How to Make and Use Compost: The Ultimate Guide

How to Make and Use Compost: The Ultimate Guide

by Nicky Scott

Whether you live in a flat with a balcony or have a family and garden that generates large amounts of food and green waste, this book shows you how to compost everything that can be composted—at home, work, or school, and in spaces big or small. It covers how to create the right mix for successful garden compost; how to compost food waste safely; the full

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Whether you live in a flat with a balcony or have a family and garden that generates large amounts of food and green waste, this book shows you how to compost everything that can be composted—at home, work, or school, and in spaces big or small. It covers how to create the right mix for successful garden compost; how to compost food waste safely; the full range of composting systems; composting with a wormery; making liquid feeds and your own seed and potting compost; and composting in schools, with advice on getting a school scheme started. How to Make and Use Compost features a comprehensive A-to-Z guide, which includes what you can and can't compost, concepts and techniques, and common problems and solutions.

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“Clearly written and cross-referenced, this book obviously draws from a wide range of composting experience. I would certainly recommend it.”  —Sue Stickland, author, Back Garden Seed Saving

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How to Make and Use Compost

The Ultimate Guide

By Nicky Scott

Green Books Ltd

Copyright © 2010 Nicky Scott
All rights reserved.
ISBN: 978-1-907448-69-0



"Why would you want to deny the Earth your cauliflower stalk?" – Satish Kumar

At the end of a meal, many leftovers go straight into the bin along with any peelings, etc. from preparing the food. We currently throw away a third of the food we buy, but the tide is turning and more and more people want to grow their own food in healthy soil, and reduce their waste, which is why making compost is so important.

Whatever type of soil you have, compost will improve it. I've heard people talk about how compost is only a 'soil conditioner', as though somehow this was not really important. I think they mean that compost does not add much in the way of nutrients to the soil, but this is not the point. Soil conditioning really means adding humus to the soil. Humus is stable organic matter in the soil and it acts like 'glue', holding on to nutrients and water. In effect humus adds life back to the soil: doing this is the most important thing that we can do for the soil and it's ridiculously easy.

Compost has some nutrient value too, mostly held by the microbes that have proliferated during the composting process. The following are just some of the benefits of adding compost to your soil.

Healthy soil

Compost adds life in the form of microorganisms

Using compost on your soil will dramatically increase the amount of life in that soil – both life that is visible to the naked eye and, more importantly, life that can be seen only through a microscope. The addition of compost builds a healthy soil and so boosts the microbial activity, which provides food for hundreds of thousands of different species of fungi, bacteria and other organisms; these microorganisms are also food for a whole range of other organisms, which in turn are fed off by predators. What we can see when we look at compost are the creatures, mini-beasts on the macro scale; you will need a magnifying glass to see the very small ones, but many are obvious and well known to us. See 'More wildlife', page 18, for more on this.

Crucially, this microscopic world is cycling nutrients from the compost materials into a form that the plants in our gardens can easily assimilate, and holding them in the soil until the plants need them. Of all the soil organisms the worm is the one that we all recognise as invaluable for creating a healthy soil, and it does indeed possess almost miraculous powers – both the compost-dwelling species and the larger soil dwellers – but in fact it is the whole complex web of life in the soil that is kept vibrant by regular additions of compost.

Compost changes the physical structure of the soil

The humus that remains when compost has been further broken down in the soil coats the soil particles and creates the crumb structure that allows the exchange of gases and liquids. So in sandy soils compost increases not only the water-holding capacity but also the nutrient-holding capacity of the soil. In clay soils it flocculates the clay particles – it gathers the minute particles of clay together, again into a crumb texture.

Compost buffers the soil pH

Healthy, humus-rich soils 'buffer' the extremes of acidity and alkalinity – humus doesn't actually change the pH, but it enables plants to grow that would otherwise be intolerant of the degree of alkalinity or acidity of your soil.

Compost adds air

Compost helps open up clay soils and compacted soils, enabling them to breathe. Soils that cannot breathe become anaerobic (without air), and without air organic matter in the soil can ferment, with anaerobic microorganisms producing all kinds of by-products toxic to plants, such as alcohol.

Compost reduces the need to water

In free-draining soils, compost holds moisture. If soils cannot hold water then plants wither and die, so increasing the water-holding capacity of soil is a fundamental and dramatic advantage. When the compost has finally been broken down by the life in the soil, a fraction of stable carbon remains as colloidal particles (i.e. humus), which hold on to water molecules.

Less need for fertilisers

Humus improves the cation exchange capacity (known as CEC) in soils. Put crudely, as well as holding moisture within its particles (absorption), humus has a negative electrical charge, which attracts positively charged nutrients – cations – holding on to them at the surface of the particles (this is known asadsorption), making them freely available to the plants. Clay soils have strong cation exchange capacity and can be extremely fertile as a result; however, they compact easily and without enough aeration they are not productive. The addition of compost adds the necessary air.

