The Edible Garden Show
Hot Composting versus Cold Composting
What a brilliant turn out HOTBIN had in The Potting Shed at the Edible Garden show last weekend. There is definitely an appetite to learn more about the benefits of hot composting over cold composting and how it can contribute to reducing what each household sends to landfill.
If you didn’t get there you can read a PDF transcript of Tony’s presentation by clicking on the graphic below.
It essence he challenged the audience to consider during his talk whether Hot Composting was worthwhile or or just a lot of hot air!
He wanted them to reflect on these 5 key things:
- Time – is hot composting faster all year-round?
- Quantity – do you get any more compost if you hot compost?
- Endeavor – does hot composting take less effort?
- Quality – is the compost from hot composting any better?
- Planet – is hot composting good for the environment?
I think over the 3 presentation sessions that the only question mark remained was on whether it was more or less effort to hot compost! Well only you can decide whether the effort is worth it to achieve all the other benefits.
Our view is this…yes hot composting in a HOTBIN requires some active participation. This includes making sure you keep the bacteria happy with smaller pieces with a larger surface area and making sure you feed it approximately 1 caddy 2 times a week. But really the benefits of composting all food waste, more quickly, all year round to get a good quality compost whilst cutting your contribution to landfill is surely worth it!
You can read the full transcript of Tony’s talk below and let us know what you think.
Thank you to The Edible Garden Show for the opportunity to present and to Potty Innovations for the photography, we had a lovely time!
Remember you can also downlaod teh PDF form teh link above…
Hot Composting – Worth it or just a lot of hot air?
By Tony Callaghan, transcript of the Talk at the Edible Garden show 15-17th March 2013
Good morning, thank you for attending – when you volunteer for do talk, your worst nightmare is just 1 person in the audience, we have a full house and that is great!
My name is Tony Callaghan, I am the Inventor of a product called the HOTBIN. Today’s talk is about Hot Composting – is it worth it or just a lot of hot air.
I’d like to start at the end by asking, how are we going to judge if it is worth while? On the handout sheets you will see I have suggested 5 things we should ask and answer during this session:
- Time – is it faster, all year-round?
- Do we get any more compost?
- Does it take less effort?
- Is the compost any better?
- Is it good for the environment?
Keep these items in mind when we get to the summary!
I started my hot composting journey about 4 years ago. We had been in our new house 2 years, the black dalex cone had been filled with garden clippings and vegetable peeling from the kitchen, I had nailed together pallets to create a second bin and that was also full – it had carrot peelings over flowing from the top. One day the inevitable happened – the old rat popped its head out. I was politely informed to sort out the compost bin or stop composting!
Now all I really wanted was to find a compost bin online that worked and move on. I was looking for a 5-star review on Amazon etc that said this product works and customer really recommend it. I could not find it – I found instead was “it arrived on time / did not arrive on time, it was easy or hard to assemble – 1-5 stars, often with “I’ll let you know if it works in 12 months”. Of course no-one comes back to fill it the rating later. The more I looked the harder it became to find vendors that actually had case studies or evidence that the products worked. I got scared off and decided I would make my own. I had loads of attempts, kept reading website advice, adjusting, adding insulation, turning etc. They all work initially but then failed quite quickly. I soon released that something was amiss. Eventually out of frustration I bought a compost engineering book – 500 pages. Having read it cover to cover (I do have a science background!), I began to understand – some advice was out of context, other bits were just plain ‘myth’.
So let’s look at what hot composting is.
What is hot composting?
Could I ask for a show of hands – how many compost? (approx. 100/120 of audience); how many think they hot compost? (3-6 from 120); how many ever use a thermometer to check? (zero from 120)
In the UK, winter is around zero to 5C, spring 5-15C, summer 15-25C. The average over the year is 10C. Most UK compost heaps run at 10C. If you shower in the morning, that is normally around 35-40C. If you put your hand on a very hot radiator – that is about 60C. So when we say 40-60C is the hot composting range, it is very hot.
Why are we interested?
We will be looking at a number of benefits, but I want to focus on heat and speed first. I do not want to get too scientific, but there is a rule of nature called the Q10 equation. Very simply for every increase in temperature, the speed of reaction doubles. So if we take out UK compost heap as 10C, and say that is speed 1, then 20C = twice as fast, 30C 4 x times, 40C 8 x times, 50C 16 x times and 60C 32 x times faster. So a rough rule of thumb – if a material takes 12 months in a cold (10C) heap, it will take 12 days at 60C. Please do not go away thinking everything will compost in 12 days – it won’t – some things are faster than others.
How DOES it get hot?
People sometimes ask do we add heating rods and electric etc. The answer is no. The heat comes from the bacteria. As they work and reproduce they create heat. Think of it like going for a run – the faster you go, the more heat you make. There are two groups of bacteria we focus on the mesophilic who work up to 40C, and the thermophilic who work from 40-70C. Now the thing about the thermophilic bacteria is that other things do not survive above 40C. So flies get fried, worms make an exodus and come back in later as things cool down.
How do we make a hot compost heap?
We need to keep the bacteria happy. I’m going to look at 5 things. Think of them as linked circles – if they are all working, we get a virtuous circle and everything spirals up and we have success. If one of the links is broken, then we get a vicious circle that spirals down.
And we all know where it leads – the stinking pungent heap that upsets the neighbours, attracts more vermin and flies – and sorting it out is a very unpleasant task.
As I talk through the 5 items, I will try and compare it to other advice, and try to help you with the context.
