Which composter is best for me?

An image of a green johanna

If you’re new to composting it can be difficult to know which bin (or system, if you like to think in systems rather than bins) is best for your home and lifestyle. Our handy guide can help.

Food waste composter/digester

The Green Johanna Food Waste Composter and Green Cone Food Waste Digester are both designed to accept foods that regular garden composters don’t, such as cooked food, meat, fish and dairy, so all your food waste can go in together. Compare them to see which one best suits your needs.

Green Johanna Food Waste Composter

  • Produces compost.
  • Also accepts garden waste.
  • Added waste should be a balance of nitrogen-rich content, commonly called Greens, (food waste/fresh grass cuttings/fresh green leaves) and carbon-rich content, commonly called Browns (chopped branches and twigs/wood chips/dead leaves/shredded paper and cardboard).
  • Comes with aerator stick provided to aerate the contents regularly.
  •  Ideally placed on soil or grass
  • One Johanna accepts the average food waste of a household of five and the garden waste from an average-sized garden.
  • With hot composting techniques, higher temperatures are reached than with regular composting.

Green Cone Food Waste Digester

  • Must be dug into a hole in free-draining soil (not clay or chalk).
  • Accepts all food waste, even bones.
  • Doesn’t accept garden waste or paper waste.
  • Doesn’t produce compost – instead it produces nutritious water which drains from its underground basket and feeds surrounding soil.
  • No turning or stirring required.
  • Uses solar energy so requires a sunny spot.
  • Comes with kitchen caddy provided.

Lack of space?

Worm farms

Worm farms, also called wormeries, are ideal for small-scale composting and for introducing children to the fascinating world of worms, which is an education in itself.

  • Require a sheltered spot.
  • Worms will digest many kinds of foods cut up into small pieces and other kitchen waste such as shredded paper, egg cartons, scrunched up newspaper.
  • A little management is needed to maintain the ideal environment for your worms, so be sure to read the instruction booklet.
  • Produce excellent worm-made compost – vermicompost – for your garden.
  • Learning fascinating facts about these tiny eco-heroes is sure to turn children into composters of the future.

Bokashi Bins

  • Kitchen food waste bins that can sit on a worktop or under a sink and accept all chopped-up food waste.
  • Food waste is fermented, resulting in a pre-compost mixture which can be added to a compost bin or wormery, buried in soil in the garden or in large planters in order to break down into compost.
  • Requires the addition of friendly bacteria in a bran or spray to accelerate fermentation.
  • When full of food waste, the container is left sealed for two to three weeks for fermentation to take place anaerobically (without air).
  • Nutritious liquid is drained from a tap at the bottom of the bin and can be used diluted as plant fertiliser or concentrated as organic drain cleaner.
  • Bokashi comes from the Japanese term for ‘fermented organic matter’.

Choosing a compost bin – by the experts

This advice – in note-form taken from a webinar by master composters from Garden Organic – provides extra help.

Green Johanna – reaches higher temperatures – as an enclosed unit it offers greater rodent protection – the twistable top controls ventilation – the solid perforated base means liquid can drain out and micro-organisms can enter – if adding meat, add small amounts, mixed with lots of greens and browns – aerate the top layer every time you add materials – for speedier composting an insulating jacket is available. An alternative way of taking compost out, rather than accessing through the hatches, is to loosen the screws and lift off one or two sections.  Composting slows down in winter but the Johanna continues well and does better than other composters.

Wormery – small and self-contained – ideal for small amounts of waste – year-round composting – can be indoors – worms eat the bacteria on the organic matter – no spicy foods or citrus, only small amounts of meat – food scraps are placed on the top section, casts fall to the bottom. Use the worm-made compost on pot plants or round trees and shrubs. NOTE: If the liquid that is produced smells bad it has gone anaerobic and should be flushed away.

Also:

  • Wormery compost is a great improver to shop-bought compost; you can buy the cheapest of composts but turn it into black gold with the addition of your vermicompost.
  • Sheds are not a good place to house a wormery due to temperature fluctuations – a garage or indoors is better.
  • If you need your worms to move out of way as you harvest casts, add melon or banana – worms love these and will obligingly wriggle over to them.  
  • Don’t forget that with a wormery you are responsible for living creatures.
An image of a toddler using a worm farm. She looks very happy!

Bokashi bin – ferments waste instead of composting so the contents need to be transferred to a composter after a couple of weeks – this pre-compost  acts as an activator in your compost bin – Bokashi bran is needed – fermented contents of the bin will still be recognisable (some people expect compost) – produces liquid which can be used as a drain cleaner or diluted as fertiliser – good to use two bins to keep the process going – ongoing bran purchase required.

Man emptying food into a bokashi bin

Best ways to raise compost temperature

If your compost bin has cooled down, there are several steps you can take to help raise the temperature by making conditions in the bin ideal for heat-generating micro-organisms.    

  1. Aerate

The aerobic bacteria that get compost hot need oxygen to breathe. Regular aeration – about twice a week – reinvigorates microbial activity.  

 In the immediate aftermath of turning there will be a dip in temperature but ultimately it will result in a higher bin temperature for a longer time. After a couple of days, you should notice things are heating back up. Aerating the contents will prolong the time that the bin stays at these temperatures. As heat-creating bacteria proliferate they use up more oxygen so regular aeration is needed.  

