KEEPING THE HOTBIN HOT
How do I keep my HOTBIN composter working hot? My HOTBIN seems to have stalled – It won’t go above 40C any more…
Here at HOTBIN composting we are passionate about our brand promise that given the right volume and mix of waste everyone can hot compost at 40-60C.
We do not have many customers who struggle, and normally a combination of our Q&A database, email support or our unique composting photographic analysis service get their HOTBIN composting on track.
You can imagine therefore we get a bit hot under the collar when we find a customer where everything seems perfect, they have been hot composting for a while, all the settings are right (valve, door on, etc) the mix is right and there is nothing obviously wrong and yet the HOTBIN suddenly sticks persistently at 30-40C and will not rise. We have termed this “a stalled HOTBIN”.
Who is affected by stalling?
Firstly this is not to be confused with customers who have never reached 60C (if this is the case, please check out the FAQ: How to get to 60C check list. Stalled HOTBINs are where it has been working perfectly for months at 40-60 then suddenly it will not rise above 40C.
This is not a common occurrence and there are only a handful of reported cases. A dedicated customer (Andy U) wrote in and suggested an adaptation to help and this kicked off a summer of activity and research.
Why does it happen?
We have identified one central issue: restricted airflow through the base layer. (Think of the HOTBIN as a fire in the chimney, you add new waste onto the fire to fuel it. As the heat rises is ‘draws’ fresh cold air in at the base. This air is drawn up through the base layer. If not enough air flows, the bacteria are restricted and hence the heat produced is restricted.
What causes restricted airflow?
The HOTBIN works under many different waste conditions. However, we have identified the causes that can tip the balance and create restricted airflow:
- Base plate is ‘plugged’ (see below)
- Ultra compressed base layer
- Dense, compressed, wet layer of either paper or grass
Top tips for fixing A stalled HOTBIN
If you are suffering from a stalled HOTBIN, here are our tips for fixing it:
- Check to see if your base plate is ‘plugged’ (check this post to understand what we mean by plugged rather than normal operation where the holes are covered with compost).
- Sprinkle a couple of handfuls of wood chip on the base plate after each emptying to reduce the chance of plugging.
- Empty out the base layer at least every 6 months. Longer and it will lead to ultra compression of the base layer.
- Always add bulking agent – this is critical with Food waste, but it will also help prevent compression of any waste
- If stalled, stir the top half of bin to help aerate and break up any dense layers.
- Check for thick layers especially in lower half bin. – eg a solid layer of wet grass or compressed wet paper.
- Check mesh plate for leakage of water/leachate. If lots of leachate cross check to see if your real issues is that your waste is “too wet” for hot composting
Grass composting in the HOTBIN
How to compost grass in the HOTBIN composter. What can you expect when you add grass into the HOTBIN
As we explained in our previous grass post there are advantages to adding cardboard (or shredded paper) plus bulking agent (wood chip) to the HOTBIN to help you compost grass most successfully; it helps calm the ammonia smell and creates extra structure.
Here’s what happens to grass in your HOTBIN through a series of pictures.
Grass added to the HOTBIN
One hour later …
24 hours later…see how it has shrunk already!
48 hours later…
4 days later…this picture speaks for itself
7 days later…It’s almost gone and is steaming away!
Our control experiment!
We put some grass in a bag outside with no insulation… the temperature never gets above 30C
After 24 hours…
After 48 hours…We added some insulation on the top to see if this helps?
After 4 days…The insulation hasn’t made a difference!
After 7 days…there is still no real drop in volume
How to compost grass lawn mowing
To get fast superb results when composting grass lawn mowings in the HOTBIN:
Add 40 parts grass with 20 parts shredded paper and 1 part wood chip (bulking agent)
Typically this is a medium sized lawn mower collection box (40 litres) with a full carrier bag of shredded paper (20 litres) and 4 hands full (one 2-litre measuring jug) of bulking agent.
If you want to view a photographic sequence of grass compost stages, you can jump to our post on steps / stages of grass composting.
