Category Archives: Hot Composting

How and why do I use corrugated cardboard and shredded paper in the HOTBIN?

Recycling Food Waste in the HOTBINDry corrugated cardboard and shredded paper is easy for composting bacteria to digest (see table below).

Because they are also very ‘dry’, i.e. have very low water content (typically less than 5% water), they are the best materials to add to wet food waste to balance things out and ensure there is enough heat to drive off excess water as steam.

By the way this use has nothing to do with aeration and very little to do with balancing carbon/nitrogen ratios!

(Please note – Ignore the advice on many cold composting sites that scrunched up newspaper and or cereal packet cardboard will provide aeration – in the HOTBIN they WILL NOT create aeration pockets – quite the reverse – the paper and card will be soaking wet within hours and form a matted impervious layer to airflow. It is highly likely the newspaper will come out when you empty the bin as a flattened blob of soggy newspaper.

It is essential you mix both the paper and the cardboard into the waste rather than just add it in as a layer on the top. When adding food waste ALWAYS also add bulking agent. The bulking agent will form a supportive structure (think building blocks) around which air can flow.

Why will paper and corrugated paper compost quickly but not newspaper?

It is easy to think all paper products come from wood so they should all decompose at the same rate.
We know that thin high surface area materials will decompose faster – so cardboard is faster than a wood branch piece as the bacteria have more surface area to attack. If we assume and example where surface area is the same and the temperature is the same, the speed at which wood products compost is directly related to the amount of lignin contained – so hard wood decompose slower than soft woods.

We can take this analogy a little further to explain newspaper and white office paper – the comparison is made in the table below.

Comparison table

Speed
(At 60C)

Material Notes

Fast
(days)

White paper (e.g. office, A4 copier, coffee filters) The caustic part of the Kraft paper pulping process removes lignin to leave only cellulose fibres.Shredded it rather than crunch it up. Sprinkle in little and often – thick layers will quickly get wet and form an impervious mush that prevents airflow.

Fast
(days)

Corrugated brown cardboard boxes, egg cartons Although processed, about 5-10% lignin remains.Corrugated cardboard has the advantage of trapped air/air channels. Shredded or tear up – large sheet will block airflow

Medium (weeks)

Newsprint/papers
Cardboard sheets
This is low cost paper – the expensive lignin removal stage is not undertaken – it is small wood fibres. (Compare to white office paper above).Ensure shredded or scrunched up. It will compost far more slowly than food, grass and most other wastesDo not add whole cereal boxes – tear up and spread / mix into waste. Add sparingly – if attempting to dry wet waste, much better to use office paper or corrugated cardboard.

Medium
(weeks)

Gloss printed,
waxy papers
Wax coatings are slow to decay. Higher temperature allows addition in HOTBIN


How do I create lots of chopped up cardboard quickly?

 Everyone tends to have corrugated cardboard boxes, but tearing them up can be tiresome. You can quickly cut into strips using a craft or Stanley knife – but you need to take care and do this correctly to avoid taking your fingers of! A safer way is to see if your office shredder is a ‘multi sheet’ unit. If it is it will shred 8 sheets of paper at a time and you will find it will shred most cardboard boxes. See photo’s below. Please keep in mind if you put too much strain on a low sheet feeder it will just overheat and conk out!

A useful post on dealing with excess water in the HOTBIN can be found on our online FAQ : Excess Water Post

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Can I add Autumn LEAVES to compost in my HOTBIN

Adding Leaves to the HOTBINLeaves can go in the HOTBIN and they make great humus.

If you have a lot of leaves (>10 litres, a bucket load), you need to tweak the recipe to ensure they HOT compost.

If you only add thick layers of leaves into the HOTBIN, it is unlikely they will rise above 20-30C as the woody nature means they are hard for bacteria to digest and hence heat is released slowly.

To HOT compost autumn leaves, see the recipe below:

How to HOT Compost Autumn Leaves

There are two parts to successful composting of autumn leaves.

1) Adding a nitrogen source to balance the high carbon in leaves

2) Ensuring that there is enough ‘easy to digest’ waste (e.g. greens, food waste, shredded office paper’ (which creates heat quickly) to keep things hot whilst the hard to digest woody material (in which heat is released slowly) are also digested. In some cases solving (1) & usually solves (2).

Here’s what you need to do to ensure you get the best out of your HOTBIN

Step 1: Shred leaves

Leaves tend to form a dense matted layer that restricts air and oxygen flow within the HOTBIN. We advise shredding the leaves (e.g. using mower or a hedge trimmer).

Step 2: Mix leaves with easier to digest materials like food waste

Many people simply will not have enough food waste to mix with high volume autumn leaf fall. You can cheat a little by adding another easy to digest waste to go with the leaves such as chicken poo, chicken pellets, or a sprinkling of blood bone meal.

The ideal waste to mix with autumn leaves is grass lawn mowing – unfortunately, it is rare in UK to be able to get the mower out in Autumn as it is too wet and compacts the lawn soil. If you have room storing leaves in a wire frame box ready for spring and first grass cut can work really well . (Avoid sealing in black bags – the leaves will go anaerobic (see below for anaerobic method).