Aeration also helps all the materials to make their way to the heat in the middle and to decompose at an even rate, as well as distributing water and nutrients to all areas.  Without air, the contents will turn anaerobic – the breakdown process will slow down and the contents start to smell unpleasant. 

  The aerator stick that comes with the Green Johanna has retractable blades which release after you have pushed the stick into the compost, helping to stir the materials.

An image of a man mixing composter in a green johanna with the aerator stick

If adding food waste in home compostable bags, use the aerator stick to split the bags open in several places to ensure microbes can easily access the waste. Tearing the bag up means it will also decompose faster.  

Tip – For deeper aeration, a manure fork is lighter and easier to handle than a garden fork.

2. Check moisture

The heat a compost pile generates can lead to dry spots.  Stirring enables you to check how dry the compost is inside. As you aerate you can check moisture levels to ensure the compost isn’t dry, especially if the bin is in a sunny spot.  Bacteria need moisture to move around the compost. But if there’s too much moisture, air will be forced out of the bin. With experience you can tell by looking.

The ideal moisture content is around 50 per cent. You can check by using a moisture meter or by doing the squeeze test – wearing gloves, grab handfuls of the bin’s contents and squeeze. Only one or two drops of liquid should appear. The ideal consistency is like a wrung-out bath sponge.

 If compost is too wet there is less air for the microbes – if this is the case, add carbon materials and aerate. If it’s too dry, add water from a small watering can with a fine rose spray and aerate so moisture is spread through the bin.

The presence of a lot of ants is a sign the compost is too dry; a lot of slugs means it’s too wet.

TIP – If you need to water compost that is dry, use rainwater from a water butt if you can – it’s naturally soft and free from minerals and salts and treatment chemicals. This also saves on using tap water. If compost is only slightly dry, add wet materials such as coffee grounds and fresh grass in small amounts.

3. Chop or shred

Items should ideally be 2 to 5cms.Smaller items provide a larger surface area for more microbes to work on.  The more micro-organisms at work means faster, hotter composting of waste.

TIP: If you have a lot of dead leaves throw them in an empty dustbin or compost bin and whizz them up with a strimmer. Or you can spread them over your lawn and mow, so you shred the leaves as well as grass, giving you a useful mix of nitrogen and carbon.  

4. Provide air pockets

Carbon-rich materials are often called bulking agent. They add structure and substance to the compost; high nitrogen materials can compost very quickly down to very little. They also trap air through the compost, getting oxygen to the aerobic microbes, and absorb excess moisture, which makes them essential to add alongside foods with a high moisture content such as cooked foods and fruit waste.

Cardboard can be torn into strips or squares. Look out for corrugated cardboard in packaging; the holes are great for adding air pockets. Other good sources of air pockets are egg cartons and the tubes from toilet rolls, which can be added whole.    

TIP: Wood chips (from untreated wood) are great for adding airflow, providing food for fungi and absorbing moisture from wet foods.   

5. Store carbon

It’s well worth the effort to prepare plenty of bulking material ahead of time.  If not, you might be tempted to skimp on the carbon that’s needed in the bin if you don’t have it ready to hand. 

 In home composting, food waste is usually plentiful (providing nitrogen) but carbon takes a bit more preparation. Prepare it in advance and keep it near the compost bin in tied bags or lidded containers – an old dustbin, empty composter, or lidded plastic tubs – so it’s ready when needed.

Doing this in autumn when you have lots of garden waste will keep you going through winter. Don’t let it get wet or it will start to break down.

Many people bag up and store dead leaves in autumn so that they’re readily available throughout the year.  Then when you add food waste or grass cuttings to the bin, you can add your carbon at the same time.

Some of our customers get into the habit of having cardboard tearing sessions while watching TV (don’t knock it till you try it!), or they get the kids involved as a family activity, introducing them to the basics of composting.   

Always cover fresh waste with a layer of carbon to prevent smells that could attract pests.

TIP: Cardboard is easier to tear into strips when wet.

6. Add soil

A quick way to add more beneficial microbes is to add a bucketful of soil or mature compost. A single teaspoon of soil can contain up to 100 million bacteria and 400 – 800 feet of fungal threads.

TIP: A layer of soil added to the top of the contents of a full bin that’s going to be left to mature will reduce heat loss and conserve water.

7. Try Bokashi

The fermented contents of a Bokashi bin turn into pre-compost – added to a compost bin this acts as an accelerator and speed up decomposition.

Great Green System carried out trials using the contents of a Maze Bokashi Bin that had been left to ferment for three weeks and were then added to a Green Johanna. Temperatures in the Johanna rapidly increased over a few days from around 36 degrees to 66 degrees Celsius (see photos).

Pre-Bokashi – compost temperature at about 36 degrees Celsius.

The fermented contents of a Bokashi bin are added.

Post-Bokashi – compost temperature is raised to about 66 degrees Celsius.

8. Add DIY accelerators

Nitrogen-rich materials that provide a useful boost to the composting process include chicken manure, bird feathers and grass clippings.

 Fresh grass will quickly heat up the compost and decompose rapidly, providing ample fuel for microbial activity, but too much will clump and turn slimy so it needs to be added in thin layers.   

