The report underlines that more could have been done on engaging with Non-Governmental Organizations and cutting the Olympic and Paralympic Games' carbon footprint.
But overall the UNEP assessment, conducted by independently appointed assessors, concludes that Beijing raised the environmental bar and the Games left a lasting legacy for the city.
These achievements are all the more impressive given that the Games were held in a rapidly developing city in a country facing multiple development challenges in the first decade of the 21st century.
Achim Steiner, UN Under-Secretary-General and UNEP Executive Director who attended the summer Olympics, said: 'The public attention of the world focused on the Beijing Games and whether the authorities could pull off a landmark event on many fronts including the environment. They have fulfilled the promise of a Green Games in many areas including public transport, waste treatment and green Olympic venues.'
The challenge now facing Beijing is how to consolidate the achievements of the Games and turn them into a green legacy in the long term. UNEP's assessment of Beijing's achievements and challenges also provides key recommendations for the organizers of the Games in Vancouver, London and Sochi - as well as other mass sporting events - as they strive to realize their goals and set the environmental bar ever higher.
The Beijing Games and the environment
The Beijing organizers' goal was to offer a 'Green Olympics' to the world - overall, it is estimated that the authorities in China invested more than US$17 billion on environmental projects for the Games.
This plan was laid out in a series of twenty key environmental commitments ranging from the improvement of the city's transport infrastructure to the upgrading of the waste system and an increase in the city's green coverage. The city authorities also achieved a complete phase-out of hydrochlorofluorocarbons (HCFCs) - an ozone-damaging greenhouse gas -years ahead of the 2030 target.
Along with environmental improvements across the city, a powerful legacy of the Games is increased awareness of environmental issues in China, particularly among Beijing residents and businesses.
Conclusions and recommendations
The report highlights several areas where the Beijing Olympic organizers exceeded their commitments, including:
On emissions, the organizers had committed to implementing vehicle emission standards equal to Euro II for light vehicles - in fact, Beijing switched to Euro IV emission standards for cars in time for the Games.
The greening of Beijing and the Olympic venues, with the creation of 720 green spaces in central Beijing. Since winning the bid to host the Olympic Games, approximately 8,800 hectares of green space was developed using more than 30 million trees and rose bushes.
The number of blue sky days(days with an Air Pollution Index of 100 or below) rose from less than 180 in 2000 to 274 days in 2008.
Waste classification and recycling goals were exceeded by 2 per cent and 5 per cent, respectively. Further, hazardous and medical waste treatment facilities were expanded and updated, all solid waste was sorted in venues, and the recycling rate in the Olympic venues was 23 per cent higher than the committed level.
The authors also identified challenges in a few areas, including:
The lack of mandatory guidelines for Olympic suppliers on materials including timber.
A missed opportunity on engaging with Non-Governmental Organizations and benefiting from their expertise from the outset of the Games preparations.
Air quality was by far the most prominent environmental issue the Olympic organizers and the Beijing municipal authorities had to manage. Indeed it has been an issue for several previous Olympic Games, including Los Angeles and Athens.
The report notes that 'significant efforts before and during the Games were focused on improving Beijing's air quality' and that 'as a result, air quality improved significantly'.
Studies show that the special measures taken for the Olympic Games - in conjunction with weather conditions in August - led to reductions in carbon monoxide (CO) by 47 per cent; nitrogen dioxide (NO2) by 38 per cent; volatile organic compounds (VOC) by 30 per cent; particulate matter (PM10) by 20 per cent; and sulphur dioxide (SO2) by 14 per cent.
The Games also 'greatly increased public awareness of air quality' in Beijing, leading the public to press for continued efforts to sustain the improved quality of life experienced during the Games.
However, the report notes that 'there remains significant room to improve Beijing's air quality' - the PM10 standard in the city remains a challenge.
Future air quality challenges in Beijing are likely to focus on the smaller particles (PM2.5), which are not currently subject to standards in China but raise health issues.
