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Tag: Hot composting

Which composter is best for me?

An image of a green johanna
Posted on by Julie Halford

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

Posted on by Julie Halford

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

Posted on by Julie Halford

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

Posted on by Julie Halford

  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.

What is hot composting?

Posted on by Julie Halford

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.  

An image of a man mixing composter in a green johanna with the 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 even hotter temperatures.

When temperatures are between 20-40 degrees Celsius, this is called the mesophilic phase; from 40-70 degrees Celsius is the thermophilic stage when fast, hot composting takes place.  If temperatures go above 72 degrees Celsius this is too hot for the aerobic micro-organisms to survive. This will cause the process to slow down or stall.

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.

How Bokashi boosts your hot compost

Posted on by Julie Halford

When it comes to boosting the composting process, we have found a Bokashi bin to be the perfect partner for the Green Johanna.

We recently carried out trials involving additions of fermented food waste from a Maze Bokashi bin to a Green Johanna and found that temperatures in the Johanna rapidly increased as a result.  

For our trials, we re-started a Johanna more or less from scratch, having previously removed large amounts of compost.  Using a permanently installed insulation jacket and large amounts of Bokashi bran and carbon-rich materials, compost temperatures were around 30 degrees Celsius. 

 We added the contents of a Bokashi bin that had been fermenting for 21 days, followed by a full 1kg bag of Bokashi bran.   We then added some mulch and stirred well with a garden fork, before completing the process with a thin layer of mulch. 

 The Johanna was then left for 48 hours.  Temperatures rose to 66 degrees Celsius whilst outdoor temperatures were in the 0-10 degree range.   After 48 hours we re-stirred to spread heat more widely through the Johanna.    Using two Bokashi bins in rotation we repeated this cycle roughly every three weeks and got the same results.

We used the Green Johanna in combination with a regular kitchen caddy (as the Johanna needs regular feeding to maintain the hot composting process), twin-bin Bokashi system, Insulating Jacket, Bokashi Bran as an accelerant and plenty of mulch.

Photos show starting temperature at 30 degrees Celsius/adding fermented waste from a Bokashi bin/ adding Bokashi bran/temperature at 66 degrees Celsius.

The Bokashi process was developed in Japan in the 1980s; the term means ‘fermented organic matter’ in Japanese.  It involves adding all your food waste, cooked and uncooked, to a specially designed airtight Bokashi bin, with the addition of Bokashi in the form of a fermented bran or spray. The food waste is compressed with a compactor to eliminate as much air as possible as this is an anaerobic process.  Once the bin is full, you close the airtight lid and leave for 2-3 weeks.  Many people use two or three bins to keep the process going.

The bacteria (lactobacilli) in the bran or spray will create lactic acid which will effectively pickle the food waste rather than letting it decompose as it would in a regular food waste caddy.  After a week or so, liquid should start to form in the Bokashi bin which should be drained using the tap.   This ‘Bokashi tea’ can be used as a drain cleaner or diluted for use as plant food.

 At the end of the fermentation period the waste food is a pre-compost mixture that can be added to a composter or buried in soil to become a soil enhancer. Its composition is such that virtually all its original nutrients, carbon and energy enter rapidly into the soil.   No greenhouse gases are released to the atmosphere as they are during regular food waste decomposition in landfill.

Bokashi composting has traditionally proven particularly popular in urban environments where traditional garden composting is difficult. 

Mark

How to get the most from your Green Johanna

Posted on by Julie Halford

When choosing a spot for your Green Johanna, look for somewhere that provides a flat surface with free drainage for any liquid produced. Make sure it’s also not too far from the house and easy to get to.

If you’re new to composting, a bit of basic knowledge will help you on your way but you will also learn as you go by paying attention to what’s going on in your bin.

Successful composting depends on three essential ingredients: materials, air, moisture.

Composting basics

 MATERIALS – The microbes in your compost bin need a diet that provides a balance between waste materials that are rich in nitrogen and carbon. In composting terms, nitrogen-rich materials are often referred to as Greens and carbon-rich materials as Browns.

Nitrogen-rich materials (Greens) include:

  • Food waste, fresh grass and leaves, plants, flowers, tea leaves, home compostable tea bags, coffee grounds. These items break down quickly and contain moisture so they keep the bin’s contents moist.

