Community composting

The city allows the holder of biodegradable waste to set up a community composting site to serve the community's own needs in a specific location. For example, groups of householders, residents in residential buildings, owners of gardens in gardening areas, schools or pre-schools and others can apply.

Community composting aims to reduce the amount of biodegradable waste in municipal waste and to produce its own compost for members of the community. The compost produced can be used in planting, the maintenance of greenery outside houses or in pots at home.

The applicant should submit the application to set up a community composting site to the following address: Primaciálne nám. 1, P. O. BOX 192, 814 99 Bratislava 1. The city, after assessing the application and if the conditions to set up a community composting site are met, issues its decision within 45 days and assigns a registration number to the community composting site. The applicant bears the costs of the construction of the community composting site.

Conditions

Pursuant to Section 15 of the city's General Binding Regulation No. 6/2020, the conditions for setting up a community composting site are as follows:

• location outside the protection zone of a water source, long-term waterlogged land or in a flood zone, away from playgrounds and sports grounds, not creating an obstacle on the road
• protection against animal access by enclosing on each side, and against rodents and other unwanted animals on the underside with mesh netting with a maximum size of 1 x 1cm or other suitable means so as not to prevent the natural drainage of excess moisture into the soil and the access of micro- and macro-organisms into the site
• stable protection against direct sunlight, rain, strong winds, i.e. sited under a tree, bush or shelter, within an accessible distance for all members of the community
• provision of a label with instructions on which wastes belong in the composting site, a list of wastes not to be placed in the composting site and the contact details of the compost-master

Flowers, wood chips, sawdust, grass clippings, branches, leaves, fruit and vegetable waste, rotten fruit and weeds can be placed in the compost bin. Biodegradable waste of animal origin, in particular dairy and meat products, is not suitable for composting.

Composting process

Proper composting requires:

• treatment of biological waste by chopping or shredding, thereby speeding up the decomposition process
• not piling waste in layers, but mixing them together, mixing soft and wet materials (grass clippings, garden scraps, etc.) with hard and dry materials (wood chips, leaves, wood shavings, etc.)
• checking the moisture content: well-mixed compost holds its shape when squeezed and does not leak water; if it breaks down, the compost should be remoistened and dug up; if it is waterlogged, dry absorbent material should be added.
• controlling the temperature: when the compost heap is properly set up and there is sufficient material, the temperature reaches 40 - 60 °C; if the temperature drops or rises outside this temperature range, the compost must be re-dug, which restarts the decomposition process
• ensuring sufficient aeration of the composted material by creating holes in the bin and by turning over the composted material
• mixing the compost with a small amount of soil (max. 10% by weight), as soil contains a number of micro-organisms that help the compost to decompose, bind moisture and odours, and help the compost to form a fine-grained earthy texture

If the above requirements are met, a mature compost can be produced in 3 - 6 months. Otherwise, the maturing period can increase up to 2 years. The maturity of the compost can be tested by sowing watercress seeds in a container of moist compost and covering it with a film to retain moisture. If most of the seeds germinate within the first week, this means that the compost is free from substances harmful to plants and can be used in the garden. Green-coloured plant leaves indicate that the compost is mature, while yellow or brown leaves indicate raw compost. If only a small proportion of seeds germinate, the compost needs to undergo further decomposition.

Apply raw compost only for mulching around trees and shrubs, not for sowing or seedlings, as it could damage the plants.

Mature compost is brown to dark brown in colour, has a fine-grained texture and is odourless. Prior to use, the compost is sieved and the unprocessed parts are placed in a new foundation heap. When applied to the soil, the compost is not ploughed in, but only worked gently into the ground.