Number 1 – Retain the heat
So we know heat increases the compost speed and we get compost faster. To hot compost, you also need to retain the heat.
We all know hot moves to cold. If we place a compost heap in the outdoors, the heat will rapidly move to the cooler air. It is a fact of life, a law of science. You cannot prevent heat moving out and the heap cooling – that is why most heaps in the UK run “cold”.
To retain heat we need to insulate and reduce the rate of heat loss. There are two ways of doing this: use compost to create an insulation layer – a very large heap (at least 1XX1m, preferably 2m3) – the outer one metre of waste acts as insulation around the central hot core. This is why when you read books about hot composting they almost always say you need a big heap with lots of material. (They might not know why – but the experience shows it works!). Alternatively we can use a modern insulation material like EPP (expanded polypropylene. 50mm of EPP has the same insulation as 1 m of compost. Think of it like insulting your loft, you can leave it losing heat, add 200mm of fibre glass wool, or add a super 50mm insulation board.
Number 2 – small bits please!
Every time you chop things up you double the surface area. Think of it like this – you can fit one million bacteria on a pin head (apologies during the presentation I think I might have said 500 million!). Now add a whole potato into the heap. The bacteria have to eat through the peel (designed to protect it) and then all the potato. If you chop it they can get to more potato faster. Give the bacteria a break and chop things up.
In the kitchen this really is not that hard. We tend to chop vegetables and even the broccoli stalk does not take much effort to run the knife through. But if you are lucky enough to have a large garden, creating wheel barrows of waste, it takes a bit more effort with secateurs. If you have a hedge trimmer you can use it to chop waste, a rotary mower is good for leaves, and if you do not have a shredder you might be able to share one with a neighbour. Chopping and shredding makes a big difference to all composting.
Number 4 Oxygen / aeration
All the audience has heard about greens and browns and Carbon/Nitrogen ration of 30:1. I do not want to focus on these…they are important but are not high priority. After all we can compost grass (10:1) and compost wood (200:1).
I want to focus on how easy things are to digest. So I would like you to think about your diet! If you had consumed a bottle of coke (other fizzy drinks are available!), then you would be running around for an hour or so on a sugar high. You can digest glucose very easily. Now if you had porridge oats for breakfast, the theory is the more complex carbohydrates are harder to digest and energy is released more slowly – so you have less of a high, but keep going to lunch time. Bacteria are very similar – there are things they can digest easily and things that are hard. Sugars and carbohydrates are easy, cellulose (the main parts of plants) are in the middle – relatively easy and things like wood that contain lignin are very hard for bacteria to digest.
If you want to get your heap hot – you need to add some easy to digest materials! Grass and food waste are both very easy for bacteria to digest.
How many people add newspaper to the compost bin (a fair few) And how many add shredded office paper (less). Has anyone added newspaper (especially balled up) only to find in 6 months it is a small blob of non composted mush? Newspaper is “bits of wood” (hard to digest), but office paper goes through another step and is de-lignified – it is cellulose and much easier for bacteria to digest – Try them both and see who much faster one is…
Number 4 Oxygen / aeration
You all know we need oxygen/air to have aerobic composting. If we have no air we end up with anaerobic conditions, and all the odour issues.
Where do we need the air/oxygen? Well remember our tiny little bacteria trying to eat the waste. They need air on a microscopic level – everywhere in the heap. Getting air to all the heap is a big task. Often you will read the books and they state drill holes in the side for aeration, or that turning is essential. Others will describe complex ducting and airflow tubes. We researched loads of different designs. It turns out the compost engineers really know their subject. Turning does not really help – unless you want to turn it every second of the day! Most turning takes the outer none composted waste in to create a new central hot core of waste. Aeration holes in side of bins do not work – air has a particular way of flowing – it follows the path of least resistance – so through the wall and up and out. Tubes and central aeration is even worse the hot air rises up the pipe and out. After much failed experimentation we started to do what the industrial composters do – we added bits of wood chip. Think of this like building blocks – the bits stack on top of each other, they do not collapse and the air flows up and over. So add cold air in at the base, draw it up, keep it flowing up to all parts using wood chip. Because the structure does not collapse into a slushy mess – you will find you no longer need to turn. We have found no aeration system that gets even close to the success of using “buoyant airflow’ with wood chip.
Number 5 – water – We know as composters that if the waste is dry nothing happen. The bacteria need water to develop. But excess water is also a problem. It blocks all the holes around the food and wood chip and no air can flow. Food waste has a lot of water. So if you see advice to wet your material until wringing like a sponge, that might be ok for a cold heap where the water can drain away, but it is a ‘no-no’ for hot composting. We normally have to add dry materials (like shredded paper) to balance to excess water in food waste.
So the 5 things to keep bacteria happy: 1) Retain heat (insulation); 2) Small bits (shred/chop); 3) Waste mix (some easy to digest); 4) Oxygen to all bits (wood chip – bulking agent); 5) Water (need, but not too much). Get all five right and we have the virtuous circle. If one is wrong then a vicious spiral down.
What about other things
Manage residual odour – all composting produces odour! We want to avoid the putrid horrible anaerobic odours. But aerobic still produces odour – if it is released slowly you probably do not smell them. When you are hot composting and they are released quickly you do. We call it the boiled cabbage odour. It is preferable to filter hot compost odours before they leave the heap. We tend to call this a bio filter – and they are normally made form materials like charcoal and compost.
Protect from vermin and flies – you need to enclose the heap in a protective enclosure that that will prevent odour leaking out. If the odour is released then vermin and flies will be attracted. So you have to enclose the heap, and yet keep the aeration flowing through!