The Beijing organizers'comprehensive measures to cut emissions and improve public transportation in the sprawling city included a switch more stringent vehicle emission and fuel quality standards in 2008, in line with Euro III and Euro IV emission standards.
The authorities also improved the city's public transport infrastructure, bringing the number of railway tracks from four to eight. Some of the temporary measures introduced during the Games - including a ban on heavily polluting vehicles and restrictions on the number of cars in the city centre - were extended for several months after the Games.
The report concludes that the Games played a crucial role in Beijing's transition to more stringent vehicle standards and smoothed the way for the Beijing authorities and China's Central Government to implement future sustainable transport initiatives.
However congestion remains a challenge, with 1,000 new vehicles registered daily. The authors recommend that the city further expand its public transport capacity by building more subways and railways, and consider policy options including tax cuts for clean vehicles and congestion fees in crowded areas.
The report also recommends that the integrated approach for fuels and vehicles taken in Beijing be pursued at the national level.
Reducing Beijing's dependence on coal and improving energy efficiency and air quality were a priority for the Game organizers.
The report notes that the Olympic Games accelerated the introduction of energy-efficient infrastructure in Beijing - more than 20 per cent of the total electricity consumed in all the venues was supplied by renewable energy - and that the Games' showcase of best practices in clean energy and energy efficiency 'provided a basis for the organizers of other mass events to learn from'.
The city of Beijing continues to rely on coal for 40 per cent of its energy consumption, and the report recommends 'a more deliberate effort to reduce coal consumption in Beijing, in tandem with increasing the supply of clean and renewable energy'.
Protecting Beijing's limited water supply was a key objective of the organizers, and the report concludes that the measures they took 'serve as an international example of creative and aggressive measures that can be taken to minimize water use, maximize the efficient use of existing water resources and protect the water ecosystems'.
To build on these achievements, the report recommends that the Beijing Municipal Government ensure that innovative water-efficiency measures (including storm water capture and storage) be increasingly applied throughout the city, especially in all new buildings and developments.
The authors also say the International Olympic Committee should promote in all the cities hosting Olympic events the adoption of sustainable water management strategies that will benefit host cities well beyond the staging of the Games.
Beijing achieved all of its commitments in the area of waste - waste classification and recycling goals were exceeded, and the in-venue recycling rate was 23 per cent higher than the committed level.
The report recommends that additional policies and infrastructure be used to increase waste treatment and capacity, along with economic incentives to complement waste reduction and more comprehensive policies and regulations on waste and recycling.
The report praises Beijing's 'remarkable results in incorporating an array of environmental elements into the planning, construction and management of Games venues'.
In several areas, particularly efficient design and renewable energy use, the Games pioneered technologies and planning that leave a green legacy for further planning across China, but also for the organizers of other mass events.
Areas where there is room for improvement include sustainable forestry - with a lack of mandatory timber purchasing guidelines for the Beijing venues - as well as the lack of a systematic environmental footprint analysis to assess the benefits of the green measures.
The IOC should encourage future host cities to invest in new and innovative approaches in energy efficient design and water-saving technologies, and to adopt mandatory purchasing policies for Games-related construction materials.
For the first time for a global sports event, Beijing's climate neutrality programme took into account the carbon emissions from international flights. However, the lack of a clear methodology and reliable figures make it difficult for UNEP to assess the carbon footprint of the Games and the impact of the measures to mitigate and offset the emissions.
The report says organizers of upcoming major sports events should be encouraged to seriously look at their carbon footprint and analyze primary data from events. It would also be useful for the IOC and other sport organizations to come up with a harmonized standard for addressing the issue of carbon neutrality in sport.
Relations with Non-Governmental Organizations
The report says the Beijing Organizing Committee missed an opportunity to fully engage with NGOs and benefit from their expertise from the outset of the Games preparations. The organizing committee only began engaging NGOs from the end of 2006, by which time the construction of most Games facilities was nearing completion and many policies were already in place.
The authors say it would be useful for the Beijing Municipal Government to engage NGOs in discussions on how to carry forward and reinforce the full range of environmental measures undertaken for the Games.