The hows, whys and wheres of composting… – University of Bristol Botanic Garden

By Alida Robey

I have had some intriguing responses to my previous post on composting– most commonly “Hurry up and tell us how to do it!” ; so without further delay, I give you the why, where and (most importantly) how of composting….

Why compost?

There is so much more to composting than simply meeting our own personal needs. For me, the global urgency is such that I would have us label all shop bought fruit and veg: WARNING: Not composting will lead to the depletion of our soils! Here’s why:

Compost helps regenerate soils and improve soil structure

Current agricultural practices suck nutrient out of the soil. The resultant produce has less nutritious value than in previous generations, [1] meaning we are needing to eat more to get the same nutritional benefits. [2] Commercial fertilisers are designed to promote maximum growth, not necessarily superior nutrient content of the fruit and vegetables produced. Nor do these fertilisers benefit soil structure and health. The fibre of compost added to soil helps improve water retention and also helps moderate temperature extremes.

It provides a slow release of nutrients (especially nitrogen)

Unlike synthetic fertilisers, compost adds a bank of biological activity to the soil, which encourages beneficial worms and helps to make significant quantities of nutrients (such as nitrogen, phosphorous and potassium) bio-available slowly over time.

Composting keeps organic waste out of the landfill

About a third of household waste is likely to be kitchen-generated organic matter. Composting it yourself reduces increases in your council tax by saving some of the huge costs of domestic waste collection transport and disposal. Also, organic matter in landfill produces methane (a greenhouse gas that contributes to global warming) and nitrogen-rich leachate (pollutes rivers and streams).

Composting transforms plant material, food waste and other organic matter into humus or compost, which is a richly nutritious soil-like material with the added benefit of microorganisms that help plants take up the goodness in the soil. In other words, it turns otherwise smelly, unwanted waste into something really productive and pleasant to handle.

Where to compost

A community composting bin in the Shelton Community
Garden in Shelton Stoke-on-Trent, Staffordshire.
Photo credit: Joshua Whiton via Wikimedia Commons

The traditional means of composting is a bin, a heap or an enclosure in a sunny spot in the corner of a garden. However, you can do some very effective composting even without a garden of your own:

Community composting bins require one or two people to maintain but can receive compostable materials from a community. The compost can then be used for community gardens or by individuals in the community . They can be located in parks, communal gardens, unused corners, on the edge of school grounds and other public/semi-public spaces.

Wormeries are a wonderful alternative for those in apartments or with limited external space. A wormery is usually a small stack of trays, which is home to a colony of compost – eating worms (NOT earthworms) that will convert most kitchen waste into wonderfully nutritious ‘worm wee’ and worm castings that can be used to feed indoor or outdoor plants or given away to friends and neighbours to use on theirs.

How to compost

This is what I consider to be the basics. Once you have tried some of this and found it’s not going as badly as you had imagined, then I suggest you access some of the online information that will help improve your productivity.

What goes in?

IN:

Veg peelings & fruit

Coffee grounds, tea bags, egg shells – crushed by a crunch of your hand

Cardboard (torn up no larger than a standard envelope), tissues, loo roll tubes & waste paper – shredded or scrunched up.

Especially welcome are egg boxes (ripped up a bit) and the contents of paper shredders

Grass-cuttings (so long as you haven’t used weed-killer) and discarded pot plant contents including old compost and dead flowers

Plant prunings – chopped up to help decomposition

Weeds – so long as they are not in seed, otherwise you will have them sprouting merrily back in the soil.

OUT (of compost bins but IN for wormeries)

Pasta, rice, couscous

Beans, pulses, lentils, cereals

Bread, chapatis, biscuits etc

Plate scrapings

Cheese and dairy products

Meat, fish and bones

Cooked potatoes

The reason many of the items above are excluded from compost bins but not wormeries is their attraction for vermin.

OUT (of everything)

Nappies

Cat and dog poo from animals that have been wormed.

Location, location, location

A typical compost available from
local councils.

For general composting, find a warm sheltered corner preferably reasonably accessible so you are not put off taking stuff there. Set up your means of containing your compost, a compost bin or bins is the easiest, but a boxed-in area or even just a pile will do. Your local council may, like Bristol, sell plastic compost bins and deliver them, all for as little as £12-15. You need to bear in mind that you will need to be able to turn the contents occasionally and that worms need access from below.

The great compost bake-off

Underlying the composting process is the chemical transformation of carbon materials (shredded paper, straw, vacuum cleaner dust, leaves, egg boxes, egg shells) and nitrogen materials (grass clippings of untreated grass, weeds, kitchen scraps, coffee grounds) into a whole new product – compost. It is a bit like baking a cake where the ingredients are deliciously transformed by mixing and baking. We can control the conditions in our compost to encourage the materials to decompose faster and effectively (i.e. to produce a really good cake rather than a baked lump of goo).

The other factors your composting recipe needs to include are a mix of particle sizes that assist aeration and hold enough (but not too much) moisture. As with the cake, the mixing and aerating are important success factors between it just working and it being great. If it’s getting smelly, add more carbon materials and aerate it more frequently by turning it over.

Depending on your method, the transformation process can take just a few months.

Layer dress

Start layering your contents, bearing in mind the need to mix carbon and nitrogen items (roughly 2 carbon:1 nitrogen, but adjust according to whether it seems to look and smell healthy). And just keep adding, remembering that it will all break down a lot smaller. I prefer to have 2 or 3 bins, and empty them out completely from time to time, retrieving the made compost from the bottom and piling the rest back into one bin. This can be a lot easier than turning the contents of individual bins. You can keep one bin of nearly decomposed compost at the ready for when you want to use it in the garden.

Happy composting!