Below we explain why this recipe works, why just adding large amounts of grass can be problematic and offer 6 different options for handling large volumes of grass cuttings
The problem often seen when composting grass is you end up with a black slimy layer that stops the compost heap working.
In a HOTBIN you should get brown mulch in 7 days
Grass is one of the quickest materials to compost. In the HOTBIN you can typically convert grass to mulch within 7 days. Grass is so quick to heat up to 60-70C, the HOTBIN team recommend it to help accelerate and increase temperature quickly.
BUT! You can end up with a black anaerobic slime
In traditional compost heaps, it is one of the most troublesome materials to compost. Grass often heats up for 2 days and produces a very distinctive whiff (ammonia/urine). After 2-days it then ‘collapses’ into a cold, wet, slimy black mass that smells horrible (anaerobic mush).
Funnily enough we don’t have a picture of this as if you do it correctly in a HOTBIN it shouldn’t happen!
Composting grass successfully requires a little bit of extra composting knowledge but the real secret is matching the amount of grass you generate with the time and effort you have available.
Why does grass turn into a slimy putrid mess?
The ‘black slime’ is due to anaerobic conditions, i.e. excess water and too little airflow. Grass (lawn mowing) has a high water content (>80%) and no lignin (i.e. no woody stalk). As grass starts to decompose, the plants cells break down and become soft; water is released. The grass collapses and forms a thick impervious layer and airflow decreases. This in turn means the water is trapped, the process slows and a vicious circle is created where water is not removed, all oxygen stops flowing and aerobic bacteria cease to release heat. The heap cools and anaerobic bacteria take over releasing obnoxious odour and resulting in a ‘black slime’.
The golden rules for successfully composting grass are:
- Remove excess water
- Keep the grass aerated
- Balance the mix to avoid ammonia odour
So how do we get rid of excess water, keep the waste aerated and avoid both ammonia and or anaerobic odour?
- To remove excess water
You need lots of heat, i.e. you need to be ‘HOT composting’
- To keep the grass aerated (i.e. get air/oxygen into the grass layer)
You need buoyant airflow which requires a temperature gradient and a structure with spaces and gaps so the air can flow up.
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 via the chimney principle” – and this requires the grass to maintain a structure with small air spaces (ie not a thick wet slimy mass!).
To get a structure that stops grass collapsing into a slimy heap, you need to add what we refer to as a bulking agent (typically this is wood chip). The bits of wood chip act like ‘stacking blocks’ and the air flows around them. Simple but essential!
- To avoid ammonia odour
To prevent excess ammonia, you need to be adding a fast/easy to digest carbon material like shredded office paper or chopped up corrugated cardboard.
The odour is caused because grass has an excess of nitrogen which the bacteria are unable to use as fast as it is released. So it forms ammonia gas and evaporates away. You are most likely to notice this when composting and/or turning large quantities of 1-2 day old grass lawn mowing. After 3 days things slow down and the nitrogen is no longer in excess. Turning grass heaps does not prevent the odour – it enables the trapped gas to escape ‘all in one go’. (If you have done this job, you may well come back inside the house and realise your clothes smell of ammonia!).
The HOTBIN does have an odour filter in the lid that does remove ammonia odour. But, when you add a whole box of grass in one go without anything else, the filter gets temporarily overload for 2-3 days. To prevent the odour during the initial 2-3 days you need to balance the carbon/nitrogen ratio.
You achieve this by adding a dry high carbon waste. The key here is to add ‘easy to digest carbon’ such as corrugated cardboard or paper shredding. Woody items like sawdust, shavings, wood chips are high carbon – but they are not easy to digest, so will not balance the C/N during the critical 2-days of intense activity. Here is the challenge – you need a lot of dry carbon! A 40L grass box (a typical mower box), needs 20L of paper – that’s a whole carrier bag full. It also needs to be mixed with the grass. Not everyone wants to do this, especially after cutting the grass. Below we outline a few options about different methods you might want to follow.
