Welcome to the GardenWild guide on composting. As gardeners in North Yorkshire with over 50 years experience, we know that it takes more than soil and water to grow your garden. You have to have the right elements to unlock your gardens true potential and we’re going to show you how!

Hopefully, during this guide, we will be able to answer all of your questions from ‘What is ericaceous compost?’ to ‘Why should I use peat-free compost?’ and everything in between. However if you have any questions you’d like us to answer, or you can think of anything you think we should be writing about: please get in touch!

What is compost? 

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First things first, what actually is compost? In short, compost is organic matter that has rotted down or ‘decomposed’. When we say organic matter we mean anything from dead leaves to food scraps. This waste material, once made in to compost, contains nutrients essential for plants and soil organisms to live. It not only improves soil fertility but also the structure, aeration, pH balance and water content of your soil. This in turn leads to improvements in plant health and increased yields of crops in our flower gardens and vegetable gardens. As you can tell from just this small paragraph, compost is really important for the health of your garden! And this is only the start!

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So, I know everyone is talking about climate change and how we should be planting trees. And yes, I am all about planting trees - but I think a big problem of our time that often gets overlooked is the problem of food waste.

Anyone as old, or older than me (not telling btw) will remember scraping their left over school dinners in to the ‘Pig Bin’ and watching the swill man come to collect the waste to be treated and turned in to feed for pigs. This system of food recycling was normal and actually makes a lot of sense. The food we didn't eat was fed to animals which in turn were fed back to us. Simple, low waste solution.

The BSE scare in the 1990s followed by the Foot and Mouth outbreak in 2001, blamed on the use of swill for animal feed, lead to a blanket ban across Europe on the use of catering waste in animal feed, with severe penalties for farmers who broke the rules.

“And rightly so! “ I hear you cry - but the reality is, the outcome has been a detrimental knock on effect on the natural environment.

The banning of recycling food waste as animal feed has left a protein gap in the nutritional cycle of livestock, which is now being filled by cheap soy based animal feeds, often grown at the expense of valuable wildlife habitats and carbon sinks. Swathes of rainforest are being cut down to clear land for monocultures of soy, an estimated 90 - 97% of which is used for feeding livestock animals, often miles away.

But what has this got to do with me? Well in a sense not much. But I encourage you to think hard about the actual cost of the food you throw in the bin everyday. Is it an orangutans home? Is the pollution of an Amazonian villages water supply? Is it the carbon footprint of the animal feed shipped around the world? Is it your local farmers pension pot? Everything comes with a hidden price. And the small decisions we make everyday compound in to huge effects on a global scale.

And what has this got to do with gardening? Well - at GardenWild be believe sustainable gardening is one small step for gardeners, one giant leap for mankind! And we want to tell you - YOU can help.

Now I'm not suggesting you buy a pig and feed it your kitchen scraps. Nor that you feed your kids the mouldy cheese from the back of the fridge. No! Of course not! But you can COMPOST!

scary stats!

WRAP estimates that in the UK alone we waste 6.5 million tonnes of food a year and 4.5 million tonnes of that is food that's fit for human consumption. That's enough to fill the Royal Albert Hall 90 times! That’s some terrifying maths.

Some more frightening statistics : - if food waste worldwide was a country it would come in third behind China and America for its greenhouse gas emissions. The land required to grow that 4.5 million tonnes is estimated to be the size of China and uses a staggering 25% of global freshwater supplies. That's land we could be planting trees on. And I like trees!

It is important to add that composting should only be done after you have made all other efforts to reduce your food waste.

You can make, design, create, build or buy a composting system for your home so you can recycle all your kitchen waste and give it back to the planet. By putting it on your garden border you are making your little bit of the planet healthier, happier and more sustainable. Check out our articles on soil and improving your soil for more information on how this works! (Coming soon!)

How does compost work?

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Good organic compost consists of a balance of carbon, for energy, and nitrogen for tissue building or growth. The microorganisms in the decomposing organic matter require the correct ratio of carbon to nitrogen for optimal rates of decomposition to occur. There is always more carbon than nitrogen but a ratio of 25-30 parts carbon to 1 part nitrogen is considered a good balance. Too much carbon and decomposition slows down, too much nitrogen and the microorganisms can't use it all and it is lost to the atmosphere as ammonia.

