Public power has always rested on the three-legged stool of affordability, reliability, and environmental responsibility. Municipal utilities are nimble, able to respond quickly to the needs and preferences of their customers. These utilities are not answerable to remote shareholders or driven by profit margins. Whether it’s the generation mix or electricity rates, all decisions are driven by the community’s best interests.
The American Public Power Association, in a news release responding to the proposed Affordable Clean Energy rule, notes that carbon dioxide emissions from the U.S. power sector have declined 28 percent since 2005. Public power utilities have supported this decline by investing in low- and non-emitting generation from solar, wind, hydro and nuclear sources, and natural gas. Many Association members continue to actively reduce emissions in coordination with local, state and regional programs targeting standards exceeding those in the proposed ACE rule.
The efforts of three public power utilities in different parts of the country are testaments to public power’s commitment to sustainability.
From waste to wallboard
The U.S. could fill up its landfill space within the next two decades, according to a 2018 study by a solid-waste standards organization. Muscatine Power & Water in Iowa won’t have that problem. The public power utility has barely touched the capacity of its coal combustion residue landfill space because of a robust capture and reuse program for coal ash by-products from coal-based generation units.
“We have a long history with making good use of our coal combustion byproducts,” said Brandy Olson, general counsel for the utility and director of its legal and regulatory services department. Muscatine was one of the earliest generation companies to employ flue gas desulfurization technology, a move it made in the early 1980s.
Flue gas desulfurization systems reduce sulfur dioxide emissions using lime or a limestone reagent, which produces synthetic gypsum via a chemical reaction. The product is nearly identical to the natural stone and has multiple uses in agriculture and industry.
The utility’s synthetic gypsum goes to farmers, who use it as a soil amendment, and has also gone to a local wallboard manufacturer. Fly ash, the lighter particles that get captured, is used as an additive in products such as concrete. “It’s very sought-after because it makes a strong, durable product,” Olson explained.
“As an early user of that FGD system, we spent a lot of time working out the bugs in our processes so that we would have a marketable byproduct,” said Olson. “We’ve always looked for opportunities to recycle, reuse, and keep materials out of the landfill.”
Other coal-burning byproducts such as bottom ash, a heavier residue that settles to the bottom of the generator’s boiler, and slag, which is the melted form of coal bottom ash, can also find a useful second life. Some products can be used to manufacture asphalt and roofing shingles; some may go into sand-blasting processes.
This is how Muscatine has been able to preserve its landfill space far beyond original expectations. The original permit from the 1970s covered 30 years. Today, the utility still has more than 30 years’ worth of capacity available. This saves the utility expenses associated with opening new landfill cells, buying more landfill space, or managing landfill operation. When synthetic gypsum is used for wallboard, it also spares the local wallboard manufacturer from having to rely on gypsum mining that scars the land.
The recovery and reuse program for coal combustion by-products is operating in all three of Muscatine’s local electric generating units, which together have a production capacity of some 293 megawatts.
The coal-ash reuse program produces some cost savings for the utility, but Olson said its biggest values are environmental stewardship and its ability to support local business. “We’re making good use of the materials and helping other industries at the same time,” she said. “The biggest benefit is that we are able to keep material from becoming a waste.”
Have a diverse portfolio? Talk about it
Sustainability isn’t a new initiative for Southern Minnesota Municipal Power Agency, a joint action agency that provides wholesale power and other services to 18 public power utilities in Minnesota. Since 2005, SMMPA has reduced some 5.5 million tons of carbon dioxide emissions, which is equivalent to pulling 1.2 million passenger cars off the road or planting 6.5 million trees.
Here’s what’s different: Now, the organization is talking about it.
“Our member utilities are aware of what we’re doing, but that doesn’t always translate down to the retail customers,” said Christopher Schoenherr, SMMPA’s director of agency and government relations. “We felt it was important that our members’ customers understand what their wholesale energy provider was doing on this front. Twenty years ago, it wasn’t something people talked about, but, in the last five years, climate change has gotten increasing attention.”
To help member companies communicate, SMMPA has a sustainability report online, drives people to its website with online ads, and communicates through member utilities. These materials “talk about what we’re doing on the renewable energy side, the diversification of our portfolio, and stress energy efficiency programs” that SMMPA helps member companies provide, Schoenherr said.