Large amounts of grass waste need extra steps to compost quickly, without ammonia and without turning putrid. Is the extra effort worth it? We think so! Each year fertilising grass lawns consumes considerable inorganic fertiliser – adding the nutrients back via compost is environmentally better.
Below are six options/choices for composting grass. Often you can ‘mix ‘n’ match’ routines at different seasons and times of the year to cater for the varying grass volumes.
1) Small to medium lawns – add grass into your HOTBIN each week
The HOTBINn will easily compost grass from a small-medium lawn (approx 40 litres/week or 1 large grass box per week, filling about a quarter of the bin each time).
This will generate some odour that you may well notice for 2 days. If this bothers you, there are a couple of methods to solve this:
- add shredded paper or corrugated cardboard in ratio 2 parts grass to 1 part paper
- Only add half a box, then return 3 days later add the other half
|Grass volume / Weight
||To Avoid wet slime
||To Avoid Ammonia
|40 litre (approx 20 Kg)
||Add 2 litre (a measuring jug) of bulking agent. Mix in well
||Add 20 litre (a full carrier bag) of shredded office paper or chopped up corrugated cardboard).
Results in approx 1.6 Kgs of compost in 30-90 days
2) Large lawn – use a dedicated HOTBIN for grass
If you have a large lawn and generate 3, 4 or more boxes each week, then you will need to consider a dedicated HOTBIN. It will cope with 2-4 boxes (about 60-80L) per week.
The same rules apply – but adding and mixing in large amounts of paper is intensive and requires a high degree of commitment – perhaps not what you want straight after cutting the lawn! Large lawns allow the HOTBIN to be located away from your seating area – so we suggest you save your effort of adding shredded paper to eliminate ammonia odour – just leave the HOTBIN down the garden and reap the benefit of fast compost without anaerobic slime.
|Grass volume / Weight
||To Avoid wet slime
||To Avoid Ammonia
|80 litre (approx 40 Kg)
||Add 4 litre (a measuring jug) of bulking agent
||Leave remotely and accept ammonia for 1-2 daysAdd 40 litre (a full carrier bag) of shredded office paper or chopped up corrugated cardboard).
Results in approx 1.6 Kgs of compost in 30-90 days
3) Leave the cuttings to compost on the lawn
Many gardening sites now actively promote leaving grass cuttings on the lawn. Normally you use an adapted/special mower blade that chops the grass into very small pieces (2-5 mm) and thoroughly spreads them. The method is to weekly trim of top third of grass and spread this evenly so it composts quickly, adding nutrients back to soil, but not creating thatch. If you have the grass ‘trail line’ down side of mower, then this will rot into mulch that blocks light and growth and does create thatch. Please refer to manufacturer for correct mower blades/settings. If you walk regularly on your lawn – you may find bits get on your shoes and are walked back into the house!
4) Best of both worlds’
Add the first few cuts of the year which tend to be large (say 3-4 boxes) into your empty HOTBIN. The bin is full for a week or so, and then rapidly becomes half-empty allowing ongoing use with food. After the spring cut, leave grass cuttings on lawn. Occasionally (e.g. when cutting hedges) add the grass box back on the mower and collect grass to complement garden ‘browns’.
5) Transfer grass to Local Authority
This is unlikely to interest HOTBIN users, but it is possible to have grass collected at the kerbside and taken to the council recycling centre. We are strong believers in home composting and believe in the environmental benefits of saving fuel and transport.
6) Allocate a large, remote area of garden to build smelly grass mounds
The mounds will tend to be smelly and go anaerobic, but it is fast to empty and dump lots of grass. We had rave reviews on how fast and efficient the HOTBIN is with grass – so maybe you do not need this option anymore!
So in essence it is easy to compost grass in your HOTBIN but depending on the amount you need to consider which methodology is best for you.
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!
BEST NEW COMPOST BIN 2012 TWO AWARDS FOR HOTBIN COMPOSTING
THE HOTBIN WINS TWO AWARDS ON FIRST BIRTHDAY
HOTBIN composting is celebrating its first Birthday with two awards under its belt. Just after being awarded Northumberland Green Business 2012 they were told that Grow Your Own magazine readers had voted the HOTBIN ‘Best New Product 2012’.
