is good for cooking or barbecuing foods. But it isn’t ideal for making heat in a greenhouse, because it won’t last very long.

Nitrogen – this is the “growth-promoting” element in a pile. It’s what makes the pile go from brown to green.

Compost Greenhouse Heat Source – Heating A Greenhouse With Compost - Image

When you have a lot of nitrogen, the pile will start to smell really bad. It’s important that you have the right ratio of carbon to nitrogen, or else your pile won’t break down properly and will smell up your greenhouse.

Protein – this represents the nitrogen content in your pile. It’s brown and looks like sand.

It is essential that you incorporate a lot of it into your pile, otherwise the pile will not heat up properly.

What Are The Best Ingredients To Use?

The best ingredients to use are horse manure, grass clippings, and leaves. You can also throw in some dirt, sand, or sawdust to give it some extra carbon. But keep in mind, the more of these ingredients you add, the longer it will take for the pile to heat up. If you want to grow something that requires high levels of heat, such as hot peppers, you can use the following formula to calculate exactly how much nitrogen, protein, and carbon your pile will need:

(Amount of plant material (ie. leaves) x .

2) + (amount of dirt x .

05) = Amount of carbon needed

(Amount of plant material (ie. leaves) x .8) + (amount of dirt x .05) = Amount of nitrogen needed

The numbers inside the parentheses represent the amount each ingredient contributes to your pile. For example, if you add 500 grams of leaves to your pile, you need 200 grams of carbon and 100 grams of nitrogen.

You can get more plant material by cutting up old newspapers. You can get dirt from your garden, and you can get sand at the playground.

When you do get dirt and sand, be sure to sift through it and remove any stones or twigs. They will not break down like the other ingredients and will ruin your pile.

How Do I Start My Pile?

It’s best to soak all your ingredients before throwing them in your pile. This helps them break down faster. You can also throw a piece of fruit or vegetable in there to act as a starter for the pile. Once you finish soaking everything, throw it all in a pile in the center of your greenhouse. Cover it with a thin layer of soil to prevent moisture from evaporating. Keep it moist and piled high for about one month. After one month, it should be ready to use.

How Can I Make Sure It Stays Hot?

You can mix in some peat moss or wood ash to your pile to keep it at a steady heat of around 130 degrees for months at a time. Make sure you keep the pile covered with a tarp to prevent moisture from evaporating. Every month or so, you’ll need to turn the pile over to allow for even heating. This part is a little tricky, so be careful when you do it. The best way is to start from one side and begin turning the pile with a pitchfork.

How Can I Make Sure It Stays Green?

(Note: this only applies to a closed-in greenhouse)You can mix in some leaves or grass clippings to your pile to keep the pile from turning brown. To do this, add a small amount of nitrogen (20% of the total nitrogen) to the pile every week. You can also keep the pile moist to prevent it from turning brown. This is especially important during the winter when moisture in the air is scarce.

What If My Pile Smells?

If your pile starts to smell, you should turn it over immediately. This will expose the rotten parts to the air and allow them to decompose properly.

What If It Doesn’t Heat Up At All?

If your pile doesn’t heat up within a couple of weeks, you can try adding more plant material. It should heat up eventually as long as you have enough nitrogen in the pile (ask a parent for help with this).

What If I Want To Add A Plant Later?

First, you need to test to see if the ingredients are already mixed well enough. Stick your hand into the middle of the pile. If it is not too hot, you can start digging. Make sure you only dig out a small hole. Then, cover it back up and wait three days before checking to see if it is heating up properly. If it is, then you can start putting plants into the pile.

What If I Need To Add More Carbon?

You can use things like shredded newspaper to help boost the pile’s carbon content. You should only need to add a little bit at a time until you notice the temperature of the pile going up. It should not go much higher than 115 degrees Fahrenheit though, or else you might kill the bacteria in the pile.

Sources & references used in this article:

The Compost-Powered Water Heater: How to heat your greenhouse, pool, or buildings with only compost! by G Brown – 2014 –

Compost heated greenhouses by S Diver – 2001 – Citeseer

Application of exergy concept to the steady state heat exchange process of greenhouse heating by heat generated in composting by H SEKI – Environment Control in Biology, 1996 –

Sustainability of using composting and vermicomposting technologies for organic solid waste biotransformation: recent overview, greenhouse gases emissions and … by SL Lim, LH Lee, TY Wu – Journal of Cleaner Production, 2016 – Elsevier



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