Green buildings are essential in the city environment. In cities, buildings are responsible for a huge share of energy, electricity, water and materials consumption. Buildings account for 18 per cent of global emissions today, or the equivalent of 9 billion tonnes of carbon dioxide annually (Vorsatz, 2007). According to the United Nations Environment Program, if new technologies in construction are not adopted, emissions could double by 2050. Green construction or sustainable buildings should be resource-efficient and environmentally responsible throughout the building's life-cycle, that is, planning, design, construction, operation, maintenance, renovation and demolition (Green Building - U.S. Environmental Protection Agency (US EPA)). Well-designed buildings aim at efficient use of natural resources, generation of renewable energy through solar power like sunlight and photovoltaic equipment, wind power, hydro power, biomass, use of renewable resources using plants and trees through green roofs, rain gardens, reduction of rainwater run-off, use of packed gravel or permeable concrete instead of conventional concrete or asphalt to enhance replenishment of ground water and reduction in the amount of waste generated by the occupants by providing on-site solutions such as compost bins to reduce matter going to landfills, which can significantly reduce the environmental impact of the building.
Technologies employed in green buildings are constantly evolving and may differ from region to region. However, the fundamental principles of structure efficiency, design efficiency, energy efficiency, water efficiency, materials efficiency, indoor environmental quality enhancement, operations and maintenance optimisation, waste and toxics reduction are the same everywhere. Green building practices expand and complement the classical building design concerns of economy, utility, durability and comfort (U.S. Environmental Protection Agency, 2009). Green architecture involves designing a building in harmony with the ecosystem, using 'green' building materials from local sources and optimising the system. Delhi needs to construct green buildings to generate significant environmental, economic and social benefits, thereby protecting the health of the occupants and reducing level of pollution and environment degradation.
Water harvesting means capturing and storing of rainwater or runoff water. Water harvesting also helps in mitigating floods and promoting plant growth. Delhi desperately needs water harvesting plants throughout the city. The semi-arid climate of the region requires water to be stored in aquifers. Massive concretisation and poor percolation of water in the soil have led to urban floods in some parts of the city during the monsoons. Delhi receives rainfall during both the monsoon (June to September) as well as by western disturbances in winter. Around 80 per cent of the rainfall occurs during the monsoon season. Heavy downpours sometimes lead to floods. Delhi depends massively on ground water, which gets replenished by rainfall. Despite heavy rainfall in certain years, the city was not able to replenish its ground water because of lack of bare open or green land. Water harvesting thus becomes an important requirement for Delhi’s ecology. Very little planning and implementation has been done on this front.
Cloud seeding for artificial rain
Recently, Central Pollution Control Board (CPCB), Indian Space Research Organization (ISRO), (IIT Kanpur and Indian Meteorological Department (IMD) have considered the option of cloud seeding to ease the air pollution in Delhi. Cloud seeding is a technology in which the salts (silver iodide or dry ice) are being dispersed in the air to get moisture and formation of clouds for artificial rain showers. This technology is successfully used in several world cities like Beijing, United Arab Emirates and New York to combat the air pollution. Though environmentalists and some scientist believe that it is not a very suitable option for Delhi, but considering an alarming situation, the Delhi Government has given its approval to it.
Carbon engineering is a new way of dealing with pollution. A Canadian start-up, carbon engineering, captures carbon dioxide directly from the atmosphere and then utilises it to produce fuel.
The company assures that the direct air capture can remove far more carbon dioxide per acre of land footprint than trees and plants. The company is already running a demonstration plant in Squamish, British Columbia, that removes one ton of carbon dioxide from the air every day.
Meanwhile, a Dutch design company has developed a ‘smog-free tower’ - an air-purifying tower that sucks in pollution and expels clean air. The extracted pollution is turned into pieces of jewellery. The first tower was installed in Rotterdam, and the company claims that a single tower can clean 3.5 million cubic metres of air per day. The company plans to roll out smog-free towers across other global cities.
Several companies are building computer systems capable of learning to predict the severity of air pollution in the city several days in advance by managing large quantities of data. This is considered to be an extremely complex computational challenge. The systems would eventually offer specific recommendations on how to reduce pollution to an acceptable level.
In another development, in China’s most polluted cities, a 60-metre-high chimney stands among a sea of high-rise buildings. The chimney is installed to clear the air. The outdoor air-purifying system is powered by solar energy and it filters out noxious particles and exhausts clean air into the skies. Chinese scientists claim that the system could significantly cut pollution in urban areas in China and elsewhere.