Other accelerators include nettles or comfrey leaves, fresh or wilted, laid in a thin layer.

9. Ventilation

With a Green Johanna, if the weather is very cold, limit ventilation through the lid’s ventilation system – twist the lid towards the minimum setting to keep heat in the bin.

10. Fit the jacket

Add the Green Johanna’s Insulating Jacket – this provides insulation to retain heat but is easily removed if the compost temperature is getting too high (above 70 degrees Celsius).

The jacket is designed to fit snugly so that cold air can’t circulate round the bin. Follow the instructions so the vents in the base are left exposed and the top jacket sections overlap the one underneath by a few centimetres. This ensures that the vents at the top and bottom of the Johanna are kept free so the ventilation system can work efficiently.

TIP: In autumn and winter ensure the vents at the bottom do not get covered by leaves or snow.

Top 10 tips for composting in schools

Composting is a fantastic opportunity for communities to get together to create a greener environment.

Nowhere is this more valuable than in schools, where children can be taught skills that will last them a lifetime.

Composting enables people to take responsibility for their own waste and deal with it in the most environmentally-friendly way – onsite where it is produced – reducing the energy and cost required to transport it further afield for treatment.

 When people compost they become aware of how much waste they produce; as a result they tend to waste less and recycle more.

What is composting?

Composting is the natural process that occurs when insects, worms and micro-organisms break down organic waste (food scraps, garden waste, paper waste) into a nutritious substance – compost – that can be used to feed soil and plants.

By managing the composting process, we help the micro-organisms to thrive and produce compost faster.    

What are the benefits of composting?

Composting is one of the most worthwhile things you can learn. There are only a few rules, and you only have to learn them once – the laws of nature don’t change. This knowledge will serve you well through life.

Composting:

 * creates free nutrient-rich soil food for your own use

* retains moisture in the soil, so reduces the need for watering

* helps plants to grow stronger and healthier

* cuts the amount of waste sent to landfill or incineration

* reduces your carbon footprint

* has a positive impact on the environment

*  inspires children to become composters of the future

How to make it work

Compost bins are not ordinary bins; some degree of management is needed and there are a few golden rules to follow.

Experience has taught us to give composting communities the following advice:

  • At least one person/member of staff should have overall responsibility and check in on the composter every couple of days to prevent issues developing.
  • Ensure as many people as possible have access to an instruction manual so they get to know the three golden rules: the balance needed between materials; aeration; moisture levels.
  • In a school, composting should ideally be a whole-school project. For example, a lot of carbon-rich materials will be needed and it’s much easier if this can be stored in lidded containers so it’s ready for use. This can prompt fun activities such as cardboard tearing sessions. Children could also bring cardboard from home to get parents involved too.
  • To educate the whole school – staff as well as pupils – put up posters giving basic composting information for everyone who will be adding organic waste to the bin. We have A3 posters available for schools and groups, or children could design their own.  
  • Help everyone to understand that every time a caddy of food waste is added to a compost bin (adding nitrogen-rich materials) this should be followed by an equal amount of carbon-rich materials.
  • Many schools produce a lot of fruit waste, especially in the younger classes, and this needs particular attention as it has a high water content which can create a soggy mess if it’s not balanced with appropriate materials and aerated well.  Sawdust works well as a biofilter to absorb unpleasant smells. Fruit waste and sawdust should be added in thin layers and mixed well.
  • It’s a good idea if someone can keep the composting going during holidays by taking waste from home every couple of days so the bin continues to be fed.
  • Teach children that micro-organisms are living creatures, and the composting process is all about nurturing them.
  • Our blog – Compost School – a guide for absolute beginners – is a useful aid for lesson planning. It’s written simply for children to understand but is also aimed at anyone who may not have composted before.
  • Master composters are people who are passionate about composting and have trained as volunteers to share their composting knowledge. They visit schools and groups to offer advice. Check with Garden Organic – www.gardenorganic.org.uk – to see if there are any in your area.

If all goes well, your composting project can expand to compost even more waste by using several compost bins or a Ridan giant tumbler, which has a cog and gear system that makes the handle easier to turn.

 Get a ‘compost chief’!

Projects involving a lot of people can hit problems if composting methods are not followed by everyone.

Occasionally, Green Johannas have been used in schools as general wastebins for food waste, without the necessary balance with carbon-rich materials, and this has inevitably led to problems. This has usually been the result of there not being a nominated ‘compost chief’ in charge.

Disappointing experiences give the impression that composting doesn’t work, which isn’t the case, so we are keen to help where we can.

What about the Green Cone?  

If you think a Green Cone Food Waste Digester might suit your aims, consider the following points:

  • You need a sunny spot in well-draining soil (not clay or chalk) where you can dig the hole required for the Cone’s underground basket.
  • One Green Cone can accept the food waste of the average family of four – about 1kg per day.
  •  Food waste lands in the underground basket; once the underground basket is full, you should stop adding waste until there is space in the basket for more.
  • Regular additions of accelerator powder are recommended – aim to use one sachet per month. Accelerator powder contains beneficial bacteria which digest the waste and boost the breakdown process.
  • As this is a food waste digester rather than a composter, no compost is produced. Instead, a nutrient-rich liquid seeps from the Cone’s underground basket and feeds surrounding soil.
  • The Green Cone doesn’t accept garden waste or paper waste.

