Category Archives: Recycling Food Waste

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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Filed under Hot Composting, How to get the best out of your HOTBIN, Recycling Food Waste

There is more than ONE alternative to sending food waste to Landfill

Ban food waste from Landfill?
Collect and reprocess it via anaerobic digestion (AD) instead? Well yes and no!!

Respect the 3Rs: we should reduce food waste. Accepting there is always going to be some waste to treat…

There have been renewed calls to ban food waste from landfill in the Guardian today .  The report’s co-author Quentin Maxwell-Jackson is reported by the Guardian to state: “Anaerobic digestion technology has so many clear advantages over other waste treatment and energy generation options that it is very surprising it has not taken off in a big way yet in the UK.”

Calls to ban food waste have been made before. The Government’s stated policy is collection and reprocessing food waste via AD.

It is still probably still too early for the policy makers to ban food waste from landfill as the UK does not have the capacity ‘coming on stream’ to reprocess it via alternative means.

Every new AD plant takes time to get planning permission, to build and commission. At out last reckoning, about 3 major were due to come on stream next year and we estimated the UK needed 300 to divert food waste from landfill – it is going to be a huge cost and long path.

AD makes a lot of sense – we need a collection/reprocessing technology that caters for the majority and we know only about 15-20% of the UK population does (or will) home compost and traditional home composting has never been appropriate for all food waste.

We should not let the historic issues of home composting all food waste (including cooked food, meat, fish, bread, cakes, rice, pasta etc) that create a stinky odour that deters people and attracts rats, flies from continually reviewing technology for home composting. The HOTBIN team has real factual evidence that the HOTBIN has changed home composting of food waste for the better. Users have changed behaviour and are diverting all food waste from landfill. We estimate 5m current home composting households could divert all food waste and make a contribution – immediately.

100,000 HOTBIN users would equate to 1 new big AD plant.  Delivering a million units a year (we wish!) is a logistics co-ordination issue – the capacity can be made available very quickly.  We understand home composting is not for everyone – but we need to make a dent in landfill now and it can be done now.

There are other reasons why AD is not the ‘be all and end’ of reprocessing food waste. Reprocessing is a complex combination of user behaviour, logistics and technical facts. Yes AD has advantages, but so does home composting. Home composting removes the need for collection and transport, the compost can be used in the garden (reducing fertiliser and peat consumption) and adding organic matter and humus back to into soil is essential to soil fertility.

Help us win government support – HOTBIN composting diverts domestic food waste.
[At present we are pushing water up a hill and knocking on closed doors.]

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Filed under Compost, Hot Composting, In the news, Recycling Food Waste

How to compost ALL food waste

Below we explain how to Compost ALL domestic food waste
(i.e. at home, in a garden, or via backyard composting).

Why do we need this blog?

Surely food waste is just like other waste for composting – we just add it to the compost heap and it breaks down?
What’s the big problem? Well to a degree this is true, food waste is carbon/organic and will compost. The problem is NOT that food waste does not compost, it’s just that more often than not, it creates a putrid stinky mush that attracts rats and flies.

What are the specific issues with food waste composting

Here at HOTBIN Composting we talk to a lot of people who compost – from Master Composters, Council Recycling Officers, expert gardeners to complete novices and we have also read hundreds of composting forums and blogs: the advice is near universal:  ‘do not add meat, fish, cooked food waste, mouldy bread, left over bones, cakes, bits pizza, chip boxes, dairy products, gone off fruit, out of date fridge contents to your compost heap. If you do, they will rot, produce putrid odour which in turn will attract vermin and flies. Only add kitchen peelings and tea bags,coffee grinds’.

Kitchen peelings,tea bags, coffee grinds only account for 40% of domestic food waste.
The other 60% falls into the “do not” add to a compost heap.

[We know this because very detailed waste analysis of what goes in our disposal bins and onto municipal refuse collection and landfill was undertaken by the Love Food Hate Waste campaign in 2011 (recycle Now, WRAP) . Teams of people sifted and weighed the contents of 1000’s of household waste bins over many months (nice job!). So we know on average, a UK household produces 250Kg/year of food waste.  Every item wasted was listed and weighed (what they call a composition analysis), so it is easy to look at the list and reclassify per the compost “in/out” list.]

So even those with a compost bin, will most likely still be sending food waste to landfill.
They might still have stinky food waste sitting in a kitchen or wheelie bin for two weeks. (We accept there is a growing number of councils rolling out kerbside collection to be used in AD/EfW recovery plants  – but this is a small part of the total).