“To receive these two awards just a year after launching the HOTBIN makes us feel really special,” says Tony Callaghan, Managing Director. “It certainly has been a busy year helping HOTBIN users to break with some of the traditional composting dos and don’ts. It is great to know that so many people are supporting us and enjoying a more sustainable future.”
“I invented the HOTBIN as I got frustrated with an overflowing compost bin and failed to find an alternative that could compost all food waste satisfactorily together with garden waste. These awards show the ups and downs were worth it and I appreciate everyone’s acknowledgement and support for HOTBIN,” Callaghan continues.
In a recent HOTBIN survey users suggest having the ability to hot compost food waste at home has a huge impact on a more sustainable future. 90% of users agreed that it was important to have the ability to compost cooked food waste; 61.5% of users are now adding all food waste to their HOTBIN and 72.9% are now diverting a lot or nearly everything from landfill.
And as one user said “The HOTBIN quickly converts waste into good stuff for the garden whilst taking me a step further towards the good life.”
From a standing start HOTBIN will have sold nearly 2000 units by year end and has been told on good authority (the biggest retailer of compost bins) that it could easily be the best selling specialty compost bin. It has already appeared on The Radio2 Simon Mayo show, the Alan Titchmarsh Show and was declared one of the best three composting bins by The Telegraph.
The HOTBIN is made from a robust insulated engineering material to help defy Newton’s law of cooling. The unique design makes hot composting manageable by the average family in their own back yard. As the HOTBIN truly reduces heat loss you can achieve temperatures between 40-60C allowing you to recycle all food waste alongside your garden waste all year round.
The HOTBIN can help millions of existing home composters to compost ALL food waste without the inherent problems of odour, vermin and flies. Traditionally only 40% of domestic food waste goes into the compost bin, the HOTBIN can increase that to 100%, reducing the amount sent to landfill.
Why choose to HOT compost
HOT composting means you can actually compost ALL food waste which is much harder to achieve in COLD composting bins.
Now we really do understand £185.00 is a lot for a household to pay for a HOTBIN. However when you look at the big picture there is certainly more than £185.00 worth of argument for people to support the ‘concept’ behind HOTBIN composting!
There is a staggering 7.5 million tonnes of food waste going to landfill every year. Based on the “Love Food Hate Waste” analysis, even if you already home compost, it is likely that you only compost about 40% of your food waste (i.e. kitchen peelings, tea bags). Most food waste has to be collected, transported and dumped in landfill. Going forward it will be collected (at the kerbside) in buckets and sent to anaerobic digestion plants. In the UK, we will need to build around 300 of these plants, one in each district! Each one will cost around £10-20 million to build and then we’ll still need to give every house a plastic caddy plus starch bags for the waste and load it on a lorry each week before it is reprocessed.
The HOTBIN can and does handle ALL domestic food waste.
We can compare the cost of handling food waste via a HOTBIN directly with what we all pay our councils to collect and dump and/or reprocess food waste. At present, the HOTBIN will breakeven with the alternatives in 2.5 years. If we can get support and move the production forward from thousands into tens of thousands then the price will eventually fall and this breakeven will be 1.5 years. Our breakeven estimate excludes the environmental cost of carbon emissions from transport fuel.
The HOTBIN was launched a year ago and as you will know most councils have no budget to give anything away in the current climate so unfortunately there are no more subsidies available to help home composting any more.
We have tried to compensate for this by having our ‘TWIN packs’, ideal for bigger gardens or those who want to share and save. For businesses or larger groups of friends there is the ‘QUAD pack’ and more recently we have launched the ‘Composting Dozen’, to help support local community groups who want to make a collective difference.
If you are interested to learn more about hot composting take a look at our extensive FAQ on www.hotbincomposting.com
Have you got an insulated compost bin?
How to challenge the marketing waffle and avoid buying a duff ‘hot composter’
This post is one of a series that help explain hot composting and how to choose a hot composting bin that performs in a domestic environment.