At the start we asked can we add more. Well if it is breaking down faster the bin will compost more. But there is another aspect – hot composting in a bin allows us to compost all food waste. Let me describe what we mean by “all” A couple of years ago, WRAP under the Love food, hate waste’ banner, did a huge study, It was something like 10,000 homes; they collected the black bag (general waste with food in) and took it away. A brave group of workers unloaded, took out, weighed and measured every piece of food waste to create a big long list. They found a huge 7.2 million tonnes of food waste was sent to landfill – about 250 Kgs for every household in the UK. Most of this was unnecessary waste (poor planning on sell by dates etc). Within the list of items we then went through and identified if it was recommend to add to compost heap (cold). About 65% of the items are on the “do not add” list – think about these items – meat, fish, bones, rice, pasta, bread, cakes – a vast amount of the food we waste is on the out list. With a correct hot composting bin, you can compost a whole lot more.
Now let us think about the garden waste. Has anyone dug up all the weeds, composted them used the compost only to find a lovely patch of weeds where the compost has been used? A few of you. Weeds seeds (and a few others seeds) tend not to be broken down in cold composting – so you replant them in natures best growing medium. In hot composting seeds breakdown – se we can add more weeds even difficult stuff like couch grass – as long as we get the high temperatures.
What about grass treated with weed killer herbicides? OK good to see not many using weed killer. If you read a lot of advice it says do not compost grass. People take it down the recycling centre – guess what they compost it! Herbicides break down in composting – faster in hot composting. So if the instructions say 12 months before using compost, you are on the safe side if grass composted at 60C and it has been in for 90 days.
The last item on our list was – is it better for the environment? Well if we have anaerobic digestion we get methane and that is 24 times worse than CO2 for the environment. It is great if we have large scale AD where the plant collects all the methane and uses it for energy, but not if we have anaerobic piles or landfill piles.
If we can compost all food waste we no longer have to collect – so we save on fuel and transport and landfill.
Summary – is it worth it
It is not easy to create via DIY techniques a domestic hot composting system that controls all 5 virtuous items and stays hot with relatively small amount of food waste through winter. If you have lots of garden waste (not food waste) you can create big hot heaps, but it takes a lot of effort to turn it.
Most food waste comes in small amounts each week all through the year. We think you need a specialist hot composting bin to handle this. The HOTBIN was specifically designed to achieve HOT composting to allow ALL Food Waste to be composted.
CATERING FOOD WASTE
Is the HOTBIN an effective recycling solution for businesses producing catering food waste?
As many as 50,000* UK businesses could utilise food waste composting to tackle catering food waste. It can save the company collection and disposal costs and help the environment by reducing the need for landfill. (*50,000 businesses might divert as much as 25,000 tonnes – derived from WRAP campaign on catering food waste statistics).
Over the past 12 months, we have been working with a group of corporate sites to test the HOTBIN in a business environment. Various teams in cafes, B&Bs, hotels, and business / corporate catering facilities have been using the HOTBIN.
The sites testing/using HOTBINs include:
||Hotels, cafe, B&Bs
||Kitchen Garden, Meldon
|Rose Lodge Care Home
||BrockBrushes Farm shop
||down south garden centre
||Plants R Ross
Does the HOTBIN work on catering food waste?
Yes – this was never in doubt, catering food waste is the much the same as domestic food waste.
Can the HOTBIN cope with a catering waste sites volumes?
Yes, however, the amount of food waste varies enormously across the sites – from very small amounts barely enough to keep the HOTBIN hot, to too much and right on the limits of practical use.
Top Tips When Looking at Composting Catering Waste
Capacity: match how much food waste to to number of HOTBINs needed. Few sites know how much food waste they have, so we have developed the following chart.
|Kgs / week
(rotating one per day)
||5Kg (10 litres)(2 small, 1 large kitchen caddy)
||20 Kg (40 litres)
||35 Kg (70 Litres)
||15-20Kg (30-60L)(60 litres is a mid-sized kitchen bin)
||60-80 Kg (240-320 litres)(200 litres is a std wheelie bin, or half a 4-wheel bin)
||100-200 Kg (200-600 litres)(600 litres is large 4 wheel wheelie bin a week
Notes: weights relate to just food waste – adding garden waste will significantly change capacity.
Find a compost aware champion: hot composting needs to be actively managed. No matter how good the equipment, mishaps will occasionally happen. In a business environment, it is important to plan for these by having a member of staff ‘on call’ with the knowledge to sort problems out. Your champion may have to sort out occasional issues (eg odour if the mix was incorrect, flies or maggots if the waste was left accessible to flies and HOTBIN was not running hot).
Avoid excess water: catering food waste is often ‘too wet’ for hot composting. Staff will have limited time to check what is being collected. Behind the scenes you need to:
- Balance the mix by adding shredded office paper and bulking agent.
- Find a storage space for bags of paper and bulking agent
- Plan for occasional leachate – check where you locate the HOTBIN
- Factor in time to chop up waste: a whole cabbage will takes ages to compost –and affect HOTBIN performance. Plan in time ‘to chop’ and be aware of business conflicts – eg staff need to clear and restock shelves versus chopping waste.
Housekeeping: Any waste dropped needs to be picked up. This is vital – your site is likely to be very quite at night and no noise plus food on the ground is a ‘rat magnet’. Store all waste prior to adding to HOTBIN in covered container.