Helpful advice

Some people are put off composting because of a fear of pests, but there are steps you can take to make a compost bin and the surrounding area so unattractive to unwanted visitors that they will go somewhere else instead. Read our blogs about how to deter pests and flies.  

How we can help

We are keen to support community composting projects. We can send you several copies of the instruction manuals for the Green Johanna and Green Cone so they can be shared out, as well as colourful A3-size posters about the Green Johanna.   Contact us at [email protected].

Benefits of the Green Johanna’s jacket

  As the temperature outside plummets so the compost in your bin might cool down, but by maintaining good composting techniques you can keep your compost ‘cooking’ even in the coldest winter periods.

In the case of the Green Johanna, adding the insulating jacket also helps.

The Johanna pictured below in January in Leeds kept its compost warm at 40 degrees Celsius while the ground temperature was at zero.

This particular Johanna received all food waste from a family of four, rising to 10 people over the Christmas period. Carbon sources include stored shredded leaves from several trees in the vicinity, as well as Christmas paper waste such as cardboard packaging, compostable wrapping paper and Christmas cards.

The Great Green Systems team tend to keep the jackets on our Green Johannas for most of the year, not just in winter, as we’re based in the chilly north of England.      

Don’t worry that using the jacket will make the Johanna too hot for worms, as one customer suggested. This is not a problem because worms can easily enter and leave the composter through the small holes in the base plate. At temperatures approaching 30 degrees Celsius they will move where it is cooler, usually the bottom of the bin where the compost is maturing, or they can leave the bin entirely.

 The jacket is made from foamed polyethylene – a lightweight, water-resistant material that is tough but flexible and designed to fit snugly to prevent cold air from circulating round the Johanna. It’s made for Great Green Systems by a specialist foam manufacturer in Northamptonshire.

When fitting the jacket, it’s important to ensure that the bottom section doesn’t cover the vents at the sides of the Johanna’s base as these are necessary for airflow.  

The jacket should be installed with the two upper sections pulled down so they overlap the section underneath by about 5 cm. Doing this means the ventilation holes are left clear.

Green Johanna wearing the Insulating Jacket

 Also check throughout autumn and winter that the vents at the bottom of the Johanna are not blocked by leaves or debris or snow. Air is taken in at ground level so keep this area clear so that air can enter freely.

The jacket can easily be removed if the compost gets too hot (above 70 degrees C) in warm weather. Compost thermometers, which have a stem to reach down into the compost, are a useful aid.    

  • TIP: Give the bin’s contents a boost by adding beneficial bacteria in bokashi bran or a layer of soil or mature compost. You can also add coffee grounds or chicken manure to add a hit of nitrogen to your mix.  

Johanna planner for winter:

  • In freezing weather limit ventilation through the Green Johanna lid’s ventilation system – twist the lid towards the minimum setting.
  • Wood chips are a great addition, creating airflow and adding plenty of fungi to the bin.
  • Keep adding to the bin – ideally about three times a week – to maintain the composting process. The Johanna’s generous 330 litre capacity means the compost mass acts as an insulating factor. 
  • Chop items up. Smaller items provide a larger surface area for more microbes to work on. 
  • Aerate regularly – about twice a week – to ensure the aerobic microbes breaking down the waste get enough air.  Without air, the contents will turn anaerobic and start to smell.   
  • Check moisture levels – by doing the squeeze test; grab handfuls of the bin’s contents and squeeze. One or two drops of liquid should appear. The ideal consistency is like a wrung-out bath sponge.

When I got the kids a wormery

It can be hard buying presents for the children in your life; you don’t want to get it wrong and add to a pile of unused clutter in their household.   

Last Christmas I thought long and hard before getting gifts for my best friend’s grandchildren – Reggie, 6, and Maggie, 2.

I always like to get practical, useful things – I’m not bothered about being popular (‘Oh great, another swimming cap/homework bag from Auntie Julie.’)

But this time I really upped my game.

Eco gifts are gifts that keep on giving. It would be easy to drive children to despair about the climate crisis, but how much better to show them instead what they can do to help? Yes, tackling the climate emergency is a big job, but it’s one that each and every one of us – no matter how young – can play a part in.

And so I gave Reggie and Maggie a wormery.

Why? Because wormeries (also called worm farms) are a great way to introduce children to small-scale composting and the marvellous way that nature deals with waste. Not only does vermicomposting (from the Latin ‘vermis’ for worm) keep organic waste out of landfill, but it also shows how easily worms can turn our food scraps into a highly nutritious food for plants

Yes, there were quizzical looks from the kids as they opened the box – it was clearly not a fort or a unicorn castle – but they were very keen to set up the Maze Worm Farm and probably very relieved that it wasn’t a pack of thermal vests. As it was the coldest time of year, they set the worm farm up in the greenhouse, which provided warmth and shelter for the winter, and waited excitedly for their worms to arrive. (The worms come separately through the post from a supplier of specially selected composting worms.)

The children’s reaction when the worms arrived was a mixture of ‘Eurgh’ (Maggie) and ‘Ooh’ (Reggie).

Reggie was keen to show how brave he was and gently introduced a worm to his sister, who also became brave but was happy just looking. They made a cosy home for the worms, providing a blanket of newspaper to keep them warm and safe in the dark.   

