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.
Preventing a wet HOTBIN
How and why do I use corrugated cardboard and shredded paper in the HOTBIN?
Dry corrugated cardboard and shredded paper is easy for composting bacteria to digest (see table below).
Because they are also very ‘dry’, i.e. have very low water content (typically less than 5% water), they are the best materials to add to wet food waste to balance things out and ensure there is enough heat to drive off excess water as steam.
By the way this use has nothing to do with aeration and very little to do with balancing carbon/nitrogen ratios!
(Please note – Ignore the advice on many cold composting sites that scrunched up newspaper and or cereal packet cardboard will provide aeration – in the HOTBIN they WILL NOT create aeration pockets – quite the reverse – the paper and card will be soaking wet within hours and form a matted impervious layer to airflow. It is highly likely the newspaper will come out when you empty the bin as a flattened blob of soggy newspaper.)
It is essential you mix both the paper and the cardboard into the waste rather than just add it in as a layer on the top. When adding food waste ALWAYS also add bulking agent. The bulking agent will form a supportive structure (think building blocks) around which air can flow.
Why will paper and corrugated paper compost quickly but not newspaper?
It is easy to think all paper products come from wood so they should all decompose at the same rate.
We know that thin high surface area materials will decompose faster – so cardboard is faster than a wood branch piece as the bacteria have more surface area to attack. If we assume and example where surface area is the same and the temperature is the same, the speed at which wood products compost is directly related to the amount of lignin contained – so hard wood decompose slower than soft woods.
We can take this analogy a little further to explain newspaper and white office paper – the comparison is made in the table below.
|White paper (e.g. office, A4 copier, coffee filters)
||The caustic part of the Kraft paper pulping process removes lignin to leave only cellulose fibres.Shredded it rather than crunch it up. Sprinkle in little and often – thick layers will quickly get wet and form an impervious mush that prevents airflow.
|Corrugated brown cardboard boxes, egg cartons
||Although processed, about 5-10% lignin remains.Corrugated cardboard has the advantage of trapped air/air channels. Shredded or tear up – large sheet will block airflow
|This is low cost paper – the expensive lignin removal stage is not undertaken – it is small wood fibres. (Compare to white office paper above).Ensure shredded or scrunched up. It will compost far more slowly than food, grass and most other wastesDo not add whole cereal boxes – tear up and spread / mix into waste. Add sparingly – if attempting to dry wet waste, much better to use office paper or corrugated cardboard.
|Wax coatings are slow to decay. Higher temperature allows addition in HOTBIN
How do I create lots of chopped up cardboard quickly?
Everyone tends to have corrugated cardboard boxes, but tearing them up can be tiresome. You can quickly cut into strips using a craft or Stanley knife – but you need to take care and do this correctly to avoid taking your fingers of! A safer way is to see if your office shredder is a ‘multi sheet’ unit. If it is it will shred 8 sheets of paper at a time and you will find it will shred most cardboard boxes. See photo’s below. Please keep in mind if you put too much strain on a low sheet feeder it will just overheat and conk out!
A useful post on dealing with excess water in the HOTBIN can be found on our online FAQ : Excess Water Post
Worms and HOTBIN composting
A question we often get asked is; do I need to keep my Wormery now I have a HOTBIN?
The simple answer is no and the key benefit is that the HOTBIN can compost both food waste and garden waste. Therefore you can save space, reduce costs and still keep your food waste out of landfill.
So what is worm composting?
Worm composting is using worms to recycle food scraps and other organic material into a valuable soil amendment called vermicompost, or worm compost. Worms eat food scraps, which become compost as they pass through the worm’s body.
So what is HOTBIN composting?
The HotBin is a simple design that helps maximise what nature does by bringing together the right conditions to make hot composting easier. It does this by providing effective aeration between the bottom air inlet plate and the air outlet rotating valve, removing excess water through the valve as steam and allowing you to control the rate of heat loss. You can compost 100% of all domestic food waste in the HOTBIN without inherent problems with odour, vermin and flies. This includes left over meals, plate scrapings, meat, fish, small bones, bread, cakes, pasta and rice. Your food and garden waste will be turned into rich organic matter for the garden every 90 days.
Worms in the HOTBIN?