Loading routine: The HOTBIN has a minimum and maximum loading amount and it works best when fed twice a week. Plan the right collection routine and have enough HOTBINs to load based on that rota.
Emptying: empty the compost out every 3 months and take/spread it on the garden. You can load without any special kit – but emptying needs gloves, buckets trowels – it’s not an office dress task!
You may not want to use the compost there and then – in which case a storage area for ‘maturing compost’ is needed – normally a 1m3, ie a palette box is ideal
Is it worthwhile?
The test sites are demonstrating that with planning you can compost catering food waste onsite. It is still a little early to say if they have saved cost over the collection and disposal costs, but the environmental benefits by reducing transport and landfill are achieved. This is a good message around recycling and being sustainable.
Here are some items to add into your evaluation:
- Know your waste collection costs, and do not forget to add in your costs to load the wheelie bins with waste.
- The compost generated (1-3 mt) would save you perhaps £80-240/year if you compared to buying compost to spread on site gardens
- Bulking agent and browns should cost less than £40/year
- Cardboard approx £15-30/year (but free if you use office shredded paper)
- Staff time – we currently estimate 30 mins a day to load and unload 2 units
- Capital cost for HotBins (c£400), write of over 5 years
- Corporate messages – there is a great message around recycling and being sustainable. This can be extended for some into organic gardening.
- Carbon offsetting – no detailed information at present
We think as many as 50,000 UK businesses could utilise a HOTBIN. This would equate to 25,000 tonnes diverted from landfill. (Derived from WRAP campaign on catering food waste statistics).
Come on UK business – you know it makes sense – sign up today!
Research Twin packs and Quad Pack here.
It makes absolute sense for B&B’s and small hotels plus some cafes who have use for their compost! You can even compost the Vegware range of completely compostable food packaging and catering disposables as you can see in an earlier post.
One size (or even four) does not fit all. If you need a really big onsite composter do not despair, we have some big friends and we are happy to introduce you. http://www.tidyplanet.co.uk/, Ridan http://www.ridan.co.uk/, HotRot http://www.hotrotsolutions.com/
RUNNING AT 20-40C
My HOTBIN is running at 20-40C, is it OK?
HOTBIN is very proud of its ability to hot compost at 40-60C. We “go on” about it all the time that given the right amount and mix of waste all customers can hot compost. However there are HOTBIN customers who love the HOTBIN and are happy to leave it trundling along at 20-40C.
And it is perfectly alright for HOTBIN customers to choose to bask in a ‘warm glow’ rather than sit in the ‘blazing heat’! Some of our customers know they will be warm composting through winter until they get more garden waste.
However here is the key Top Tip to remember:
If you want to ‘warm’ compost rather than ‘hot’ and still add ALL food waste you need to take extra care to ADD MORE shredded paper/corrugated cardboard and bulking agent than normal. Less water will leave the HOTBIN as steam, so you need your mix to have more dry material (paper) and ensure it stays aerated (bulking agent). If you don’t there is a real chance that you could end up with a soggy anerobic HOTBIN.
So now you know you need be strict about ADDING MORE shredded paper/corrugated cardboard and bulking agent than normal you can just sit back, relax but remember:
- Seed destruction will be less
- There is a slightly higher risk of fruit flies (they are harmless!)
- It will take longer to destroy pathogens, herbicides and pesticides (you may not have use or have any, so it could be irrelevant
- It will take longer to create you compost – so be patient, but relax – speed is not what everyone needs
Here’s a quick refresh of compost speeds and temperature:
Even when you are taking a relaxed WARM not HOT approach remember for every 10C above the external air, your compost will still decompose twice as fast as an open heap running at ambient air temp.
The things you need to watch out for when the temperatures in the HOTBIN are between 20-40 C.
Flies, maggots and fruit flies
There is a slightly higher risk of fruit flies and maggots from house flies.
- Temperatures below 40C will not kill maggots (flies can lay eggs in the food in your kitchen caddy, on garden plants etc.
- If you get an infestation either leave them be, or be patient – they will die of in winter, and you will be able to hot compost again in spring if you have grass / nettles / comfrey and more easy to digest material available in the garden.
Pathogens, herbicides and pesticides
It will take longer to destroy pathogens, herbicides and pesticides (This could be irrelevant if you have not used them – see full pathogen blog)
- Herbicides & pesticides – follow mfg guidelines – all info assumes cold composting, so if it says leave six months – leave a batch to stand for an extra couple months in bags
- Pathogens – it is defiantly safer to compost meat, fish etc at higher temperature. If you decide to warm compost, the key is to keep the waste aerated. You will lose less water as steam and see more leachate. Compensate with MORE bulking agent and more shredded paper- – keep the mix drier than normal.
Some seeds (eg tomato, melon, weeds, grass) are likely to survive when composted below 40C so they can germinate when compost is used.
- Ease the problem – do not add weeds that have seeded – get them into the HOTBIN early as greens.
- Does it really matter if a bunch of tomatoes seeds sprout where you used the compost. Pull them out and add to compost heap.
- Take extra care with invasive weeds. Do not add them to a bin operating warm – consider burning them
Bottom line – Compost
If you have any queries about warm composting in the HOTBIN or you just want to try and get into the hot composting zone between 40-60C, then please contact the HOTBIN team and we will work with you to get you hot composting.
Even if you do not have enough waste, there are often very simple solutions like taking in your neighbours kitchen caddy, stocking up with shredded paper and a bucket of chicken pellets, etc.
The bottom line – given a your compost a little longer as after all the compost coming out from a warm heap will be good for your garden!
