Ranking of the 10 cleanest cities on the planet

The ranking by global consultancy Mercer Eco-City provides valuable and reliable information about the sustainability and environmental viability of cities around the world.

Every year, it compiles a list of the most sustainable and clean cities on the planet. To create this ranking, it takes into account the following basic environmental parameters:

  • Quality and availability of drinking water
  • Recycling and waste treatment
  • Quality of wastewater treatment systems
  • Levels of air pollution
  • Traffic flow

In 2023, the following ranking was determined based on these criteria:

1. Copenhagen, Denmark: The cleanest city on the planet

Copenhagen is the capital of Denmark, with a population of 1,990,000, and has become the cleanest city in the world thanks to social awareness and environmentally friendly practices. Since 1973, coinciding with the oil crisis, Denmark has sought its economic alternative in the energy sector, with Green Business.

Notable facts: the country’s GDP has grown by 100% since 1980, while energy consumption has only increased by 6% and water consumption has been reduced by 40%. Currently, the energy mix exceeds 30%, and it is expected to achieve energy independence by 2050.

Notable features:

  • Bicycle implementation: Copenhagen has 700,000 bicycles. 62% of its citizens use them.
  • Clean energy: Photovoltaic and wind energy are essential for decarbonizing the city. The Holmen project will have 9 islands that will contain wind farms and waste conversion (300,000 MWh).
  • Urban management using AI: BIG DATA is used for optimizing buildings and public services, and AI-driven management is increasing.
  • Green city: 25% of its surface is occupied by public gardens. Work is being done on vertical gardens.
  • Concern for polluting gases: The aim is to neutralize 100% of emissions by 2025.

2. Singapore: The Cleanest City in Asia

Singapore, with a population of 6,036,000, is a clear example of a city that has successfully combined cleanliness, sustainability, and urban development.

Some of the measures it has implemented to create a culture of responsibility and environmental awareness among its citizens are:

  • Clean and Green Policy: In the 1960s, Prime Minister Lee Kuan Yew introduced the “Clean and Green Policy.” This initiative included changes in public health laws, the relocation of street vendors, and disease control measures.
  • Sustainable Design: Singapore is a leader in sustainable building design, such as vertical gardens and futuristic supertrees surrounded by thousands of plants.
  • Disease Control: Due to the warm and humid climate, cleanliness is crucial in preventing the spread of mosquito-borne diseases.
  • Urban Replanning: Over the years, Singapore has relocated factories, businesses, and populations to improve quality of life and sustainability.
  • Efficient Water Use: Singapore is a technological leader in water treatment. The NEWater system allows for the production of drinking water from wastewater. Rainwater harvesting and desalination also contribute to water security.
  • Public Transportation: Singapore has a well-developed and organized public transportation system. The subway and buses are popular, significantly reducing traffic congestion and greenhouse gas emissions.
  • Renewable Energy: Singapore is investing in renewable energy and clean technologies.
  • Green Spaces: Despite being a densely populated city, Singapore has preserved green areas and parks.
  • Waste Management: Singapore has an efficient waste management system. Solid waste incineration generates energy. The Semakau landfill is an example. Much of Singapore’s cleanliness is due to the high fines imposed by the government on those who litter or dispose of waste in inappropriate places.

3. Calgary: The Cleanest City in Canada

This beautiful Canadian city located at the foot of the Rocky Mountains has a population of 1,436,000. It bases its sustainability and livability values on the city’s environmental assets and the quality of life of its residents.

Calgary is known as a place for ecotourism and winter sports. Important vacation spots are located near the city, and in 1988, Calgary became the first Canadian city to host the Winter Olympics.

It is also the host of several annual festivals, such as the Calgary Stampede or its Folk Music Festival.

Calgary tied with the Australian city of Adelaide as the fifth-best place in the world to live. It was also rated as the cleanest city in the world in a survey conducted by Forbes magazine in 2007. Regarding its environmental integration, it stands out for:

  • Protection and restoration of natural areas: This includes the conservation of wetlands, parks, and trees.
  • Protection of water resources: Efforts are made to maintain water quality and manage floods.
  • Improvement of air quality: Measures are implemented to reduce air pollution.
  • Reduction of pollution: Waste reduction and recycling are encouraged.
  • Sustainable transportation: Public transportation, walking, and cycling are promoted.
  • Adaptation to climate change: Calgary strives to be more resilient to the impacts of climate change, for example, by reducing greenhouse gas emissions.
  • Reduction of environmental impact: The evolution of environmental impact is constantly monitored and evaluated.

Calgary has become a prominent example of how urban development and cleanliness can coexist harmoniously.

4. Helsinki: Nordic beacon of cleanliness

Helsinki is the largest political, educational, financial, cultural, and research center, as well as one of the most important cities in northern Europe, with a population of 675,750. Approximately 70% of foreign companies operating in Finland have established themselves in the region.

Helsinki was chosen as the World Design Capital for the year 2012, hosting the 1952 Olympic Games and the 52nd Eurovision Song Contest in 2007.