Reggie and Maggie noticed the worms were not very active for a few weeks, probably because of settling in at such a cold time of year, but then they soon started tucking in (the worms, not the kids).

 Like most young children they were expecting fast results, so were surprised to learn it can take two to three months to get worm casts (poo, since you ask). You can’t rush these things…

Maggie and Little Bear waiting for worm casts

But when you do harvest the casts you realise why gardeners call this stuff ‘black gold’. One tablespoon of worm casts provides enough nutrients for a plant to thrive throughout the growing season.

Ten weeks in and Reggie and Maggie were the proud harvesters of some of this black gold.

It was great to see the change in Maggie’s attitude to the worms – she went from being afraid of them to become knowledgeable and confident looking after them.

Harvesting worm casts

Wonderful things about worm farms

  • They make great projects for children as this subject can grow in complexity as the child grows – it can be super simple for pre-schoolers but gradually takes in chemistry, biology, ecology, the food cycle and carbon cycle as well as gardening and growing your own food.  
  • Children will develop respect for these humble but mighty creatures. Through tunnelling, worms aerate and improve the soil, providing nutrients for plants to flourish. Without them the earth would become cold, hard and sterile.
  • Studies have shown that the simple act of introducing worms to degraded soil in poor regions of the world has increased plant yields by 280%.
  • Worms are easy to feed on vegetable and fruit scraps, coffee grounds, tea bags, and crushed eggshells.
  • Convenient to set up indoors or outdoors in a sheltered spot.

Encouraged by how well Reggie and Maggie took to vermicomposting, I decided that when it came to Easter they didn’t need yet another boring Easter egg from Auntie Julie.

Not when there are other fabulous presents to be had, such as membership of the Earthworm Society!

 I like to think they’ll thank me one day.

Julie

Why should I compost?

‘I don’t garden so why should I compost?’ This was what a friend said to me recently.

Where to start to answer this question?

Composting is an obvious activity for gardeners – you make your own top-quality plant food by recycling your organic waste.

 Like my friend, I too am no gardener.  I started growing a few things during the pandemic and finally realised when I saw the transforming effect of plants why gardeners do what they do.   

But the point I tried to make in answering my friend was that it wasn’t for the sake of plants that I started composting but for the sake of the soil itself.

A health soil sign that reads 'Healthy soil is the beating heart of organic growing - full of life and support life'.

 When I learned a few years ago what magical powers compost has in rebuilding the poor, degraded earth of the Earth, I realised that composting was a no-brainer.

The health of our soils is fundamental to life as we know it, but according to the charity Garden Organic, half the planet’s topsoil has been lost in the last 150 years.

And yet there’s something we can all do about it! Home composting might seem a small act on an individual level but multiplied by millions it’s huge.    

Climate crisis ally

For instance, did you know that one of compost’s superpowers is to help soil capture carbon in the atmosphere and pull it down into the ground? Along with oceans and forests, soil is an important carbon storage medium. And yet we’ve been letting the organic ingredients for compost rot in landfill for years, emitting greenhouse gases instead of capturing them. It makes no sense to throw nutrients away as rubbish when we can easily separate them to speed up the natural breakdown process.

 According to WRAP, the waste reduction charity, a home composting bin can divert approximately 150 kg per household per year of organic waste from landfill or treatment centres.

Save our soils

The minimum we can all do is to ensure that soil is not left bare. Bare soil is vulnerable to erosion, weeds and carbon loss.

  • Cover soil with mulch and just leave it. Chuck it on in layers of around 5cms. You can cover borders, around shrubs, trees and bushes. Worms will come up and take the compost back down into the earth where it will improve the soil structure.
  • Compost also helps worms to thrive, and they need all the help they can get, under onslaught as they are from chemical sprays, artificial grass and the paving-over of gardens.    
  • Give your lawn a boost by spreading compost thinly over it. Worms will pull it down into the soil, which will boost soil quality and by extension the grass.

Benefits for us

Michael Kennard (pictured) the founder of the food waste collection service Compost Club, has studied soil biology and is keen to spread the word about how soil is the foundation of our health. If we destroy it, it’s to our detriment.

‘Everything is a reflection of the soil,’ he says. ‘If the plants have that natural cycle going on, they’re really healthy. When we eat those plants, that’s what informs our gut health.’

Other benefits that compost provides include:  

  • preventing erosion
  • improving drainage
  • encouraging worm activity. Studies have shown that the simple act of introducing worms to degraded soil in poor regions of the world has increased plant yields by 280%.
  • preventing flooding. As more and more gardens are paved over there is less and less earth to absorb heavy rainfall. In order to slow down runoff and encourage water infiltration into soil, swap paving for plants and mulch, or ensure paving is permeable. In his book The Science of Gardening, Dr Stu Farrimond says that covering soil with mulches in late autumn protects it from pummelling winter rainfall (each bullet-like drop travels up to 20mph).

Benefits for plants;

Used on plants, compost holds on to important nutrients, improving the plant’s quality while also protecting it from pests and diseases.

 As compost breaks down further, it releases important nutrients into the soil, including the main nutrients that plants need: nitrogen, phosphorous, and potassium. Compost also increases the number and variety of beneficial bacteria and fungi in the soil, which helps plants to grow.