170 THINGS TO COMPOST
Want to know what you can compost? HOTBIN’s complete list of things to compost guide is for you!
We compost every day and know what can go in at a practical level. Based on what type of compost bin you have and how hot it gets, we tell you how long it will take. Our list is technically accurate and hopefully more valuable (and most of it is tried and tested too!). There are over 170 items. It was a blast creating it and we hope it is valuable! Click on the graphic to see the full list
Who will find this COMPOST list USEFUL?
- Recyclers who want to make a real positive difference by composting more waste
- Gardeners who want a large amount of quality compost
- HOTBIN Customers who know they can add more than the ‘Traditional List’ to their HOTBIN and want to give it a go!
PLEASE GIVE THE LIST SOME RESPECT
This list is not for anyone seeking to ‘copy and paste’ to make their own list longer to attract traffic. This list is © copyright of HOTBIN Composting & AC Innovations Ltd, 2010-2013. It took significant time to author, research the facts and correct the ‘dross’ lists on the web. It is not OK to copy. As a bare minimum, be courteous enough to reference us as the source and use a reference hyperlink back to us at www.hotbincomposting.com
Producing another list has no value. We think we have added value by understanding what people need to do, why they need to do it and advising if it practically works and ultimately is worth the effort. We have adding context and value by adding categorising and indexing the table as follows:
Categorised waste by source
- Food, garden, manure, home/other. Sub sorted alphabetically.
Indexed by science i.e. Is it biodegradable or not?
- Biodegradable means it breaks down back through the carbon cycle to water, carbon dioxide and the trace elements (NKP, Ca, etc). But there is no standard that defines how long. Few list the critical conditions when they quote how many years it takes. The scientific fact of biodegradation and how long it takes are different. Time can vary by a factor of 100 relative to the conditions (notably temperature) – 1 year can become 50 and so on. It can also become never if a critical part of the system is not present.
Indexed by compost method – Is it compostable in a hot or cold system?
- Your composting method and equipment does make a massive difference! (Most all readers will only have the equipment to cold compost. Here at HOTBIN we make a hot composting system which changes everything).
- Is it practical and worthwhile? Can it be done with relative ease? What volume of waste, collection, time, risks, rewards. What do people making compost want – lots of good compost. That requires lots of starting material. A tonne of manure will make around 250Kg of compost. It would take you a lifetime to create the same compost by collecting the cotton from Q-tips (see end of list!)
Compost things that makes a real difference
- Compost all garden waste (plants, grass, branches, weeds)
- Compost ALL food waste
NB – A typical household throws away 250Kg of food waste – that is second only to green garden waste. But it has to be easy!
WHY COMPOST FOOD WASTE
Benefits of composting all food waste – is it worth it?
Why compost food waste?
An estimated 7.2 million tonnes of food waste is collected by UK Local Authorities and sent to landfill. This is approximately 150-250 Kg per household per year (ref. WRAP, 2011). Around 7m UK homes already home compost, but they compost as little as 35% of their total food waste – typically adding vegetable peelings and tea bags. The other 65% of food waste (plate scrapping, meat, fish, cooked food, rice, pasta, leftover bread, cakes, etc) is on the “do not add” to your compost bin list. This advice is well founded when cold composting food waste as it often results in odour, vermin, yuck and mess (ref Defra funded, Brook-Lyndhurst 2008).
Successful home composting of all food waste has environmental benefits as it reduces fuel used to collect and transport waste to landfill, prevents methane release in landfill, [methane is a potent greenhouse gas] and reduces the number of new industrial composting / anaerobic digestion plants required in the UK.
WHAT SAVIINGS does this TRANSLATE into?
A quick estimate is 250Kg/house x 65% x 7m households upgrading to hot composting = 1.12 million mt of food waste diverted from landfill. This equates to roughly 50 large scale AD/IVC central plants. Whilst costs vary, this is around £500 million of capital costs and 10 years of planning and building.
We clearly have a vested interest, but it would appear to be a good environmental case to subsidise the more expensive “all food waste compost bins” for those households that want them. If the government exempted the compost bin from VAT (£25) and matched 3 years of food waste collection cost (£20/yr/hh for FW), then that would get to around a £75-85 subsidy!
(No VAT? – Within the overall UK energy & environmental programme there are a number of energy saving devices classified as zero rated VAT goods. So if we lobby politicians along the lines of “what’s the difference between energy saving and saving the environmental impact of transport/landfill/building AD processing facilities)
We need to get a couple of council officers thinking £75 subsidy. At a price point of £75 per HOTBIN we know people would buy on mass. From here it is a virtuous circle – high volume production reduces costs, which means lower prices which equates to more volume. We are miles away from this – but our goal has to be large scale diversion!
It’s a big lobbying task, but the rewards could be large.
Just for clarity – we are not anti the WRAP/government strategy to build anaerobic digestion (AD) plants to extract energy from food waste. Technically sound and matches the council’s need to build solutions that cater for most of the population. Composting is not going to work for all (flats, no gardens etc come to mind). At best composting is relevant for 20-30% of households, but this 20% can make an immediate and large impact winning time for the planning consents and large AD facilities to handle the other 80%.
My Council Collects food waste in Kerbside containers –
Is it still worth composting?
Some Local Authorities collect and transport food waste to either a large composting or anaerobic digestion processing plant – well done your council. To meet UK commitments on landfill diversion, we estimate 300 new reprocessing plants will be needed across the UK. Each will cost many millions to build and take many years to fully commission.
