How to Make Compost at Home
Table of Contents
One of the gardener’s greatest secrets to a cost-effective and bountiful garden is all a simple trick of nature. By sustainably recycling used food scraps and organic material like cardboard and paper through means of creating compost, the gardener obtains an efficient growing medium for pennies on the dollar. What processes are involved in creating compost? How much space is required? What are the best practices? Let’s take a look together, and I’ll share my secret to a successful compost heap.
Note: This article contains affiliate links that contributes to the writer a small financial commission for each purchase. You can support this site by purchasing from the links provided! Read more about our affiliate program in our Privacy Policy.
What is compost?
Picture a rich and fertile soil filled with nutrients and life that allows air and water to circulate more effectively. Chances are, your natural soil lacks these properties. Where soil can be anything from sandy to loamy to full of clay, compost is a combination of various organic matter that has been broken down until it looks and feels like rich and warm soil. However, the two materials are entirely different.
Where soil is made of inorganic components such as rocks, sand, clay, and sediment, compost is entirely composed of living and decaying materials, such as food scraps, leaves, and microorganisms that break up the waste.
How is compost made?
When scraps of waste are left to rot, microorganisms like bacteria and fungi, as well as bugs and wasps and worms, break down and decompose organic materials. There are three phases of decomposition that utilize separate microorganisms, as each phase has differing conditions. Read this excerpt from Cornell Waste Management Institute, which explains the various phases:
Different communities of microorganisms predominate during the various composting phases. Initial decomposition is carried out by mesophilic microorganisms, which rapidly break down the soluble, readily degradable compounds. The heat they produce causes the compost temperature to rapidly rise.
As the temperature rises above about 40°C, the mesophilic microorganisms become less competitive and are replaced by others that are thermophilic, or heat-loving. At temperatures of 55°C and above, many microorganisms that are human or plant pathogens are destroyed. Because temperatures over about 65°C kill many forms of microbes and limit the rate of decomposition, compost managers use aeration and mixing to keep the temperature below this point.
During the thermophilic phase, high temperatures accelerate the breakdown of proteins, fats, and complex carbohydrates like cellulose and hemicellulose, the major structural molecules in plants. As the supply of these high-energy compounds becomes exhausted, the compost temperature gradually decreases and mesophilic microorganisms once again take over for the final phase of ‘curing’ or maturation of the remaining organic matter.
The key takeaway here is to know that in the first phase, organic matter breaks down quickly. When the bacteria digest the organic material, they release the energy in the form of heat, so your compost pile gets toasty inside.
As the pile heats up, human- and plant-based pathogens, pests, weed seeds, and diseases are destroyed, and proteins, fats, carbohydrates, and cellulose break down. These hot temperatures also kill off most of the microbes that have taken up residence in phase two, allowing for a third and final phase of breaking down and curing to occur. Once the pile is cool again, it’s ready to use.
What is needed to successfully make compost?
There are a few key components to ensuring success in your compost pile: heat, airflow, a bit of moisture, and the right ingredients.
Heat
Thankfully, this factor is naturally-regulated, usually, and simple means can be taken to ensure the process is maintained. While too much heat will kill off microbes in the first phase or release nitrogen significantly, too little heat will cause the decomposition process to slow down, and the pile will not reach the second phase.
The optimum temperature range is 135° to 160° Fahrenheit with a requirement to hit 150° for safety.[1]Whatcom County Extension, Washington State University A higher temperature is easier to maintain when a compost pile is larger in size, about 3 ft. by 3 ft. by at least 1 ft., as compost is made of well-insulating materials. Additionally, adequate heat usually occurs after the first phase when organic material begins to be digested, but if the pile isn’t reaching that 150°, a gardener should look toward the second factor: airflow.
Airflow
From Washington State Extensions:
A drop in temperature in the compost pile before material is stabilized can mean that the pile is becoming anaerobic and should be aerated. High temperatures do not persist when the pile becomes anaerobic.
Essentially, these bacteria breaking down organic matter require oxygen to carry out decomposition. When the pile becomes stagnant, lacks airflow, or gets waterlogged, the pile stops breaking down, and heat-releasing bacteria stop releasing heat.
How do we fix this problem? A few solutions exist. First, the container of the pile is important. If the pile is free-standing, that allows the most air to infiltrate from each side. If containment is required, opt for a more open container, such as a wire frame or pallet sides. A tumbling composter bin is an easy way to aerate a pile, but keep in mind that when the turning is completed, the door should be opened such that temperature can be regulated and air introduced.
Secondly, a gardener should make sure to turn the pile regularly. Not only will this mix up the varying ingredients and spread out the already-developed compost, it will also aerate the pile and restart the composting process. While mixing the pile will decrease the internal temperature at the time of mixing, the bacteria with fresh air will start digesting materials again, increasing the temperatures enough to make up for the lost heat. This will also help keep temperatures below 160° in hot weather.