The ability of compost to absorb water is important as it’s able to slowly release water to grass and plants so they need watering less frequently. This is obviously vital in hot weather and droughts. Studies on compost’s water-retaining abilities have shown that for every 1% of organic matter content, soil can hold 16,500 gallons of plant-available water per acre of soil down to one foot deep.

Compost also helps water to get to plant roots more effectively by reducing crust forming on soil, so water can get into the soil more easily, and by helping to disperse water laterally from where it hits the ground, which means it will evaporate less quickly.

But I don’t have time to compost

Composting can be as time-consuming as you want to make it. If you’re pushed for time, go for cold composting.  If you want to invest a bit more time and effort, try hot composting, which means a wider variety of food waste can be added to the bin and compost produced faster.  

Or use bokashi bins, which ferment food waste thanks to the addition of beneficial bacteria in the form of a bran or spray. Once it has been left to ferment for a couple of weeks, this pre-compost mixture can then be added to a composter.

People whose local council operates a food waste collection might think, Well the council composts my food waste, so I don’t have to. But many people take the view that if they are already separating food waste to leave out for the council to collect, they might as well compost this valuable resource themselves at home for the benefit of their own garden or allotment.

 By 2026 all councils throughout the UK will have to comply with regulations requiring them to operate separate food waste collections.  

There are around 15 million gardens in the UK. We call them ‘our’ gardens but of course that portion of the earth isn’t really ours – we’re merely its custodians for a while.

Once you see the difference you can make to that tiny patch of the planet, without much effort, you can’t help but become a compost convert.

Julie

What is hot composting?

Hot composting is a way of composting that uses various techniques to achieve higher temperatures than the traditional method of composting. As a result, you can add a wider variety of food waste and compost will be produced faster.    

A compost bin isn’t absolutely necessary for hot composting – you can hot compost in a large pile – but using a container makes the process more manageable and less messy.

Hot composters are designed to nurture heat-generating micro-organisms and to retain the heat they create as they break down organic waste and multiply.

For hot composting, you need the right ingredients in the correct proportions mixed properly.

What are the advantages?

Hot composting takes more effort than traditional composting but most people find it’s worth it for the benefits, such as:

  • A wider range of foods can be composted that are not usually recommended for composting, such as cooked food and meat.
  • Pests are deterred because food scraps break down faster at higher temperatures.   
  • Pieces of natural clothing, such as wool, cotton and linen, can also be added. These usually take a long time to break down in traditional composting (usually called cold composting).
  • Weeds can be killed at high temperatures.
  • Faster compost is produced in around 4-6 months. Cold composting takes between 6- 18 months.

Materials:

The eco system in a compost bin thrives on a balanced diet of nitrogen and carbon. Nitrogen is needed by the micro-organisms for growth and reproduction, while carbon provides them with energy.  

Nitrogen-rich materials are wetter and faster to break down. Carbon-rich materials are dry and slower to break down. In composting terms nitrogen materials are often referred to as Greens and carbon as Browns.

Nitrogen (Greens)

Food waste

Coffee grounds

Fresh green garden waste, such as grass mowings and green leaves

Wilted flowers

Seaweed/kelp

Tealeaves, tea bags (non-plastic)

Natural fabrics

Manure from herbivore animals

Carbon (Browns)

Dead leaves

Paper

 Cardboard

 Woody garden waste, such as twigs, branches and stalks

Wood chips from untreated wood

Sawdust from untreated wood

Pine needles/ cones

Straw

An image of a very full Green Johanna composter

Balance

Ingredients are added in proportions referred to as the Carbon: Nitrogen ratio (C:N ratio). The ideal C:N ratio is considered to be around 30:1 but it would be difficult to calculate this exactly as every item has a different ratio. Most plant materials are a mixture of both, but more carbon than nitrogen as they get older and tougher.  You don’t have to be too precise with this or worry about it too much.  

A good guide is to simply add equal amounts of carbon to nitrogen (followed by a thin covering layer of carbon to prevent smells), then observe the bin’s contents and make adjustments if your compost lets you know something is wrong.

For example, if your bin starts to smell unpleasant, it’s likely that there’s too much nitrogen and not enough air. If breakdown is very slow, there’s probably too much carbon.

Adding waste

Hot composting can be achieved using different methods; our focus here is on active home composting where householders use one or two bins in an ‘add as you go’ system, adding food waste as it occurs every couple of days, mixed with carbon content.

Aeration

Good airflow is essential for hot composting. The micro-organisms that create heat are aerobic so need oxygen to survive. This is achieved by regularly aerating the bin’s contents, stirring and turning the waste materials with an aerator stick.  

In the immediate aftermath of turning there will be a dip in temperature but ultimately it will result in a higher bin temperature for a longer time.

At the outset, covering the bin’s base with a layer of 15-20cms of twigs will help to create airflow through the contents.

Aerating compost:

  • Helps all materials to make their way to the heat in the middle and to decompose at an even rate. 
  • Prolongs the time that the bin stays at higher temperatures.
  • Helps to distribute water and nutrients to all areas. 

Moisture

Moisture is essential for efficient composting. The contents should be moist but not saturated, with a moisture content of roughly 50 per cent.