You do not need to add worms into the HotBin however you can – either directly by adding into the base layer (which is cooler) or inadvertently by adding worm eggs and worms into the bin via small bits of soil and old compost . Most of the worms and worm eggs will be killed by high temperatures (>45C) but a some will find there way down into the base layer and continue to work on the base layer compsot.
However, worms can be beneficial to composting and can be added if you want to. But a word of warning do not add them into the upper active layer (60°C will kill them) only add worms via the hatch panel where the compost will be cooler. Worms will help to decompose waste and leave mucus in the compost which is proving beneficial to soil fertility.
As the HOTBIN is no ordinary composting bin as you can use it to recycle than just vegetable kitchen waste in it. The hot temperatures achieved during hot composting make composting all food waste in the HOTBIN a safe home composting system that recycles a whole lot more than just potato peelings.
So if you were thinking about a Wormery as a form of recycling food waste why not consider a HOTBIN as it composts both your food and garden waste together.
This AUTUMN could be the time to RETHINK composting?
Autumn is coming – It’s will soon be time to start that big garden clear up again! Should you start to RETHINK your composting method now too?
You may well have wheel barrow loads of plant and weed being removed over the next few weeks.
What are you going to do with all your autumn garden waste?
1) Pile it all up as normal in that big heap – come back in spring hopeful of compost but most likely disappointed that you face the prospect of waiting another 12 months for your compost?
2) Take a different approach – join the HOTBIN composters and be sure of a fabulous batch of compost ready to dig in with you spring planting preparation?
3) Leave it out for the council green waste team to sort out – Oh dear! All that fuel, cost and effort to centrally reprocess it. Taking all that goodness from your soil this year, which means next year it has to be replaced by buying even more fertiliser, that takes even more energy and resources to make?
Composting during the cold autumn, winter and early spring months can usually be a very slow process. Especially when the temperature falls below 5C, the rate the bacteria work is almost nonexistent. The secret to fast composting is heat – and lots of it. Compost forms 64 times faster at 60C than it does at 10C. If you can keep your waste hot (between 40-60C), it will compost in 20 to 90 days!
There are many help sites that recommend building huge piles (minimum 1X1X1 m3), and then turning them regularly to keep them aerated and hot. But even this technique will struggle in winter as the heat produced by the bacteria is quickly lost to the cold air. (And it requires quite a bit of effort and space too)
This is why so many HOTBIN composters are happy – all the hard work to help support natural high temperature composting is provided by the HOTBIN. As long as you keep feeding it every week with enough waste – it will keep running at 60C. It has been tested and proven even with outdoor temperatures as low as -15C.
Not only can you get rid of all that garden waste, you will also be able to compost all your food waste over winter too.
Now if you were an early HOTBIN starter, your HOTBIN might be full already! If the bottom layer has been in there for 90 days, now is a good time to empty it to make room for your Autumn garden clear up.
It is always best to shred as much as you can (the smaller the pieces, the larger the surface area, the easier it is for the bacteria). Now if you don’t own a shredder then you can always use your lawn mower!.
Now you are ready to fill up HOTBIN to the top and get it back up to 60C .
If you have a large garden you may still have too much waste . So the best thing is to store it in pop up bag or on another heap. Remember to keep it covered to protect it from the rain. Where possible we suggest you store bags on stones/gravel so water drains out and some air can get in through the holes in the bottom.
You can add the excess waste every 4 days (about 20 litres 10 cms depth). As the ‘waste pile’ gets colder and older, reduce how much you add each week – But keep adding your food waste! (The bacteria need some easy to digest waste to keep the temperatures at HOT composting levels between 40-60C).
Keep going until all autumn waste is gone.
As soon as you start to collect a lot of autumn leaves – check out the ‘composting autumn leaves post’ as you need to tweak the recipe to hot compost leaves.
Remember the key to keeping it HOT is a BALANCE of ‘easy to digest waste’ made up of green stuff, food waste, plus shredded office paper’ (which creates heat quickly) with the hard to digest woody cuttings (heat released slowly), or partially composted waste (energy depleted).
Why not take up the challenge – find out what others have experience by visiting our ‘product reviews’ at www.hotbincomposting.com. Explore more about how it works by looking at our extensive ‘how to compost’ database, for example our ‘principles of hot composting’ article.
The HOTBIN is a simple design that helps maximise what nature does by bringing together the right conditions to make HOT composting easier. It does this by providing effective aeration between the bottom air inlet plate and the air outlet rotating valve, removing excess water through the valve as steam and allowing you to control the rate of heat loss.
