Collecting Liquid Fertiliser

All About Liquid Fertiliser

Water is released during the composting process. In the HOTBIN, much of this water is evaporated and leaves as steam/water vapour through the valve in the lid. However, when there is excess water it will drain down towards the ground, as it does, it dissolves humic compounds from the compost to form a dark brown liquid fertiliser.

Is Liquid Fertiliser the Same as Compost Tea?

No. Compost tea is used to describe the liquid produced during anaerobic digestion where the goal is to convert all the waste to liquid. This liquid contains all the original plant nutrients but very little humic compounds. Whilst there are some aerated compost tea processes, most compost teas occur as a result of anaerobic digestion (e.g. Bokashi liquid).

Will the HOTBIN Produce Liquid Fertiliser?

Yes, however liquid fertiliser can only be harvested from the HOTBIN and HOTBIN Mini. On average you should expect to harvest approximately a mug full when draining regularly (every couple of weeks) however this can vary depending on the types of waste that are added into the HOTBIN. Food waste, for example, has a very high water content and each 3-4kg (small 5 litre caddy) of food waste can contain up to 2 litres of water (i.e. a large mixing jug). If the HOTBIN is not operating at hot composting temperatures 40-60°c, this excess water is not evaporated as steam/water vapour and will drain to the base of the HOTBIN and, model dependent, exit via the mesh (HOTBIN Mk 1 model) or collect under the base plate ready for harvesting (HOTBIN and HOTBIN Mini models).

Tip: Excess water can lead to the compost/waste becoming saturated preventing effective aeration which will require remedial action.

How Can I Collect the Liquid Fertiliser?

Collection of the liquid fertiliser differs depending on the HOTBIN model.

HOTBIN (2019 -) & HOTBIN Mini (2019 -)

The latest models feature a liquid fertiliser collection system which allows the liquid to collect under the base plate ready to be harvested by unscrewing the blue cap at the bottom. Simply place a shallow container underneath and collect the liquid – if you are looking to pop a small watering can underneath, the height of the units can be increased by placing some bricks or flagstones underneath or by using the HOTBIN Plinth.

HOTBIN Mk1 (2011 -)

Liquid fertiliser can still be collected with the original HOTBIN Mk1 model but will require a DIY solution such as:

  1. Place a shallow container close to the mesh plate and allow the liquid to seep through into the container.
  2. Or, raise the height of the unit using slabs or bricks allowing a container to be placed underneath the mesh to collect the liquid.

Do I Have to Collect the Liquid Fertiliser?

HOTBIN (2019 -) & HOTBIN Mini (2019 -)

Yes otherwise it will continue to pool in the bottom of the HOTBIN.

HOTBIN Mk1 (2011 -)

No, if you don’t want to collect the liquid fertiliser it will continue to drain out from the front mesh. To avoid any mess in this situation we would recommend placing the HOTBIN on a flat area of soil to allow the liquid fertiliser to drain directly back into the earth.

Can I Use the Liquid Fertiliser?

Yes – collect the liquid fertiliser and use around the garden. The brown odourless liquid does not have a high NKP (Nitrogen, Potassium, Phosphorus) value so can be used as a fertiliser and will be mainly Fulvic Acid and Humic Acid, both of which improve the uptake of minerals and can stimulate plant growth.

Health and Safety for Liquid Fertiliser Use

  • Only use liquid around plants, avoid wetting or spraying any foliage
  • When using fertiliser and compost to feed veggies, fruit or salad, DO NOT eat those items straight away, leave it a minimum of 20 days to allow microbial organisms in the soil to consume it
  • Water down any liquid fertiliser you collect from HOTBIN 10 parts water to 1 part liquid.
  • ALWAYS thoroughly wash edible items that you feed with compost, fertiliser and or leachate - especially uncooked items
  • Once collected ensure the liquid fertiliser is used within a 12 month period and stored in a plastic container.
  • ALWAYS wear gloves

Tip: Liquid fertiliser should be odourless and dark brown in colour. DO NOT USE if you have a fruity, acidic yellowish coloured liquid, or a black pungent drain like thick slimy goo.
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