Waste Treatment

Waste-to-energy plant (ZEVO)

Mixed waste from Bratislava residents’ black containers is recovered in the ZEVO OLO waste-to-energy plant, which is operated as a waste recovery facility with R1 activity – mainly as fuel and energy generation.

The purpose of the technological equipment of the ZEVO OLO plant is the thermal disposal (incineration) of waste that can no longer be used otherwise, combined with the production of heat and electricity.

The facilities also reduce the volume of landfilled waste, remove the biological activity of the waste and reduce the organic carbon content of landfilled residues.

The ZEVO OLO technology is fundamentally divided into four parts:

  • incineration
  • energy recovery
  • flue gas cleaning
  • handling generated waste

The heat generated by the incineration of the waste is used to produce steam. Part of the heat produced by waste incineration is used for the self-consumption needs of the ZEVO technology – the heating of the primary combustion air, the heating and thermal degassing of the supply water, and the heating of the ZEVO site – and the rest is used for electricity production. An average of 44,000 MWh is produced annually, and 33,000 MWh of electricity is supplied to the grid.

The energy use of waste after the planned modernisation of the ZEVO OLO plant will result in the highly efficient combined production of electricity and heat with a maximisation of waste heat utilisation. It is estimated that approximately 30% of the total heat demand of the centralised heating system (approx. 225,000 MWh) will be met, which would mean a full substitution of fossil fuels (natural gas) and a significant reduction of carbon dioxide emissions compared to the current form of heat production.

Sorting line

The sorted waste from the blue and yellow containers flows to the sorting line, where the materials are re-sorted, baled and sent for further processing in the recycling process.

The automated workplace of the complex separation line designed mainly for a sorted component of municipal waste, i.e. plastics and paper, is located on the premises of the existing re-sorting plant at ZEVO OLO in Vlčie hrdlo.

It is a Best Available Technique (BAT) facility, which is currently the most efficient and advanced stage of development of the used technologies and the operational methods developed in the waste disposal, treatment and recycling industry. Under economically and technically acceptable conditions, and taking into account costs and benefits, these facilities are the most effective in achieving the highest possible degree of protection for the environment as a whole.

The automated sorting line is used for primarily sorting and baling plastic municipal waste and for the separate sorting and baling of paper waste.

The re-sorting of the individual components is based on colour sorting and material composition.

Building a municipal composting plant

Bratislava aims for biodegradable waste (garden and kitchen waste) to be treated in its own facility and for the compost from the facility to be used within the city. In cooperation with OLO, the city is working to build its own ZAZO facility.

The municipal company OLO plans to build a facility for the aerobic processing of biodegradable waste in the cadastral area of Podunajské Biskupice (Hon Vekňa); this will be the ZAZO Bratislava industrial composting plant.

There is currently a great debate among experts in EU countries about the organisation of biodegradable waste management. All biodegradable waste that is free from contaminants and other unsuitable additives should preferably be used for composting or first undergo anaerobic digestion in order to obtain biogas and then be composted.

The planned capacity of the composting plant is 48,500 tonnes of mainly garden and kitchen waste per year. Unlike other common composting plants in Slovakia, the design of the Bratislava plant takes into account the maximum elimination of dust and odour particles, which are usually not welcomed by residents living near such facilities.

  • The first and intensive phase of composting – and, in the case of kitchen waste, also its sanitation – will take place in a closed hall within ZAZO Bratislava with the discharge of process air into a scrubber and biofilter which will ensure the binding of dust particles and odour emissions at a demonstrably monitored level of at least 95%.
  • An automated aeration process with the elimination of unwanted leachates and filtrates will also be used in the secondary ripening area.

We believe that ZAZO Bratislava will become an integral part of the circular economy and that every environmentally-minded household actively involved in the collection of biodegradable waste will see the rewards in a high-quality substrate.

For the time being, external companies are used for bio-waste processing. For garden bio-waste, there is a composting plant in Pezinok and for kitchen waste there is a biogas plant in Bošany.