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.
Is your HOTBIN compost good, bad or fabulous?
It could be any of these!
Even if your compost looks brown, at one extreme compost can be harmful to plants, at the other, it is nature’s best growing medium. Not all ‘compost’ is the same and you need to know what you have before spreading it on your garden. It is hard for a home composter to do detailed testing.
We have outlined some simple guides that should help you ensure your compost is good. We have also given you a summary of answers we might get from a range of experts.
What is bad compost? Compost that contains toxic or potential toxic elements (chemicals) – it would be rare for domestic (home) compost to be polluted and there are no home tests you can do. The best option is to ensure no waste laden with toxic chemicals are added. This is often why wood containing preservatives or coloured pigments (inks) are not added – but use of toxic chemicals like arsenic, chromium and lead have been banned for many years, so the advice can get out dated. Industrial compost should be made and tested to the PAS 100 standard (a BSI pre-standard) and this includes testing for toxic items.
Anything else? You do not want your compost to ‘rob’ nitrogen from the soil. Immature compost can do this. You want to avoid compost that is phytotoxic (ie dangerous to plants). Various organic acids created during both aerobic and anaerobic composting can be phytotoxic – ensure your compost is mature. You can do a Solvita C/N test at home. You can also smell the compost – an earthy musty smell is good. Do not spread if you have a fruity or putrid like smell – leave it to breathe/aerate and compost longer.
What is good compost? There is general gardening and academic agreement that adding organic matter (compost) to soil is beneficial. The HOTBIN team has spent considerable time ‘digging’ into the subject of soil fertility. The science indicates that whet really matters is not the total soil organic matter (SOM) but rather the amount of humeric substances (a special group of compounds remaining at the end of composting). These compounds add the really powerful benefits to soil: water retention, nutrient hold and release, soil aggregation and tilth.
Do soils vary in the amount of humeric substances they contain? Absolutely yes, from 0-8%. Many soil fertility issues are directly traced to lower or a decline in humeric content.
Do composts vary in the amount of humeric substances they contain? We have some personnel evidence this might be so. We have found academic papers that evidence humeric content can vary in compost from 2% to 50% of the dry weight. Most soil scientists will state that quantity of humerics in soil is determined by the soil environmental conditions.
Can we determine what sort of compost we have? Not easily. Here is what the experts would say:
Ask a gardening expert to describe good compost and you may well get a list like this:
- It smells earthy (not putrid, acrid or drain like?)
- It is fine particles with no sign of original waste or big bits
- It is a dark brown material
Some might add a footnote that peat is not compost, farm manure is not compost and that the term ‘humus’ is better reserved to describe ‘very well matured compost’.
Ask a worm composter (vermicomposter) what good compost is and they will probably say:
- Worm cast / vermicompost is the best compost
- It smells earthy
- It is always fine particles with no sign of original waste or big bits
- It is dark brown
- It is ‘extra good’ as the worms leave a sticky mucus (from digestion tract) in the compost that promotes mycorrhizal root zone activity
Ask an industrial compost maker and you should get the following:
- It meets the PAS 100 standard
- The C / N ratio has been tested and is within spec for “stable and mature” compost
- It all passes through a given mesh sieve (ie below 8mm particles)
- All potentially toxic elements (e.g. mercury, heavy metals) are below the guideline levels
- NKP will be present, but compost is a soil amendment not an NKP fertiliser, so we only measure them in some compost formulations.
Ask a soil scientist to describe compost and they will struggle!
It has no scientific definition – they will refer to “Soil Organic Matter” (SOM). This is the total sum of all dead plant and animal matter in the soil – it excludes roots, living plants, living worms and bugs). They measure the labile part (compostable to you and me) fraction and the non-labile fraction (the bit that resists further decay and is known as the humeric substances fraction. They will then offer you +10 soil types, each with a different ratio of sand, clay and SOM.
The ‘fertile soils’ (what gardeners want) typically will have:
- SOM of 2-10% (UK norm 2-4%)
- Within this, humeric substance content of 1-5% (i.e. 50% total SOM)
- A fertile soil is a balanced mix of SOM, sand (silica) and clays
What if you Googled ‘best compost‘, or ‘the world’s best compost‘?
- There are claims and methods that profess to offer “colloidal compost”.
- There are methods such as Luebke, CMS, biodynamic and QR that all purport to make fabulous compost
And what if we ask the HOTBIN expert (Tony Callaghan, head of R&D at HOTBIN) to describe good HOTBIN compost!
- It smells earthy (not putrid or drain like)
- It is fine particles with no sign of original waste or big bits
- It is a dark brown material
- It is very wet and sticky – so much so it appears ‘large and lumpy’ – but looks can be deceptive – for more information see the FAQ on sieving compost.
- When dried, about 80% will pass through an 8mm sieve, 5% will be oversize (too large) and 15% will be 0.5-1cm pieces of wood chip (bulking agent) coated in humus.
- It will be pliable i.e. show signs of high levels of colloidal humeric substances
- The C/N ratio will be in the “stable and mature” zone (when tested using the Solvita compost test kit)
We have found no definition or standard that can be laboratory tested for a good, bad or fabulous compost. Only tests for ”stable and mature compost’. There is no system that routinely tracks ’cause and effect’ for any difference in compost quality directly back to a composting method.
The question remains: can one compost method deliver better compost than another?
There is ample scientific evidence that nature’s composting (i.e. on/in the soils) does produce different levels of residual humeric substances – varying from 0 and 3% depending on a range of conditions (soil structure, temp, water, oxygen).
The HOTBIN is composting outside the soil environment. The HOTBIN (subject to correct operating practice) offers a degree of control and conditions not often encountered in most soils or even most compost bins!
Does the HOTBIN deliver a better, richer compost than any other compost bin?
We do not know the answer – only detailed testing will tell us. We do know the HOTBIN offers a degree of control over the composting conditions. We have evidence that some batches appear to be high in humeric content (based on simple tests). We will not be able to substantiate this until numerous samples have been analysed under laboratory conditions and a theory has been produced and peer reviewed for why. Is it due to temperature (unlikely), quantity of aeration (possibly), the mixture of wastes (possibly).
For now we know this – HOTBIN compost often appears much wetter and more colloidal than other composts.
Why not join the debate and help us sort this out – you never know, one day we might see an annual award for the best compost and best composting method!