The consistency of compost should be damp like a wrung-out sponge.  You can check this by doing a squeeze test – take a few handfuls of compost from different parts of the bin and squeeze – only one or two beads of liquid should be visible.

If compost becomes too wet the water will deplete the amount of oxygen in the bin. Then microbes that thrive in anaerobic conditions will take over, causing slow breakdown and an unpleasant smell. In this case, you should add more carbon content and aerate well.

As micro-organisms become more active, they use up water, causing the compost to dry. In dry compost, microbes will not be active or reproduce.

 If you are regularly adding food waste, there will usually be enough water content in the bin. If you do need to add water, ideally use stored rainwater from a water butt added to a small watering can with a fine rose spray.

Chop or shred

For hot composting, it’s best to chop or shred the materials before adding them. This increases the surface area in contact with microbes in the pile. Smaller pieces – ideally 2 to 5 cm – also make turning the pile much easier.

If you have access to a shredder, you can shred Greens and Browns at the same time, blending materials as you shred. This creates a fine-textured mix that heats up quickly.

Alternatively, you can chop materials using a pair of hedge clippers and a board.

Large pieces will still break down but will take longer. You can get away with larger pieces if you also have other ingredients with a much smaller surface area, such as grass or sawdust.

 If items are too small, they can clump together, reducing the ability of air to circulate through the bin.

What happens?

When there’s enough carbon to fuel these billions of micro-organisms, enough nitrogen and water to help them grow, and enough oxygen to let aerobic bacteria thrive, composting magic happens.  

Heat builds in the bin and heat-loving bacteria multiply, breaking down the materials.

As the temperature increases in the bin, different populations of micro-organisms rise and fall, either going dormant, or becoming fodder for the next wave of bacteria that thrive in hotter temperatures.

The power of observation

Composting depends on a blend of factors: contents, moisture, size of materials, size of bin, the composter’s efforts, climate and soil conditions.  Even neighbouring households will experience different outcomes due to a difference in diet.  

 Ultimately the best guide is your own observations – how your bin looks and smells. With experience you develop a feel for your materials and can tell what’s needed just by looking.

 Most people find the fact that they can influence the quality and speed of their compost a rewarding aspect of hot composting.  

Why a Green Johanna works well for hot composting

  • The Johanna has been designed so that vents take air in at the bottom to send it upwards through the bin. Incoming air goes up past the four ventilation plates on the inside of the base plate, past the maturing compost layer up into the decomposing compost where it provides oxygen for the micro-organisms.
  • Ventilation in the lid helps control airflow depending on conditions. Switch to minimum in cold weather to keep heat in the bin.
  • Use of the Insulating Jacket helps to control temperature.
  • The conical shape encourages compost to fall back into the centre and not stick to the sides.
  • The generous capacity of 330 litres means the mass of materials acts as an insulating factor.

For more information about composting in general we recommend A Gardener’s Guide to Composting Techniques by master composter Rod Weston.

Green Cone still going strong after 25 years

Although a Green Cone is expected to last for at least 10 years, customers often report their Cone has lasted a lot longer than this.

The oldest Cone that we’ve heard of belongs to a lady in Scotland, who got it through her local authority, Argyll and Bute District Council, 25 years ago.

The customer’s daughter contacted us when the Cone’s lid blew off in a storm and Great Green Systems replaced it free of charge.

 She said: ‘The Cone is still going strong, a real asset in a rural area where there is no specific collection of food waste. ‘

Another Cone going strong, and coping with extreme heat, is one that was taken to Spain by its owner, Angela, nearly 20 years ago when she bought an old Spanish farmhouse.   

Angela knew the Cone worked well at home in England so it would be an even greater asset in Spain, with heat, foxes and rodents to contend with. The family took their Cone over to Spain in their car.

‘We love our Cone and it is really, really useful,’ says Angela.  ‘I must say that we have been surprised and delighted that the actual Cone has lasted brilliantly all these years. We wouldn’t want to be without it.’

For several years the family made annual trips to their Spanish house, spending working holidays getting the house and garden ready for their eventual move.

On one visit a big family birthday was celebrated with 10 guests staying for a full week. The Cone’s underground basket (which is where food waste lands) was full after the week, but when the family returned months later they were delighted to find that the basket’s contents had almost completely vanished.

A long reign in Spain – Angela’s Green Cone outside her Spanish farmhouse.

The family relocated to Spain a few years ago and over the years Angela has seen big changes there in attitudes to recycling food waste.

She says: ‘Things have become easier over the past few years as Spain has started to install special organic recycling bins, which have a swing top and drop waste into an underground receptacle that is then cleared very regularly by the council.  

A good ecological cycle

‘So, from nothing less than 20 years ago, we have multiple ways of safe and hygienic organic waste disposal, the most convenient of which is our Cone.

‘To be honest, it is as much of a pleasure to take the bin out to the Cone as it is to go out and pick veggies for supper because it is useful to process things ourselves and know that we are using a good ecological cycle for production and waste.’ 

The couple grow a lot of their own produce and have had to contend with many challenges posed by the climate and mountainous geography. Their Cone has been moved four times, with placement being determined by where there is sufficient depth to site the basket, which needs to be embedded in soil.

‘When there is torrential rain and it floods over the terrace behind our land it can remove soil down to the bedrock, it was quite a shock the first time we saw this and realised just how little soil covering there is in some places,’ Angela says.

