What are the golden rules for making compost?

Making garden compost is easy. It is a process that goes on around us in nature, all we need to do is to harness the ingredients within our composter.

HOTBIN Mini composter in use

There are a few golden rules that will help you make the best compost and avoid common mistakes. Don’t be daunted, have a go.

  • Good drainage is essential for the very best results so the bin (or heap) should be placed directly onto open soil. This allows beneficial organisms to move in and out of the compost and also lets excess fluid drain away. If you’ve chosen a compost bin that is a ‘sealed unit’ it should have a tap at the base to drain off any excess fluid. Collect this exudate; it’s sometimes called compost tea. You can dilute it and use it as a plant food by watering around your plants.
  • Get the mix right. Balance the amount of dry, woody material that you add, with an equivalent amount of green material. If you can fill the bin in one go all the better.
  • Use generous amounts of waste to get it going, small quantities do not provide enough material to fire up the process. Usually you need a critical mass of material that the microbes can start working on, once you’ve got that your compost system may start to steam, this is a good sign and is an indication of a sought after hot heap.
  • If you want to speed things up, feed the workers! Use a compost accelerator. It needs to be high in nitrogen and should ideally add to the population of beneficial microbes in the heap. It’s a great way to get a new heap started quickly. You can add a pile of rich green leaves like comfrey or nettles or if there’s a man about the house, ask him to pee on the heap (in private of course), urine is rich in nitrates.
  • Insulate the heap with an old carpet or a proper compost duvet to help to retain the heat. Or choose to use an insulated compost bin like the HotBin Composter.

Speeding things up

A healthy composting system contains a high volume of beneficial micro-organisms that are crucial to the process. These are naturally occurring garden microbes. When you create a new compost heap or fill a new bin, you can wait quite a long time for the levels of these garden microbes to build up. This is what would happen in a slow heap system. If you have a gardening friend who has a good compost heap, ask for a bucketful from the middle of their system, it will be rich in all the good composting microbes and mini-beasts and will innoculate your heap.

egg boxes added to composter
Torn-up cardboard and egg boxes can be added to your compost heap. Image: Martin Mulchinock

The other important way to speed up the composting process is to prepare the material that you add to the compost heap. If you’ve composted before you will have found that any thick stems or chunks of cardboard are often still recognisable when the rest of the material has broken down. That’s because they are too big and thick for the microbes to work on. The composting microbes are miniscule and need a large surface area to work their magic. So by shredding those stems and tearing up the cardboard into smaller pieces you actually increase the available surface area to be worked on and they can get to work much more efficiently. A shredder is a big investment but one you could share with like-minded friends or consider hiring one from a machinery hire specialist for the weekend. Look out for the ‘silent’, reduced gear shredders that cut stems into mini logs and crush them before they are released. This increases the surface area hugely and helps the microbes to get right into the centre of the material, thus speeding the composting process.

shredded wood added to composter
Cut stems into mini logs before adding to the compost heap. Image: Martin Mulchinock

What can I compost?

In simplest terms you can compost most things that are ‘organic’ and basically that means things that were living like plants and leaves, peelings, prunings and more. But there are always some dos and don’ts. Good compost material includes:

  • Garden waste such as grass clippings, leaves, prunings, weeds, spent flowers and old bedding plants.
  • Pet bedding e.g. rabbits, hamsters, chickens and gerbils (vegetarian pets only).
  • Cardboard such as toilet rolls and cardboard egg boxes.
  • Kitchen waste including vegetable and fruit peel (uncooked), egg shells, tea bags and coffee grounds.
kitchen waste composting
Kitchen and garden waste can be added to the compost heap. Image: Martin Mulchinock

Things to avoid

There are some things that it’s best to avoid, these include:

  • Prickles, spines and thorns – because they can persist in the compost.
  • Perennial weeds and weeds that are seeding or flowering, or roots of weeds such as couch grass and bindweed, as these can survive in a slow heap and help spread the problem around the garden.
  • Newspaper – it can be shredded and composted in small amounts but it is better to recycle it.
  • Uncooked meat, fish, eggs, cheese and fat scraps and all cooked food – these can attract flies and vermin, which spread disease. But they may be added to some composting systems, so check with your supplier for up to date advice.
  • Diseased plants and leaves – because the diseases may persist after composting.

Never compost

  • Cat and dog waste – it can spread diseases.
  • Disposable nappies and any sort of plastic – they won’t break down.
  • The ash from coal fires – it can contain toxins.
  • Plant material that has been treated with a weed killer or moss killer – these chemicals may persist and affect your border plants.

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