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How to Use the HOTBIN Mega Composter

Tony Callaghan 07/07/2022

How to Use the HOTBIN Mega Composter

The following tips will help you check expectations and ensure the HOTBIN Mega works for you.

Hot Composting

  • To hot compost at 40-60C, it is essential to match the amount of compost material you have with the size of the HOTBIN (450, 700 litres). We are happy to help where needed.  It is hard to judge the size of HOTBIN you need based on normal compost bins which are often slow. As a guide, the HOTBIN 450 will replace 4x450 litre normal bins, but it is best to spend a bit of time looking at the bucket/wheelbarrow/grass box loads you actually generate each week
  • Composting goes through temperature phases - it warms up to 30C (mesophilic), it then gets hot 40-60C (thermophilic) it then cools down and matures (20-30C). When we say hot composting, we mean keeping the upper/new material in the hot zone.  Expect some fluctuation in temperature and don't panic! 

Winter Vs Summer Composting

  • In summer, with a lot of organic waste, there is a lot of heat generated and this can dry out the waste. Moisture is essential for microbes. You might (probably will) need to add water - so keep a watering can full and close by ready to re-wet the compost (tepid 15-20C is better than cold from the tap at 5-10C). 
  • In winter, the available compost materials change (e.g. no grass).  What you have will be woodier and less likely to enable 40-60C hot composting.  Rather than worry, adjust your expectation from 'hot' to 'warm' and let it do its thing - you will still have a base layer of great compost for Spring.

When to harvest the compost (i.e. empty) - your Mega HOTBIN

Each customer will have different garden waste volume, different plants etc (e.g. allotment of vegetables versus large lawn/borders) and different habits and working patterns.  The product is new to the market and time will tell us how different customers use it, right now we think there will be two groups of users:

  • "Maximum output, work it year-round" and
  • "Fit the bin around the seasonal garden work"

Maximum output, work it year-round 

You will get maximum and year-round hot composting when you add enough compost waste each week.  (This is not as easy as it sounds - most gardens have little waste in winter!

Subject to enough waste, you can add new waste each week and take out finished compost every 90 days (3 months). Just remember, using this method, the top layer will not be fully composted. You will skim it off and put it to one side. (It is then ready to load into the empty bin and re-start the bin quickly). The other factor to consider is where is the compost going to be used every 90 days. For some, the answer will be moving it to a cold bin until needed. This sequence maximises the hot composting ability.  

Fit the bin around your seasonal garden work

We think composting is easier when it fits around your gardening schedule.  We use our bin as follows: we empty the bin in Spring and late Autumn as this is when we need the compost for Spring planting and Autumn dressing/spreading.  In early Spring, we have an empty bin. We do the spring clean-up and add the contents to start the bin. We add small amounts of vegetable peelings and bits of garden pruning each week. Then in late Spring and through Summer, we have grass and more pruning etc. By late Autumn the bin is full. We empty it and use the compost. Any of the top non-composted material goes back in. We then have a big Autumn clear up and the bin gets full. We know we won't have much over winter. We accept the bin will get hot and then overwinter drop down to 10-20C. In spring we have a nice batch ready again.  If all goes to plan we have enough capacity, empty almost full batches and have less skimming and re-loading of non-composted material.

Emptying out the bin takes time and a little bit of care. Dismantle it correctly, and take your time removing compost from the base carefully without digging into the base plate with the fork. Clean off the edges and grooves before re-assembly. It will give years of good service. (we aim to have some videos available shortly).

Turning compost

  • All composting works better when things are chopped up. This is not always practical - so just recognise that larger bits will take longer.
  • There is no need to turn waste in the HOTBIN.  Buoyant hot air rises and draws cold air up. To aerate a hot compost heap ensure the mix allows air to travel up and around the compost particles. 

Aeration - adding wood chip 'bulking agent and or shredded paper

Users of the HOTBIN 200 litre Mark2 will spot a considerable difference between the advice for the 450 and 700 and the 200 around the use of wood chips and shredded paper.  Both HOTBINs work the same and use the same science - but with the 200,  the focus is usually food waste.  (In composting terms food waste is 'wet' (70-80% water) and quick to digest and hence slump into a mushy layer). The focus of the Mega bin is garden waste (which in composting terms is drier (50% water) and woodier - so is less prone to slumping). The former needs help to aerate and balance the water (hence the advice to add shredded paper and wood chip), the latter 'self aerates' and has the right amount of water so rarely needs any shredded paper.

Pets and Vermin

  • Pets - sorry, we know people love pets, but if yours is unruly and wants to use the HOTBIN as a scratching post, this is for you to manage - it's outside the warranty. There are tips like putting mesh wire around until pets get familiar with new things etc.
  • Vermin (rats) - if you know your plot/site already has rats - CEASE composting. Remove all waste and leave for 3-4 months (no food, no rats). When you restart, simple steps will help prevent them from returning:  if adding food waste, always check it goes into the middle of the bin. Never (no matter how hard picking up scraps of the floor is) leave bits of food around the bin. About the only material rats will not attack is steel plate. If they can smell food they will come. Once at the bin, the risk is they will eat through the bin wall to get inside for more food. The design minimises the risk - there is a filter preventing most odour, the odour rises at height - rather than being on the floor near rats.  

Do I need compost Accelerators with the HOTBIN Mega?

No - but this is only a meaningful answer if you understand the correct use of the term - see our blog. The only accelerator worth focusing on is heat and shredding waste.

Can I add the Compost Humification Agent to my HOTBIN?

Yes. Again you need to understand what the humification does in relation to other terms such as activator, inoculator and accelerator.

Can I add the biochar granules to the HOTBIN Mega Bin?

Yes. Adding biochar to your compost heap is by far the best way to ensure success with biochar. We believe our biochar-based humidification agent offers more value than just biochar,  To understand what the humification does in relation to other terms such as our humification blog.

SoilFixer has 7 years of practical hands-on experience using the HOTBINs with biochar and biochar-humification agent. Contact us if you need more expert help

Trouble Shooting

Wet sludge
If you have wet sloppy food waste, it helps to add a 'bulking agent' like wood chip and shredded paper 
Smell/ odour
When you open the HOTBIN, there will be a cabbage type of whiff. However, when the odour becomes putrid, it is a sign the waste has gone anaerobic.  it helps to add a 'bulking agent' like wood chip and shredded paper. (This is rare with garden waste)

When adding large volumes of grass, it can heat up rapidly and then form into a matted layer.  After 5 days, rake this through and mix in with compost.

On rare occasions, the grass will be very wet and might slump into a putrid layer. To avoid this, add some shredded paper and wood chips (or biochar) chips.     

If you have composted grass in the 200-litre HOTBIN - the advice for the 450/700 may seem contradictory.... see explanation above.

Waste dried out

In hot summers with lots of organic waste, the extra heat can overdry the waste. If this happens, you will need to add some tepid water - try 5 litres. 

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