Organic Gardening Class – Making Compost Fast

Making a Soil Improver that Heats up Naturally

This webpage is about making a fast compost that heats up quickly and is ready to use as a soil imporver type of compost. It will not be like the compost that you would use to plant up a haging basket or for potting up plants in. Instead you would use it for mulching or improving soils within your planted beds, borders and allotments.

The finished soil improver after just14 days of aerating and sheredding!

Creating compost quickly in less than eight weeks is an intense process requiring specific ingredients and procedures to produce usable compost free of pathogens and weed seeds. This process is known by different names, such as the Indore Process and the Invassel Method, commonly used by municipal composting companies. It involves a balance of nitrogen and carbon materials, mixed thoroughly to build up heat, which kills pathogens and weed seeds, breaking down the materials within eight weeks.

Adding green fresh grass cuttings as nitrogen
Adding brown shredded leaves form the autumn as carbon

Resources for smaller-scale composting are limited. Large commercial companies invest in machinery to produce thousands of tons per year. This resource page aims to help those with an allotment or a reasonably sized garden produce a few cubic meters of compost with minimal effort.

Here is a breif video explaining the while process in simple terms:

What You Will Need

Gathering materials is crucial for success. Grass cuttings and leaves are ideal ingredients. If you have large amounts of these, the process becomes easier, relying on the compost heating to around 70°C to eliminate weed seeds and disease-causing microbes.

Measure out 1 bulk bag or 1 cubic metre of fresh green grass clippings
Measure out 1 bulk bag or 1 cubic metre of shredded brown leaves

Designate an area for this process and gather some simple equipment, such as space for three square meters, three bulk sandbags (about one cubic meter each), and basic gardening tools. Additional items like pigtails (wire spikes with a pigtail curl) for securing the bags, and personal protective equipment (PPE) such as a face mask, gloves, hard helmet, and ear defenders with a visor, are also necessary.

If you lack grass cuttings or leaves, alternative materials like wood chips, vegetable peelings, cardboard, and hedge trimmings can be used, though they may not be as effective.

After eight weeks, the compost might not be ready for propagation use but will serve as an excellent soil improver. It can be used as mulch around established plants or in no-dig gardening methods.

One of the Roots ot Fruit gardeners using the 10 day old soil improver to add organic matter to the soil and mulch around young plants

Step-by-Step Composting Process

1. Gather Materials: Collect carbon materials (leaves, wood chips, cardboard, paper, or wood shavings) and nitrogen materials (grass cuttings, vegetable peelings, manure, or green plant material). Avoid sawdust from plywood or MDF due to trace chemicals.

Green plant growth should ideally not have flowers that have gone to seed on them
The easiest way to shred brown leaves is to suck them up off the lawn with rotary lawn mower and collection box

2. Prepare the Compost Threshing Floor: Lay out a flat area, free of stones, gravel, sticks, or glass. Spread leaves to a depth of about two inches and run a lawn mower over them, reducing the height as the pile diminishes, to shred the leaves finely. MAKE SURE THERE ARE NO STONES, GLASS, BRANCHES OR HARD MATERIALS THAT WOULD MAKE A DANGEROUS PROJECTILE PRESENT WITHIN THE MATERIAL.

Shredding the material on a flat area of lawn using a ride on lawn mower
Using the compost shredding floor with a wheeled rotary mower. Make sure there are no stones or twiggs!

3. Mix Carbon and Nitrogen Materials: Put half of the shredded carbon material in the bottom of a bag, up to halfway, and top it with grass cuttings. Mix thoroughly with a fork, add water if dry, and ensure even distribution of materials.

Adding green fresh grass cuttings as nitrogen
Measure out 1 bulk bag or 1 cubic metre of shredded brown leaves
Mix the grass clippings and leaves thoroughly using a garden fork

4. Monitor and Turn the Compost: After a couple of days, when the compost starts to heat up and then cool down, turn the pile to mix the materials from the edges to the center. Repeat this process every few days, using pigtails to help manage the bags.

If you have the mix right it will start to steam and build up heat within 24hrs of piling up and mixing
Fork and turn it regualrly atleast every other day for 10 days.
You can use a large soil auger and cordless drill to save your back, but watch you dont catch body parts with it nor the edge of the bag. The drill can push back and hurt your hand or wrist if the auger gets stuck so watch out for kick back!

5. Aerate and Maintain Moisture: Keep the compost moist (not soaking wet) and well-aerated. Water and air are essential for bacteria to break down the materials effectively.

Troubleshooting

  • Material not breaking down: If it’s not darkening or heating up, add more nitrogen or water.
  • Material is smelly and slimy: Add more carbon or shredded dry leaves/cardboard. Ensure proper mixing and aeration.
Compost is slimy and clumped together
add more well shredded and dry carbon
  • Middle is hot but edges are cool: Turn and mix the material thoroughly to ensure even decomposition.
  • Large particles remain: Sieve or run the material through the lawn mower again.

By following these steps, you can produce high-quality soil improver for your garden, improving soil health and reducing waste.

After 10 days grab a handful and squeeze and rub between your fingers if you see some black streaking then it has some humus present and is ready to use as a soil improver.

Turning the Soil Improver into Compost

If you wait another 8 weeks and carefully turn and shred it further, you can create a nice and refined compost. Watch a video on how to do this process.

Compost Couture: Refining and Transforming Your Compost into a Multi Purpose Mix

Here’s a video on how to get the compost you have made to the point of being able to use it in potting and propagation operations.