Budapest, Hungary
City population: 1728868
Duration: 2017 – 2018
Implementation status: Completed and archived or cancelled
Scale: Sub-microscale: Street scale (including buildings)
Project area: 3.5 m2
Type of area: Other
Last updated: October 2021

CityTree is a four-meter high freestanding installation that is able to purify city air of harmful pollutants by using a special moss culture. (Reference 1) The local government of the 3rd district tested the technology under a 6 month trial from September 2017 to March 2018. The CityTree pilot project in Budapest was concluded, once the district administration decided not to continue the project further due to technical reasons. The irrigation system started to malfunction very early in the trial period, which caused the mosses to dry out and thus producing no quantifiable results. (Reference 9)


Nature-based solution

  • Nature on buildings
  • Green walls or facades

Key challenges

  • Environmental quality
  • Air quality improvement


Creation of new green areas, Knowledge creation and awareness raising, Other

Project objectives

The goal of the project was to decrease air pollution by binding nitrogen-oxide and carbon-dioxide and producing oxygen, while cooling the air. (Reference 1) A further objective of the municipality was to raise awareness of air pollution. (Reference 7)

Implementation activities

The municipal council accepted the idea of renting a CityTree and worked on finding a fitting place for the street furniture with the help of air quality professionals (Reference 2). Due to technical issues with the irrigation system, the city district decided not to extend/prolong the contract with the developer company. (Reference 10)

Main beneficiaries

  • Citizens or community groups


Management set-up

  • Government-led

Type of initiating organisation

  • Local government/municipality

Participatory approaches/ community involvement

  • Unknown

Details on the roles of the organisations involved in the project

The government initiated the NBS and commissioned the company Green City Solutions to implement the project. (Reference 10)

Project implemented in response to ...

... an EU policy or strategy? Yes (The Environment Protection Action Plan of the local government aims at reducing air pollution in accordance with the norms of the EU for environmental protection (Reference 4).)
... a national policy or strategy? Unknown
... a local policy or strategy? Yes (The local government has an Environment Protecting Action Plan for the period of 2015-2020 (Reference 4) and the year of 2017 (Reference 6).The project is part of the newly accepted Environmental Protection Action Plan of the local government that aims at the decrease of air pollution and the increase of green surfaces in the district (Reference 4).)


Total cost

€10,000 - €50,000

Source(s) of funding

  • Public local authority budget

Type of funding

  • Earmarked public budget
  • Unknown

Non-financial contribution


Impacts and Monitoring

Environmental impacts

  • Unknown

Economic impacts

  • Unknown

Socio-cultural impacts

  • Education
  • Increased awareness of NBS and their benefits

Type of reported impacts

Achieved impacts

Presence of formal monitoring system


Presence of indicators used in reporting


Presence of monitoring/ evaluation reports

No evidence in public records

Availability of a web-based monitoring tool

No evidence in public records