The combustion/utilization of landfill gas (LFG) continues to evolve from flaring (without beneficial use) to Landfill Gas-to-Energy (LFGTE) and more recently to high British thermal unit (BTU) or Renewable Natural Gas (RNG) projects.
LFG typically has a methane content between 40 and 65 percent and can be directly combusted in internal combustion engines to generate electricity with minimal pre-treatment in LFGTE facilities. However, with more complex processing/treatment including removal of oxygen, nitrogen, carbon dioxide, volatile organic compounds, and other trace level contaminants (siloxanes and sulfur), LFG can be compressed into high BTU gas.
We will examine the emerging shift of LFG reuse toward production of pipeline quality RNG, and away from its combustion in traditional energy recovery engines and turbines. The benefits and challenges of these competing technologies will be evaluated.
Reasons for the shift in the status-quo technology may be largely economic, as renewable fuel programs in states such as California are providing high premiums for the RNG that can be produced by landfills. The value of Renewable Identification Numbers (RINs) may also compensate for the additional equipment needed to produce RNG. In contrast, the traditional approach of combustion and electricity generation is burdened by decreasing revenue from falling electricity prices and increased costs associated with increased emission control requirements.
The change in value of Renewable Energy Credits (RECs) and RINs over time can play a role in the decision to pursue an LFGTE vs. RNG project. However, differing regulatory constraints and costs may also be a deciding factor in which technology to pursue. For example, LFGTE facility owners are facing increasingly more onerous air standards and air dispersion modeling thresholds. In addition, state air toxic regulations and action levels have become more of a concern in issuing air permits for new LFGTE projects and LFGTE expansions. Air compliance comes at a higher cost to LFGTE owners than RNG facility owners who process, compress, and inject the high BTU gas into transmission/distribution pipelines or truck the gas off-site. On-site emissions from RNG projects are virtually negligible in comparison to LFGTE emissions making air permitting and compliance far less onerous and easier to permit as local emissions are reduced with RNG projects.
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