SMMPA is a joint action agency charged with building and operating coal-fired generation for its member utilities and the 119,000 customers they serve. Now, 17 percent of the organization’s power comes from renewable resources. According to Schoenherr, the agency couldn’t achieve that renewables percentage without considerable diversification in its generation portfolio.
“If you look at the carbon emissions from a coal facility, a natural gas facility produces roughly half as much CO2,” he noted. “The natural gas facilities that we have don’t run a ton, but they match up very well with the intermittent wind and solar resources that we have.”
SMMPA has four gas engine plants that “come online and change their output very quickly,” Schoenherr said. How quickly? Two of the gas engine plants can “go from zero to full load in less than 10 minutes.” That flexibility enables SMMPA to balance rapid changes in the power output of the renewable resources.
Another resource SMMPA uses is a methane-fueled plant that burns waste gases from a landfill. “You’re either going to have to flare that methane, or you can use it to generate electricity,” Schoenherr said. This resource operates as baseload capacity, but he said it still helps the utility balance out other renewables.
“We have natural gas, we have wind, we’ve got solar, and we’ve got waste-to-energy generation resources,” he concluded. “Each one of those things made sense from a reliability perspective, but they also made sense from an environmental perspective and contributed to our reduced carbon footprint.”
Resiliency for today and tomorrow
Like SMMPA, Seattle City Light has been focused on addressing climate change and cutting carbon emissions since 2005, when it became the first utility in the nation to reach carbon-neutral status. Partly, that achievement reflects a clean system. The utility currently produces 91 percent of its electricity from hydropower.
But producing power from waterways has its own environmental challenges. “We’re looking at the different impacts from climate change,” said Ronda Strauch, Ph.D., City Light’s climate adaptation scientist. “Declining snow and loss of glaciers— how those things affect our hydropower generation or the safety of our facilities.”
To ensure clean cold-water habitats for Coho salmon and threatened steelhead trout along the South Fork Tolt River, Seattle City Light purchased 154 acres in the Cascade Mountains of western Washington as part of the Stossel Creek Reforestation Project. The acreage was logged in 2012, and the utility is replanting it to support fish habitat restoration.
We wanted to do three things,” Strauch explained. “We wanted to make the genetic diversity higher, make the species diversity higher, and increase redundancy in case some species didn’t make it.” This would increase the long-term sustainability of the trees on the site in the face of climate change.
The surrounding area is mostly populated by Douglas fir trees. Seattle City Light and the organizations it partnered with on the project will plant more Douglas fir and add cedars, pines, oaks, and grand fir species to the mix. In addition, the utility sourced the trees from different areas in anticipation of rising temperatures. “We’re getting seed stock from Oregon and Northern California. These are warmer, drier climates, so planting some trees from there adapted to these conditions may help the trees survive better in the future,” Strauch continued.
The goal of such diversity and redundancy in plantings is a hardier forest. “We wanted to plant trees that are successful today but also will be resilient into the future, as conditions change,” she added.
To achieve its carbon-neutral status, Seattle City Light also has a robust program for purchasing greenhouse gas offsets.
“We do have some power transactions that incur emissions, so we purchase offsets to achieve neutrality. We prepare greenhouse gas inventory every year and report it publicly to the Climate Registry,” a nonprofit organization that designs and operates voluntary GHG reporting programs, said Oradoña Landgrebe, strategic advisor in the utility’s natural resources and permitting division. This inventory dictates how many offsets the utility will buy.
While each offset represents reduction of one metric ton of carbon dioxide emissions, Seattle City Light researches its offset sources carefully and targets GHG heavy hitters. They buy registered and verified offsets from commercial composters and dairy farmers who capture and destroy the methane they produce. Methane is a GHG 28 times more potent than carbon dioxide. The utility also purchases offsets from a manufacturer that uses sulfur hexafluoride, or SF6, which has a global warming potential 23,900 times that of carbon dioxide.
“We have SF6 in our substations to prevent arcing,” Landgrebe explained. “Because we use that gas, it’s meaningful for us to help another organization use something else.”
Landgrebe explains offsets this way: “We reduce emissions as much as possible, and for those we can’t yet eliminate, we pay someone else to reduce emissions on our behalf.”
Like Muscatine and SMMPA, Seattle City Light is making impressive investments that are paying off for the community it serves and for future generations.