The dollars set aside through the state’s bonding bill will cover half of the $13.5 million needed to purchase and install three generators that will convert the biogas created in the sewage treatment process into electricity. Once the operation is online, the process will power half of the plant’s initial electricity needs.
Biogas, which is mostly a mixture of methane and carbon dioxide, is created during the breakdown of organic matter in an environment lacking oxygen. In other words, microorganisms are already breaking down the sewage and creating the biogas that will be used to replace some of the plant’s dependency fossil fuels.
A small percentage of that biogas is already being used in replace of natural gas for heating the plant, Karen Anderson, WLSSD’s director of community relations, said. The excess methane gas is disposed of through the flare stack. Burning methane converts it into water and carbon dioxide, which is a less potent greenhouse gas.
“Our intention is that we never want to be wasting gas if we can avoid it,” Anderson said.
Considering the pandemic has shifted the financial priorities of the state, WLSSD Executive Director Marianne Bohren said the bonding bill news was one of the rare welcomed surprises of the year.
“The bonding bill in its entirety is not just important to WLSSD and city of Duluth and this region,” Bohren said. “It’s very important to this state and very important to help the state of Minnesota recover from the economic impacts of COVID-19. So we’re very grateful and we’re happy to be part of that.”
WLSSD is covering the other half of the project’s costs using money from the Clean Water State Revolving fund administered by the Minnesota Public Facilities Authority in the form of 1%-interest-rate loan.
Bohren said WLSSD plans to bid out the project in early 2021. A couple years ago, the facility solicited bids on the project and established potential contractors. But that expired after 60 days.
The pandemic’s impact on the state of the regional economy could delay the start date. WLSSD anticipates it will be completed about 1 1/2 to two years from the start date.
“It’s part of a suite of projects,” Bohren said. “Both to control costs for our users, but also to tap into another environmental benefit that we can provide to the community and that’s renewable energy.”
The electricity needed to operate the plant makes up one-third of WLSSD’s operating costs, or the second-highest costs after payroll expenses. By producing more its own energy, not only will that curb the plant’s greenhouse gas emissions and reduce pollution, it will also help the plant control and keep prices low for customers.
WLSSD has already installed much of the infrastructure needed in addition to the generators. It’s in the process of completing the installation of nearly $4 million in electrical switchgear that will connect generators, Bohren said. Some of the gas-conditioning equipment that will be used to clean the gas before it can be put through the generators has already been installed.
And the plant’s heating system was replaced in 2015 with boilers that are efficient and can use the biogas produced on-site.
Down the line, WLSSD would also like to strengthen its on-site electricity generating capacity by installing a system to add reclaimed wastes such as food, grease, oils and fats to the sewage breakdown process that creates the biogas.
The suite of energy self-sufficiency projects adds up to $44.8 million, including building a $16.8 million oxygen plant that went online earlier this year. The new and more efficient facility, which produces the oxygen needed to treat wastewater, has been using 28% less electricity than its predecessor, according to WLSSD. Originally, WLSSD anticipated it would allow the facility to use 25% less electricity.
“All of those things have had a really dramatic decrease in the amount of electricity that we consume here in treating wastewater,” Bohren said.