In the last 35 years, landfill gas recovety has evolved fi·om a few improvised systems to a matmc technology implemented at well over a thousand landfills across Nmth America. While gas recovery engineering has settled into a set of established practices, some of the key questions challenging designers 35 years ago continue to be posed today:
- How much gas is there?
- How rapidly is it produced?
Landfill gas modeling is the att of placing bow1ds on answers to these questions. The goal of the Landfill Gas Generation and Modeling Manual of Practice is to provide practical information on simple and widely used hndfill gas models for the gas system planner, designer, energy developer, and regulator. Landfi ll gas modeling is akin to weather forecasting: no model provides ccttain predictions. A special effott was made to explain some of the factors making landfill gas generation unpredictable and so difficult to forecast. Atmed with this knowledge, the modeler should not be lured into a false sense of certainty when forecasting landfill gas.
Though not addressed here, researchers have developed sophisticated landfill gas models using complex mathematical descriptions of the underlying physical, chemical and biological processes. These models are omitted for two reasons. First, these models arc inaccessible to all but a few expetts. Second, such models depend on a nwnbcr of ill-defined parameters and so may be no more predictive than simple models.
This manual is the product of several contJibutors rrom SW ANA's Landfill Gas Management Technical Division's Generation and Modeling Committee. Jeffi·ey Pierce, Vice President with SCS Engineers/SCS Energy and Committee Chair from 2000 to 2003, was responsible for preparing the final version of the manual. Lcs LaFountain, President of New Cure, lnc. and Committee Vice Chair from 2000 to the present, extensively edited the manual. Alex Stege, Senior Project Scientist with SCS Engineers and Committee Chair since 2003, completed the fmal review and editing. Also, many thanks go to Dick Prosser, President of GC Environmental Inc., for his substantial review and comment of the manual. Kent Drinker, Senior Manager with SW ANA oversaw publication of the manual and overall management of SW ANA LFG Division Committee activities. Rupam Soni, a Project Engineer with the Los At1geles County Sanitation Districts, and I developed the initial drafts of the manual. We si ncerely hope you find this manual to be useful and informative.