We are seeing an increasing number of articles on hot composting and more and more compost bin suppliers describing their compost bin as ‘insulated’ or ‘heat retaining’ to help you achieve faster composting and even hot composting. There is good news and bad in this – good that there is an increasing recognition that hot composting can be achieved at home in your back yard, but also a worry that some of the claims on hot bins are ludicrously misguiding buyers. The basic laws of nature (Newton’s law on cooling and the biological rate of heat production per kilo of food/garden waste) do not support most compost bin designs ever retaining enough heat to rise above ambient (air temperature) never mind get into the hot composting 40-60C range.
If you want to hot compost we suggest you read below and familiarise yourself with science and choose your hot bin carefully. Look for one with a clear application of science to create a design that works. If you do not have the time or expertise to do this then read the article below as our advice is simple. Search for customer reviews and testimonials – but look beyond the ‘it arrived and I have set it up’ type review that appear on many shop sites, search explicitly for “compost reviews 60C”, “compost bin that works at 40-60C”, “I am hot composting” “my temperature gauge reads above 40C”, “I have reached 60C”, i.e. hot temperature in my compost bin”
The HOTBIN team spent 2 years analysing why various compost bin designs failed to deliver hot composting. Once we had the engineering solution for what would work we set about figuring out how to make it cost effectively. There are over 200 compost bins on the market. To date we still have only found 5 domestic compost bins worldwide we believe genuinely offer a realistic chance of hot composting in a domestic environment. They cost respectfully: £900, £550, £250, £185 and £175. Prizs for which is the HOTBIN!
Here’s the science and engineering you need to choose a hot compost bin:
Newton’s law of cooling – hot moves to cold until a balance (equilibrium) is reached. A cup of hot tea always cools to your room temperature. Leave it outside in the snow and it will eventually freeze. A compost heap follows the same law – all heat produced by the bacteria moves from the hot centre out to the cooler outside air. You cannot stop this, all that can be changed is the speed at which the heat lost occurs. Put your tea in a well insulated thermos flask and it will stay warm all day. Forget to drink it and return next day – at best it will be luke warm.
A very thick insulated material will slow heat loss – but this is very different to using the term “insulated” because it uses a thin insulating material (plastic). Know your facts – challenge the supplier – as for their scientific evaluation (evidence) and ask for customer reviews that prove they are hot composting (i.e. achieving 40-60C)
Here’s a quick comparison of several compost bin materials and how thick they need to be to have equal insulation value:
|U ValveMeasure of resistance to heat flow per m2
U valve is used by the building industry to stop you getting ripped off when buying roof insulation
|50 mm wall of expanded polypropylene (EPP)
||This is what the HOTBIN is made from – 50mm thick EPP walls
|To achieve the same insulation (U Value) – ie to slow conductive heat loss to the same level –below we compare how thick the walls of other compost bin materials would need to be
| 500mm thick of wet wood
||That’s about 5 railways sleepers wide! Pallets are 20mm thick wood.
|= 700mm of compost
||A pallet frame is about 1m wide. 500mm each side of a really big heap. Only the very small centre is likely to stay warm. Be prepared to turn all the outer compost into the middle!
|= 600mm of High density polyethylene
||Most compost bins have HDPE walls 2-3mm thick). Image a bin with 0.6mm thick plastics wall!! (Plastic dalexs keep the waste together and offer some protection against wind and rain. They do not “thermally insulate” your compost heap.
|= 50mm of foamed LDPE
||LDPE foam insulates as well as EPP. Most PE foam is floppy and costs significantly more to mfg. Rigid foamed PE board is available – we have only found compost bins with 15mm thick walls – i.e. 5 times less insulation than the HOTBIN.
|= 50mm of PU foam
||Most PU foam boards are ‘open cell’ which means they absorb rain water or steam/water from compost. They will be wet and cease to insulate within a few days.
