Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
Options
The prospects for power generation from biogas produced at local wastewater
treatment plants are also minimal. Kauai has four public wastewater treatment plants, all
relatively small (the highest average flow is at Lihue, 1.2 million gallons per day).
According to Mel Matsumura of the County, there is little potential for biogas utilization.
For example, biogas production at the Lihue treatment plant is flared with a small
“candle-like” flame. Apparently the County had been approached by a biogas developer
in the past, but after visiting the site, the developer did not make contact with the County
again. Most new housing and resort developments on the island are served by private
water and wastewater systems, reducing the possibility that there will be a significant
developable resource in the future. 10
3.2.2 Landfill Gas
Landfill gas (LFG) is produced by the decomposition of the organic portion of
waste stored in landfills. Landfill gas typically has a methane content between 45 and 55
percent and is considered to be an environmental risk. Political and public pressure is
rising to reduce air and groundwater pollution and the risk of explosion associated with
LFG. From an energy generation perspective, LFG is a valuable resource that can be
burned as fuel by reciprocating engines, small gas turbines or other devices.
LFG was first used as a fuel in the late 1970s. Since then, LFG collection and
utilization technology has steadily improved. LFG energy recovery is now regarded as
one of the more mature and successful of the waste to energy technologies. There are
more than 600 LFG energy recovery systems in 20 countries.
Applications
LFG can be used to generate electricity and process heat or may be upgraded for
pipeline sales. The major constituents released from landfill wells are carbon dioxide and
methane. LFG contains trace contaminants such as hydrogen sulfide and siloxanes that
should be removed prior to combustion.
Power production from LFG facilities is typically less than 10 MW. As discussed
earlier, several types of conversion devices can be employed to generate electricity from
LFG. Typically the equipment requires only minor modification so long as the gas is
properly cleaned and prepared. Internal combustion engines are by far the most common
generating technology choice. About 75 percent of landfills that generate electricity use
engines. 11
10
Mel Matsumura (Chief Engineer Kauai County Wastewater Division), personal communication, June 16,
2004.
11
EPA Landfill Methane Outreach Program.
21 March 2005 3-18 Black & Veatch