Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
The time it takes to make traditional compost (aerobic compost) depends on several factors, including the batch’s composition, ambient temperatures, and management activities.
Composting, the managed decomposition of organic matter, depends on the availability or the right proportions of carbon, nitrogen, water, and air. The composting speed depends on how optimal the environment is for microorganism activity (bacteria, fungi, and actinomyces).
Factors That Affect Composting Speeds
Several factors may accelerate or delay transforming organic waster into soil-beneficial humus. I will go through these below, remembering that a compost heap is a system – one factor affects the whole, and elements are interdependent.
Hot composting is the fastest composting process. However, process speed and finished humus quality depend on various conditions. The ideal conditions include:
- A heap with a 30:1 carbon-to-nitrogen ratio is the best mix for promoting microbial growth and proliferation while ensuring a product with the most carbon stabilized carbon.
- A constant supply of at least 5% oxygen is needed to keep the microbes from dying.
- Enough water allows microbial activity and chemical reactions without affecting airflow. You can test the moisture level by squeezing a handful of wet compost as tightly as possible. If water flows out, it is too wet, and if no moisture is evident between your fingers, it is too dry.
- Temperatures should fluctuate between 60 and about 160°F (~15 to 71°C). More on this later. The upper range is vital in eliminating pathogens and weed seeds.
- The carbon- and nitrogen-rich substrates should be chopped up to increase the available surface area for the microbes to access. While this is important, so is avoiding compaction, including some larger pieces necessary.
The Role of Microorganisms in Life
Considering that a teaspoon of compost contains as many microorganisms as there are people currently alive on earth helps us understand that these unseen creatures are tiny, present everywhere, and essential.
Shredding material increases that material’s surface area, which is why shredded leaves are so much easier to compost.
Guard against shedding everything too fine, which will cause compaction, creating an anaerobic environment.
Including larger pieces of varying size will prevent this, as will regular turning.
Composting’s final product, humus (Latin for earth), is a dark brown substance with a distinct earthy smell.
Carbon and Nitrogen Quantity and Quality
Brown plant matter generally has a higher carbon to nitrogen ratio. As seen from the table below, fresher food waste is higher in nitrogen, and older brown plant material is higher in carbon.
|C: N Ratio
|Vegetable garden waste
The ideal C: N ratio to begin composting should range between 25:1 to 35:1. The higher the carbon content, the slower the process, while a high nitrogen content (a lower C: N ratio) is likely to cause some anaerobic conditions, easily identified by a foul smell.
How Can I Speed Up My Composting Process?
1. Make sure you have the proper carbon-to-nitrogen starting ratio
As mentioned above, too much carbon and your microbial population with be slow to propagate as they need nitrogen for cellular growth. Stick to a starting ratio of 30:1.
2. Make sure your pile is big enough
You need a minimum of three cubic feet pile to provide enough insulation to create a center stage for microbial activity. To make it larger, you will need machinery to turn the pile.
Insulation helps, but remember that the organisms need air to flourish, so regular turning becomes critical.
3. Use pile core temperatures as turning notifications
Turning too early slows the time needed to complete a batch of compost. Turning too late will also extend the time required to finish the batch as microbes perish and compaction happens.
Your best bet is to turn the pile when the core temperature reaches 165°F (74°C).
4. Keep the composting batch moist
Keep the whole batch moist but not wet. A more than 60% moisture level is in the danger zone for creating anaerobic conditions; less than 40% will affect microbial activity. Follow the guide above.
How Long Does it Take to Make a Compost?
Following the steps above, you can have a batch in six to eight weeks. If a single element is out of whack, and a couple of weeks, and if more than two factors are not malaligned, it could take up to six months.
I hope that helps you speed up your process of creating what your soil longs for.