Monthly Archives: January 2012

Who Does What in the Compost Heap – the Decomposers

There are many different forms of life active within a compost heap. Below is a quick overview of who is living in your compost heap and what they are doing.

There are chemical decomposers:

Micro organisms such as bacteria, fungi, and actinomycetes.  These account for most of the decomposition that takes place in a pile.

There are larger physical decomposers:

Mites, centipedes, sow bugs, snails, millipedes, springtails, spiders, slugs, beetles, ants, flies, nematodes, flatworms, rotifers, and earthworms. These grind, suck and chew materials into smaller pieces.

The role of bacteria, fungi and other micro organisms

Without micro organisms, especially bacteria and fungi, there is no significant amount of composting. Spores and bacteria are everywhere – in the air, on food, on plants. Given the right conditions, the population will rapidly increase. Different bacteria and insects populate the heap according to temperature ranges and nature of contents. They grow; die and regrow depending on the conditions.

How many bacteria are there?

Even a few grams of compost on a teaspoon is estimated to contain up to a billion bacteria cells. No one really knows how many different types there are and only a tiny fraction have been classified. Wisegeek has some great background facts (Wisegeek). Currently, estimates of the total number of species of bacteria range from about 10 million to a billion. The number of scientifically recognized species of animals is about 1,250,000. There are almost 300,000 recognized species of plants.

Mesophilic bacteria can reproduce every 15 mins. Doubling at each reproduction (1/2/4/8/16), a population of 8 billion could be present in 13 hours. In the same 13 hours, one actinomycetes will become two. (Still impressive compared to humans at 16 years + 9 months!)

What do Fungi do?

There are many fungi species operating in a heap helping to decay waste. If the waste is left for several days, there will often be “fungus” on top of the waste. One group of specific interest are those that decompose the highly resistant lignin. These are specialists; they focus on lignin, using ligninase and lignin modifying enzymes (LMEs). Wood decay is often associated with specialist white & brown rot fungi. Fungi are a key part of the composting process you may notice a white powder and filaments which are a good sign that the more resistant lignin is being broken down. You are most likely to notice this lower down in the cooler area of the HotBin when emptying it.

Where do the worms come from?

The eggs can be in small bits of soil you add and old compost that goes onto your compost heap. Worms and worm eggs will be killed by high temperatures (>45C), so more often than not, the HotBin has less worms and they will be found in the cooler mature compost in the base layer. Worms are not essential to the heap decomposing, but worms are good because not only do they decompose waste but they leave a mucus in the compost which is proving beneficial to soil fertility. So if you have worms in your compost do not worry, if you have none do not worry either! However if you decide you want to add extra or more worms to your HotBin remember you cannot add  them into the upper active layer (as 60°C will kill them). Add worms via the hatch panel. If you find worms crawling on the walls, they are too hot! Collect them up and try adding them via the hatch door.


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Filed under Compost, Uncategorized

How to Choose a Compost Bin

How do you decide whether to pay anywhere from £20-£900 (yes really!) for a compost bin when, after all, you can compost for nothing (£0s) by piling your garden and food waste up in a corner? To justify the cash outlay you have to generate ‘value’ and you do this by checking the compost bin features deliver against your composting objectives at a price you can afford.

My name is Tony Callaghan, as a ‘Product Manager’ I used to spend my days answering similar questions on ‘value’ for software and IT service companies. One day I got frustrated with my overflowing compost bin and decided to go online and buy a compost bin to solve my problem. After a lot of effort, I concluded to get a compost bin that really worked at a price I could afford, I would have to design and manufacture my own ‘hot composting bin’ – it’s called the HotBin.

We can summarise the process of ‘How do choose a compost bin’ into seven steps:
Step 1 – WHY
Consider & define your composting objectives
Step 2 – WHERE
Review your available space and location for the compost bin
Step 3 – WHAT & WHEN
Review the seasonality, volumes and types of garden and food waste you produce
Step 4 – EFFORT
Consider how much time and effort you are willing to invest on composting
Step 5 – HOW
Consider which compost method (eg hot, cold, digesters, vermicompost) and which bin features are essential and which are nice to have (eg low odour, no rats, no flies, in/out waste list, sanitization)?
Step 6 – CHECK
Build a compost bin feature checklist
Step 7 – MATCH
Asses which compost will deliver the best price/performance

Before we go any further, let’s consider your time and effort to read this blog and research composting. Some may genuinely have the time available and interest in composting to fully research the topic – you should read the detailed steps below and take a look at these excel sheets we made to create your own evaluation.

The simple one:

The complicated one:
(We will load this on the website for you to download but if you are desperate for a copy get in touch)

















Please share how you got on and what you decide!

The majority of readers looking to buy a new compost bin probably just want a ‘fast track’ to help them make a quick decision with a degree of confidence that they are choosing a compost bin that works.  It’s not easy to fast track – there is no BSI standard, nor many user reviews of actual compost bin performance. If you are short on time, I suggest you skip the detail below and jump to the ‘reading between the lines section which has a few checks to help you gauge if the compost bin supplier has in depth expertise.

Step 1 – Consider your composting objectives:

  • Do you want to make lots of rich/great compost for your garden that will improve its fertility and lessen/reduce your use of fertiliser and maybe even peat?
  • Do you just want to keep the garden tidy?
  • Do you want to make a more positive contribution to the environment by recycling all your food waste so your local council no longer has to collect and transport it to landfill or a central AD/IVC reprocessing plant?
  • Are you just fed up with allocating more and more of your flower or vegetable patch to overflowing compost bins that never seem to do anything?
  • What are your objectives on sustainability, organic gardening, good use of limited resources.