This city is known worldwide for its great design, which is evident in its streets, shops, and buildings, being part of the UNESCO Creative Cities Network since 2014.

In the August 2012 edition, the Economist Intelligence Unit ranked Helsinki eighth overall in the best cities to live in worldwide.

In 2011, Monocle magazine established the city of Helsinki as the best city to live and develop in the world.

The city has become a benchmark for cleanliness for a multitude of reasons, including the advantage of being located a considerable distance from major European cities, resulting in low emissions of pollutants from long-distance transportation.

Helsinki is also the only prominent metropolis in Finland, which also contributes to its excellent air quality. The country’s sparse population and minimal traffic contribute to its overall cleanliness and environment, as well as innovative waste management systems, efficient public transportation, and extensive green spaces.

Helsinki stands out for its focus on environmental preservation. Approximately one-third of Helsinki is occupied by green areas, reserved for outdoor sports activities and moments of relaxation.

The extensive Central Park, an urban garden spanning over 1,000 hectares, and the city’s rooftop gardens and playgrounds complement its focus on cleanliness and sustainability.

This city is a prominent example of clean energy and sustainable public transportation. It strives to reduce 69% of traffic-related greenhouse gas emissions by 2035 and aims to have at least 30% of its buses (approximately 400 units) running on electricity by 2025.

5. Auckland: The Cleanest City in New Zealand

Auckland, the largest city in New Zealand and the South Pacific. It has a population of 1,692,770 and is considered one of the cleanest cities in the world due to significant measures taken to preserve the environment and promote traffic reduction.

Here are some of the actions that have been implemented:

  • Clean Technologies and Sustainable Development: Auckland has adopted clean technologies in various areas, such as renewable energy, waste management, and sustainable mobility. These technologies aim to reduce or eliminate negative impact on the environment, focusing on energy efficiency and responsible use of natural resources.
  • Economic, Social, and Environmental Balance: The city recognizes the importance of sustainable development, which requires a balance between economic, social, and environmental aspects. This involves taking measures that promote efficiency and responsibility in resource use.
  • Ecosystem-based Adaptation (EbA): Auckland has also studied how nature can protect its environment against the impacts of climate change. The strategy of using nature as a defense is called ecosystem-based adaptation. This involves taking care of nature so that it takes care of us. For example, to ensure water supply, measures are being implemented to protect ecosystems that regulate water flows.

Auckland can be enjoyed without the pollution one would expect from such a large city. It is nestled among stunning natural landscapes.

It has been identified as the city that has undergone the most radical transformation in the past three decades in terms of cleanliness and sustainability. This is the result of its dedication to sustainable practices, such as renewable energy initiatives and waste reduction programs.

6. Adelaide, Australia: Cleanliness in the Antipodes

Adelaide is the capital of South Australia and its fifth most populous city with 1,379,000 inhabitants. It is known as “The City of Churches” because of its diverse range of European and Asian immigrants.

It is very open, inclusive, and progressive. It stands out for its cleanliness, focus on sustainability, and care for the environment. Special mention deserves:

  • Sustainability Program: Adelaide has a sustainability program that supports its reputation as a city that adapts to climate change, reduces carbon emissions, uses resources intelligently, and protects biodiversity.
  • Water Protection: This city has the vision of becoming a “Water Sensitive City.” This involves a focus on sustainable water management and the protection of aquatic ecosystems.
  • Carbon Neutral: The city, its residents, and businesses work together to make Adelaide one of the first carbon-neutral cities in the world.
  • Urban Greening: Urban vegetation not only beautifies the city but also has practical applications. The City of Adelaide is actively involved in increasing urban greening to make the city even more livable.
  • Climate Change Preparedness: This city proactively prepares for the short and long-term effects of climate change.
  • Circular Economy: The city is committed to the circular economy and waste reduction.
  • Biodiversity: Adelaide is a highly biodiverse place. The city protects different types of ecosystems, flora, and fauna.

7. Tokyo, Japan: Cleanliness in its culture

Tokyo is the most populous city in the world with 37,115,000 inhabitants, and yet it is considered one of the cleanest cities that cares deeply about sustainability and quality of life.

The Japanese have the utmost respect for the environment and the community. Some manifestations of this are:

  • Waste management: Tokyo has implemented an exemplary waste management system, despite being one of the most densely populated cities in the world. Their efforts in this regard have contributed to their reputation as a clean city.
  • Public transportation: The efficient public transportation network in Tokyo reduces the need for private vehicles and, therefore, air pollution.
  • Technology and innovation: Tokyo also stands out for its focus on technology and smart urban planning.
  • Renewable energy: In terms of alternative energy, Tokyo has limited terrain topography in the country, making it a challenge to find enough land for installing solar panels. However, they have opted for small-scale solar plants, ranging from 1.5 to 2 MW. As for wind energy, Japan has both fixed and floating wind farms that are earthquake-resistant. The stabilization of wind turbines is based on naval technology to minimize swaying. Regarding ocean energy, Japan is testing a giant underwater turbine (Kairyu) that harnesses ocean currents along the west coast.

