#hot compost

The Built Structure:

Jude’s two-bay compost system can house about two cubic metres and was constructed with the help of a mate. They’ve used recycled pallets which are heat treated to make sure the compost is safe to put on edible produce. It has gates at the front, low enough for a wheelbarrow, and is clad with corrugated iron. Jude says the corrugated iron “makes a really good backing when you're digging into the compost, and they also heat it up.” It’s a good idea to install a chicken-wire tube in the centre of the bay for airflow.

Compost is broken down organic matter and is full of nutrients that plants thrive on. Organic matter is anything that was once alive, like plants, animals, and even manures. This material can be broken down slowly by worms in a cool compost system, but in a hot compost system, it’s broken down by millions of micro-organisms and fungi. A big mass of material paired with a lot of microbial action generates a lot of heat. Jude says, “hot compost is a great way to get a lot of compost in a very short amount of time.”

Hot compost needs to be built it all in one go, at least one cubic metre in size. Jude says smaller composts “won't generate the heat required to breakdown the organic matter.” The ideal temperature for hot compost is 60°C, anything higher is way too hot to support the microbes. Regular turning for airflow will help manage the temperature. Jude’s got the perfect ingredients for a healthy hot compost habitat to provide these critters food, air and moisture.

Green & Brown Materials:

Good compost has “a mix of greens and browns,” says Jude. Brown layers are carbon-rich material such as cardboard, sticks, newspaper and straw. These offer energy to the microbes, absorb moisture and improve airflow. Green layers are not always green in colour. Greens are nitrogen-rich materials such as grass clippings, coffee grounds and food scraps. Jude says, “as a general rule of thumb, you want at least twice as much of the carbon-rich material as the nitrogen-rich green stuff.”

Layer #1: Brown:

Cover the base with a carbon layer of sticks and twigs. The rough textures allow excess water to drain, will bulk out the base and help oxygen get into the pile. Jude says, “when I'm adding a layer of carbon, I'm watering it in. I'm aiming for a pile that's moist but not soaking wet.” A layer of wet newspaper on top of the twigs will help create this environment.

Layer #2: Green:

Repurpose your old kitchen scraps and leafy garden waste. Jude says, “avoid meat, bread and dairy” to keep rodents away, and make sure you’re “not adding any weeds with seeds, bulbs or runners.” Break big sections up with a spade to help it breakdown faster. Jude says, “adding diverse nutrients like comfrey will help fire up microbial life.”

Layer #3: Brown:

A thick layer of straw mulch will act as a blanket for all that heating mass underneath. In two weeks, this pile can be lifted and moved into the second bay and turned every few weeks. Check the pile regularly to see if it needs more water or aeration.