Step 2 – Review your available space and location for the compost bin:

  • Some compost bins are limited in location (eg keep it in a sunny spot, or the opposite ‘keep it in the shade’, ‘only use on soil’, ‘do not use on clay soil’. You may have very little choice (eg it needs to go on the concrete by the garage). Your location may limit your compost bin choice.
  • You might have a small garden and no space for a large compost bin, conversely you might have very large garden and taking 3 metre square for a traditional 3-bay New Zealand compost bin system might pose no issues.
  • Do you want to the compost bin close to the kitchen so you can pop out easily in the rain to empty your food caddy?

Step 3 – Review the volume of garden and food waste you produce:

  • Are you just going to compost seasonal garden waste (summer/autumn)?
  • Do you want to compost grass cuttings (spring, summer, autumn)
  • Do you want to compost food waste – produced all year round – ie compost through winter
  • How much of each type of waste do you have? In my experience, very few garden composters or food waste recyclers accurately know how many litres (or Kgs) of waste they produce. Very few have any real desire to record and measure it either. Choosing the right compost bin size is also further complicated as compost bins can (given the right conditions to achieve ‘hot composting’) compost 32 times faster than a competitor bin that only facilitates ‘cold composting. So 20 litres of waste a week in one bin would rapidly break down within a week, but in another bin build up over time and need a 600 litre bin.

Step 4 – Consider if you want to ‘hot’ or ‘cold’ compost?

If you are unsure and want to learn more about ‘hot Vs cold’ follow the this link to Hot v Cold composting. The headline benefits of ‘hot’ composting over ‘cold’ composting are:

  • Hot composting will destroy weed seeds – saving you time and effort in future
  • Hot composting will destroy dangerous bacteria so you can compost all food waste
  • Hot composting requires far less space to compost the same amount of waste
  • Hot composting requires dramatically less time (eg 30 days Vs 360 days)
  • Hot composting works all year round (cold heaps all but stop in winter, temperatures of 0-5C)

Step 5 – Consider how much time and effort you are willing to spend on composting:

This is hard – everyone tends to answer – ‘none / minimal’. The more a vendor knows this is critical to your choice, the more pressure to use the term ‘easy’ and the bigger the potential expectation gap and likely hood of user disappointment. There is always some effort (eg collecting food, turning, mixing, shredding). In our experience, things can be made very easy by habitually following simple method-steps. But investing the time to form habits can be challenging – especially at the start when people perceive the habits are taking more time not saving time.

So, now you have a clear picture of what you want. Next, how do you check and match the compost bin against your composting objectives?

Step 6 – Build a compost bin feature list:

Build a feature list, locate the top 10 commercial bins, score each feature, eliminate those compost bins that do not fit your needs to produce a short list; then weight/score the remaining compost bins to find the best match.

Step 7 – Asses which compost bin will deliver the best price/performance:

Rate (Score) the competence of each compost bin against each feature, ie establish the performance and derive and overall value for money score – the million dollar question!

Commercial Product managers do this kind of work as their day job – but it is likely very few composters, gardeners or food waste recyclers have the time or inclination to do this.

If you have both; follow this link to the ‘compost bin competitive evaluation sheet’. You will find 12 widely available compost bins types and brands professionally analysed. You can play around with the scores and weighting to see which you think is best.

Accepting the majority of readers will not want to do this; how do you ‘read between the lines’ and spot the vendor marketing hype (that’s the polite term!).

Reading between the lines:

  1. The obvious choice is to seek user recommendations. As part of our competitive research we scan websites for ratings and reviews of compost bins. Often they just state: the bin ‘arrived/did not arrive’ on time, it was ‘easy/hard’ to assemble, followed by ‘I’ll let you know how it composts’. There are only a few reviews where people state: it delivered great compost just like the vendor said in X days.
  2. Validate vendor promises… (eg compost in 7-days). Look for detailed scientific study from reputable independent organisation to support.
  3. Check vendor expertise – does their website offer real in-depth hands-on composting advice or does it just regurgitate the same old ‘in/out’ list that applies to ‘cold’ composting without offering explanation for how it differs for hot composting?
  4. Look for vendors with expertise in composting science & engineering. All composting (from the autumn leaf on the floor to an industrial scale IVC plant) obey the same laws of nature like cooling rates, rates/speed of biochemical reactions. Should you the consumer need to know about the science and engineering of composting? Of course not, but we believe your compost bin vendor does.

I said in the introduction, you can compost for nothing (£0s) by just piling stuff up in an open heap.  To justify the cash outlay you have to generate ‘value’ and you do this by checking the compost bin features deliver against your composting objectives at a price you can afford. We hope the above tips combined with the tools in the links will help you create ‘value’ and help you decide which compost is right for you.

In my opinion, as soon as you set an objective like ‘compost all food waste with low odour and no rats or flies’ or ‘compost using an easy recipe’; ‘compost fast’; ‘compost year round’ then you need a specialist bin that offers great performance at an affordable price.

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Filed under Compost Bins

HotBin composting invention launched

Tony Callaghan had started developing the idea for what was to become HotBin, which speeds up composting and deals effectively with food and garden waste, while he was still working as a commercial product manager at the Newcastle-based company. 

Read more:

Former Sage executive launches HotBin composting invention – Business News – News.

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