If you have a very big garden with lots of waste – build a big compost heap (>2m*2m*2m). It will stay warm in the middle for a period of time. Turn occasionally to move the outer cold, non composted waste into the middle. This is what industrial composters do in their ‘windrows’ composting and it is the system largely designed by Sir Howard back in 1930s that forms the backbone the ‘New Zealand 3 bin rotation system’. Not many have this amount of waste, or the time and energy to turn this much material.
Now you know you need to look at thickness and the thermal insulation of the walls (i.e. obtain the U value). However heat is also lost by convection. Air moves within the compost (at last we hope it does otherwise it will go anaerobic and smelly very quickly!). Moving air transfers heat very fast. Winds can cool things 100 times faster than still air. Go out in a cold wind with no clothes on and you will suffer hypothermia very quickly due to ‘wind chill’. Your compost heap is the same, it loses heat as cool air flows over it and carries warm air out.
We have discussed conductive and convective heat loss and the need to minimise it to have a reasonable chance of achieving hot composting by using insulated walls, sealed lids and airflow valves. There is one other important piece of science we have to adhere to – the first law of thermodynamics: energy and matter can neither be created nor destroyed, all we do is change the form. Focusing this down to the relevant bit; the total energy (heat) going in (from food as calories) must equal the total energy going out (i.e. heat lost).
There is a bit of chemical engineering science that looks at amount of energy available from bacteria composting each Kg of food waste, how much is lost as heat due to convection and conduction. It also defines how much needs to be retained to keep the compost above ambient (i.e. at 60C rather than air temperature at 10C. This law is the bit most compost bin designs convientely ignore and or fail to explain. Most households do not have enough waste (i.e. energy going in) to keep warm due to the amount of heat being lost.
The average house produces 5Kg of food waste a week (and maybe 10Kg -20Kg of green waste during the summer gardening season). The HOTBIN will stay hot with 5-10Kgs of waste a week. The maths are straight forward – most other compost bins lose heat so fast they need 50-100Kgs per week going in to keep warm. If you have this much waste, you can copy the hot system used by industrial composting – build big heaps 2mX2m, get a tractor and turn the waste.
Even the very best hot composting systems designs have a minimum amount of waste that needs adding each week to keep things hot. We find around 20% of HOTBIN customers struggle to hot compost and by far the biggest issue is these users who do not have the minimum amount of waste to hot compost. Garden Organic tested the HOTBIN against a leading plastic compost bin claiming to hot compost. The science explains why many compost bins can be loaded with 200-400 litres of waste in one go, they get hot for a few days and then cool. The science also explains why such bins are unable to heat up or stay warm when 5Kgs per week of food waste is added.
The HOTBIN does what is says on the BIN – it will stay hot all year at 40-60C with typical volumes of waste from a 4 person household (i.e. 5Kgs per week).
HOTBIN – it does what is says on the BIN
HOTBIN believes it has used nature’s laws of science to design a compost bins that work and explain why many others will more often than not fail to warm compost never mind hot compost. We neither want to overstate (or understate!) how the HOTBIN or any other product works.
Green Business Award for HOTBIN
HOTBIN won the Green Business Awards 2012
Businesses from across Northumberland came together last Thursday to celebrate their successes over the past year, at the prestigious Northumberland Business Awards 2012. HOTBIN were delighted to receive the Green Business Award sponsored by Banks Group.
It was a great first Birthday present for HOTBIN to help celebrate our first year.
After getting frustrated with an overflowing compost bin and failing to find an alternative that could compost food waste satisfactorily, Tony Callaghan concluded his best option was to design and manufacture a new ‘hot composting bin’ himself, which he named the HOTBIN.
He invested his redundancy from Sage UK and raised finance from a venture capital fund to go into production. HOTBIN can help millions of existing home composters to compost ALL food waste without the inherent problems of odour, vermin and flies in their own backyard. Traditionally only 40% of domestic food waste goes into the compost bin, the HOTBIN can increase that to 100%, reducing the amount sent to landfill.
From a standing start HOTBIN has sold nearly 2000 units in less than a year, has been told on good authority (the biggest retailer of compost bins) that it could easily be the best selling speciality compost bin. It has already appeared on The Radio2 Simon Mayo show, the Alan Titchmarsh Show and was declared as one of the best three composting bins by The Telegraph.