How do I prevent maggots and flies getting into the HotBin?
The quick answer is “Get your waste hot (>40C) as quickly as possible”
Flies and maggots in the HotBin are a real rarity. They can occur and it tends to be when the HotBin is in the ‘set up’ phase before the temperature has risen above 40C. Below we explain why and how to prevent this happening. House flies and fruit flies can lay eggs in the your composting waste anywhere from the kitchen, kitchen caddy / bags holding waste and possibly at any time when the lid is open or the door is not fastened tightly.
A hot (above 40C) HotBin will kill all fly eggs, maggots and flies.
In our customer surveys 99% state they are satisfied or very satisfied with how the HotBin reduces and prevents flies – but we do get the occasional issue with maggots and flies and it is a guaranteed sign that the waste inside has not risen above 40C.
We do not believe there is a 100% sure way to prevent flies laying eggs in your compost waste, but the following will reduce the chances of them laying eggs:
Ensure the lid is tightly closed at all times (unless filing!)
- Ensure the door hatch is on tight and the cam belts have been used to pull the door on tight
- Cover all waste at all times (eg kitchen caddy, collection bags)
- Clear up any waste dropped around the HotBin – it will be a fly magnet
It is often the case that your waste already has fly eggs in it. Accepting this is possible, the next step is to prevent the eggs hatching into larvae / maggots. You do this by getting your HotBin Hot (>40C) very quickly (within a few days). Heat prevents any fly eggs hatching.
The basic technique is to add lots (at least half full) of ‘easy to digest’ waste (eg grass, food waste, shredded office paper, corrugated paper).
Quick tips to help you do this:
1) Add a box of grass mowing and mix into the waste already in the HotBin
2) If no grass, add 2-3 cups of either chicken pellets or chicken poo
3) Check excess water is not seeping from the aeration mesh in base – if it is, add half a bucket of cardboard pieces and half a bucket of wood chip (from black bag supplied).
You can find more information on getting to 60C in the PDF ‘how do I get to 60C check list’
Please note: you might occasionally have flies hovering around the valve or crawling on the door hatch panel. We can’t stop this. There is always some residual odour around the valve, and often some old compost on the door. They normally give up and move on when they are unable to find the food source that generates the odour i.e. they cannot find the place to eat and lay eggs. If they bother you and you are not adverse to using chemicals, then any of the fly/crawling insect sprays can be spayed on the HOTBIN parts to keep them away – but outdoors this is a bit of a losing battle – it will wash off in the rain quickly. But do try to keep the area free of dropped food & compost.
Can you compost cigarette butts?
A number of composting advice sites indicate cigarette filters are made from synthetic plastics and do not decompose! We disagree – controlled hot Composting of cigarette butts is viable. Please read on to find out why!
Whether a material IS or IS NOT compostable (i.e. biodegradable) is a matter of scientific fact. We like to check the science and leave you better informed. It is rare for us to re-mind our readers our FAQ advice is provided on ‘without guarantee or indemnity’ – but on this occasion, as the topic is going to get people ‘hot under the collar’, a reminder that this is our reading of the science – we are only seeking to help inform your decision.
Searching the literature, we found that cigarette butts (the white filter bit) is made of ‘synthetic cellulose acetate’. That may sound non biodegradable but this is not the case. You can evidence this very quickly – a staggering 4.5 trillion butts are discarded each year (We can’t find a source for this number, but it is used widely on many sites, so let’s assume it is accurate). If these butts are not biodegradable – where are they now? Mass consumption Smoking has been around for 100 years or so. Despite the efforts of our Councils, if they did not decay, our sewers would be blocked and our streets piled high with cigarette butts. Now for the science proof!
The filters are mainly made from a synthetic polymer called cellulose acetate. All sounds a bit scary, but not really.
Acetic Acid (vinegar) is one of nature’s building blocks – life on earth needs it. Cellulose acetate is just lots of vinegar molecules joined together into a chain. Cellulose acetate is a short step away from cellulose (i.e. wood!). Most cigarette butts apparently still use natural cellulose acetate (i.e. tow from the wood pulp http://www.bat.com/group/sites/UK__3MNFEN.nsf/vwPagesWebLive/4572237B0C2D456CC1257314004EF667
). Even if they do not, synthetic (i.e. man made) cellulose acetate is man’s copy of nature’s science. It is used all around you – wrapped a present with cellotape recently, kept any photographic film (pre digital!) – that’s all cellulose acetate.
