Worms and HOTBIN composting

Worms and HOTBIN compostingA 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.


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The Ultimate Guide To Compost Sieving and Sieves

Many people will just use compost ‘as it comes’ from the compost bin by digging it in to the soil around plants or into the vegetable patch.

Sometimes it is preferable to have fine compost for use in potting up seedlings or as I often do, use as a lawn top-dressing (it does wonders to reduce moss!) but large pieces of compost are hard to rake in and can cover the grass and act as ‘mulch’ – not the desired result.

Mature HOTBIN compost at 3 months

Mature HOTBIN compost at 3 months

I have tested a few compost sieves and I thought it was time to summarise how they perform and offer a view on the how worthwhile compost sieving is.

Sieving compost can be tricky and labour intensive – it does not take too many lumps of wet moist compost to clog up the sieves.

HotBin Compost - Good and ready after 3 months

HotBin Compost – Good and ready after 3 months

The Plastic Hand Sieve

A Plastic hand sieve will cost £4-10. These work OK if you just have a bucket of compost to sieve. When you only have small amounts of compost, the price/performance is hard to beat. However, once you start to get into bags or wheel barrow loads;  the hand sieves becomes far to time consuming and difficult. Most of us will just end up with aching arms and a stiff back! The plastic pan sieves struggle with moist compost – it will just roll into balls that won’t sieve. (There are a whole range of metal hand sieves that work the  same as the plastic but cost a lot more).

A 33cm plastic garden sieve

A 33cm plastic garden sieve

The Rotary Sieve

The Rotary sieve cost approximately between £30-40.  Now it is OK with dry compost and handles typical loads/sizes from the HOTBIN. However it tends to clog up when used with moist compost. Some large pieces can jam and you’ll need to stop and clear them before carrying on. (NB this review was based on third-party input not our own test).

The RS150 Rotary Soil Sieve

The RS150 Rotary Soil Sieve

The Watford Sifter

The Watford Sifter costs approx £120-150. It definitely works better with soil than compost. It did struggle with wet compost as it tends to clog and stick in centre of sieve and it did not tip ‘up and down’ far enough to move it from this position. Good for medium or large loads and certainly a good option if you have lots of soil and compost to sieve otherwise you might struggle to justify the cost.

The Watford sieving HOTBIN compost which is 3 months old and typically wet

The Watford sieving HOTBIN compost which is 3 months old and typically wet & sticky

Likes / dislikes:

  • You get two screens – fine and coarse.
  • Easy to push ‘up and down’
  • A bit of a ‘pain’ to get the retained coarse material out of the sieve tray. In the end, I was continually lifting the whole box and tipping it out. It’s a heavy lift when not much is sieved. This issue goes away if most of the soil/compost gets sieved through – but if it is all fine in the first place there is no need to sieve!

The Scheppach Sieve

The Scheppach  costs in the region of £350-400, this has to be a serious piece of kit. It is a trommel design (rotating cylinder) and uses and an electric motor to turn it so it also needs an electrical supply! It will handle significant volumes of soil and compost. We have not used this kit, but we know three large-scale gardeners/composters who do and they all rate it highly. If you are only using it 1-3 times a year, our opinion is it is questionable how much value you will actually get. Probably one for the professional and/or allotment/community schemes where you can share it. PS: It also takes a lot storage space.

The Scheppach RS400 rotart sifter

The Scheppach RS400 rotart sifter

The Compost Sifter

Compost Sifter costs £155 (excl £40 delivery to UK). This is very new and comes from Belgium. It uses a similar rotary tunnel (trommel) design as the Scheppach – but it is turned manually via a handle. By long way, it required the least effort and sieved more faster. The mesh (hole size) is smaller than the others (8mm) and this means it won’t sieve wet compost (based on our test of HOTBIN compost). However, after initial disappoint with wet compost, it absolutely cleaned up when it came to dry compost. Our current favourite – we may even resell it with a special HOTBIN specific tweaks!!