Most plants growing in a healthy soil form symbiotic associations with the soil mycorrhizal fungi. These fungi take compounds exuded by the plant, and inexchange the plant takes minerals and nutrients from the fungi. Some plants also form associations with bacteria: the most well known of these are the azobacters, which help leguminous plants take up nitrogen.

The micro flora and fauna in the soil also hold on to and cycle nutrients around the plants' roots, helping to build the soil ecosystem.

Conversely, adding chemical fertilisers and pesticides to soils kills off soil micro flora and fauna. Chemical fertilisers are salts, which are more 'salty' than sea salt, and too much salt will kill off most plants. Furthermore, herbicides and fungicides will kill off other soil organisms; it can be the surfactants (e.g. soap, which is often used to break the water tension), not the active ingredients, that smother and kill the microbes.

Less need for pesticides

Adding compost and compost tea to soils and plants enables them to resist all kinds of pests and diseases. It is not really within the scope of this book to go into this fascinating area, but all kinds of tests have been done using compost and compost teas, and just how compost helps prevent pests and diseases is becoming more widely understood.

The soil food web is incredibly complex, and it is the soil organisms themselves that are supplying the nutrients in exactly the right form and location to the plant, right to its feeder roots. Bacteria form a protective layer around the plant root hairs, preventing viruses and diseases from getting in. The mycorrhizal fungi also form a barrier around the roots, so that they can exchange nutrients with the plants. What goes on in healthy soil is quite amazing and worth several books in its own right. One of the best contemporary authorities on this area is Elaine Ingham; her website is well worth a visit.

Less need to dig

You can never have too much compost in your garden. Clay soils are heavy work to dig, but spreading generous amounts of compost on the surface enables you to sow and plant into this layer, leaving the earthworms to do the digging. Sandy and peaty soils are easier to dig, but digging accelerates the 'burning up' of organic matter in the soil and so it is also good to add compost on the surface. Even if you have a beautiful friable loamy soil, too much digging will disturb the soil ecology, chop up earthworms and can result in soil being compacted, waterlogged and airless. Compost helps to counteract this, but in my opinion it is better to dig as little as possible and to add compost to the surface instead. If you aspire to being a 'nodig' gardener, you need as much bulky organic matter as you can get, in the form of compost or well-rotted farmyard manure to set up the system in the first place. (See Chapter 6 for how to set up a no-dig garden.)

Carbon sequestration

Well-made compost becomes humus, which consists of long stable carbon chains with properties that are still not fully understood. This carbon is locked up in the soil for a very long time, as long as the soil is not ploughed or dug up; if it is, the carbon will combine with atmospheric oxygen and be released as carbon dioxide (CO2) gas.

Since this book was first printed I have been reading Graham Harvey's excellent book The Carbon Fields. It seems that in 1996 a new compound called glomalin was discovered, and that this is a more potent compound than humus for locking up carbon. For more on glomalin I recommend Graham's book (see Resources section).

Less waste

Think of all the reusable or recyclable materials that we put out for collection. We cannot reprocess glass bottles and tins at home but nearly all of us can make compost and thereby eliminate the need for many lorries having to truck all that material either to be composted centrally or, worse, incinerated. With landfill sites filling up, local authorities have been bringing in recycling and compost collections, but even the best local authorities can divert only about half of the waste from landfill or incineration. The wastage of food is still huge; around 20 per cent of all waste is food and about a third of that waste is food thrown out, still unwrapped, within its sell-by date.

It is obviously far better to eat food than to waste it, but even the preparation of fresh vegetables generates a certain amount of waste in the form of peelings and tops and tails – and, unless this is home composted, it has to be dealt with by local authorities. But why give this precious resource to the council to deal with when we can transform it ourselves into compost?

More wildlife

By creating a living compost to feed your soil you are also feeding a whole food chain, right up to the top predators. A healthy soil will have a thriving worm and invertebrate population, which is food for many birds and other animals.

The compost heap itself is full of life – indeed I like to think of it as a living organism in its own right. Compost heaps become a magnet for all kinds of creatures, including some bigger ones. Predatory beetles move in and hunt for food, larvae and smaller creatures; frogs and toads do likewise, as do slow worms and grass snakes, which love the warmth in a heap. Birds will visit to pick off insects, invertebrates and larvae, and bats will visit at night. For wildlife value alone it's worth making compost, and the wildlife benefits continue through to the soil and the ecosystem you are building and maintaining by adding compost and avoiding chemical fertilisers and pesticides.

Saving money

Making compost at home saves money in so many ways. You don't have to buy in compost and growing media, or fertilisers – you can make them yourself.



Everything that once lived will start to decompose when it dies unless it is preserved in some way by being frozen, pickled, dried, fermented or salted, etc. The microorganisms that decompose dead animals and plants mostly need air, water and warmth to be active. Some of them manage without air, and there are many examples of specialist microbes (extremophiles) that survive in extreme situations.

We are all familiar with the process of rotting – whether from fruit spoiling in the fruit bowl or a fallen tree covered with fungi in a forest. The process of decomposition is happening all the time in the environment, and our soils contain millions of different species of microorganisms in every gram; in fact healthy soil is a more complex ecosystem than a rainforest.