Millions of home composters want to add ALL food waste to their compost bins.
This is what why the HOTBIN was invented: ‘to create a compost bin and method that enables millions of existing home composters to compost ALL food waste without the inherent problems of odour, vermin and flies’

Why does food waste rot and go putrid

As food waste starts to breakdown it forms a thick slimy mush. This soft mush prevents airflow and so the waste quickly turns anaerobic. As soon as anaerobic bacteria take over, the waste releases putrid gut wrenching odours. From here it is all downhill – the smell attracts vermin and flies and everything becomes unpleasant. As food is composted, the structure/fibre of the food weakens and water is released. There are three places the water can go – it can drain to the ground, it can be driven off as steam (water vapour) or it can remain in the waste. Under most composting conditions the water stays in the waste until it becomes saturated and then it will start to drain into the ground. Composting soft food waste naturally produces a mushy slime.

The alternative is to use heat produced by the bacteria to drive of water as steam vapour. This happens when we hot compost.

The golden rules for successfully composting ALL food waste are:

  1. Remove excess water
  2. Keep the waste aerated

What is composting?

The biggest part of the composting process relies on bacteria and if you refer to our  post So What is Composting?  you will note their requirements are not dissimilar to what humans need to survive and grow!

So how do we get rid of excess water and keep the waste aerated?

We take a lead from industrial composting and apply the science and engineering they use to a domestic compost bin.

(If you want to look up the science and engineering, have a read through Haug – Practical Handbook of Compost Engineering)  on Amazon book review.

Let’s cut to the chase

  • To remove excess water
    You need lots of heat i.e. you need to be ‘HOT composting’
  • To aerate you need to keep adding lots of oxygen/air 
    Unless you have the means to force airflow (e.g. a pump / blower), or you can constantly turn/tumble (yes we mean constantly), then you are reliant on “buoyant airflow’ or the chimney principle of hot air rising creating a pressure drop that pulls cold air through from below. You only get buoyant airflow if there is a temperature gradient – i.e. you need heat.
  • To maintain buoyant airflow (even with heat)
    You need to a heap structure that maintains buoyant airflow. To get a structure that stops food waste collapsing into a mush you need to add what we refer to as a bulking agent (typically this is wood chip).

In summary to compost food waste, you need to get the waste hot, aerate it (via buoyancy airflow) and ensure it stays aerated by adding a bulking agent. It sounds technical and it would be easy to achieve where it not for nature’s laws on heat production and heat loss!

Nature has a law on how much heat is produced

Bacteria release heat as a by-product when they ‘eat’ the waste– just like humans release heat when we eat and exercise.  The amount of heat is capped by the calorific value – the more calories the more energy and potential heat. The rate of heat released varies by food type.

Think of it like this human analogy – eat  coke and sweets (sugar!) for breakfast and you’ll be on a sugar high for a few hours, then hungry again. East oats/muesli and it will be digested more slowly but over a longer period – you’ll make it to lunchtime.

Bacteria are the same – they digest and release heat from sugars and carbohydrate food very fast, from cellulose (plant material) slower, and from lignin (wood) even slower. The amount and rate of heat generated is determined by what goes in and how much goes in. For most households – it is a challenge to create a hot compost heap, you need about X10 more food waste than most households create.

Nature has a law on how much heat is lost

Heat transfers from a hot place to a cold place until they both reach equilibrium, i.e. the same temperature. This law is scientifically defined by Newton’s law of cooling. Let’s simplify it for a compost heap – even in summer (25C), a compost heap will not stay hot (40-60C) for long as the heat rapidly moves to the cool air. If you want to keep your waste hot, you need to reduce the rate of heat loss ie you need to insulate it. There are two ways of doing this – by having a large heap so the outer metre of waste acts as insulation or use a specialist insulation material.

Oh, one last thing – odour, vermin and flies

Lets assume we are now hot composting away. All composting creates odour and food odour attracts rats and flies. Unless you want a heap infested with rats and flies then you are going to need to control odour so it does not attract vermin and control access the compost heap just in case. In other words, compost in a container that won’t attract rats or let flies in.

Summary

Successful food waste composting needs heat (for water removal), oxygen (to ensure aerobic bacteria active), which in turn needs a heat gradient, which needs bulking agent to allow airflow. We need to balance the heat produced with the rate of heat loss (insulation, protection from wind) to keep the bacteria warm and composting fast and then protect the whole operation from infestation with rats and flies.

Achieving the above without a specialist bin is very hard.

The HOTBIN was specifically designed to achieve HOT composting to allow ALL Food Waste to be composted. To find out more please visit our extensive FAQ

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Filed under Compost, Hot Composting, Recycling Food Waste