Many landfill owners and operators have been monitoring and tracking emissions data for months in preparation for meeting the March 31, 2011, reporting deadline established under the U.S. Environmental Protection Agency's (EPA) Mandatory Reporting of Greenhouse Gas rule. The EPA is developing the electronic Greenhouse Gas Reporting Tool (e-GGRT), a Web-based application that facilities will use to submit the required greenhouse gas (GHG) emissions data. The e-GGRT system will provide two options for reporting GHG emissions:
1) The user can enter the required data manually on a series of web pages with data entry forms; or
2) The user can bypass the manual data entry step and instead upload a data file, which must conform to EPA's published electronic format — an Extensible Markup Language (XML) reporting schema.
The second option provides the best opportunity for integrating enterprise-wide software or environmental management systems with e-GGRT.
EPA has made a draft of the schema publicly available on its website. However, as the site indicates, the current draft is "not suitable for use as a specification document." EPA's Greenhouse Gas Reporting Program (GHGRP) rulemaking activities are ongoing. There are two proposed rules under development outlining a number of changes to the program, including changes to 40 CFR 98 Subpart HH — Municipal Solid Waste Landfills. Because these rules are undergoing revisions, landfill operators should check the EPA website before the end of the year for the final version of the schema.
While the final file format is not yet available, landfill owners and operators can start preparing to integrate their environmental management systems with the e-GGRT. Operators should ensure that their systems track all of the data required to calculate GHG emissions according to the formulas specified in the rule and that they can generate the output necessary for reporting and records retention.
Tracking Landfill Data
The proposed rule specifies the data municipal solid waste (MSW) landfill operators need to report. Refer to the final rule and proposed rule amendments for the complete list of data required for reporting and recordkeeping, but some of the key data required include:
- Annual methane generated, destroyed and emitted by the landfill;
- Annual carbon dioxide, methane and nitrous oxide emissions from stationary combustion devices;
- Annual quantity of waste disposed at the landfill (including a description of, and rationale for, how this quantity was estimated);
- The composition of the annual waste quantity by type (e.g., food, garden, plastics/inerts, etc.)
- Fraction of methane in the landfill gas (and an indication of whether this is a default or measured value);
- The surface area of the landfill containing waste, by type of cover;
- Annual quantity of recovered methane, measured annual gas flow rate, measured methane concentration, and monthly average measured temperature and pressure for landfill gas collection systems;
- Destruction efficiency of landfill gas destruction devices;
- Gas collection efficiency used in emissions calculations; and
- Descriptions of landfill characteristics that influence collection efficiency.
Calculating GHG Emissions
The proposed rule is highly prescriptive in terms of the monitoring, measurement and calculation methods that must be used to estimate GHG emissions, so environmental management systems need to follow the prescribed methods to comply with the rule's requirements. Modeled annual methane generation at MSW landfills must be calculated based on:
Measured or estimated values of historic annual waste disposal quantities. If measured data are not available for all historic years, the rule specifies three options for estimating past quantities of waste disposed, based on (1) measured data for the first year for which such data are available, (2) population served by the landfill and default values of the average per capita waste disposal rate, or (3) quantity of waste in-place (based on design drawings or engineering estimates).
Appropriate values for degradable organic carbon fraction in the waste and the methane generation rate. EPA provides default values for these parameters if actual measurements are not available.
The modeled methane generation amount must be adjusted prior to being reported as emissions using a default factor to account for soil oxidation (i.e., methane that is converted to carbon dioxide as it passes through the landfill cover prior to being emitted). For landfills that do not collect landfill gas, the resulting adjusted value is to be reported as both the annual methane generation and the annual methane emissions.
Landfills that collect landfill gas are required to separately account for methane collected and destroyed. The quantity of methane recovered and destroyed must be calculated based on the gas flow rate (from either continuous or weekly measurements), methane concentration, and temperature and pressure of the collected gas. Then, two separate estimates of methane emissions must be calculated and reported.
One emissions estimate is to be calculated by subtracting the amount of methane recovered (as adjusted based on the efficiency of the methane destruction device) from the modeled methane generation. The other estimate is calculated by first applying a gas collection efficiency default value to the calculated amount of methane recovered to obtain a second estimate of methane generation. The quantity of methane recovered is then subtracted from this second methane generation estimate to yield the second estimate of methane emissions.
In addition to verifying that their environmental management systems support the calculation methodologies described, landfill operators will want to ensure that their software tracks all of the data required for reporting, including the most up-to-date default values specified by EPA. Keep in mind, this article merely summarizes the key points landfill operators may consider when integrating their environmental management systems with the EPA's e-GGRT reporting system. For full details on the GHGRP and reporting requirements, landfill owners and operators should consult the EPA's website.
Chris Minnucci is a senior analyst with Science Applications International Corporation's (SAIC) Climate Change Services practice, with 30 years of experience in the analysis of a broad range of issues related to energy and climate change.