Composting is an artificial acceleration of this decomposition, utilising the same natural process. You need materials high in carbon (the 'browns' – dry, often woody, materials – dead plant material, stems, twigs, chippings, autumn leaves, paper and cardboard, etc.) layered or mixed with materials high in nitrogen (the 'greens' – often wet, sappy materials – grass cuttings, fresh weeds, peelings and skins from the kitchen, urine and manures, etc). The drier materials provide air, either through hollow stems acting like snorkels or, as in the case of twigs and sticks, by creating an internal structure to a heap that allows air and water to pass through freely. The green, wet materials provide the water, which is released as the cell walls break down.

The right balance of these materials provides the perfect environment for an explosion of microbial populations. The whole secret of compost making is to set up this ideal environment for the bacteria, fungi and other creatures that are involved in the decomposition process. They thrive in a moist but not waterlogged environment, with plenty of air: ideally everything is coated with water but there are air spaces in between.

The concept of composting is really simple: once you really take on board that composting is a living, dynamic, natural process then I think you stop thinking of your heap as a kind of dustbin and more as the living, breathing entity that it actually is – a bit like a pet really!

If you constantly remind yourself of these simple but vital needs of your compost heap, then you will make good compost. If you forget them – well, everything decomposes given time, so what's the worst that can happen? Actually the worst that can happen is a smelly anaerobic (airless) mess that produces toxic leachate – but after reading this book that is not what you are going to create!

The four-word mantra

Air Water Food Warmth Air Water Food Warmth Air Water Food Warmth

These four basic requirements are the same for us humans and pretty much every life form on the planet, so the mantra shouldn't be hard to remember. What you are doing when you construct an aerobic (with-air) compost heap is creating the right environment for the billions of microorganisms that make the compost happen. Their food is the materials that you put on the heap.


It is most important to think in terms of whether the material you put on your heap will add air or water. A happy heap will have a balance of the two, just like a squeezed-out sponge: the whole surface area is coated in water but there are air spaces in between. If the pile is too dense, squeezing out all the air, or the air spaces get filled up with water, then all the beneficial life forms in the compost heap are not going to survive and will be replaced by the 'bad' microbes – the anaerobic (without-air) ones that are responsible for all the bad odours you get from putrefying substances. This is bad news for your compost and if you put this material on your plants it can be toxic to them.

So, creating air spaces in the compost is vital.

Use these materials to add air to your compost

• Twigs from hedge clippings

• Prunings

• Wood chippings

• Shreddings

• Dry plant stems

• Straw

These materials all serve to open up denser, wetter materials and allow air through. People often want to keep these things out of their compost because of the subsequent 'nitrogen robbery' that occurs when woody material is incorporated into the soil (see Chapter 6, page 83), but it is absolutely vital to maintain airflow throughout the heap, and the problem of uncomposted woody chunks is a minor concern.


The microorganisms that we want to dominate the compost heap are all aerobic (with-air) organisms that nevertheless also need water to live. If we create a dense, wet, anaerobic (without-air) heap then only anaerobic organisms (predominately anaerobic bacteria) will survive, and create unpleasant smells. If your compost heap smells bad then it isn't really composting, it's fermenting or anaerobically digesting. (However, this anaerobic process can be controlled in a positive way – see the Bokashi system in Chapter 4, page 56).

Use these materials to add water to your compost

• Fresh fruit and vegetable peelings

• Green leaves – fresh weeds and soft hedge prunings

• Grass cuttings

• Tea leaves

• Coffee grounds

It is important to include materials that will add water to your compost, but beware of adding too much wet stuff – with small domestic heaps there is often a surfeit of over-wet material without anything to absorb it or let the air through.

Use these materials to absorb water from your compost

• Envelopes (remove the windows first)

• Sawdust Half-rotted straw – partially rotted materials become more absorbent

• Half-rotted woodchippings

• Autumn leaves

• Packaging – if you scrunch it up you will adding some temporary structure too

• Shredded paper – but make sure you don't put too much in as it doesn't compact and goes into sludge

• Newspapers – a little at a time; in bulk it is probably best to send them for recycling

All the ingredients in the box above will absorb any liquid, but they can also dry out the compost rather than adding air spaces. It helps to scrunch up paper and card, but this will only provide short-term air spaces, since as soon as the paper or cardboard gets wet it loses its structure (this is why newspapers should be added only a little at a time).

On the other hand, adding only dry plant material leads to a heap that can get too dry. If you feel your heap is too dry, water it – and don't forget that urine is not only wet but a fantastic compost activator!


Excerpted from How to Make and Use Compost by Nicky Scott. Copyright © 2010 Nicky Scott. Excerpted by permission of Green Books Ltd.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Meet the Author

Nicky Scott is the coordinator of the Devon Community Composting Network; he helps set up community composting groups and advises schools and businesses on composting kitchen waste. He was involved in the development of the “Ridan” composter, now widely used for composting food waste. He is the author of Composting for All and Composting: An Easy Household Guide.

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