How fast cellulose acetate decays is directly related to the composting conditions – and principally the temperature of the heap (Q10 equation). You will often see quotes of 3,10 or 50 years as estimates for cigarette butt decomposition time. This is directly comparable the time it takes to decompose lignin (i.e. wood). Most of these tests are done outdoors (so an average of 10C is the temp for most tests). If you increase the decomposition temperature to 60C, you can divide this number by 32 and you’ll get the time it takes to hot compost it. So 10 years at 10C = 4 months at 60C (Again this is directly comparable to wood in an outdoor heap and wood in an IVC composting plant.
Even if we agree it is biodegradable, surely we do not want cigarette butts in our compost bins – they are full of toxic, carcinogenic tar chemicals the list of additives runs into 600 approved of by FDA for addition to cigarettes. If you really want to see some serious chemical names have a look at Wiki – http://en.wikipedia.org/Wiki/List_of_cigarette_additives
. Yes there are carcinogens in butt filters, but don’t forget – burning wood, fire smoke, the original tobacco plant, and much of nature – also has these nasty chemicals. Someone may have tested every single item and may challenge back, but looking through the list, from our knowledge of composting bacteria, they all look like readily biodegradable organic chemicals (i.e. bacteria food). These chemicals are built up in plants and broken down by bacteria all the time. (Take the logic to the extreme – if the carcinogenic chemicals made in plants were not biodegraded, then over the millennia they have been made by plants, they would have built up in soils – maybe even to a level that would have made soil toxic to humans?
What about the risk from “TMV – tobacco mosaic virus”. From our reading on the subject, claims are made that small fragments of tobacco carry the virus over from the tobacco leaf into the cigarette and onto the filter. TMV is known to be resistant to low temperature composting. However read wiki: http://en.wikipedia.org/wiki/Tobacco_mosaic_virus
. If your heap is hot (60C), the virus is going to outcompeted, die and be eaten by the thermophilic bacteria. If you add in the fact that remote chance TMV survives the burning process at 200C, a small chance a tiny fragment gets into filter and that a tiny fragment is not then eaten by bacteria – TMV from composting butts looks a really low risk.
Only you, as the composter, can make the decision whether to compost your cigarette butts. I do not smoke, but if I did, I’d be more worried about smoking than composting cigarette butts!
So finally – what’s the alternative? Leave them lying around, hope someone cleans them up and takes them to landfill! Then what? Well they will just decompose anaerobically and release methane!
Proper HOT Composting of cigarette butts looks sound!
HOTBIN investigates an interesting composting method
We had an interesting question come in last week!
Was Black Soldier Fly (BSF) composting the most efficient composting system ever?
After many years in composting, we had not come across BSF before, intrigue and a hint of competiveness that any system might be better than the HOTBIN, we did a bit of googling. You learn something new every day!
- BSF (Hermetia_illucens) is a species of fly with native to America (with a cousin down in Australia). There will be a UK entomologist who will no doubt identify a cousin in UK, but so far not aware – and hence possible reason we have not come across them in UK)
- It has a niche habitat – rotting food/manure. The fly lays eggs in compost and the larvae (some would say maggots) eat the food waste – and they appear pretty good at it. (This is no different to house flies and or vinegar/fruit flies – BSL are much bigger and eat more!)
- The larvae are not meant to be allowed to hatch into flies (ie pupate), they are collected and used as chicken feed and/or fishing bait
- There are a number of specialist bins designed to house, retain and harvest the larvae. As a food waste disposal system, it more closely resembles worm composting.
What about claims to be the “most efficient”? We are always suspicious of ‘fastest and best’ and try and uncover the scientific facts. There was no reference to a specific quote and we did not see the claim on sites listed below. It looks like there is enthusiasm for BSF, as highly efficient and this enthusiasm comes from the visible disappearance of food waste as BSF larvae eat food within 2-4 days. If you compare 4 days to “composting” even hot composting at 30 days – you might think it’s more efficient. But decomposition (eating waste food) is just a set of biochemical reactions involving enzymes – the rules are fixed: the rate at which reactions take place is governed by the Arrenhenius equation – which basically boils down to temperature. BSF Larvae die at 40C, thermophilic bacteria operate at 60C and in many cases 70C.
