We manage all the aspects of our environmental performance in accordance with our Environmental Management System (EMS) framework, which addresses environmental risk and regulatory compliance management processes.
Combustion of fuels to generate electric power results in the release of both conventional and greenhouse gas (GHG) emissions. Depending on the fuels used to generate power, these conventional air emissions may consist of sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM) and mercury (Hg). Also, the combustion of fuels results in the direct emission of Scope 1 GHGs, primarily carbon dioxide (CO2).
Air emission levels and intensities depend on many factors, including generation diversity and efficiency, demand for electricity, weather, fuel availability and prices, and emission controls deployed. Variations from year to year result primarily from the acquisition and divestment of assets.
We follow the principles and requirements of the Greenhouse Gas Protocol's Corporate Accounting and Reporting Standard to prepare its GHG inventory. Further details on how the emissions are calculated are disclosed in our response to the CDP Climate Change Questionnaire.
We account for NOx and SO2 emissions at all thermal power plants on an equity adjusted basis. We have accounted for SF6 emissions in all locations on an equity adjusted basis since 2014. Until 2013, the values reported included only our businesses within the Brazil SBU. In 2014 we also began accounting for mercury emissions at all the coal- and petcoke-fired power plants on an equity adjusted basis. Data previously reported only included the plants located in the United States SBU.
In 2014, we also started company-wide Scope 2 emissions quantification. Prior to 2014, we reported only Scope 2 emissions and targets that were set by our businesses in Brazil.
Although Scope 3 emissions are traditionally considered to be de minimis for the electric utility industry, in 2014, we started tracking indirect emissions from electricity sales to our customers in our distribution businesses in El Salvador, Brazil and the United States. We follow the methodology provided in the GHG Protocol's Scope 3 Standard and associated Technical Guidance.
Our methodology, data completeness, consistency and accuracy for all these emissions in 2014 were audited by a third-party assurance organization (Lloyd’s Register Quality Assurance Inc. [LRQA]).
Our businesses are continuously researching ways to improve power generation efficiency and reduce emissions. Also, some of our distribution businesses offer renewable energy and demand-side efficiency programs. The characteristics of the programs depend on the market conditions.
Refer to the 2014 Sustainability Report for details of Scope 1, Scope 2 and SO2, NOx, and mercury emissions, as well as for emission reductions programs.
Coal Combustion Products (CCPs) generation, recycle and reuse
Coal combustion products (CCPs) include bottom ash, fly ash, synthetic gypsum (also referred to as flue gas desulfurization (FGD) gypsum), FGD solids and cenospheres. CCPs are generated when power plants burn coal to generate electricity, or through the use of emission control technologies. CCPs represent the vast majority of the total waste combustion byproducts generated by our businesses.
We make every attempt to recycle whenever and wherever possible. Our businesses continuously recycle and reuse CCPs in engineered products including cement, concrete, road bases, wallboard and even bowling balls.
LRQA has conducted limited assurance of our CCP generation and recycle/reuse data since 2013. Refer to the 2014 Sustainability Report for the amount of CCPs generated and recycled as well as programs in place that reuse and recycling of coal combustion products, which results in both cost savings and revenue generation for our businesses.
Water availability is a critical for the electric power industry and, in particular, for our operations at locations where we need water to operate efficiently. On an annual basis, our individual facilities may use from only a few hundred cubic meters of water, like wind generation sites, to millions cubic meters of water, such as in thermal power plants. The water is predominantly used for the steam cooling process at our thermal plants.
We include cooling water, process water and potable/drinking water, with the exception of bottled water, in our water withdrawal inventory. Our water discharge inventory includes cooling water and process water discharges from open cycle cooling systems; however, domestic sewage, rainwater and storm water effluents are not considered to be discharges and are not included in the inventory. Facilities with closed circuit systems are considered to be "zero-discharge."
The water used by hydroelectric power plants only passes through the turbines and immediately returns to the environment.
All the water withdrawal and discharge data for 2013 and 2014 was verified by LRQA.
Refer to the 2014 Sustainability Report for details of water withdrawal and water returned to the source of extraction as well as examples of water conservation effort implemented by our businesses.