The environmental impact of the burning of fossil fuels has been profound and nothing short of disastrous, and could merit a separate report itself. However a brief look into this subject is essential at this point. The conventional fuels such as coal and to a larger extent, oil are greatly responsible for the grim state of the Earthís protecting envelope-the atmosphere. We are now paying the price for uncontrolled industrialisation and material progress of the past century. The term global warming has become synonymous with the deterioration of the Earthís environment. Temperatures world-wide have risen significantly due to the `greenhouse effect`. The pollutants released into the atmosphere by the emissions of vehicles, industrial wastes, etc., which get concentrated in the upper atmosphere, trap the heat within the envelope due to which temperatures increase with potentially disastrous consequences. The health levels of the population have also suffered due to degradation of the living environment. The only conventional form of power that is renewable and also environment friendly is hydro-electric power but huge river valley projects are running into problems due to the vast tracts of land that are required for these projects and the imbalance they create in the ecology of the region. In addition the question of resettlement of the displaced population is never answered to the satisfaction of everyone concerned. The time has now come for us to consider alternatives to existing sources of power supply that are renewable and also environment friendly thus leading us into a secure and self-reliant future.
Buildings have been responsible for a large part of environmental degradation contributing significantly to effects such as Ozone depletion, global warming and acid rain. An understanding on how buildings influence the environment is essential in order to create designs are more environment friendly at the same time looking for solutions that are energy conscious.
The earth is protected by a layer of ozone gas at high level in the atmosphere, or stratosphere, which filters almost all of the harmful ultraviolet radiation from the Sun and stops it from reaching the earthís surface. Use of synthetic compound chlorofluorocarbon (C F C) is the principal chemical leading to ozone depletion. When C F Cís are discharged to the atmosphere, they react with sunlight to produce chlorine. Chlorine destroys ozone by means of a chemical reaction, which turns ozone into oxygen. C F Cís are stable compounds and therefore once released into the atmosphere, they remain there for a long time. By this process the ozone layer is becoming less efficient in screening ultraviolet light. The effect of increased levels of ultraviolet light at the earthís surface could include a higher incidence of skin cancers, cataracts and possibly an adverse impact on human immunity. Furthermore, ozone depletion may reduce crop yields.
C F Cís are used in a number of building components including some forms of insulation, air-conditioning, refrigeration and fire fighting systems as well as some packaging foams, aerosol sprays and soft furnishings. Avoiding the use of C F Cís buildings would therefore go a long way in combating the issue of ozone depletion. Unfortunately, substitute chemicals have not been developed in all cases. Therefore efforts should be made to meet the insulation, air-conditioning and so no by other means which include natural cooling, passive design features, etc., at the same time efforts should be made to prevent the leakage of these gases into the atmosphere by use of leak detectors and efficient maintenance. However, efforts in this field have already produced encouraging results such as the development of hydrochlorofluorocarbons (H C F C), but the ultimate substitutes are likely to be hydrofluorocarbons which are significantly less damaging to the ozone layer than C F Cís. But it should be kept in mind that both H C F Cís and H F Cís are still greenhouse gases albeit to a lesser extent compared to C F Cís. at the same time it is possible that some of these chemicals may be less efficient and more toxic than the C F Cís that they replace. Therefore, development of design solutions to problems of maintenance of comfort levels, lighting, etc. are necessary to really reduce the consumption of these compounds in the quest for cleaner and greener buildings.
The Earthís atmosphere contains a number of protective greenhouse gases in the lower atmosphere or troposphere. These include carbon dioxide, methane, nitrous oxide and C F Cís. These gases allow light to reach the Earthís surface but absorb some infrared radiation. This phenomenon is referred to as the greenhouse effect because, like in a greenhouse, sunlight passes in and it becomes warmer inside than out. Similarly the greenhouse gases produce a higher temperature at the Earthís surface which is essential to support animal and plant life; without greenhouse gases the Earth would be cold enough to freeze the oceans.
The blanket of greenhouse gases is now becoming thicker due to manís industrial activities. A number of factors such as emission of carbon dioxide when fossil fuels are burnt, release of C F Cís into the atmosphere and methane produced by, amongst other things, intensive agriculture, contribute to the troposphere becoming denser with the accumulation of greenhouse gases. A thicker layer absorbs larger amounts of infrared radiation thus increasing the temperature on the Earthís surface. This is known as the global warming effect. Although there is now a general consensus that global warming is taking place, the amount of global warming that is going to take place and the time-scale of the process are still a matter of debate. There is also speculation as to the effect of sustained global warming on the environment which include partial melting of the polar ice caps and thermal expansion of the oceans with the loss of low-lying land to the associated flooding. Also, a change in the climate would lead to shift in deserts and fertile areas. It is also anticipated that changes in climate will not be limited to rise in global temperatures but would also lead to unsettled weather with a greater range of temperatures and rainfall rates.
Of the main greenhouse gases being emitted, carbon dioxide and C F Cís are most directly related to the use in buildings. Most electricity generation relies upon the burning of fossil fuels, which is the main cause for the release of carbon dioxide into the atmosphere. Therefore, reduced and more efficient use of electricity in our buildings will surely help in reducing greenhouse gas emissions. In the long-term it will be essential to invest in the development of alternate, renewable energy systems which are more environment friendly. At the same time, Building Regulations should be tightened to encourage energy conservation and the use of alternate energy systems. C F Cís, in addition to depleting the ozone layer also contributes to the greenhouse effect by as much as 25%, according to some estimates. Therefore the use of C F Cís should be avoided and care must be taken to prevent the leakage of C F Cís by improving operating and maintenance procedures.
The acidity of rainfall is a result of a number of natural occurrences, such as growth of plants and animals, and man-made sources, such as the burning of fossil fuels. The gases responsible for acidification include sulphur dioxide, nitrogen oxides and hydrocarbons; sulphur dioxide being the most significant contributor. Hydrocarbons and oxides of sulphur and nitrogen fall near their source as dry deposits causing harm to building materials like stone and metal, as also trees, crops and human health. High concentrations of these oxides lead to the production of sulphuric and nitric acids due to the action of sunlight. These dissolve in the clouds and fall as acid rain, many thousands of kilometres from the source. These wet deposits increase the acidity of soil and water courses, thus releasing toxic metals from their compounds to poison plants and animals.
Most sulphur dioxide emissions arise from the burning of fossil fuels in power stations, therefore maximising energy efficiency of individual buildings and lesser dependence on power from fossil fuels will help to reduce acid rain by reducing demand for power.