The first step of a successful monitoring plan is to identify and document sources that produce GHGs and describe what's included or excluded in the relevant industry source category. Many facilities at this time only will need to report stationary combustion sources such as boilers, process heaters, small heaters and combustion turbines. Reporting of emissions from pilot lights isn't required. GHG Rule updates, finalized in September 2011, exempt emissions from emergency generators and equipment.
A site also must evaluate the GHG Rule's industry-sector-specific emission sources, if applicable, for inclusion or exclusion from the list of identified sources. For example, the technical clarifications, finalized in September 2011, require a petrochemical production facility to include and report GHG emissions from process vent stacks not associated with stationary combustion units. The site must trace such process vent stacks back to the process being vented that's generating the GHG emissions. Other specific industry sectors, like suppliers of industrial GHG as a final product, needn't report emissions from the destruction of fluorinated GHGs removed during the production process as byproducts or other wastes.
The source determines which covered GHGs must be documented — for example, CO2, CH4 and N2O are required for stationary combustion sources while CO2 and CH4 are required for asphalt blowing.
Tools that teams can use to identify GHG emission sources include process flow diagrams, piping and instrumentation drawings, equipment lists, stack location diagrams, as well as total process byproducts or wastes generated throughout the site. The team should conduct a walkdown and visual verification of the facility and sources because diagrams and drawings may not always be accurate or up to date.
The next step is to determine the monitoring methods and measuring device or procedure based on the specific source. Various methods can measure GHGs; it's imperative to use ones that not only are accurate but also suit a facility's operations. Sometimes installing a monitoring device will require shutting down the process. The EPA has provisions in the rule for utilizing best available monitoring methods until the facility has a scheduled shutdown. A plant must identify these interim methods in the plan along with the schedule for implementing permanent ones.
A site may develop measuring strategies based on the source and source categories listed in the rule subparts. The specific calculation methodologies for each source type will help determine what data must be collected. Examples of potential measuring methods and strategies include:
• Grouping or aggregating smaller stationary combustion units combined with larger units if they share common fuel sources. Consider physical proximity of grouped units when sharing a measuring device.
• Material balance.
• Direct measurement of GHGs via continuous emissions monitoring systems (CEMS) already in place to comply with other EPA programs such as the Acid Rain Program that applies to most power plants.
• Indirect measurement using process parameters such as fuel consumption, material throughput, heat and temperature, pressure, or mass or volumetric flow rates that will require specific calculations to determine the GHG emissions.
Consider updating only measurement sensors or transmitters for newer, more-accurate devices instead of replacing the system, to reduce the cost of upgrades. Also consider wireless transmitters where capital costs and potential production disruptions to install a hardwired system aren't cost effective.
• Invoices or purchasing records for utilities such as natural gas. Don't use these "as is" for a material utilized both as a fuel and as a raw material in processes that don't generate GHG unless the amounts for each purpose are clearly separated.