‘As a consequence, we have built raised beds for some of our produce and will be looking to make deeper beds for some others as time goes by.’

A 5000-litre tank for rainwater has been an essential investment.

Angela says the Spanish are becoming much more interested in tending gardens.

 ‘People have been quite interested in our approach (raised beds, adding marigolds for insect control and so on). Possibly they will become more interested in composting as well since many areas have banned burning of waste, partly as a fire hazard and partly air pollution, so things are changing gradually.’

How to get the most from your Green Cone

The Green Cone’s basic needs are:

  • A sunny spot
  • Well-draining soil (not clay or chalk)
  • Additions of food waste – no garden or paper waste
  • Accelerator powder to boost digestion
  • Food waste should never come higher than the underground basket into the Cone itself

Where shall I put my Green Cone?

As well as finding a sunny spot, it’s a good idea to think about how easy it will be to get to the Cone in winter months to empty your kitchen caddy.   

More than 90% of the waste added to the Cone will be turned into water, which must be able to drain freely away for the unit to work properly, so the Cone needs to be embedded in soil that has good drainage.

How do I know if I have good drainage?

If you’re not sure whether your soil has good drainage or not, you can check by doing the following: dig the hole required for the Cone (about 70cm wide by 54cm deep) and pour a bucket of water into it. If the water remains for more than 15 minutes you have poor drainage and will need to enlarge the hole to 90cm wide by 70cm deep.

Provide extra drainage by mixing soil from the hole with gravel, stones, or small pieces of broken bricks and pots and placing some of this mix in the base of the hole so that when the assembled Green Cone is added the basket sits 3cm below ground level. Then use the gravel/soil mix to backfill gaps around the Cone until the bottom rim of the green outer cone is fully covered.

How do I look after my Green Cone?

Basic maintenance involves ensuring that the Cone’s green rim always remains below ground level.

In the first few weeks after installation check that soil has not settled and left the green rim exposed. This could also happen after heavy rain. If this is the case, make sure to add additional soil and compact it around the Cone to keep the rim securely underground.

How much waste is too much for the Green Cone?

Remember that food waste should only ever be in the underground basket: never allow waste to build up so that it is above ground level inside the Cone itself.

The Cone is expected to cope with the food waste produced by the average family of four, but this can vary greatly. If you find you regularly have more waste than the Cone can cope with you may need another Cone to cope with all your leftovers.

If you find that in autumn and winter the digestion process has started to slow down and the waste in the basket doesn’t appear to be reducing, simply add a little more accelerator powder.

Why the Green Cone is a bear necessity

The Green Cone was designed by an engineer in Canada to solve the problem of bears pushing over rubbish bins to get to food waste. While bear-proofing may not be on your list of requirements, the Cone is sure to deter local foxes.

If vermin are a problem locally, you can add additional deterrents by hardening the area close to the Cone with bricks or rocks and by positioning the Cone away from fences, woodpiles and bushes.

If pet waste is to be added to the Cone, the unit should not be placed in soil where vegetables are grown or close to any water source. Pet waste should only be added  in small amounts and never in bags.

No bags of any kind should ever be added to the Cone as this will hamper the digestion process.

Why our Green Cone was a very good buy

Before buying their Green Cone in 2009, Jack and Joan Milner, from Leicestershire, thought the prospect of being able to safely dispose of all their leftovers sounded almost too good to be true.

‘We were a bit sceptical at first,’ admits Jack. ‘We had already tried having a compost bin but we were not systematic enough to make it work.’

But at the time Leicestershire County Council was offering residents subsidised Cones to encourage them to recycle food waste at home instead of sending it to landfill. So the couple decided to give it a try.

A place in the sun

Under the scheme at the time, the council arranged for Green Cones to be installed on their residents’ behalf since the units must be dug into a hole in the garden.

 Once this was done, and the Cone was in place in a sunny spot near the kitchen door, the Milners began to feed it their leftovers, including bones.

‘It wasn’t long before the Green Cone was called ‘George’ (don’t ask us why!) and we fed him daily,’ says Jack.

 A pleasant surprise

The couple, now in their eighties, were quickly won over by George’s powers of digestion. ‘We have been very pleasantly surprised.’

Jack and Joan sometimes have to deal with the common problem of visiting dogs and cats leaving a little deposit on their lawn, but ‘George’ has even been efficient at dealing with this.

Most of the waste deposited in the Cone breaks down to become nutritious water that drains from the underground basket into surrounding soil. The Milners have noticed the effect of this soil conditioner on their garden.

A very good buy

Their Cone was placed in an arid spot which sported a few Lily of the Valley flowers and these soon began to flourish, becoming ‘a superb patch two metres in diameter.’

Jack adds that their Cone is now becoming a bit brittle but still ‘completely serviceable’, and it is only now after 13 years that it might need emptying.

‘Overall, George has been a very good buy.’

What’s in a name?

Incidentally, the Milners are not the only customers who have found themselves giving a name to their food waste digester. In our reviews section is a family who named their three Green Johanna Hot Composters Bertha, Belinda and Beryl. Whatever you may wish to call your Cone (and names are not obligatory, we don’t check!) we’re sure life with your own George, or Daisy or Engelburt will be just as good as the Milners’ experience.

Spare Parts