In simple terms, larvae at 40C work at the same speed as bacteria at 40. If we say composting at 10C is rate X1, then larvae and bacteria at 40C are X8 times faster, but bacteria at 60C are 32 times faster – speed wise, we think no contest!
But is speed what we need to focus on? What are we trying to accomplish? Are we seeking to dispose of food waste fast, make fish bait or make great humus with high nutrient and water holding capacity that dramatically improves soil fertility? (With the added plus of diverting food from landfill).
Nature eventually recycles all plant and animal matter back to carbon dioxide and water. Does it matter if the larvae eat food, then the chickens eat the larvae and then the bacteria eat the chicken poo? Or that the bacteria eat the food (and release carbon dioxide), but leave some residual waste (compost) that gets eaten much later and then finally becomes carbon dioxide. Both routes are carbon neutral and better that sending it to landfill where it will decompose anerobically releasing methane. BSFL larvae eat the food and produce a small amount of residual compost like material. Composting and hot composting produces a lot of compost for the garden. Compost is beneficial to the soil before it is finally returned to carbon dioxide.
We should perhaps note that for many humans, the reaction (rightly or wrongly) to flies, larvae & maggots are negative. Even though BSF appear as good guy (does not bite, sting or carry diseases problematic to humans), we know from experience (backed up by surveys), that one of the biggest reasons people stop composting is flies and maggots. The prospect of actively promoting lots of maggots in waste food seems at best destined as a specialist area.
A text book start for the HOTBIN
The Compost Woman, who knows an awful lot about composting, reviews the HOTBIN! And I’m pleased to announce she has had a text book start as she has already reached 60C!
She started with an very full HOTBIN having plenty of material available for her base layer.
After 24 hours there was already a noticeable difference as the the material started to decompose.
She is a freelance Forest School Leader and Environmental Educator who works with both adults and children on all sorts of things. As well as a volunteer Master Composter and Master Gardener, helping people make compost and grow veg at home or at school.
There is more than ONE alternative to sending food waste to Landfill
Ban food waste from Landfill?
Collect and reprocess it via anaerobic digestion (AD) instead? Well yes and no!!
Respect the 3Rs: we should reduce food waste. Accepting there is always going to be some waste to treat…
There have been renewed calls to ban food waste from landfill in the Guardian today . The report’s co-author Quentin Maxwell-Jackson is reported by the Guardian to state: “Anaerobic digestion technology has so many clear advantages over other waste treatment and energy generation options that it is very surprising it has not taken off in a big way yet in the UK.”
Calls to ban food waste have been made before. The Government’s stated policy is collection and reprocessing food waste via AD.
It is still probably still too early for the policy makers to ban food waste from landfill as the UK does not have the capacity ‘coming on stream’ to reprocess it via alternative means.
Every new AD plant takes time to get planning permission, to build and commission. At out last reckoning, about 3 major were due to come on stream next year and we estimated the UK needed 300 to divert food waste from landfill – it is going to be a huge cost and long path.
AD makes a lot of sense – we need a collection/reprocessing technology that caters for the majority and we know only about 15-20% of the UK population does (or will) home compost and traditional home composting has never been appropriate for all food waste.
We should not let the historic issues of home composting all food waste (including cooked food, meat, fish, bread, cakes, rice, pasta etc) that create a stinky odour that deters people and attracts rats, flies from continually reviewing technology for home composting. The HOTBIN team has real factual evidence that the HOTBIN has changed home composting of food waste for the better. Users have changed behaviour and are diverting all food waste from landfill. We estimate 5m current home composting households could divert all food waste and make a contribution – immediately.
100,000 HOTBIN users would equate to 1 new big AD plant. Delivering a million units a year (we wish!) is a logistics co-ordination issue – the capacity can be made available very quickly. We understand home composting is not for everyone – but we need to make a dent in landfill now and it can be done now.
There are other reasons why AD is not the ‘be all and end’ of reprocessing food waste. Reprocessing is a complex combination of user behaviour, logistics and technical facts. Yes AD has advantages, but so does home composting. Home composting removes the need for collection and transport, the compost can be used in the garden (reducing fertiliser and peat consumption) and adding organic matter and humus back to into soil is essential to soil fertility.
Help us win government support – HOTBIN composting diverts domestic food waste.
[At present we are pushing water up a hill and knocking on closed doors.]