Processing at home can start immediately; it saves labour, transport costs and the need to build as many reprocessing plants. If you have very little waste (less than 2.5Kg, or a small 5 litre kitchen caddy per week), or have no garden to use compost, then using a kerbside collection makes sense.
My Council Offers cheap/free dalex/plastic compost bins –
Is it worth using a HOTBIN?
We believe so. The key issue we see is this – almost all compost advice sites (government, user, expert) will state: “do not add cooked food, meat, dairy, fish, bone etc to a traditional cold dalex type composter – the food is likely to decay anerobically and generate odour which in turn will attract rats and flies”.
1) This means around 65% of food waste items are not added to a coldcomposting bin
2) You only get significant diversion if home composting can handle all food waste
3) You need a special food waste compost bin to handle all food waste
In our opinion, as soon as you establish an objective like ‘compost all food waste with low odour, without attracting rats or flies’ or ‘compost using an easy recipe; ‘compost faster’; ‘compost all year round’ then you need to look at ‘hot composting’.
You can find a full list of the benefits of hot composting and how to evaluate a specialist HOTBIN over a traditional heap at our post on choosing the right compost bin.
Things to consider unclude;
- Do you want to make a more positive contribution to the environment?
- Recycling all your food waste so your local council no longer has to collect and transport it to landfill or a central AD/IVC reprocessing plant?
- Are you just fed up with allocating more and more of your flower or vegetable patch to overflowing compost bins that never seem to do anything?
- Do you only have seasonal waste, or do you also have regular weekly amounts of food waste all year round
You will find a full list of the benefits of hot composting over cold composting at this post
My Council Collects Green waste –
Is it still worth composting?
Many councils charge for green garden waste collection (e.g. £20-30 per year) and these charges are likely to increase. Many green bins are collected near empty (wasting time and fuel). Most of the time they are filled with mainly grass – grass is really easy to compost!
If you are a keen gardener, more than likely you will buy fertiliser, peat and/or compost to maintain the quality of your garden. Why not make your own compost and fertiliser. It takes no more effort and you could save you money.
Why is COMPOST & Composting Important?
Most gardeners just ‘know’ compost is good – they use it and they see the benefits in terms of plant growth etc.
Perhaps less well known is that humus (see definition below) is absolutely critical to soil structure, tilth, fertility, etc. It is hard to grasp just how many aspects of life on earth are linked to humus – agriculture, sustainable agriculture, reduction in inorganic fertilisers, peat, carbon sequestration, biochar, desertification, land rehabilitation, the list goes on.
So just an opinion – humus is hugely important.
Soil chemistry books are well reviewed on Wiki etc. However we do think it is helpful to clarify that humus as defined in soil science has a different meaning to the more colloquial gardening use of the term where it often used as another name for compost. In soil science, humus is a distinct fraction of the soil organic matter (SOM). Humus is:
- Dark (almost black), mushy, sticky and watery
- Is a colloidal mass, ie it holds many times its own weight in water – squeeze humus and water will come out.
- The water in humus dissolves and holds the critical plant nutrients (NO3- nitrate ion, ammonium ion (NH4-), Sulphate ion (SO4-). As soluble ions, roots easily absorb them. The ions are not easily washed out (leached out). In humus, both water and the soluble ions are retained but are ‘plant available’, ie absorbed via plant roots
- Humus has the capacity to hold and exchange cations (e.g. metal ions such as so sodium, calcium, aluminium, iron). Soil cation exchange capacity “CEC” affects fertility – CEC increases as you move from poor soils (e.g. heavy clay) to good (e.g. rich loam). Adding humus increases soil CEC, i.e., soil fertility.
- Humus is highly resistant to further mineralisation (decomposition). It is routinely carbon-14 dated at 200-500 years old
- Humus is made of large polymeric chains. However, when extracted for chemical analysis, it has the following constituents: humeric acid, fulvic acid and humin. This family of ‘aromatic ring compounds’ are used as ‘building blocks’ linked in many different ways to create a complex polymeric substance.
‘Mature compost’ is not ‘humus’, although it will contain humus. The more humus in your compost the better for your plants, soil and the environment. There is an awful lot of soil fertility and soil science that indicates humus is one of the most important items in soil fertility. Nutrients from decay end up in the soil at some stage. These nutrients are retained and made available for plants via humus. It is a sad and growing fact that nitrates and other nutrients added to soils tend to leach very quickly from soils with low humus content.
So if you are keen to get hot composting take a look through this blog or visit our website which also has a substantial composting FAQ
Out and about with the Master Composters
HOTBIN has been working with Master Composters and Recycling Officers for the past 12 months. We donated 15 HOTBINS to be used with various teams across the country. We were keen to get the Master Composters to try the HOTBIN and see how it compared against the other composting bins they work with.
HOTBIN composting is quite different from traditional composting methods and we knew Master Composters would definitely put the HOTBIN to the test!
What do we want to achieve via the HOTBIN project?
WRAP( July 2011) estimated there are around 7 million homes in the UK composting. About 65% of household food waste is classed as “do not add to compost bin”. Most composting is therefore adding 35% comprising mainly of vegetable peelings and tea bags from the kitchen. The HOTBIN can compost ALL food waste including meat and cooked leftovers.
If we can upgraded all home composters to compost all food waste, then that would divert an additional 1.12 million tonnes from landfill and collection. (250Kg/house x 65% x 7m households = 1.12 million mt of food waste). This equates to roughly 50 large scale AD/IVC central plants. Whilst costs vary, this is around £500 million of capital costs and 10 years of planning and building.
