Composting

Equipment

• For composting biowaste, you need a compost bin that is protected against vermin. If composting year-round, it needs to be thermally insulated.
• Garden waste can be composted in a managed open-air compost heap.
• Composting toilet waste requires a composter designed for the purpose. Ask municipal environmental protection authorities for more information when starting to plan the composting of toilet waste.

The kitchen waste produced by a family of four requires a composter of about 200 litres. If you also intend to compost garden waste, you need 400–600 litres more capacity. In larger residential buildings, we recommend reserving about 20 litres of capacity per resident. The most affordable solution for garden waste is a compost heap, a frame or non-insulated composter. Waste decomposes quicker in a composter or frame. You can also build a compost bin yourself. Instructions for building one can be found in books or on websites on the subject.

As well as a thermal composter / frame for composting, you will need:

• a separate container in the kitchen for organic waste
• bedding (coarser substances such as milled bark, branch chips, cutter shavings) and a container and scoop for it
• a pitchfork and spade for maintenance and emptying
• a person in charge of it, especially if there are several composting households involved

Filling the composter

Start composting by putting a layer of coarse bedding at the bottom. Then fill the composter in layers of biowaste and bedding. Organic waste, such as fish guts, should be buried deeper and covered carefully. Check your compost regularly to see what it looks, smells and feels like. Good compost smells of dirt but it should not smell bad.

Well-functioning compost

• Is warm
• Becomes compressed
• Smells of soil – does not smell bad
• Does not contain maggots or ants

Mix the compost as needed. Fluffing up the top layer once or twice a month is usually enough. You can make air holes in the compost once a week with a pitchfork. Suitably moist compost material feels like a damp sponge in your hand. Dried compost needs watering and fluffing up.

The compost is emptied when its contents have decomposed into a mass of uniform quality that looks like soil and where the initial materials can hardly be distinguished. The decomposed material is further composted in a frame or heap, for example, with leaf compost. The resulting earth can be used to fertilise lawns, flowerbeds and bushes and for soil improvement or mixed in with sand in a flowerpot.

What goes in the compost?

• Fruit, vegetable and root vegetable peelings
• Coffee and tea grounds and used filter bags and tea bags
• All other food waste
• Potting soil and plant debris
• Kitchen paper, paper napkins
• A newspaper double page or paper bag as a wrapper for biowaste
• Natural fibres in very small volumes, such as wool, cotton, linen, silk

What doesn’t go in the compost?

• Materials that do not decompose or that may contaminate the compost
• Cigarette stubs, vacuum cleaner dust bags
• Plastic bags, milk cartons
• Plastics, glass, metals
• Products made from synthetic fibres, leather or rubber
• Ash or lime, which make the compost too alkaline and prevent micro-organisms from functioning
• Medicine and other hazardous waste, such as oils, petrol, solvents, paint, pesticides, herbicides, disinfectants or wood preservatives.

Problems with the compost

Problems with biowaste compost are usually caused by an insufficient amount of bedding. It leads to the compost becoming waterlogged, a lack of oxygen and a bad smell. The most common problem with garden waste compost is slow decomposition due to nitrogen deficiency and dryness. Sometimes there may also be uninvited guests, such as flies and maggots. You can try to improve the functioning of the compost with commercial products but it is worth trying some environmentally and pocket-friendly methods first.

Bedding

Carbon-to-nitrogen ratio is important for successful composting. Fresh garden and food waste provide the compost with plenty of nitrogen. The bedding acts as a source of carbon. In addition, the bedding mulches and aerates the compost and binds excessive moisture, potential smells and ammonia. When choosing bedding, it is good to consider the quality of the material to be composted and the price and availability of the bedding. In small-scale composting, the ratio of waste and woodchips is usually 1:1.

Bedding sellers

Bedding is sold, for example, in garden centres. You can also ask for cutter shavings at planing mills or neighbourhood schools and youth clubs with woodwork facilities. Sawdust and shavings created through sawing wood also make excellent bedding.