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The Difference between Energy & Emissions Reduction
Posted by Arash Guity on March 08, 2010 at 3:23pm
As an attempt to provide clarification, I’d like to look at how we calculate greenhouse gas (GHG) emissions from the two most common sources of energy for buildings; electricity and natural gas. Natural gas is considered a Scope 1* emission, which refers to emissions created on site by a facility’s operations. When natural gas is burned in boilers and kitchen equipment, GHGs are generated as a product of combustion and are typically exhausted into the atmosphere with the other gasses. The amount of GHGs emitted is fairly easy to calculate using a calculated factor* based on the amount of gas consumed, which is the same regardless of where that fuel is burned or its use. Emissions related to electricity consumption on the other hand, are not as straight forward to calculate. Electricity emissions are typically of Scope 2* type, which means that they are created indirectly in a process that occurs off-site at a power generation facility. The fuel used to generate this electricity will significantly impact the emissions factor associated with the power consumption. A facility receiving electricity from a utility provider that has a fuel mix consisting mostly of coal power plants, will have a dramatically higher emissions factor as compared with a facility receiving power form a utility provider that has mostly hydroelectric plants. Thus, the fuel mix of the utility provider is a major variable for determining the emissions factor. This is a big reason why much attention is being given to the Renewable Portfolio Standard, or RPS. An RPS ensures that a minimum amount of renewable energy is included in the portfolio of the electricity sources in a state to help minimize emissions associated with electricity consumption. The greater the amount of renewable energy in the power mix, the lower the associated emissions will be for a given amount of consumed electricity. Just as the price of electricity and natural gas fluctuate across the nation depending on the utility provider, so can the associated emissions. GHG emissions factors for electricity production are developed by EPA through their Emissions & Generation Resource Integrated Database (eGRID), a comprehensive source of data on the environmental characteristics of almost all electric power generated in the United States.
Another important variable that will affect indirect emissions related to electricity consumption is loss due to the actual transmission of power. More electricity is required to be produced by a power plant than will ultimately be consumed because of the inherent losses in the system. The farther away your facility is from the power plant, the more electricity that will need to be produced to overcome the losses and satisfy the demand. This is a big reason why careful attention must be given to understanding from where energy reductions should come. We need to not only look at the specific technologies that can help make energy reductions, but also, we should also be evaluating the fuel source involved with the technologies to understand the economic and environmental impacts of a particular approach. This highlights the importance of evaluating technologies not only based on pure performance and traditional efficiency improvement, but also from the perspective of total environmental impact, which takes fuel mix and transmissions losses into consideration. By understanding more about our energy sources, we begin to get a more complete understanding of their true costs.
*Emission scopes and calculation factors are defined by the World Resources Institute and the World Business Council on Sustainable Development (WRI/WBCSD) protocols
WRI
WBCSD
GHG Protocol
EPA’s eGRID
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