What goes in the compost bin for a good carbon : nitrogen ratio?

The basic rule is Green for Nitrogen and Brown for Carbon. So think 30 Brown things to every 1 Green thing!

Green things…

• Grass clipping

• Fresh Leaves (if you have loads best to make leaf mould)

• Annual weeds ( be careful not to add any seed)

• Vegetable scraps

• Fruit

• Pruning from plants

• Aquatic plants

• Tea and Coffee grounds (not tea bags though, unless they are plastic free)

• Animal manure from omnivores

• Cat and dog poo can be added to worm bins and bokashi bins but not if you are going to use it on your veg patch or where children play

• Flowers

• Hege clippings

Brown things…

• Dry Leaves

• Eggshells

• Sawdust

• Shredded paper and newspaper (not glossy)

• Straw and hay

• Chopped up twigs and branches

• Shredded cardboard (not shiny)

• Anything made with natural fibres ( I have seen someone compost an old futon with great success)

 The organisms making your organic compost

Science alert

There are millions of organisms busy at work making  your organic compost.

The composting process can be explained by the actions of these organisms. Three distinct groups made up of macroorganisms and microorganisms. These are:-

Actinomycetes

Actinomycetes are somewhere in between a bacteria and a fungi. They are the second most abundant organism in your compost, with 100,00 - 100 million per gram of compost. They are often found working around the edges of your compost bin, but they really come in to their own in the final stages of the composting process. They can function in dry acidic conditions and are really useful as they will go to work on difficult to degrade complex molecules such as chitin, cellulose and hemicellulose contained in plant material like avocado skins and glossy leaves which are often the things you'll find still composting when you empty your compost bin. They also produce geosmin, an organic compound which is what makes earth smell, well, earthy!

Fungi

If you are already composting, you have probably noticed a fine white web like substance in your compost. This is the hyphae of fungi that break down the cellulose and lignin found in plant material. Fungi also form threadlike filaments known as hyphae, which spread through the compost heap or bin. Fungi play an essential role, as they are able to breakdown the more resistant organic material e.g. cellulose and lignin found in bark and stems. Fungal hyphae also aid the aeration and drainage of the compost pile by physically aggregating into small particles and opening pore spaces in the compost to allow air and water to circulate. A gram of compost contains around 10,000 -1,000,000, fungal cells. Different fungi function at different temperatures in your compost but most will not survive in your hotbin. Only thermophilic heat tolerant species of fungi can survive in these temperatures.

 Bacteria

PSYCHROPHILES

These aerobic bacteria are active at lower temperatures of between 12 C right down to - 17 C. They are very slow acting however but be reassured by these guys, your compost will probably still be active even in the winter.

THERMOPHILES

Other factors to consider when making your organic compost are:-

Temperature  

The organisms involved in the composting process have optimum temperatures at which they metabolise. The more they metabolise, the more they eat and the more compost they produce. Most microorganisms involved in composting require temperatures between 10℃- 35.6℃ to be most active. Soil microbial activities decrease with low soil temperatures and at freezing point, everything stops. The composting process itself generate a lot of heat. I have found composts heat smoking in the middle when I have turned them and it is actually possible for them to set on fire if they get too dry and are not aerated sufficiently. The type of microbes active in the compost are different at different temperatures. At temperatures between 10 and 45°c ‘mesophilic’ bacteria are active. When the compost gets up to temperatures of 45– 70°c ‘thermophilic’ bacteria are more active. 

The decomposing macroorganisms have an increased rate of metabolism at a soil temperature range of 10℃-24℃. At temperatures below freezing soil macro-organisms die. Its likely that your composting system will be generating enough heat to stop it freezing completely but it means it is not going to be working as efficiently in the winter if you are in a cold climate like we are here in Yorkshire. If you have a worm bin you are going to need to take it indoors or wrap it in an insulating material if you want your worms to survive the winter.

