What is a sustainable city?
It was during the Stockholm Water Week that I visited the sustainable city - Hammarby Sjostad in Stockholm, but in order to have a thorough understanding of it, I went there for a second time with some energy experts recently.
Integrated planning—an introduction of new concept
Erik Freudenthal, information officer in environmental issues in Hammarby Sjostad or lake city in English showed us what has been called the Hammarby Model. This model shows the interaction between sewage and refuse processing and energy provision, as well as the added benefits to society of modern sewage, energy and waste processing systems.
With the current popular terms like ‘closing the loop’, there should be a natural cycle---the waste water is treated and reused or discharged to the lake, the solid waste is used for heating and producing biogas while the solar energy is used for offices and hotels. Ideas of using more public transport than private cars and easy accessibility in the area as well as the wetland area where birds can stay easily, all these create a good picture of the city.“This approach for handling energy, waste and water is called Hammarby Model.” says Mr Freudenthal. “It’s the water that has inspired the inception of the whole project.”
The original plan started in 1990 and a total of 30 thousand people would live and work here while a total of 10 thousand residential units would be built. Today, almost 10 thousand people live in the area. And the whole sustainable city will be fully built by 2015.
Implementation--innovative solutions and new technologies
With a wonderful idea, one must carefully implement it and translate the concept into reality.
This is a showcase project that technical solutions have been found through the cooperation among Project Hammarby Sjostad, Stockholm Water, the Department of Sanitation and the energy company Fortum.
“From day one, the City has imposed tough environmental requirements on buildings, infrastructural solutions and the traffic environment.” Freudenthal said to attain these goals, integrated planning, innovative solutions and new technologies have been necessary.
First they cleared up the old industrial garbage so that the soil met environmental requirements, then they decided that all the materials for the construction should be environmentally friendly, for example they don’t use copper or PVC in their construction materials. In transporting construction material, they also calculated very carefully and built up a logistic center so that the traffic will not be blocked or crowded because of the construction. Although this way the cost increased by about 3%, they also calculated that if not doing so, the waste for the whole project would be about 6%.
Coming out of the information office in GlashusEtt, we see a row of cars parking there.
“This is the car pool.” said Freudenthal.
About one third of the residents here are members of the car pool. They can book their use on the internet. Most people use the car pool to shop in the supermarket over the weekend. Usually it can be two or three people using a car for shopping. One can take tram, which is specially built for the people here to go to work in the Stockholm center which is about 15-20 minutes away by all means. Water taxies are also ready among many private boats by the lake. People can take water taxi for free between the city and the subway Slussen, a transfer stop near the center. There are also several buses coming through the city.
Then we can see the beautiful channels in front of the buildings. That is the way they collect rainwater from the houses and gardens and then the water will flow into the lake. Rainwater from the streets are also collected and purified through sand filters or in artificially established wetlands in the area and then released into the lake. This way, it reduces the burden of the waste water treatment plant and also avoids rainwater pollution.
The main footpath, the carefully preserved oak forest, the green surfaces and all the other trees that have been planted help to collect rain water locally before it drains into the sewage system. The vegetation also ensures cleaner air and provides a counterbalance to the dense urban landscape. Meanwhile the roofs covered in stonecrop or sedum plants are not just an attractive detail. The plants also absorb rain water that would otherwise drain into the sewers.
For convenience, the road light was installed underground, while on the top of the poles, there is some special material to reflect the light. The light energy of the sun is harnessed and transformed into electrical energy in solar cells. The energy from a single solar cell module covering one square metre provides around 100 kWh/year, which is equivalent to the household energy used for three square meters of housing. Freudenthal said scientists calculated that the sunshine for two days could supply the use of mankind on earth for a year. But the question is how to save such energy.
We also saw solar panels on some of the roofs to absorb the heat from the sun and use it to heat hot water. The solar panels on top of the building can provide sufficient energy to meet half of the building’s annual hot water requirements.
From waste to energy
Hammarby Sjostad has its own waste water treatment plant that was built to test new technology. Four different and brand new processes for purifying waste water are currently being assessed here. Once the evaluation is completed, a new waste water treatment plant may be constructed for coping with waste water from the whole of Hammarby Sjostad.
Biogas is produced in the waste water treatment plant from the digestion of organic waste or sludge from the waste water. The waste water from a single household produces sufficient biogas for the household’s gas cooker. Most of the biogas is currently used as fuel in eco-friendly cars and busses.
The heaviest and bulkiest waste fractions are sorted and collected via an underground waste collection system. The waste is sucked through pipes into a central room, one fraction at a time. The containers are collected from the room by refuse collection lorries, thereby reducing vehicle traffic in the area.
Of course the necessary facilities such as a church, schools, kindergarten and clinics are all built in the area. And bear in mind accessibility, it mostly refers to the accessibility to disabled people so wheelchair can go through easily, and all the places and roads are connecting with each other. In winter, one can also ski from the nearby forest hills.
“The Hammarby Sjostad Model shows the environmental impact will be halved and the standard is doubled than normal houses or apartments.” Freudenthal said, “and the most important idea is the integrated planning and built in all the system as much as possible so that people can use it immediately. This is also a way to balance your money, your environment and your happiness.”
Glashouse. Sjostaden’s environmental information center disseminates knowledge via study trips, exhibitions and demonstrations of new environmental technology, including fuel cells and the building’s double-glazed façade. The center can organize the trip almost every day if you book it. .
By Chen Xuefei, People’s Daily Online correspondent in Stockholm.