The country aims to achieve carbon neutrality by 2050, and its renewable energy strategy sets an ambitious target of 36%-38% by 2030. Despite the challenges, Japan is proving to be a leader in clean and sustainable technologies.

Tokyo is a testament to these values. Even smoking is treated differently there, where outdoor smokers are required to stay in designated “smoking areas” to avoid polluting the air for non-smokers and to prevent cigarette butts from littering the city.

In public transportation and even in taxis, you will notice how clean the stations, trains, and cars are.

8. Zurich, Switzerland: Excellence and Cleanliness

Zurich is a Swiss city with a population of 1,443,350 inhabitants, and it has stood out for its commitment to sustainable development and environmental protection. Some interesting aspects about Zurich and its focus on sustainability are as follows:

  • Sustainable Economy: Zurich has fostered sustainable industries and promoted green jobs. Its financial sector also stands out for its commitment to ethical and responsible banking.
  • Public Transportation and Bicycles: Zurich has invested in improving public transportation and promoting the use of bicycles, reducing car traffic.
  • Energy Efficiency and Renewable Energy: Measures have been implemented to improve energy efficiency and the use of renewable energy in buildings.
  • Green Spaces and Recreational Areas: This city protects its green spaces and creates recreational areas for its residents.

Flagship projects:

  • Zurich Forest: In 2020, the Zurich Forest project was launched to support reforestation and biodiversity restoration in Brazil.
  • Commitment to Reforestation: Since 2022, this city has acted on 12,800 hectares, planting over 7,900 trees to accelerate the recovery of natural areas affected by fires.

The Zurich Department of Civil Engineering and Waste Disposal has the monumental task of collecting over 30,000 bags of garbage daily. This tireless team operates 24 hours a day to ensure that the 737 kilometers of public roads and 1,080 kilometers of trails remain immaculate.

They also meticulously clean all public transportation stops in their pursuit of an impeccable urban environment.

9. Oslo, Norway: The Clean Future

Oslo is the capital of Norway, with a population of 711,300 inhabitants, and it is an excellent example of a city committed to the environment and green energy.

Here are some of the actions that Oslo has implemented to achieve this goal:

  • Climate Budget: Oslo has an ambitious climate strategy that includes a “Climate Budget.” This budget consists of 42 measures grouped into three sectors: energy and the built environment, transportation, and resources. Its goal is to reduce emissions by 50% by 2020 (compared to 1990) and achieve carbon neutrality by 2050.
  • Electric Mobility: Oslo is a leader in electric mobility and is nicknamed the “electric car capital” (almost 60% of vehicles sold in Norway are electric). The city offers tax benefits for these vehicles and has established free charging points.
  • Biogas and Public Transportation: Oslo uses biogas to power urban buses and waste collection trucks. Additionally, it is investing in strengthening its public transportation network, including metro, trains, and buses.
  • Efficient and Green Buildings: Since 2017, new buildings owned by Oslo must be energy-efficient and constructed with sustainable materials. The goal is to produce more energy than they consume.

10. Honolulu, Hawaii: Cleanliness in an Island Paradise

The capital of Hawaii has a population of 338,455 inhabitants. It is a clean city that is concerned about the environment and biodiversity. It has been taking significant measures to address climate change and promote sustainability.

Here are some of the actions that Honolulu has implemented:

  • Climate Action Plan: Honolulu has developed its first “Climate Action Plan” called “One Climate: One Oahu.” This plan focuses on three sectors within the city’s control: land transportation, electricity, and waste. The goal is to significantly reduce the island’s greenhouse gas emissions and work towards the ambitious target of being carbon neutral by 2045.
  • Clean Transportation: Honolulu is promoting the use of electric vehicles and has incorporated electric buses into its public transportation fleet.
  • Energy Efficiency: The city is improving the energy efficiency of its municipal buildings. This includes measures such as installing renewable energy systems and promoting sustainable construction practices.
  • High-Density Development: Honolulu is encouraging high-density development to reduce urban sprawl and the need for motorized transportation. This contributes to a lower carbon footprint.

Honolulu was ranked by the American Lung Association’s State of the Air 2021 report as the U.S. city with the cleanest air.

This is largely due to the Pacific winds that sweep through the city and the scarcity of industrial manufacturing operations on the islands.

Despite these efforts, carbon dioxide emissions in Oahu have increased in recent years, primarily due to transportation and air travel.

However, the climate action plan aims to reverse this trend and reduce emissions in the target sectors by 80% by 2045 compared to 2015.

In summary, Honolulu is committed to sustainability and is taking concrete steps to protect the island’s environment and biodiversity.

By Sergio Tuset

Over 30 years’ experience in management of industrial companies. Specially focused on environmental projects for customers, recognized specialist in conceptual engineering applied in wastewater, liquid &solid wastes, and air pollution. Teamwork, leadership, and expertise in Project Managing. Industrial process consulting