Carbon-rich materials (Browns) include:

  • Twigs, branches, dead leaves, paper, cardboard, straw, wood chips, sawdust. These contents are drier and slower to break down.

 A mixture that contains a 50:50 balance of nitrogen (Greens) to carbon (Browns) is a good place to start for composting. You may find that you have a lot more nitrogen-rich inputs (food waste) than carbon so it can be handy to store carbon-rich items such as paper, cardboard and autumn leaves so you have them ready to add with food waste.

 The smaller the waste items are chopped or shredded, the greater the surface area for microbes to work on and the faster the pile will heat up. Items that are added whole, such as apples or carrots etc, will take longer to break down. Egg shells should be crushed or ground. Garden waste should be chopped into pieces no larger than 5cms or shredded.

Getting the nitrogen/carbon ratio right can be a case of trial and error but you will learn quickly through paying attention to conditions in the bin. 

As the micro-organisms break down the waste, they generate heat. As the temperature in the compost fluctuates, the types of micro-organisms present also change.

AIR – The fastest form of composting is done by organisms that need oxygen.  To give microbes air to breathe we need to add air to the mixture by aerating the contents to make sure there’s oxygen throughout the bin.

You can create air pockets by adding the cardboard tubes from toilet or kitchen rolls whole and keeping cardboard egg boxes whole. Waste paper can be added scrunched up so that it provides pockets of air, or shredded. Cardboard should be torn up. Wood chips are useful as they hold structure and create pathways for air.

WATER – You want your compost pile to be moist, rather than wet or dry. The consistency of the bin’s contents should be damp like a wrung-out sponge.  Microbes struggle if their environment is too wet or too dry. They need water to live, yet too much moisture can limit the amount of oxygen they receive. If compost is too wet, it will start to smell bad. If this happens you need to add shredded paper and cardboard and aerate well so that moisture is absorbed.  

Add water to compost that is becoming dry by gently watering with a small watering can, preferably with rainwater collected in a water butt.

Adding food waste

Food waste can be added directly or in home compostable bags, never plastic. If you tie the bags, once you have added them to the Johanna make sure to break them open using the aerator stick to allow oxygen and microbes to reach the waste.

Add food waste and other Greens first, gently stirring these in with the older waste below.
This helps the micro-organisms working below to become part of the newly added materials.
Then cover with an equal amount of carbon materials (Browns) and gently stir again. If you
prefer you can premix these nitrogen/carbon materials before adding them to the bin. Finishing with a layer of carbon, such as dry dead leaves or shredded paper/cardboard, helps to prevent smells from food waste attracting flies and vermin.

The only food-related materials that are not efficiently digested by the Johanna are those that require a very long time to break down, such as bones, large amounts of cooking oil/fat, the hard shells of nuts and seafood (such as oysters and crabs) and avocado stones.

If bones are added to the Johanna they will not break down and it would be
necessary to remove stripped-down bones from the finished compost, which could present
a danger to dogs. For this reason we do not recommend that bones are added.

You can boost the breakdown process by adding bokashi bran (available separately), fermented waste from a bokashi bin, or a bucketful of mature compost.

The Green Johanna Insulating Jacket (available separately) helps to boost temperatures for hot composting and to maintain composting performance in colder weather for regular composting. It should be removed in hot weather or the internal temperature in the bin could become too hot for the composting creatures to survive (above 70 degrees Celsius).

And finally…

To access your finished compost simply unscrew the hatches at the bottom of the Johanna and remove the compost using the aerator stick or a garden hoe.

If you want to access larger amounts of compost that have been left to mature, you can unscrew and remove the Johanna’s top sections. Return any fresh organic waste to the reassembled composter to continue breaking down.

The Johanna was designed and originally manufactured in Sweden, but is now made for Great Green Systems in Droitwich, Worcestershire.

How the Johanna’s design promotes efficient composting

  • Vents leading in from the base plate allow air to flow upwards into the container.
  • The twist-lock lid regulates the ventilation system, helping you to adjust air circulation and temperature.
  • The container’s round shape ensures there are no cold corners so heat is spread evenly through the compost.
  • The tapered design means that compost sinks towards the centre of the unit and not to its sides, allowing air to circulate and oxygenate the compost.

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