A final solution is one taken from Monty Don of the BBC’s Gardeners’ World, though his method requires at least 6 ft. by 3 ft. of garden space. Monty segments his piles into two, if not three, separate compartments. The first pile is directly on the ground level. Over time, he adds organic materials to the first pile, then mows it over to grind up the larger pieces into small particles, which also contributes to better heat control, oxygen exposure, moisture retention, and pest control[2]Materials & methods to ensure quality compost, Washington State University Extensions. He then throws all of this into the second pile. In the second bin, this shred-up pile undergoes the first and second processes of compost, where microorganisms and bugs digest and then heat up the pile. This pile must be turned to introduce more oxygen. If a third pile is accommodated, the oxygen is introduced when the pile is moved from the second to the third bin. Otherwise, opt to turn the second bin regularly.
Moisture
Just like heat and air, microorganisms and worms and bugs need moisture to survive and decompose organic material into compost. From Washington State University Extensions, we read:
Some microorganisms use the film of water to move—slipping and sliding to another section of the pile. Biological activity stops when the pile dries out. […] Too low moisture content deprives organisms of water needed for their metabolism, and inhibits their activity.
The article goes on to explain that home compost piles should contain 40-60% moisture, which is the moisture of a wrung out sponge. Too much water will waterlog the pile and kill any living organisms, so a gardener should watch carefully for the pile’s moistness.
Do I need a compost starter?
While many gardening sites advocate for a bit of compost starter to begin the process of decomposition in a pile, a patient gardener technically doesn’t need it. Our air is filled with microorganisms, and our dirt is full of worms and bugs. Each of these will contribute to the decomposition efforts if the mix of material in a compost heap is balanced. If a gardener finds it hard to get the ball rolling, by all means, they can buy a small bag of compost from a local nursery to jumpstart their efforts.
What organic material can go in compost?
The composition of a compost pile is by far one of the most important factors for the success of a gardener’s efforts, and it has a simple formula: mix a 30 to 1 ratio of carbon (brown) and nitrogen (green) materials, according to Cornell University. We get a pretty good idea of why these are both needed from Cornell’s Extensions program:
Carbon provides both an energy source and and the basic building block making up about 50 percent of the mass of microbial cells. Nitrogen is a crucial component of the proteins, nucleic acids, amino acids, enzymes and co-enzymes necessary for cell growth and function.
However, I’ve had success matching volumes of brown-to-green directly, such that for every bucket of green material, I add one bucket of brown material. Let’s dive deeper to see what this means.
What are carbon-rich materials in compost?
Materials that are brown, woody, and dry typically hold a lot of carbon and little nitrogen. Leaves that have fallen in the autumn, wood chips, sawdust, twigs, branches, and paper are made of cellulose fibers and full of carbon. However, because the cellulose is difficult to break down, these materials have difficulty releasing carbon, which give energy to microorganisms (which then release it as heat). The trick is to shred these components to small particle sizes so that they have more surface area exposed to be digested.
Carbon-rich materials
- Fall leaves
- Wood chips
- Sawdust
- Twigs
- Branches
- Cardboard
- Paper
- Bark
- Newspaper
- Cotton fibers
What are nitrogen-rich materials in compost?
Nearly all green and moist living ingredients you’d put in a compost bin contain nitrogen in high quantities. Grass clippings, plant cuttings, fruit and vegetable scraps, and coffee grounds have nitrogen readily-available for organisms to feast on, but this nitrogen is often too abundant and contributes to a smelly ammonia-like sludge in the pile. If this occurs, quickly add more brown!
Nitrogen-rich materials
- Fruit
- Vegetables
- Coffee grounds
- Grass clippings
- Chicken or rabbit (herbivore) manure
- Seaweed
- Blood meal (note, unless ground to meal, bones may attract creatures)
- Worm castings
- Tea bags
Other good compost materials
Note that when organisms digest organic matter, they often require more nutrients than carbon or nitrogen, and they also release organic acids that increase the acidity of your pile. To combat these things, consider adding additional materials to your pile:
- Egg shells contain minerals like calcium
- Wood ashes are alkaline and contain potassium and lime
- Fish bone meal (note, unless ground to meal, bones may attract creatures)
What to avoid in compost
To deter unwanted pests such as raccoons, mice, or bigger creatures, and to maintain the health of the compost (which is going to bring nutrients to the food you eat), avoid adding the following materials in your compost pile:
- Cooked foods will attract mice
- Coal ash has harmful byproducts
- Dairy, fats, and oils will attract critters
- Plants treated with pesticides will leech into your produce
- Grass clippings with weed-suppressant will stop your plants from growing
- Commercial hay or straw, which is likely treated with pesticides and weed-suppressant
While there may seem to be many guidelines on composting for the garden, the key takeaways are: add more brown than green, shred materials so they are easier to decompose, turn your pile regularly to aerate it, and be patient. Turn your waste into a wonderful and cheap growing material that feeds your garden, which then feeds you.
References
