As I was wandering up in the hills of coastal California today, I could not help but think about lasagna. I was not thinking of that wonderful Italian American dish that my grandmother used to make with those delicious layers of sauce, pasta, cheese, meat and more cheese. Although, now that I am writing this I am getting hungry. No, I was thinking about part 2 of a 2 part series on compost. If you are an avid follower of our blog (c'mon its ok to admit it) you would know that we previously wrote on the wonders of vermiculture, or worms eating your food waste and turning it into superfood for plants. Today, I will give you a brief outline on building a 'hot' compost pile.
In regards to compost, it is always important to remember everything breaks down eventually. For instance, it takes Mother Earth about 75 years to build up an inch of top soil through good old fashioned natural processes. If you don't have that long, there are ways of speeding it up. Such as creating compost piles. Which brings us back to lasagna.
The concept is that you are creating a compost pile that is based upon alternating layers of carbon and nitrogen. The goal is that you end up with a combined ratio of 30 parts carbon to 1 part nitrogen. It is important to keep in mind that that is the ideal, and not the rule. Compost, can be a very exact science, and require all kinds of subtly. Trust me, I have personally observed that there are all kinds of really thick books on the subject. Just check out the bibliographies of many gardening books. Then go out and build a compost pile, and don't really worry about it too much.
So you might be asking, how do I tell what has carbon and what has nitrogen? Simple, carbon is brown and nitrogen is green. Now granted it really is not that simple, but for our purposes we'll say it is. This is a good way to think about whatever plant matter you might have kicking around your yard. Those grass clippings after you just mowed the lawn are a great source of nitrogen, and the big pile of leaves makes a good source of carbon. Food waste that has not yet broken down makes a good nitrogen source, as well as animal manures (horse, goat, chicken). In fact if you want to make a really good hot pile, and you have a source of manure, it makes a great addition.
So what is a "hot" compost pile and what is a cold pile. Composting is a process of creating an environment for microorganisms to break down organic matter and turn it into humus. A hot pile is when you create your "lasagna" layers all at once which allows the nitrogen to heat up the pile to a temperature high enough to allow the micro-organisms and fungi to multiply and break down their food source, the carbon material, faster and potentially kill any pathogens or weed seeds in the pile. A cold compost pile is just piling up your carbon and nitrogen material as you collect it. This process does not immediately trigger the nitrogen to activate the pile, therefore, the carbon will take longer to breakdown.
How to make a layered hot compost pile:
Take your time and make some soil!
- Pick a spot in your yard that you don't mind things rotting and perhaps smelling a little (if you make it right and maintain it, it should not smell too bad )
- Think about access to the pile. You will want to get future materials to the pile and the ability to distribute the pile back on your garden after it has become humus
- Access to water. You want to have the ability to water your compost periodically if it dries out.
- Ideally it is on bare ground, which allow earthworms and other critters to come up and eat and contribute to the process.
- If you have a chicken coop, you might want to think about all the wonderful nutrition they could get from feeding off the bugs and worms that live in the pile.
- To create fully functioning 'hot compost' you need to start with a minimum of a cubic yard. 3 feet wide, 3 feet deep and 3 feet high. Or a little under a meter if you are metric minded.
- If you are making a hot pile, it is recommended that you have a system in which to contain it
- The three bin system is popular and works well. The idea is 3 adjacent boxes, that are 4 cubic feet (or bigger). Pallets work really well for this and you can often get them for free or cheap.
- You can also build a frame and then use chicken wire to contain the compost material.
Making the pile
- Start with a layer of small branches and or brush and twigs. Something that allow air to get under the pile and circulate in. Make sure that your base footprint is 3 square feet.
- Then put down your first layer of carbon. Maybe those leaves you raked up last fall. You want your carbon layer to be about 4-12 inches. It depends on whether it will compress with additional weight (ie leaves you might want to go pretty thick).
- Add some water. Not too much, but you are going for the consistency of a rung out sponge. If your materials are already wet, then don't add water
- Then you add a layer of nitrogen about 2-3 inches. Grass clippings, wet food waste, manure (dry food waste tends to lose most of its nitrogen).
- Then add another carbon layer
- Then more nitrogen etc.
- Water every layer or every other layer as appropriate
- Do this until your pile is a a minimum of 3 feet high
- Top it of with some straw or leaves or something to suppress any smell.
- Add some soil to the top to prevent the nitrogen from escaping.
- If possible, track the temperature of your pile ( a meat thermometer works well) . You are looking for a temperature of 131-150 degrees. Anything higher means you have too much nitrogen and are losing it as methane gas and killing the beneficial micro-organisms. After three days above 131 degrees, it is beneficial to turn the pile to re-ignite it. You should turn the pile several times a month for the first 2-3 months. Once the temperature cools down to ambient air, then it is time to let the pile sit.
- Turning the pile will continue the process that you have started. Using a pitchfork you want to move the pile to the adjacent bin. Because the middle of the pile is the hottest, it is important to activate the entire pile so turn the material from the outer edges into the middle of the new pile and the hotter material to the edges. If you need to add more nitrogen sources it is good to layer them in.
- Turning will aerate the pile and restart the microbial activity
- Composting is a very variable enterprise. It can take from 1-6 months or longer
- You know that you are done when you have a rich dark brown humus instead of a bunch of identifiable rotting parts.
- It's a good idea to put it through a sifter before using in soil.
- Keep it covered if it is raining so valuable nutrients don't leach out and the pile does not become saturated and stop the composting process.
- If you have manure, it's better to put it in the middle layers or towards the top
- Keep your pile moist, but not soaked. You are trying to create an ideal climate for microorganisms. Like plants, too much water and they drown and too little and they die of thirst
- If you are putting weeds in your pile, make sure that they have not gone to seed. If they have, you may get your pile hot enough to kill them off, but you might not.
- A great time to build your pile is after harvesting in the fall. You will have plenty of great nitrogen (from the freshly pulled plants) and it will have the winter to break down.