Environmental Engineering Reference
In-Depth Information
1. Defining the goals: The inventory may serve one or multiple purposes; therefore, all goals
need to be clearly declared so specific boundaries can be set to fulfill those goals (e.g.,
comparing the emissions of different facilities, for units in different countries, or knowing
the emissions for a particular product for labeling purposes).
2. Setting organizational boundaries: The purpose of setting boundaries is to identify the
operations that a company owns or controls. Sometimes, for large organizations, this can
be a complex task. Two approaches are normally used for the purpose of setting bounda-
ries: the equity share approach and the control approach. The equity share approach is
based on percentage ownership of an operation. In the control approach, which can be
financial or operational, the entity takes responsibility for 100 percent of the emissions for
those operations that it has control over. The entity does not take responsibility for emis-
sions from operations in which it has interests but not control.
3. Defining operational boundaries: Consist of identifying the sources of emissions and the
gases that will be reported. It also includes the scope level that the report will contain.
Scopes I and II, which encompass all the direct emissions within the organizational
boundaries and indirect emissions from purchasing electricity, cold, or heat that is used
within the organizational boundaries, are mandatory. Scope III, which includes indirect
emissions that take place outside the organizational boundaries (e.g., air travel and freight
for raw materials), is optional.
4. Selecting a base year: A base year can be a particular year, or it can be an average of
several consecutive years. The important factor when choosing a base year is the
availability of reliable data and a justification for making that selection.
5. Identifying and calculating GHG emissions. This step consists of identifying sources of
emission, selecting the calculation approach, collecting data, selecting the emission
factors, calculating the emissions, and converting the emissions to carbon dioxide
equivalent (Bauer, 2007).
6. Reporting: The report should be relevant, complete, consistent, transparent, and accurate.
It will contain a description of the boundaries, the emission sources, emission factors,
calculation methodology, sinks, emissions separated in different scopes and expressed in
metric tons of carbon dioxide equivalents, and any assumptions.
7. Verification: This is an optional step that may be accomplished by hiring a third-party
auditor to verify the inventory.
Calculation of emissions
With the boundaries set, the next step is the identification of the expected sources of emissions
followed by the estimation of the emissions. Emissions can be estimated using a physical
approach, which includes direct measurement, inferred measurement, and mass balance, or
data from information systems, such as operational data, facilities management and mainte-
nance reports, financial accounting systems, environmental reporting systems, and reports
sent to agencies (Department of Energy [DOE], 2007).
Direct measurement
is conducted with specific instrumentation over a continuous or
periodic interval of time. Generally, equipments that emit large amounts of carbon dioxide
have systems that monitor the emissions continuously.
Inferred measurement
is derived from a measurement or a series of measurements made in
one single point in time; it is generally used for sources difficult to measure, for instance,
mobile sources.
Mass balance
is based on the difference between inputs and outputs.
Operational data
keeps track of the physical quantity of materials consumed (e.g., fuel or
electricity) or products manufactured.