A survey of HOTBIN users suggest it has a huge impact on a more sustainable future as 90% of users agreed that it was important to have the ability to compost cooked food waste; 61.5% of users are adding all food waste to their HOTBIN and 64.9% are now diverting a lot or nearly everything from Landfill.
And as one user said “The HOTBIN quickly converts waste into good stuff for the garden whilst taking me a step further towards the good life.”
HOTBIN is currently looking at license agreements to try and meet the many requests to have it overseas. The HOTBIN was invented in Morpeth, made in the UK and is 100% recyclable. To find out more about the Awards event visit The Northumberland Business Awards
CAN I COMPOST DISEASED PLANTS?
Yes and No!
We often see Q&A posts along the lines of: “this year was ideal for mildew X, fungus Y, disease Z – badly affected crops should be disposed of” And “do not compost diseased plants and do not compost plants treated with fungicide A and or pest killer B”.
This got us thinking, how exactly are you supposed to dispose of them?
- Take it to your local green waste collection tip and let them handle it?
- Add it to your black/general waste? (General waste normally ends up in landfill)
- Burn it?
- Ignore the advice and cold compost it
- Ignore the advice but ensure you hot compost it?
Here is a quick rundown of our views on the pros & cons – but please take on board this is a complex topic and there is no single right answer
Take it to the Local authority green waste tip and let them handle it
Cons: there is a risk some spores will spread from your car/boot/loading/unloading to surrounding areas.
Pros: the green waste will be taken away, composted (most likely hot composted) and resold to you. (This raises the question if it’s safe to industrially compost why is it not safe for you to compost)
Add it to your black/general waste to be taken onto landfill?
The material (and spores) are buried in landfill and eventually anaerobic bacteria will digest the dead pathogens.
Cons: With any transport it is likely the spores and disease are spread on the trip from your drive all the way to landfill. It costs time and money and has an environmental impact to collect and dump any waste in landfill and we are fast running out of landfill sites. Huge effort is going in to avoiding biodegradable waste going to landfill – because it can be recycled!
Should you burn it?
If you have a raging fire and no local control on burning (rare these days!) then burning diseased plants at high temperatures will ensure 100% kill. If you have a smouldering mound going all for hours and only achieving a very low temperature, there is a risk some spores will be carried off in the warm smoky air. Also be aware burning wood – can also be dangerous to your health – many surprisingly dangerous and toxic chemicals can and are released when wood is burnt – once it gets to a high temperature wood burning is much safer.
Should you compost it?
How long the spores survive and whether they become active again is a dependent on many variables (time, temperature, water, food sources). Lets simplify things – the higher the temperature is above 40C and the longer the time the pathogens are in the compost heap and away from their natural home (the live plant they grow on), the less likely the dangerous spores and bacteria will survive. Cold composting for short periods (lets choose a year) is somewhat risky against cold composting for 2 years and only using well-composted material. Hot composting at 60C, even for relatively short periods of 1 day ensures excellent pathogen destruction (ref DEFRA paper)
The vast majority of all plant disease treatments (i.e. pesticides and herbicides) are just a bunch of chemicals. These chemicals are broken down by the combined action of UV rays (sunshine), oxygen and composting bacteria. Almost all fungicides, herbicides and weed killers are compostable and the compost is usable afterwards – you just need to ensure enough time and or a high enough temperature within the pile. (A very small number of chemical herbicides and pesticides decay but are still highly toxic to plants in very low doses have proven problematic when the compost has been used too early – these chemicals were not generally available to the public).
No one wants the disease to return. It is your waste so you need dispose of it responsibly. If any method was 100% sure to clear the disease, we would by now have a sanitised planet with no diseases! If we agree all disposal methods are imperfect, then we should also agree that composting is actually one of the better, more environmentally friendly, methods of controlling most plant diseases. Composting bacteria flourish in their natural home (dead plant material) and out compete and kill off their troublesome disease cousins who are not in their natural home (i.e. a growing plant).