Power generation local pollution

The presence of polycyclic aromatic hydrocarbons in the environment is of obvious concern and, apart from specific occupational environments, human exposure to these compounds derives from combustion products released into the atmosphere. Estimates of the total annual benzo[aJpyrene emissions in the United States range from 900 tons (19) to about 1300 tons (20). These totals are derived from heat and power generation (37-38%), open-refuse burning (42-46%), coke production (15-19%) and motor vehicle emissions (1-1.5%) (19,20). Since the vast majority of these emissions are from stationary sources, local levels of air pollution obviously vary. Benzo[aJpyrene levels of less than 1 pg/1,000 m correspond to clean air (20). At this level, it can be estimated that the average person would inhale about 0.02 pg of benzo[aJpyrene per day, and this could increase to 1.5 pg/day in polluted air (21). 

Currently, the stationary power market penetration of the fuel cell is based on reduced local pollution rather than superior performance. Indeed the internationally demonstrated Ballard fuel cell bus generates more pollution from the power plant stack which generates its hydrogen supply from an inefficient incomplete electrolyser, than it saves by emitting steam from its exhaust. The industry has to rescue itself from this untenable position. 

Predictions by several fuel cell organisations for incomplete systems are not in unison, but all see economic improvements coming from mass production, notably ITM. That will be very necessary to meet the intense competition as improved vehicles with new engine schemes enter the market. The industry needs complete fuel cells to achieve competitive performance and any kind of mature economics. The difficulty of the situation is highlighted by the fuel cell bus which saves local pollution on the road, but generates at the power plant stack more pollution... 

It should be noted that not all water systems contained all the pollutants listed. The data are further broken down by state and local water supply systems on the Enviromnental Working Group website [65]. It should also be noted that many of the individual pollutants have more than one source. Heavy metals in potable water, e.g., may have their origin in mining, manufacturing, and/or power generation. 

Larsen, ., . F. Boyle H. . B. Birks, 1996. Variation in the geochemistry of recent lake sediments along a west-east pollution gradient in the Bergen area, Norway. Wat. Air Soil PoUut. 88 47-81. Laxen, D., 1996. Generating emissions Studies of the local impact of gaseous power-station emissions. A National Power publication, 74 pp. 

It is thus clear that cogeneration improves the economic profitability of a snlfuric acid plant, and by contributing power to the main grid can reduce the load on local generating stations. In the case of thermal power plants operating on snlfur-containing fuels, this can reduce atmospheric pollution since the quantity of pollutants released per MWH generation is less in the case of a sulfuric acid plant than a thermal power plant. 

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