William B. Jones, Zephyr Environmental Corporation, USA
While the roots of environmental awareness can be traced back several hundred years, it wasn’t until the 1960s in the United States that the environmental movement began to gain significant momentum. That movement quickly spread throughout much of the developed world, and by the early 1990s it was important enough to attract 108 heads of State from around the globe at the Earth Summit in Rio de Janeiro, Brazil.
As this movement has gained notoriety, more and more governments have established environmental regulatory agencies to protect and improve their nations’ environment and natural resources. These regulatory bodies have developed various rules and regulations to govern a wide array of environmental issues, from the preservation of selected pristine areas to the minimization or mitigation of industrial pollution.
Large-scale industrial projects, such as power plant projects can contribute to poor air quality
Today, virtually every major industrial project in the developed world must address their impact on the environment in some fashion. While the specific requirements are different for each country, typically they involve conducting a study that characterizes the impact on the environment that the project itself will have, and proposing appropriate mitigation measures where the environmental impact is deemed unacceptable.
Beyond this regulatory driver, environmental issues often can play a significant role in the siting of a facility. For instance, costs associated with mitigating a disturbed wetland may be so great that it is cost-effective to build the project in another location. Therefore, considering environmental issues in the early stages of project development can often be beneficial to the bottom line.
This article provides an overview of environmental issues generally faced by power projects. Typical environmental issues associated with these types of projects are presented, along with the types of analyses usually conducted to address them. Finally, common mitigation measures associated with these issues are discussed. Ultimately, an insight will be provided as to the kinds of environmental issues likely faced when implementing a power project, and standard ways to deal with them.
Common environmental issues
While there are many types of environmental issues faced by power projects, for the purposes of brevity this article focuses on three: air, water and climate change. Each of those categories is addressed below.
Often the most significant environmental issue faced by any major industrial project is the impact on air quality (Figure 1). Not only is it arguably the most complex, but frequently it is the most expensive to assess and mitigate.
There are hundreds of different air pollutants that are regulated in various capacities. This article will focus on the most commonly addressed pollutants: sulphur dioxide (SO2), particulate matter (PM) and nitrogen oxides (NOx).
It is very likely that any major power project will have to demonstrate that its emissions will not cause or contribute to an exceedance of applicable ambient air quality standards. These standards, usually established by the government of the country in which the project is located, are pollutant-specific and are given in terms of pollutant concentrations (i.e. µg/m3).
In circumstances where there are no country-specific air quality standards, standards from the US EPA1, the World Health Organization2, or the World Bank3,4 are often used as surrogates.
To demonstrate compliance with these air quality standards, an air quality dispersion model is usually used to predict a project’s impact on nearby air quality. While there are different dispersion models for different situations, all dispersion models require the same fundamental inputs:
- Information about the source(s) being modelled (e.g. location, height, flow rate, emission rates, etc)
- Meteorological data and points at which the user wishes the model to predict pollutant concentrations (receptors)
In the case of power projects, sources typically addressed in air dispersion modeling analyses are boilers and turbines. However, in some more detailed analyses, sources as small as fugitive dust generated from truck traffic also may need to be addressed.
Of particular concern with power projects is the water that is used during the power generation process. If the plant is located on the coast and uses once-through water for cooling – pumping in seawater for cooling and discharging the warmer water back to the sea, thermal pollution must be addressed. Thermal pollution is an increase in water temperature caused by industrial discharge; temperature increases that are too great can decrease oxygen supply, which can kill fish and harm the overall ecosystem.
Thermal pollution by coastal power plants can seriously damage the surrounding marine ecosystem
Also of concern is the quality of the water that is discharged from the facility at various outfalls. In countries where no such standards exist, often the World Bank’s effluent standards are used.
As a general rule, once a facility is constructed, some type of water quality sampling programme will be required to regularly monitor the quality of the water being discharged from the plant. In many instances this monitoring will be conducted quarterly and the results of this monitoring may be required for submittal to the regulatory authorities.
Another environmental issue related to water has to do with the presence of bodies of water or wetlands in the vicinity of the project. Some regulations call for a determination of the presence of any navigable waterways or wetlands that may be disturbed by the construction of the project. In some cases, mitigation measures may be required to offset the disturbance of a wetlands area; some of these mitigation measures can be quite costly.
Over the past generation or so the concept of climate change has been gaining more and more attention. The theory is that the growing industrialization of the Earth is resulting in an increase in greenhouse gases (GHG) that are causing the planet’s climate to warm. Such a warming could lead to a myriad of harmful consequences, according to some (but not all) models.
Care must be taken when bodies of water or wetlands are located in the vicinity of a proposed power plant
While there are a number of GHGs, the one most often focused on is carbon dioxide (CO2), a natural result of the combustion of fossil fuels. The generation of electricity from fossil fuels is typically credited with the largest contribution to man-made CO2 levels in the atmosphere today5.
The Kyoto Protocol (an update to the United Nations Framework Convention on Climate Change, or UNFCCC) was adopted in 1997, establishing GHG reduction levels for various members of the international community. One of the key facets of the Kyoto Protocol is the market-based trading program, through which GHG emissions “credits” are traded amongst participating countries, thus encouraging the least costly GHG reductions first.
Participation in the Kyoto Protocol varies throughout the world. The majority of the world’s nations have no responsibilities to reduce GHG emissions under the Kyoto Protocol (in fact, one of the primary reasons that the United States and Australia have not ratified the Protocol is because of the exemption of China and India). The European Union (EU) has had the most consistent participation, particularly in France and the United Kingdom. However, even in the EU there is not uniform participation – in 2006 Germany announced that it would exempt its coal-fired industries from the requirements of the Kyoto Protocol6.