We clearly have a vested interest, but we think there is an environmental case for councils to subsidise the more expensive “all food waste compost bins” for those households that want them. If the government exempted compost bins from VAT (£25) and matched 3 years of food waste collection cost (£20/yr/hh), then that subsidy would allow a price point of £75 per HOTBIN! The subsidy leads to a virtuous circle – more units leads to high volume production, which reduces costs, which reduces prices again which increases volume which diverts even more. We are miles away from this – but our goal has to be large scale diversion. (If you want to read more on the benefits of hot composting topic jump to this post).
This year will see HOTBIN enter all the major Council framework agreements (ESPO/YPO/Scotland Excel) giving us more visibility and opportunity to discuss removing food waste via home composting. With the help of Recycling Officers and Master Composters we hope to divert more food waste in 2013.
HOTBIN test SITES include:
||What & Why
||2 units with Waste Recycling Officers
||4 units, 2 with Master Composters & 2 with Recycling Team
||1 unit with Waste Minimisation Officer
||1 MC – Sarah, aka ‘Compost Woman’ Follow her blog and review here
||1 unit with Master Composter
||On display Snibston recycling centre
||1 unit with waste recycling Officer
||1 unit with MC
||1 unit with MC
||1 MC & 12 Units with Waldringfield Community Composting
||1 unit with MC
||1 unit with MC
||2 Units, on display at York Rotters See St Nicks field website
|Zero waste (Scotland)
||Waste Recycling Officer
|If you would like contact details for the above, please email us at firstname.lastname@example.org
REMEMBER MASTER COMPOSTERS;
- Already use many different composting systems
- Work with many different users from novice to expert
- Have undergone formal compost training and accreditation
So What Do the Master Composters say ABOUT THE HOTBIN?
Jane Griffiths, MC Network Manager: The HOTBIN processed a very challenging food waste mix into compost after 90 days. During the trial we were really impressed that when checking the temperature it read 60°C when the outside temperature was around 10°C.”
Lesley Tulitt, Buckinghamshire: I got the bin going and have not looked back. The time of year is irrelevant, as the key point is to introduce a large amount of fresh greens like grass clippings which start the process and then keep adding waste every few days to maintain the temperature. As long as you keep feeding it with material it works. (Lesley recently blogged at http://recycles.buckscc.gov.uk/).
Sue Baines, Oxfordshire: The HotBin website is fascinating, I can spend hours looking at it when I think I should really be gardening, but it’s good to have access to so much information. I received the straps a couple of weeks ago and they do seem to help to hold the hatch in place. I’m still having problems with leachate, although not as much as before. …The compost in the bottom of the bin was extremely compressed and wet and seemed anaerobic and smelly although it was mainly composted…. Having said all that, I’m still getting good quantities of reasonable compost out of the bin, so I’m not complaining.
Sarah, Herefordshire (see Compost Woman – blog): I filled the bin mid afternoon on a sunny but cool day (18C). After 24 hours the top layer of material was at 50 Celsius with an ambient temperature of 20 Celsius. It was very easy to load the HotBin and so far I am impressed with the ease of use. I am also VERY impressed with the comprehensive and user friendly information on the HotBin website – especially the FAQ pages, which are full of all sorts of useful information about composting.
Rod Weston, Leicestershire (HOTBIN at Snibston Discovery Museum): The bin is attracting a lot of interest, particularly the external thermometer just about everyone has to open the lid to confirm that it is hot (60-70C) inside. We are using it to compost food waste from the on-site cafe so it is a bit of a challenge but the bin is performing well.
Betsy Reid, Suffolk: I am the satisfied owner of a HOTBIN. What I am now wondering is whether you could offer any price reduction for a Community Composting scheme?
(We did and Waldringfield is our first community Composting scheme with 12 HOTBINS last year and another 12 HOTBINs to be delivered in March 2013!).
Linton Waters, Shrewsbury: Having now experienced the HOTBIN, I’d be very happy to talk positively to members of the public at events etc and recommend it where it seems appropriate.
Hugh Baker, Compost Works, Mole Valley: Thanks for the HOTBIN – Very impressed with it.
Lessons learnt with Master Composters
Our first year has flown past, but not without challenges. Our policy is to learn and fix problems as soon as possible. Here’s a short review of issues and fixes that came up from the Master Composter testers:
Bulging doors and straps: The first batch of HOTBINS had some hatch panels that appeared to slip. We supplied cam straps to all existing and new customers and subsequently made a design revision which solved this problem.
Rats: MCs know rats can get into just about any compost bin – plastic, wood or metal. They always ask: Is it rat proof? No, but 99.5% of all customers report no issue with rats. The key defence against rat attack is the removal of odours that attract them – the HOTBIN achieves this – you can read more on rats by jumping to our rat FAQ post.
Not getting warm: a small percentage of all customers struggle to get into the hot composting zone. The % of MC who struggled was no different to customers. We solved each incident and have got them going. The causes are usually human factors (prior experience cause skipping key steps – like adding plenty of bulking agent when adding food waste or not adding enough chopped cardboard or shredded office paper with wet waste) or practical (not enough waste).
Leachate & avoiding excess water: If the mixture is too wet – leachate (brown water) comes out of the base. We now:
- Plan for occasional leachate – and ask users to check location of HOTBIN
- Advise how to minimise leachate by adding shredded cardboard or office paper to waste
Flies and maggots: A hot HOTBIN working above 40C kills flies, maggots and other critters. One MC spotted an infestation of fruit flies. We advised how to get hot composting and the flies disappeared.