Step 3 – Do not add too many each time – little and often is best

More than 10cm (20 litres) of cold wet leaves in one go will “stall” the HOTBIN. The cold leaves will lower the temperature of the HOTBIN below 20°C and the heat production falls below that needed to re-heat. So store the leaves in a pop up bag, protected from rain and add over a couple of weeks – you’ll be amazed how fast they compost.

If you have a large garden with lots of trees and mounds of leaves then possibly doing a little bit each week in the HOTBIN is impractical. Try the following – shred the leaves (e.g. using lawn mower), store in a wire frame or cold compost heap until spring. Mix with first grass cuttings in large volume piles. Turn occasionally.

Leaf Mould Versus Composting

If you are collecting leaves into a wire frame then you might go down the route of just leaving them in the box and waiting 1-2 years for leaf mould.

Leaf mould versus ‘bagging’ i.e. anaerobic digestion

Many compost sites note that ‘bagging’ leaves in black plastic and tying off will create a black slime that can be used as compost. What this really means is you are anaerobically digesting the leaves down to compost. To an extent this is ok, our point would be AD creates methane and you are releasing a GHG that is 24 times more harmful than CO2. And we hope you would agree that every little bit avoided helps.

Aerobic composing is carbon neutral. Also to be honest – the black bags absolutely stink when you open then!

You can now successfully compost large amounts of Autumn leaves in your HOTBIN.

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This AUTUMN could be the time to RETHINK composting?

RETHINK composting this AUTUMNAutumn is coming – It’s will soon be time to start that big garden clear up again! Should you start to RETHINK your composting method now too?

You may well have wheel barrow loads of plant and weed being removed over the next few weeks.

What are you going to do with all your autumn garden waste?

1) Pile it all up as normal in that big heap – come back in spring hopeful of compost but most likely disappointed that you face the prospect of waiting another 12 months for your compost?

2) Take a different approach – join the HOTBIN composters and be sure of a fabulous batch of compost ready to dig in with you spring planting preparation?

3) Leave it out for the council green waste team to sort out – Oh dear! All that fuel, cost and effort to centrally reprocess it. Taking all that goodness from your soil this year, which means next year it has to be replaced by buying even more fertiliser, that takes even more energy and resources to make?

Composting during the cold autumn, winter and early spring months can  usually be a very slow process. Especially when the temperature falls below 5C, the rate the bacteria work is almost nonexistent. The secret to fast composting is heat – and lots of it. Compost forms 64 times faster at 60C than it does at 10C. If you can keep your waste hot (between 40-60C), it will compost in 20 to 90 days!

There are many help sites that recommend building huge piles (minimum 1X1X1 m3), and then turning them regularly to keep them aerated and hot. But even this technique will struggle in winter as the heat produced by the bacteria is quickly lost to the cold air. (And it requires quite a bit of effort and space too)

This is why so many HOTBIN composters are happy – all the hard work to help support natural high temperature composting is provided by the HOTBIN. As long as you keep feeding it every week with enough waste – it will keep running at 60C. It has been tested and proven even with outdoor temperatures as low as -15C.

Not only can you get rid of all that garden waste, you will also be able to compost all your food waste over winter too.

Now if you were an early HOTBIN starter, your HOTBIN might be full already! If the bottom layer has been in there for 90 days, now is a good time to empty it to make room for your  Autumn garden clear up.

It is always best to shred as much as you can (the smaller the pieces, the larger the surface area, the easier it is for the bacteria). Now if you don’t own a shredder  then you can always use your lawn mower!.

Now you are ready to fill up HOTBIN to the top and get it back up to 60C .

If you have a large garden you may still have too much waste . So the best thing is to store it in pop up bag or on another heap. Remember to keep it covered to protect  it from the rain. Where possible we suggest you store bags on stones/gravel so water drains out and some air can get in through the holes in the bottom.

You can add the excess waste every 4 days (about 20 litres 10 cms depth). As the ‘waste pile’ gets colder and older, reduce how much you add each week – But keep adding your food waste! (The bacteria need some easy to digest waste to keep the temperatures at HOT composting levels between 40-60C).

Keep going until all autumn waste is gone.

As soon as you start to collect a lot of autumn leaves – check out the ‘composting autumn leaves post’ as you need to tweak the recipe to hot compost leaves.

Remember the key to keeping it HOT is a BALANCE of ‘easy to digest waste’ made up of green stuff, food waste, plus shredded office paper’ (which creates heat quickly) with the hard to digest woody cuttings (heat released slowly), or partially composted waste (energy depleted).

Why not take up the challenge – find out what others have experience by visiting our product reviews at www.hotbincomposting.com. Explore more about how it works by looking at our extensive ‘how to compost’ database, for example our ‘principles of hot composting’ article.

The HOTBIN is a simple design that helps maximise what nature does by bringing together the right conditions to make HOT composting easier. It does this by providing effective aeration between the bottom air inlet plate and the air outlet rotating valve, removing excess water through the valve as steam and allowing you to control the rate of heat loss.

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