Composting organisms are affected by moisture levels in two ways. Water is essential for organisms to metabolise and be active in the compost. Water holds essential nutrients in solution for organisms to use. Also, as a good conductor of heat, water helps to retain optimum composting temperatures. The movement of water through the compost improves aeration by allowing the movement of microorganisms through it. However, under really wet conditions oxygen levels may become depleted and become unavailable to organisms, leading to anaerobic conditions, and quite frankly a stinky, smelly pile of goo. (Think cow pats.) Best thing to do is have a removable cover if your are using the open wooden compost bin system, so you can keep rainwater out if needed. You can also consider watering your compost if it gets too dry. 

pH

Composting organisms can function within a limited range of pH. The macro organisms are more sensitive to pH the microorganisms, for example earthworms don't like very acidic low pH conditions. At extremes of pH, essential nutrients become unavailable to composting organisms and they cease to function.

When decomposition occurs in the presence of oxygen the process is called aerobic. Oxygen levels of at least 5% are required for microbes to decompose organic wastes efficiently. This is called aerobic composting. The more oxygen there is present, up to at least 10-12%, the more quickly the composting will take place.

It is possible to compost in the absence of oxygen. This is called anaerobic composting. The anaerobic process is slow, and smelly, but recent trends for anaerobic digesters and bokashi bins have made anaerobic composting quite popular in recent years.

Plan your composting system

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We talked to Yorkshire garden designer Robert Hardy and asked him what factors he considers when designing composting systems for his clients. He told us,

“People often don’t think about how big their compost area needs to be, or how they will access it.”

Robert is right. Working at GardenWild we often come across poorly located compost heaps that just aren't big enough to take the amount of compost produced by the garden. 

So how big?

The first thing you need to decide is how big you will need your pile to be. Consider the size of your garden. A compost heap needs to be at least 1m squared and 1m high and should be enclosed by timber or brick. You may only have room for one pile but if you have room its always better to have a 3 bay system for cold composting.

Typical sizes for a 3 bay system range from:

W80cm x D80cm x H75cm to W140cm x D140cm x H125cm.

You can have as many bays as you like but ideally you will be turning your heap from one bay to the next and have the contents of the 3 bays at different stages of decomposition. One filling, one composting and one composted and ready to use. A removable cover will allow you control how much rainwater enters the heap.

Where shall I put it?

You probably want to make sure your compost heap is well hidden from the house or any seating areas but also you need to ask yourself - do I want to wheel a heavy barrow load of compost uphill to empty it on to the garden? And is there enough room to maneuver my wheelbarrow and be able shovel the compost into it? Are there any steps to navigate? Do I need a separate leaf composting bay? Will I have to cross my pristine lawn with the wheelbarrow repeatedly during wet weather? It's tempting to tuck your composting system far away at the bottom of the garden but if you have a vegetable patch you might consider locating it nearby to reduce the amount of wheelbarrowing you have to do.

What do you want to compost?

Is it just garden waste or will you be composting food as well. It's fine to chuck your vegetable scraps on the cold compost heap but if you want to compost everything that comes out of your kitchen, you'll need a hot composting system or aerobic composter. Similarly If you want to compost perennial weeds you might decide to add a Bokashi bin, drying rack or weed drowning bin to your system. If you have a lot of trees you might decide to add a leaf composting bay. Leaf mould is one of the best composts you can make.

How physically able are you?

Now I am definitely speaking from experience here! Turning and emptying a compost heap or bay is no picnic! It's hard, heavy work. Be honest with yourself and decide if you are going to be able to manage a large composting system. Or if you can food to have someone do it for you. If not you might decide to look at a small compost bin, hot bin or bokashi bin. Also there are lots of tools out there to help you manage your composting system. Check our articles to see what we recommend.

What is your budget?

If you are on a tight budget and you are quite practical, you might decide to make your own compost bay. For those of you with a bit more to spend and not too much space look at a small compost bin or a plastic compost bin or hotbin. A hotbin will get you a fast turnaround on your compost without taking up too much space. If you have a large garden with lots of space and lots of waste I would recommend a large 3 bay wooden compost bin system. Check out our article on Compost Bins For Sale 2020 for more information. (Coming soon)

Check out our articles on the different composting methods to help you make your decision.