Switched from being flared at the sewage plant to lighting residents’ stoves, leftover biogas will find new life at a city wastewater treatment facility.
Hawaii Gas Co. said recently it expects to act on plans to integrate biogas from the city’s Honouliuli Wastewater Treatment Plant into its pipeline.
“We are figuring out ways to take waste and turn it into useful forms of energy,” said Joseph Boivin, senior vice president of business development and corporate affairs at Hawaii Gas. “There is more of this type of work that can be done in Hawaii.”
State Consumer Advocate Dean Nishina recommended in March that the state Public Utilities Commission approve the fuel supply agreement between Hawaii Gas and the City and County of Honolulu under which the utility would buy biogas from the city. Biogas is a fuel made up of roughly 60 percent methane and 40 percent carbon dioxide, which the sewage plant had been capturing and burning off.
Nishina said he appreciates the gas utility’s efforts to use renewable gas available at local facilities that is otherwise wasted, but “is concerned with the costs associated with the use of biogas.”
The gas company would buy the biogas from the city at $2 a therm. Currently, the gas utility purchases gas at about $1.75 per therm.
Boivin said the consumer advocate’s support will help move the process along. When laying out a timeline, Boivin said, the gas utility plans to begin injecting the refined biogas into its system a year after the PUC approves its contract with the city.
“When the consumer advocate releases its statement of position, it is a month or two months more before the PUC (members) make their decisions,” Boivin said. “We’re really not sure, the (members) will make their decision when they can get to it.”
The gas utility said it plans to spend about $5 million on equipment to purify the sewage plant’s biogas before pumping into the pipeline.
Honouliuli has an anaerobic digester in which the solid waste is broken down by microorganisms and turned into the biogas Hawaii Gas wants to purify.
Hawaii Gas said in its application the money would be used to purchase biogas purification equipment and construct approximately a mile of new pipeline to connect the purification system to Hawaii Gas’ existing synthetic natural gas pipeline. Hawaii Gas’ Oahu pipeline runs approximately 1,000 miles, distributing synthetic natural gas to roughly 28,000 customers.
After the facility is operational, “roughly half of our Hawaii Gas customers would have access to the renewable gas,” Boivin said.
Nishina said he supported Hawaii Gas’ plans because they advance Hawaii’s renewable-energy goals.
The facility would make Hawaii Gas’ fuel supply 5 percent renewable. The amount of renewable energy the gas currently has in its fuel portfolio is just higher than 2 percent.
Boivin said Hawaii Gas is interested in working with all of Oahu’s wastewater treatment plants, eyeing the one at Sand Island for its next project.
“I’m looking forward to getting this up and running so that we can then replicate this at a number of other facilities in Hawaii,” Boivin said.
But municipal biogas is not what will get the gas utility to 100 percent renewable.
Boivin said it would make up only 15 percent of the gas utility’s fuel supply.
Hawaii Gas is also looking at growing its fuel to increase its renewable portfolio.
Boivin said TerViva is one company that Hawaii Gas could work with to provide feedstock to produce a gas the utility could use. TerViva, which harvests biofuel crops on 300 acres on the North Shore of Oahu, grows pongamia oil seed trees on distressed agricultural land.
Utah-based Clean Energy Solutions is working on a demonstration project with Hawaii Gas growing Viaspace Giant King Grass to produce biogas. Boivin said the utility is planning a demonstration project with CES later this year.
“Now we’re working with CES to identify land,” he said. “We’ve been looking at energy crops for over five years. This is the first time we have found an energy crop with a substantially higher yield of energy than any crop out there. … Now that we’ve started working with Giant King Grass, it appears we can actually do it.”
