ACID RAIN IN CONTEXT

This Case Study has been concerned with acid rain, which is just one limited aspect of pollution. However, the lessons learned have important consequences for environmental protection more generally. Widespread appreciation of the damage that can be inflicted by lack of restrictions on waste disposal, and sulfur dioxide in flue gases in particular, have strongly influenced industrialists and politicians in alerting us all to the necessity for maintained vigilance, if we are not to suffer from the unexpected, unwelcome and often expensive consequences of our activities. 

Sulfur is a less severe problem for fuels based on petroleum because it can be extensively removed by catalytic hydrodesulfurization during the refining process. Unfortunately this method is not applicable to coal. Nevertheless, debates continue about what upper limit of sulfur can be regarded as acceptable in the large amounts of petroleum burned. All the present is released untreated into the atmosphere, much of it in urban areas and at low levels. 

Finally, it should also be remembered that there are natural sources that discharge acidic compounds into the atmosphere, such as SO2 and HCl from volcanoes, and sulfur compounds that are formed in marine biological cycles. These represent a balance in nature that, as seen here, is readily and unacceptably disturbed by anthropogenic activities. 

In some countries, including the UK, coal consumption is decreasing. The high cost of sulfur removal is one significant economic motivation towards replacing the exploitation of natural carbon deposits with natural gas (CH4) as a primary energy source. Methane fuel contains less sulfur and yields proportionately less CO2 for 

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