Emptying: It could be easier – but also noted no harder than other compost bins.
Bulking agent, food waste and how to handle food waste: of all our challenges taking trained composters who know you should not add food waste to a compost bin and asking them to do it was hardest. Very few are trained in compost engineering and hence the theory and practise of using bulking agents and hot airflow. What we ask is counter intuitive too many aspects of cold composting – but when they get it and see it working there is an addiction and smile that at last composting can be fast and fulfil its potential for recycling.
For more information on the HOTBIN please call the HOTBIN team on 0845 6210095
We can also arange 12 HOTBINS for a community composting group purchase, you just need to find 12 friends who want to compost all food waste!
For bulk pricing and sales to Councils, please call Straight plc 0113 245 2244
Compost bin review – Tom Pattinson who writes a garden column in the Morpeth Herald is also a HOTBIN composter owner and he says, “it is brilliant”.
How to use your compost
Spring is on its way!
Well done, you have composted food waste all winter and you are now ready to use your first HOTBIN compost. But how are you going to use it?
Firstly check it your compost is ready to use – if you are unsure, after all looks can be deceptive – have a read of our blog here or take a peek at my first batch of HOTBIN compost.
Here are 10 ways to use your compost;
- Dig in to flower beds
- Dig in to vegetable plots
- Make a tomato or cucumber bed in your greenhouse
- Top dress your indoor plant pots
- Top dress your outdoor flower beds
- Top dress your lawn
- Mulch – perhaps not! (see tomorrows blog)
- Use it to plant seeds/seedlings – take care! (See tomorrows blog)
- Use in pots and containers
- Don’t use it – bag it and store it for later
We will explain each of these and provide more hints and tips in our next HOTBIN blog on ‘How to use compost’.
Compost: How Long Does It Take To Make?
How long does it take to make compost?
This is one of the most asked compost questions – most gardeners want rich compost fast. You will see all of the following on various sites:
- Promises of compost in 7 or 14 days
- Compost in 21 days
- HOTBIN says 1-3 months (30-90 days)
- Other sites say 6-12 or 12-24 months
- We meet composters who say ‘I have been composting for 2 years and still had nothing out’
Who is right?
Are some people telling porky’s or is there something that can explain the differences? Each of the above is possible and below we explain a bit more on how and why.
Before doing this, for the record: we advise anyone thinking of buying a compost bin promising “compost in 7, 14 or 21 days” to walk away. Hot composting in the HOTBIN composter at 60C is just about as fast as it gets and we advise a minium of 30 days for mulching compost and a typical time of 90 days for mature compost.
So why does the time vary so much?
Anyone following Prof Brain Cox’s latest TV programme ‘Wonders of Life’ will know all life on earth follows a set of laws.
If we know the exact mix of waste materials, oxygen flow, water content and temperature, we can say how long it would take. These items vary hugely from compost bin to compost heap – hence how long it takes can vary from days to years. The easiset way to to estimate how long it will take is to look at the three most significant things.
Three major things that will affect how long it takes to compost
- Temperature (which can range from freezing (-10C) up to a very hot 70C
- The composition of the material (is it all bits of sugar or dense lignin fibres (wood)
- The size and shape of the waste (small pieces or one big lump)
Of these, temperature is the most important factor – it has an ‘exponential effect’ based on the Q10 equation – we can try simplify this in this simple illustration:
Examples of time for domestic food and garden waste
||70 / 60 /50 /40
||10 / 0
||60 to 1000’s
||Starch, Carbohydrates, proteins
||90 days – never
||2 years – never
||Lignin (wood), latex rubber, acetates
||10 years – never
||500 years – never
The chart can only be a rough guide.
What should be clear is that it depends on your mixture, for instance;
How chopped up it is?
How aerated will it stay?
How is the water controlled or not?
What materials have you added will also deeply affect the time it takes to compost. (see 160 things to compost)
What we can also say is the HOTBIN is designed to maximise and help achieve optimum conditions (notably aeration and high temperature). Plus it is insulated to reduce heat loss. A typical 4 person household should see waste decreasing in volume very quickly and on average get a batch of mature HOTBIN compost every 3 months.
Can I Compost Newspaper
Can I compost Newspaper?
If you have check out our 170 things to compost list you will see Newspaper is on the list – yes you can compost it!
However, we do not recommend adding it to the HOTBIN composter as it is SLOW to decompose and can cause aeration issues. We think it is best to be recycled in the paper recycling bin but not in the HOTBIN.
Should I wrap food waste in newspaper? The normal reason to wrap food in newspaper is to stop the flies getting at it*. However in the HOTBIN wrapping causes issues. Newspaper is slow to decompose (read why at our wood and paper post), so the sheet acts like a blanket stopping air flow for many days or even weeks. This can cause the food inside to anerobically decay. (Which can be smelly!)
Always best to add food waste loose in a HOTBIN, then mix in bulking agent, if you have used newspaper scrunch it up into a ball and add.
However if you are collecting in caddies and trying to keep them clean – grab 4 sheets of used A4, fold and place in the caddy or add a handful of shredded office paper. They make a great temporary lining, and when done, the white office paper composts rapidly see our collecting food waste post.
* The HOTBIN has an airtight lid which reduces smells and stops flies getting into the compost – In a correctly operated HOTBIN, once the heat gets above 40C, all creatures (except thermophilic bacteria) will die off. Find out more in our FAQ post