Not long ago, the wastewater treatment plant was the biggest power user in municipal operations for the city of Gresham, Ore. Then, 12 years ago, the city entered into a long-term sustainability partnership with Veolia and began the process of turning the city’s energy hog into an energy asset. First step was a cogeneration system that met about half of the power needs of the plant. Five years ago, the city brought in fats, oils, and greases (FOG) from food manufacturers as an additional organic source of biogas, co-digested with sewage sludge through anaerobic digestion. It was a natural fit: the heat from the cogeneration system kept the FOG from hardening as they were processed. Five years and 9,000 gallons of biogas per day later, Gresham’s wastewater treatment plant is now “net-zero,” generating at least as much power as it uses.
Transforming waste to energy (WTE) isn’t new, but communities like Gresham demonstrate how much of a municipal operation can be sustained on it. Traditionally, WTE has meant combustion of municipal solid waste (MSW) – the trash collected by garbage trucks – which would otherwise be headed to landfills. Increasingly, it has become recognized that organic matter in the waste stream – not just in wastewater but in trash as well – is a source of energy that can be captured rather than buried. As organics account for more than half of all MSW in the United States , the energy potential is substantial – as is the savings potential for communities that capture it. As a result, communities have gotten more creative. From food waste to methanol, here are three more examples of WTE from organic matter.
1. Pelletizing in Toronto, Canada
This year, fertilizer demand in the Americas is expected to increase by more than 200,000 tons from 2016, according to the Food and Agriculture Organization of the United Nations. This makes efforts to conserve resources in farming increasingly important. Toronto is now taking a circular approach to fertilizer production, using organic waste to fertilize new crops.
Most of our food’s nutrients, which plants extract from the soil while they’re grown, eventually end up in sewage systems after we eat and dispose of this produce. The Ashbridges Bay Treatment Plant in Toronto collects this organic mass, treats and tests it for safety, and condenses it into fertilizer pellets so farmers can inject it back into fresh soil. Named the “pelletizer,” it produced more than 19,000 tons of fertilizer in 2016.
2. Methanol in Danbury, Conn.
A critical aspect of wastewater treatment is denitrification. Newly collected wastewater is high in ammonia, and turns into nitrates, which can harm the environment if not broken down by bacteria first. Bacteria need methanol or a similar carbon source for this to happen, and Danbury’s wastewater facility is obtaining it in a smart way.
Rather than buying virgin methanol, the plant in southern Connecticut reclaims waste methanol from a biotechnology manufacturer, and uses it as a catalyst for denitrification in Danbury’s water treatment process. It’s a shining example of one natural resource cleaning another natural resource.
3. Biomass in British Columbia
Not all organic waste comes from food.
In woods across North America’s west coast, beetles and pine are at war, and the beetles are winning. Pine trees depend on stable winters and humidity to maintain a healthy lifecycle, which means warmer and drier climates have made them less protected against hungry organisms. Beetles migrating to newly warm regions are feeding on ripe timber, but two facilities in British Columbia are containing this epidemic by creating a public benefit.
Because dead wood and falling trees are common wildfire-starters, sawmills are now collecting and sharing this wasted lumber with biomass energy facilities in two British Columbia communities – the Fort St. James Green Energy Project and Merritt Green Energy Project – to prevent forest fires and generate electricity. The plants, under construction and slated to open later this year, will generate biomass-fueled electricity for up to 80,000 homes.
As municipalities search for ways to better manage waste, new forms of WTE focused on recapturing energy from organic waste will see more adoption. It’s a matter of knowing where these opportunities are, and finding ways for organic mass previously discarded to be repurposed and its energy value reclaimed.
Tim Muirhead is Vice President, Municipal & Commercial Business, Veolia North America.