Green Johanna fact sheet

The Green Johanna composter was developed in Sweden to provide a way of composting kitchen (including cooked and processed foods) and garden waste all year round. It looks similar to an ordinary compost bin but is different in a number of ways:

  • it has a specially designed base which makes it rodent proof so you can compost food waste in it (including cooked and processed foods)
  • it has an adjustable ventilation system
  • you can buy an insulating jacket for it which allows the composting ‘season’ to be extended into the colder months
  • it is easier to empty the finished compost

The Green Johanna can seem expensive to initially purchase but as it can compost both food and garden waste, it may be a single solution instead of having to buy two or more systems to deal with your waste.

Getting started

  1. Build the Green Johanna according to the manufacturers instructions. That is, build from the bottom and add, align and screw into place one layer at a time. All you need is a Philips type screwdriver and the process will take approximately 10 minutes.
  2. A Green Johanna should be placed directly onto level soil, preferably in an area of your garden that is partly sunny and partly in the shade.
  3. Good air circulation is important for the efficient operation of a Green Johanna. To aid circulation, place a 20 cm (8 inch) layer of branches and twigs on the base of the Green Johanna. After that you can begin to add your garden and kitchen waste.
  4. As with traditional composting, it is important to get the mix of materials right. Add an equal amount of nitrogen rich ‘Greens’ such as grass cuttings, fruit and vegetable peelings as well as carbon rich ‘Browns’ such as twiggy garden waste, scrunched up paper and card, hay and sawdust. Unlike traditional composting you can also add cooked, processed and raw dairy, meat and fish products too. These are nitrogen rich materials and should be added as ‘Greens’.
  5. The Green Johanna comes with a stirring stick to mix the top layer of materials. You can avoid the need to stir the mixture if you create plenty of air pockets by adding twiggy garden materials and scrunched up paper and card.

Common Questions

Can I place the Green Johanna in direct sunlight?

No, because high temperatures may kill off the beneficial microbes that break down the contents. Place your bin in an area of part sun and part shade.

How much waste can it take?

It is designed for a household with up to five people together with the compostable waste produced from an average garden. However, since this is extremely variable, if you believe you are filling it too quickly it may be worth investing in either a traditional composter for your garden, fruit and uncooked vegetable waste or a second Green Johanna.

Why are there holes in the base?

This allows naturally occurring insects and worms to gain access which will help the composting process. It also lets excess moisture out into the ground.

Where should I locate a Green Johanna?

Aim to have the Green Johanna as close to the kitchen as possible because you are likely to want to add food waste regularly. The composter should stand on soil or grass, so that the worms can get in through the holes in the base. A good place is among trees, which will offer some shade. They will also provide a certain amount of protection from the cold in winter.

Why are the contents in the Green Johanna warm?

When the micro-organisms are actively breaking down waste, energy is released. How warm the compost gets depends on what you have put in together with levels of oxygen and moisture. The micro-organisms work at between 2 and 75 degrees. Different micro-organisms work at different temperatures. The optimum working temperature in the compost bin will be around 45-65 degrees.

Can I put kitchen waste directly in the Green Johanna without the branches and twigs first?

No, you need the branches and twigs to ensure that there is a good flow of air at the base. This is essential for efficient operation of the Green Johanna.

Can I still use the Green Johanna if I only have kitchen waste?

Yes, if you add other sources of carbon rich ‘Browns’ such as scrunched up paper, card or sawdust.

What can I put in my Green Johanna?

From the kitchen: Fruit, vegetables, dairy products, fish, shellfish, meat, bones, coffee grounds with filter, teabags, eggshells, bread, sauce, soup, egg cartons etc. From the garden: Grass, leaves, twigs and branches.

Which materials are classed as nitrogen rich ‘Greens’?

Fruit, vegetables, eggs, fish and meat, bread, sauce, soup, grass cuttings.

Which materials are classed as carbon rich ‘Browns’?

Sawdust, twigs, leaves, paper and card.

What should I do if I put a lot of meat in the compost bin?

Put sawdust or other ‘Browns’ on the top and close (but not entirely) the ventilation for a few days, so the flies can't get in.

The contents of my Green Joanna are slimy and smelly what should I do?

You have probably added too many ‘greens’ such as grass cuttings or fruit and vegetable peelings. Adding too many ‘greens’ will cause the mixture to compact and become anaerobic resulting in a smelly, slimy heap. The addition of fine woody material or scrunched up paper and card will ensure that air pockets are incorporated into the mixture.

Why does my compost smell of ammonia?

If you do not put in enough material that is rich in carbon you will get a surplus of nitrogen. This nitrogen turns into ammonia and gives off an odour. Carbon rich items are listed above.

What should the composter smell like?

There should be little or no smell coming from a working composter.

How do I use the stirring stick?

The stick is made of wood with two metal wings at one end. The wings will fold when you push the stick into the material and unfold when you pull it up again. Oxygenate the compost with the stick every time you throw something in, blend the new material with the old. Do not use the stirring stick deeper than 10-15cm (4-6 inches), because only the top layer should be aerated. Remember though, that stirring is unnecessary if you introduce plenty of air pockets through the addition of twiggy material and scrunched up paper and card.

Can I use my Green Johanna during the wintertime?

In the winter months the composting process slows right down. This is because the organisms responsible for decomposition are too cold to work quickly. However they are still there and will speed up as soon as the warmer weather comes. To help speed the process up you can add animal manure or urine. These are excellent compost accelerators and work far better than anything you can buy from the garden centre. Green Johanna’s can also be insulated by purchasing a special jacket that protects against the cold and the wind. It is guaranteed to work down to minus 25°C. It is recommended that the winter jacket be used when the temperature drops below approximately 5 degrees Celsius. An alternative to purchasing a winter Jacket is to make your own using bubble wrap or carpet.

How is the winter jacket assembled?

Full instructions come with the winter jacket and it is very simple to put together. It is important that you add the winter jacket with the Green Johanna standing on its base. If you do not, you may find it prevents the lid from closing.

Can I leave the winter jacket on during the summer?

No, you should remove it when the temperature will no longer fall below 10 degrees Celsius. If you leave it on, the Green Johanna may overheat and stop working correctly.

Can I put citrus peel in my compost?

Yes you can, but ideally break it up a little first and mix in with other food or compost.

Can I put cat and dog litter in my compost?

No, you should avoid this, as it can contain dangerous pathogens which will not be killed off in the composting process.

What can I do about fruit flies?

You may find fruit flies in your Green Johanna which are about the size of midges. They are present in every bin during the summer months where fruit and vegetables have been added. They do no harm and are part of the composting process but they can become a nuisance when they are present in large numbers. To help keep numbers down it is important that you reduce the opportunities for the flies to access the food waste by doing the following:

  • use a lidded container for storing your kitchen scraps
  • bury food scraps under garden waste in the compost bin
  • peel fruit and vegetables onto newspaper, then wrap the peelings and add to the compost bin
  • sprinkle soil over the surface of the bin (but not too much as this will slow down the composting process)

There are ants in my Green Johanna, what can I do?

Ants in your compost bin can indicate that the mixture of materials is too dry. Open a hatch door at the bottom of the compost bin and check if the material looks dry and/or isn’t composting properly. If so, you will need to add more ‘green’ materials that are high in moisture, such as grass cuttings and fruit/vegetable peelings and leave the lid of the compost bin off next time it rains, or you can add water using a watering can.