To what degree climate change needs to be addressed in the near future for a power project depends greatly on the location of the project. However, the momentum for climate change regulations is clearly building, so even if nothing is required today the issue may have to be addressed in the future.
Common mitigation measures
Of the three common environmental issues described above, all of them have mitigation measures that are typically applied. Some of the solutions more commonly employed by the power industry are described below7.
The installation of air pollution control devices to reduce the impact of the project on the environment may be required prior to construction. For the purposes of this article we will focus on control techniques for reducing air pollution from the combustion of oil. These techniques can be divided into three categories: fuel substitution, combustion modification and post-combustion control. For the three air pollutants that are the focus of this article (SO2, PM, and NOx) common control techniques are described below .
The primary means of reducing SO2 emissions through process modifications is to switch to a fuel with lower sulfur content; such a switch may be more cost-effective than an add-on SO2 control device. In those instances in which process modifications do not achieve the desired emissions level, a control device to reduce SO2 emissions is needed, the most common being a flue gas desulfurization (FGD) system, consisting of either a wet scrubbing or a dry scrubbing system. FGD systems can typically achieve control efficiency of between 70-95 per cent.
To reduce emissions of PM, the first step is to consider improving combustion or switching to a cleaner fuel. If such process modifications cannot achieve the desired PM emission levels, then some set of add-on pollution control devices should be employed. A common system for a power plant is a cyclone to remove large particles followed by a baghouse or electrostatic precipitator (ESP) to reduce smaller particles. Typical control efficiency for a cyclone is less than 90 per cent, while a baghouse or ESP typically achieves 99.9 per cent control.
Control of NOx can be generally classified into two fundamentally different methods – combustion controls and post-combustion controls. Combustion controls reduce NOx by suppressing its formation during the combustion process while post-combustion controls remove NOx emissions from the flue gas. In boilers, combustion controls include low excess air, flue gas recirculation, overfire air, and low- NOx burners. These techniques generally involve some combination of operating at low excess air and reducing peak temperatures, which inhibits NOx formation because less oxygen being available in the combustion zone.
Common post-combustion control methods include selective noncatalytic reduction (SNCR) and selective catalytic reduction (SCR). These controls can be used separately, or combined to achieve greater NOx reduction. Both control techniques involve the injection of ammonia into the gas stream to convert the NOx to nitrogen and water, but SCR also uses a catalyst to accelerate the process. SCR usually operates at a much lower temperature than SNCR8. SCR systems typically achieve between 70 per cent and 90 per cent control, while SNCR systems usually control 30- 70 per cent of NOx emissions.
Wastewater streams from a power project typically include the cooling water, boiler blow down, water contaminated with oil, and sanitary wastewater from throughout the plant. Typical methods of dealing with these streams are as follows:
- Cooling water – for a project near the sea the once-through cooling water would be directly discharged into the sea, but care must be taken to ensure that the difference between the temperature of the returned water and that of the seawater is not too great.
- Boiler blow down – collected in storage tank, and after mixing to reduce pH it can be used for various activities at the facility (e.g. landscaping)
- Oily water – captured and routed to an oil/water separator. The treated water can then be discharged (e.g. into the sea)
- Sanitary wastewater – collected and routed to wastewater treatment plant. The treated water can then be discharged (e.g. into the sea)
Another concern, depending on the configuration of the plant, would be runoff from storage piles – this is of particular importance to coal-fired power plants in relation to their coal piles. In circumstances where pollutants may leach into the groundwater, appropriate preventive measures such as liners and collection/treatment of runoff may be required.
As described above, reducing emissions of CO2 (the most prevalent of the GHGs) is difficult, because it is a natural result of combustion. The most practical way to reduce energy consumption is by increasing the efficiency of the fuel-burning process.
Another method that may sound far-fetched, but is in practice in some areas today, is geosequestration. Essentially, CO2 is captured as it leaves the stack and injected hundreds of meters underground (a declining oil field is a potential candidate). Some have suggested that injecting CO2 into oceans would be another potential option.
Today the concern for the environment is stronger across the globe than it has ever been. Accordingly, it is likely that any major power project will have to consider the impact that it will have on the environment, and adjust its designs to ensure that its impact will adhere to applicable standards and thresholds.
Issues associated with air pollution are likely to be the most onerous of the environmental issues for a major power project. Not only will analyzing those issues for the purposes of identifying the best possible solutions be complicated, but the solutions themselves will likely be the most expensive of the suite of environmental requirements.
Ultimately, the environmental issues presented in this article and others will most certainly need to be addressed in some way during the permitting of a major power project. As the environmental regulatory community throughout the world continues to mature and its reach continues to expand, it can be anticipated that major industrial developments will be subjected to increasingly stringent requirements.
1. 40 CFR Part 50
2. World Health Organization Air Quality Guidelines, available at https://who.int/phe/health_topics/outdoorair_aqg/en/ (accessed May 15, 2007)
3. World Bank Air Quality Guidelines, available at https://worldbank.org/html/fpd/em/power/standards/airqstd.stm (accessed May 15, 2007)
4. Pollution Prevention and Abatement Handbook, The World Bank, 1998, p.419
5. US Greenhouse Gas Inventory, US EPA (available at https://epa.gov/climatechange/emissions/usgginventory.html)
6. New German Rule could increase Greenhouse Gas Emissions, New York Times, June 29, 2006. Available at https://nytimes.com/2006/06/29/business/worldbusiness/29green.html?ex=1309233600&en=4cd4442637d83026&ei=5088&partner=rssnyt&emc=rss (accessed May 15, 2007)
7. Stern, Boubel, Turner, and Fox. Fundamentals of Air Pollution, 1984.
8. World Bank, Selective Catalytic Reduction (available at https://worldbank.org/html/fpd/em/power/EA/mitigatn/aqnoscr.stm)