Storage of materials for batch (Hot) composting

Traditioinal  Hot Composting Systems involve batch composting where  the objective is to have a sufficient volume and mix of wastes available to  enable the compost bin to be  filled on the same day. This page covers these systems. the techniques for using modern hot composting bins, such as the Hotbin, where material is added twice a week are not covered here.

 In the UK and other temperate climates there may be a constant supply of kitchen waste throughout the year (although the target should be to Love Food and Hate Waste by keeping cooked food waste to a minimum) but there will be  very little fresh garden waste during the winter months. During the summer there may be a glut of garden waste when the batch composting bins are fully occupied by material already being composted.  

 This brings us to one of the aspects of hot composting that is often only mentioned in passing. The need to store organic material ready for composting until the bin is available or sufficient material is at hand to fill the compost bin.  It is not just a question of having storage space, in the form of separate compost bins or dustbins but a suitable system for each type of materials to be stored.

Storage of Browns for hot composting

The holding bin(s)  are best located near to the  composting area. 

Some materials such as shredded paper and cardboard are easily stored in sealed dustbins, and provided they are kept dry, the material will not decompose during the storage period. Similarly, woodchip used as a bulking agent if kept dry does not create any problems although I prefer storage in a dustbin rather than a covered pile.

Straw can be left in bales or bags and covered. It can be chopped immediately before use to speed the composting process.

Autumn leaves can be stored in wire netting cages  or if dry in olythene or burlap sacks

The storage bins should be suitable for the intented contents for some items such as leaves could be stored in a simple  circular or square wire netting bin. Autumn leaves stored in such containers can to be added to the hot composting bin during the late autumn and winter.

 Shredded woody prunings, brassica and similar stalks can also be stored in an empty commercially available plastic or wooden compost bin and homeade bin  made from pallets scrap timber or even old doors. Some recommend using a compost pit and keeping them slightly damp allowing moisture to penetrate the material to make it easier to compost. This offers advantages when using a batch composting with a set of New Zealand or pallet bins where material can be easily added using a garden fork.  Personally, I prefer to keep them dry making handling easier when transferring to commercial composting bins especially when using a horizontal tumbler or bin with a top lid. The stalks will need chopping or shredding before being added to the hot bin and if being stored in a moist pit it is probably best to chop them before they Are mixed with other waste.

Whether stored damp or dry cardboard, paper, woody materials and other materials will be soaked when added in layers to construct a hot compost heap or pile. heap 

Vegetable, herbaceous, bedding plants & flowers for hot composting

One of the simplest storage method for garden waste is to use two bins or covered  piles. One pile is for coarse materials such as stalks, finished annuals and pot plots  and prunings. The second bin is used to collect grass clippings and green leaves. 

Green vegetable tops, material such as annual weeds and green manures are best exposed to the sun to dry for a few days to reduce their moisture content before storage. Although the heat generated during hot composting should kill perennial weeds I would suggest that such weeds  are completely dried before being added to the storage bin.

Water plants removed when clearing ponds can also be sun dried before storage if they are not to be immediately added to the compost bin. Once dried this green waste can then be stored in a covered pile or New Zealand bin until required

Grass clippings

Freshly cut grass is high in nitrogen i.e. is a ‘green’ material and if stored directly in a bin may decompose quickly forming a dark, wet, smelly anaerobic mat. This can be avoided allowing the grass clippings to dry out completely before adding them to a storage bin. The dried grass will be classified as a “brown”.

I have found one report that suggested that it is possible to reduce the likelihood of fresh grass clippings being stored in a bin becoming anaerobic by turning it every other day using a fork or aerating tool creating “buoyant airflow” (I have not tried this). When I cannot dry the grass mowings I prefer to mix them with a bulking agent such as dry wood chip or autumn leaves until they can be added to the hot composting bin.

Kitchen waste: Fruit and soft vegetables for hot composting

Kitchen food waste at home is usually collected in a 5 litre kitchen caddy with an airtight lid. The caddy can be emptied into a larger food waste container (such as used by councils for kerbside collections). It is best to put sheets of folded newspaper in the bottom to absorb some of the liquid and to make it easier to empty. It is said a  little compost placed on top of the waste will reduce odours.  Newspaper can be used to cover the material and discourage flies. 

Small quantities of fruit and vegetable can be stored in a refrigerator or deep but on an allotment or when larger scale composting is being undertaken this is not practicable. Stored in the garden, fruit and vegetables will start to decompose although the rate of decomposition will vary. The decomposition of the more putrescible fruit need to be kept to a minimum to reduce the risk of fly infestation and so that most of the decomposition can be restricted to the compost bin so that most can take place in the actual compost heap.

Plastic compost bins, preferably with a base and lid covered compost bin can be used although I prefer a wooden New Zealand bin with a removable front to make the removal of the stored material easy, but such bins may be more difficult to protect from rain and will not be as effective in preventing fly access. If a plastic bin is to be used one with a tightly fitted lid is recommend. Restricting the access of air will reduce the rate of decomposition during storage as will keeping the bin as cool as possible by choosing a shady location.

 

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More detailed information will be added soon