The Compost Sifter - Assembled with just wheels to go

The Compost Sifter – Assembled with just wheels to go

Likes / dislikes:

  • Ease of turning – real winning feature
  • Retains oversize and easy to get it out via panel that detaches
  • It is very heavy – fine once set up on wheels, but you may need 2-people to get it out of box and set up on the frame.
  • It still struggles with wet sticky compost – but so do all the rest!


Sieving compost can be tricky and labour intensive, especially if it is wet and sticky as it tends ball into large lumps and clog sieves.

After numerous tests on HOTBIN compost, we think we are on solid ground to say if you want to sieve the naturally sticky wet HOTBIN compost you will have to dry it first (see how below). All the sieves will perform significantly better with dried compost.

Our next question is: Is it worth sieving compost?

This is not just about the cost of the sieve and the time and effort that goes into sieving. The most beneficial part of compost is the group of humeric substances. These compounds impact soil fertility as they enhance root uptake of minerals and water. It therefore follows the biggest benefit comes from digging humeric substances into the root zone. If digging in, one has to question if the effort to sieve out any big bits.  Large over sized lumps will compost down in soil over 12-24 months. As long as the total volume of large pieces is low, the ongoing composting of these pieces is unlikely to affect nitrogen availability during the final composting period. With HOTBIN compost there is always about 10-15% of small 0.5-1.5cm wood chip (bulking agent) pieces that remain in the compost. Our tests show these pieces are covered in layers of humeric compounds. We believe these pieces of wood chip are slowly composted as they are coated and protected from rapid decay. Whilst in the soil, small pieces of wood chip also aid aeration and soil tiling.

There are applications where sieved compost is useful e.g. when used as a lawn top-dressing (i.e. raking in a thin layer of compost on to the grass), or when creating a potting mix for seedlings. Lawn care is a huge part of British gardening. I personally have seen good results from top-dressing moss ridden lawns (high clay, poor drainage) with sieved compost. For those of you that want to drop dress, the method is outlined below.

In summary, for most compost users and most types of compost application, we do not believe drying compost and then sieving is worthwhile.

Compost and lawn top dressing

  • In late Autumn take out your HOTBIN compost and dry it (we spread it out as a thin layer on patio / large sheet polyethylene)
  • Add dried compost to compost sifter or like to sieve
  • Sieve and bag up
  • Spread on grass and rake out to about 1cm layer.

This will take huge quantities of compost – but the rewards is you won’t be spending much on lawn fertiliser or moss killer!


Filed under Compost, How to get the best out of your HOTBIN, Products

Is your HOTBIN compost good, bad or fabulous?

We do not know the answer – only detailed testing will prove things one way or another.

What we do know is this – composts differ in physical structure and chemical composition. HOTBIN compost often appears much wetter and sticker than other composts. We believe some composts will be better for soil fertility than others. We believe those with higher humus content will be better for your soil and hence plants and vegetables.

We have a some evidence it might be better. This is related to the physical properties which in turn we believe are linked to higher humeric substance content.

Humeric substances are the essential component in compost that delivers the benefits – the more humeric substances in your compost the better your compost. It also is the case that the more humeric substances in your soil the more fertile your soil.

To explore if composts are different, we can look at the analysis of composts.

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 unravel this.

However what we do know is this…

Composts differ in physical structure and chemical composition. HOTBIN compost often appears much wetter and sticker than other composts. We believe some compost will be better for soil fertility than others. We believe those with higher humus content will prove to be the best. We have some evidence it might be better based on the physical properties and that these properties are potentially linked to higher humeric substance content.

Why not join the debate and help us sort this out.

We need to define and analyse what makes fabulous compost. This has to be tested by soil science labs, it has to follow all the norms of science (evidence, repeatable methods).

If we have a standard for the very best compost, it is pretty easy – You never know we could even have an annual competition and give a prize for the best compost and best composting method!


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