GREENHOUSE GAS INVENTORY OF LOS ANGLES COUNTY SANITATION DISTRICTS LANDFILLS: DEVELOPMENT AND POLICY IMPLICATIONS

摘要

California has taken one of the first steps in the nation to develop a comprehensive greenhouse gas reduction program. The process began with a report by California's Climate Action Team that developed the framework for reduction programs. Then, passage of Assembly Bill 32 (California Global Warming Solutions Act of 2006) laid out the groundwork and programs to enact the Governor's greenhouse gas reduction goals that called for reducing by 2020 greenhouse gas emissions to 1990 levels. In this process the landfill industry was identified by California's Climate Action Team as a significant emitter of methane, a potent greenhouse gas, even though its contribution was estimated to be less than two percent of all industry emissions. A key component of this Bill was the requirement for mandatory reporting of greenhouse gas emissions and development of inventories. Developing accurate greenhouse gas emission inventories is critical for the landfill industry since the methane emissions from landfills is thought by landfill industry representatives to be overstated in the California State inventories. Overstating greenhouse gas emissions could lead to unnecessary regulation for the landfill industry. In order to develop a complete and accurate emissions inventory of landfills and establish a landfill emissions quantification protocol, members of the industry, including Los Angeles County Sanitation Districts (LACSD), joined a voluntary registry, the California Climate Action Registry (CCAR). One of the challenges of creating a greenhouse gas inventory is developing a protocol for landfill methane emissions that also provides an estimate of collection efficiency; a critical component of the landfill methane emissions protocol. Unfortunately, there is no accepted means of determining collection efficiency, only default values used by the USEPA. LACSD have been working on an innovative methodology for measuring gas collection efficiency based upon a combination of readily acquired integrated surface methane (ISM) concentration data and modeling using US EPA's Industrial Source Complex (ISC) air dispersion model. Using the ISM/ISC method with verification through a flux chamber study at the LACSDs' Palos Verdes Landfill, a collection efficiency of +99.2% was determined. LACSD has extended the use of this method to estimate collection efficiency at all its landfills for a specific reporting year, as a first step to completing the greenhouse gas inventories. Presented in this paper will be a complete review of the California greenhouse gas reduction programs, and the results of LACSDs' CCAR GHG inventory for 2006 using the ISM/ISC method as well as other industry-generated factors. This gives the first look at the carbon footprint of a major landfill operator. In addition, the results will be compared to results derived from using default collection efficiency values, as well as results adjusted for carbon sequestration. This comparison gives a valuable insight into the importance of collection efficiency estimates and other factors in deriving greenhouse gas emissions from landfills. Also in this paper, the inventory results will be used to provide a perspective of the accuracy of state and national inventories for methane emissions from landfills. Finally, the global warming policy issues surrounding landfills will be discussed from the perspective of greenhouse gas emission estimates derived in this paper.