Page 31 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

4 1 Air Emissions

The twentieth century marked the beginning of the understanding that human
activity was having deleterious effects upon the natural world, including human
health and welfare. These effects included increasing pollution of air, water, and
land by the byproducts of industrial activity, and the permanent loss of natural
species of plants and animals through changes in laboratory settings, water usage,
and human predations.
The topic of indoor air quality (IAQ) has become popular, due to the awareness
of asthma and allergies triggered by indoor air pollutants such as mold. IAQ
awareness also increased with the involvement of the United States Environmental
Protection Agency. The energy crisis in the 1970s resulted in tighter building
envelope, sealing, and insufficient ventilation. Most existing heating, ventilation,
and air conditioning (HVAC) systems were designed for temperature control
without consideration of air pollutant accumulations. As a result, IAQ degraded,
and problems arose. Recent findings have demonstrated that indoor air is often
more polluted than outdoor air in many developed countries (except for regions like
Beijing, China, where outdoor air is extremely polluted), thereby causing a greater
health concern as current lifestyles demand more time indoors.
The later twentieth and early twenty-first centuries saw a boom in nanotech-
nology. Nanotechnology has been tested for air quality remediation in such areas as
noncatalytic combustion and photocatalytic oxidation of volatile organic com-
pounds (VOCs). On the other hand, the environmental effects of nanotechnology
are not well understood; and, concerns have recently begun to increase. The world
is not ready for nanotechnology because “the future is coming sooner than it is
expected” [15]. The effect of nanotechnology to air quality is still waiting for
systematic studies to confirm its environmental effects. Scientific evidence is nee-
ded before definitive conclusions can be made.

1.2.2 Greenhouse Gases

Greenhouse gases (GHGs) include CO 2 , methane (CH 4 ), hydrofluorocarbons
(HFCs), perfluorinated compounds (PFCs), and others. Most of them have been
produced by natural sources and present in the atmosphere for a long, long time. It
is only recently that extra anthropogenic GHGs may have contributed to global
climate change and extreme weather.
CO 2 emissions are sometime referred to carbon emissions and are largely due to
the combustion of fuels in electric power generation, engines, building heating, and
industrial plants. In addition to oil and gas industry, CH 4 emissions can also be
produced by the biological degradation of biomass from agricultural activities and
landfills. Industrial processes produce HFCs and PFCs. Chapter 13 discusses the
capture and storage of CO 2 .