A Complete Guide to Hot Composting
Hot composting is a great method of breaking down waste to produce nutrient-rich compost. The heat makes it a quicker process than traditional methods of composting, although it can take slightly more effort.
In this guide we’ll look at the pros and cons of hot composting and what you can put on a hot compost. We’ll also take you through a step-by-step guide to setting up and looking after your hot compost pile. Read on to learn how to do it.
What is hot composting?
Hot composting is a method of rapidly decomposing organic materials by creating optimal conditions for heat-loving microorganisms. It involves mixing nitrogen-rich “green” materials with carbon-rich “brown” materials and regularly turning the pile to aerate it.
The elevated temperatures in hot composting break down organic matter quickly, resulting in nutrient-rich compost in a matter of weeks to months, ideal for enriching garden soil.
Benefits of hot composting:
- Hot composting accelerates the decomposition process, producing nutrient-rich compost in a matter of weeks, much faster than traditional composting methods
- The high temperatures reached in hot composting (usually between 49 °C and 71 °C) can kill weed seeds and harmful pathogens, making the resulting compost more weed-free and safe for use in gardens
- Hot composting produces compost that is rich in nutrients and beneficial microorganisms which enhances plant growth and reduces the need for chemical fertilisers
Limitations of hot composting:
- Hot composting requires more effort than traditional methods. Monitoring and turning the pile regularly to maintain high temperatures can be time-consuming
- Hot composting often requires a larger compost heap or bin, and you’ll need a steady supply of both green and brown materials
- Hot composting can generate strong odours, especially if not managed correctly
What temperature should a hot compost be?
In hot composting, the temperature range is typically between 49 °C to 71 °C. These elevated temperatures are necessary to create an environment that promotes the activity of heat-loving microorganisms. The high temperatures help break down organic materials quickly and efficiently, resulting in the rapid decomposition of the compost pile’s contents.
Monitoring these temperatures using a compost thermometer will help to keep it on track and show when to turn the pile. We recommend the ETI Compost Thermometer for this as it has a large colour-coded dial that makes it easy to see whether your pile is in the warm, active or hot stage.
What can you put on a hot compost?
Hot composts require a mixture of green and brown materials. You should aim for 25 parts carbon materials to one part nitrogen. Here are some examples of materials you can add to your pile.
Greens (nitrogen-rich materials):
- Fruit and vegetable peels, coffee grounds, tea bags, eggshells, and spoiled produce
- Fresh plant trimmings, weeds (avoid seeds), and grass clippings
- Animal manure from herbivorous animals like cows, horses, goats, and chickens (ensure it’s well-aged or composted to avoid excessive ammonia)
- Fresh green leaves from trees and shrubs
Browns (carbon-rich materials):
- Dry leaves, straw, or hay
- Small wood chips or twigs
- Shredded paper or newspaper (avoid glossy paper and coloured ink)
How to make a hot compost
A step-by-step guide to setting up and maintaining your pile to produce healthy compost.
What you’ll need to make a hot compost:
- Mixture of green and brown materials
- Compost thermometer
- Gardening fork or shovel
- Tarp for rain
Step-by-step guide to making a hot compost:
- Select a well-drained and sunny spot in your yard or garden for your hot compost pile. Ensure it’s easily accessible and away from structures or trees.
- Collect a mix of green and brown materials for your pile. You should aim for around 25 parts carbon materials to one part nitrogen. Ensure they are chopped up into small pieces to help them to break down quickly. An easy way to do this is to run over them with a lawn mower a few times.
- Use a compost thermometer to monitor the pile’s temperature. It should heat up within the first day or two. You should turn the pile once the temperature starts to drop. Turning it will introduce oxygen, speed up the decomposition process and ensure even heat distribution.
- As well as temperature, keep an eye on the moisture of your pile. It should stay damp but not soggy. If it looks dry, you can add water to the pile. But if it starts to smell, it’s too wet. Adding a high carbon material like shredded newspaper will help to soak up excess moisture.
- Make sure to cover the pile with a tarp if rain is due. This prevents it from becoming waterlogged.
- After around three weeks, your compost will be ready when it looks dark, crumbly, and has an earthy smell. Remove finished compost from the bottom of the pile and enjoy using to enrich your garden.
Hot composting involves maintaining a combination of carbon-rich and nitrogen-rich materials in warm, damp conditions to produce compost quickly. The resulting compost is rich in nutrients and low in harmful pathogens, reducing the need for chemical fertilisers.
Green materials to put on the pile include plants, vegetables and animal manure. Brown materials include wood, paper and dry leaves.
Monitoring the temperature using a compost thermometer and turning the pile when it drops will help to do this correctly. Maintaining a healthy level of dampness is beneficial for the pile, but covering it with a tarp during rain will prevent it from becoming waterlogged.
Sticking to these tips will help to produce healthy compost in a matter of weeks.
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