How to Maintain an Aerobic Compost Heap?

How to Maintain an Aerobic Compost Heap?

Good airflow is key to efficient hot composting.

These are the primarily things you can do to maintain and aerobic compost heap and ensure the bacteria have oxygen supply to help them work effectively and efficiently to break down your waste:

  1. Add wood chippings every time you feed the HOTBIN waste that is high in moisture (a good rule of thumb is to add chippings with when you add any kitchen waste and any non bulky garden waste like grass)
    Note: If you are adding woody items these don't require extra woodchips.

  2. Give the heap a quick stir every time you add waste - This will help to evenly incorporate the woodchips and shredded paper you add to the mix, it will also encourage bacteria into the  incorporate the fresh waste with , in rare occasions it may be useful to perform maintenance on the aeration plate and aeration mesh to promote good airflow.

  3. If you are maintaining regular feeding and have the bin over half full but notice the internal thermometer is not reaching normal temperatures try the following steps:

    Step 1 - Break up the top 6 inches of the heap with the rake - occasionally matted layers can form that can completely block the airflow - It is important to break up layers like this as soon as possible. Layers of grass are the number one cause of a stalled temperature in the HOTBIN.
    Top Tip - We would recommend that a week after adding grass to the heap you break it up with the rake. Don't let this put you off adding grass as it's a great natural accelerator, just remember this tip.

    Step 2 - If you have tried step 1 and see no improvement after the addition of fresh waste consider this: If the HOTBIN has been in operation for longer than 4 months and you haven't harvested any compost yet you may find that the heap has become so dense and compact that it is difficult for air to circulate. Top Tip - In this situation remove the front hatch and harvest the lower layer of compost from the heap. This should remove the most compacted layers and breathe some life and heat back into the top layers of the heap.

  4. Perform some additional checks to further investigate a potential airflow issues and watch these videos. You could include these as part of annual maintenance, our at a timely moment as part of a post harvesting task.

Aeration Base Plate – Can It Become Blocked?

The holes in the aeration base plate can become blocked and this is completely normal in the bottom of the HOTBIN 200 and HOTBIN Mini to be covered or filled compost. That said it is rare that all the holes will get completely blocked, but it doesn't hurt to check from time to time when suits

If you do clean out the base plate and below the base plate this n the positive side is going to be black gold (the very best compost). 

Can I Test to See if the Base Plate is Blocked?

If your HOTBIN is working at 40-60°c, by definition the airflow cannot be restricted and the base plate is not clogged.

To test for a blockage, take off the door and push back the waste and slowly pour half a cup of water onto the middle of the base plate. If the water drains down below plate within 2-5 minutes the plate is not clogged, if it just sits on top - then it is blocked.

Should I Clear the Aeration Base Plate?

The answer is you shouldn’t need too as problems are so rare but you can if you wish!

To reduce the likelihood of the base plate become blocked, do the following:

  • Empty the bin every 3-4 months minimum. never longer than 6 months. The longer the period the compost sits in the HOTBIN, the more humus can drain to the base plate.
  • Before first fill and after each empty, sprinkle a thin (1 cm) layer of wood chip over the base plate, this will help with air flow and water drainage.
  • Do not add soil to the HOTBIN. Clay in the soil will make the situation worse.
  • When starting your HOTBIN for the first time place a thin layer of woody pruning's / twigs on top of the base plate to keep composted material above the holes to minimise any blocking.

How Do I Clean the Base Plate If I Wish To?

If you would like to give the HOTBIN a Spring clean and clean the base plate please check out our video showing how to carry this out.

Can the Aeration Mesh Become Blocked?

It is very rare for the aeration mesh aeration to become fully blocked. What you may see is the mesh ‘gunk’ up with silt as the liquid fertiliser collects/or drains (HOTBIN model dependant) behind the mesh.

Do not worry if the mesh plate looks rusty – it is a galvanised. It often looks a rusty colour as the brown leachate dries on the mesh. If in doubt – clean with bleach as above.

Find your HOTBIN model below for specific guidance.

HOTBIN Mk.1 Aeration Mesh

With the original HOTBIN 200 litre model the liquid fertiliser drains out of the mesh plate so this will look at times like it is blocked but that is very rarely the case. If the top section of the mesh is visible, then there is no need to worry, the air will flow through. Normally there is about 5mm of wetness at the very bottom of the mesh and about 15mm of dry mesh above - creating a clear water line. The air flows in above the water line.

For the plate to become blocked, it would require a huge amount of silt to build up in the reservoir behind the mesh plate. The design of the base reservoir and mesh plate means any small pieces of slit sink to the bottom and water flows out the mesh plate above the this.

If you find the water line very close to the top (20-25mm) of the mesh, it may be fully gunked up and restricting airflow. To clean the mesh dab with a cloth/sponge or brush on some soapy water or vinegar to kill the bio film (removing the gunk) and low the liquid fertiliser to flow out.

HOTBIN 200l and HOTBIN Mini 100l Aeration Mesh

The mesh on the HOTBIN and HOTBIN Mini is recessed so no liquid should be draining through the mesh to build up silt and cause an airflow blockage.

However, in the event that you do need to clean the mesh, simply remove the hatch and you will see a small slit above where the mesh is - wear protective gloves to avoid the sharp edges on the mesh and lever out.

To clean the mesh dab with a cloth/sponge with soapy water or you can brush this on. If this does not shift the gunk, then try a bit vinegar - this will kill the bio film removing the gunk.

Note: If the mesh plate is frequently fully blocked, please check your HOTBIN is on a flat and level surface. When tipped forward, the water and silt will collect behind the grill not in the reservoir as required.

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