Palo Alto's leading environmentalists and elected officials rallied on Wednesday morning for a highly unusual event: the construction of a concrete industrial building next to the Baylands.
The occasion marked the formal unveiling of the city's new dewatering and haul-out facility, where sludge from Palo Alto and surrounding areas gets thickened, pressed, caked and dumped into trucks that then ship it out of town for further treatment. It also marked a public send-off for a facility that has faithfully served residents for the past half-century but that few will miss: the sludge-burning incinerators that up until now, were both the biggest municipal power consumer and greenhouse gas emitter.
"We're going to bid these old friends adieu," Mayor Eric Filseth told a crowd of about 50 residents and city staff who gathered in front of the new plant. "It is time to move on to newer stuff."
The retirement of the incinerators, which have been in use since 1972, marks a significant milestone in Palo Alto's plan to address climate change and upgrade its outdated waste-treatment system. Until now, the city's water-treatment plant plan — which also serves Los Altos, Los Altos Hills, Mountain View, Stanford University and the East Palo Alto Sanitary District — was one of only two in California that burned its sludge (the Central Contra Costa Sanitary District is the other such plant). It was a point of embarrassment for officials who like to tout the city's environmentalist credentials.
At the ceremony, Filseth highlighted the environmental impacts of moving from incinerating sludge to treating and shipping it. The switch will save about 15,000 metric tons of carbon dioxide annually — the equivalent of getting 3,000 cars off the road, he said. It will eliminate the need to ship out 700 tons of hazardous ash every year, equivalent to an 85% reduction of municipal hazardous waste. And because the incinerators were powered by natural gas and the new facility relies on electric power, the change supports Palo Alto's move toward "fuel switching" — a shift from the former to the latter.
Located next to the incinerators, the new $30-million dewatering and trucking facility is a concrete cube with two stories packed with pipes, filters, conveyor belts and storage vats. Sludge that comes into the facility gets treated with polymers, which helps to thicken (or "dewater") it. The sludge then moves through a system of more than 20 belt filters, where it gets pressed and further dewatered.
The sludge cakes get progressively dryer and flatter as they move through the system, until they ultimately blend into something that resembles a layer of gray carpet. The material then passes through a "screw conveyor," which shakes up the carpet and directs the output into giant storage bins, which ultimately get emptied into the trucks through an automated system.
"Now it has the consistency of worm dirt," plant manager Jamie Allen told a Weekly reporter during a tour of the new facility. "It's still 70% moisture and 30% solid, but it resembles dirt at this point."
The new facility, while state-of-the-art, also represents a step back from the type of waste-to-energy plant that Palo Alto officials have been evaluating for much of the past decade. In 2011, voters "undedicated" a 10-acre parcel of Byxbee Park to create an anaerobic digestion facility, which would treat local food waste, yard trimmings and potentially sewage and convert it into energy. After years of evaluation, city officials backed away from the plan, citing high costs and the difficulty of building in the Baylands.
Debates over the waste treatment grew heated up in 2011, creating a fissure in the environmental community, where supporters of Measure E (which undedicated the parkland) called on the city to take care of its own waste on its own land and opponents argued that a new treatment plant does not belong in the Baylands. While the former prevailed in the 2012 election, the city ultimately did not move ahead with a waste-to-energy facility.
"We have a very small footprint here, and the cost of an anaerobic digestor went from $57 million to $75 million for total capital cost," Allen said. "The debt cost of that would be quite high. So we evaluated that and decided it would be best to build this facility, get this one ready and continue to look at emerging technologies. It's a wait-and-see approach."
The cautious approach also had the added benefit of reducing the simmering political tensions and giving both camps in the environmentalist debate something to cheer. Both former Mayor Peter Drekmeier, a leading proponent of Measure E, and former Councilwoman Emily Renzel, the measure's staunchest opponent, attended the Wednesday ceremony. Drekmeier said the incinerators, after nearly half a century of service, have overstayed their welcome. Renzel, who toured the new facility, also said she welcomes the new building, though remains concerned about the city's long-term plans.
"The jury is out on next steps. If they occur around the sewage plant site, that's fine with me. My concern is parkland," Renzel said.
In the meantime, about two-thirds of the city's dewatered sludge will be trucked out to the Synagro-WWT facility in Merced County, where it will be used for composting. The remaining third will be shipped to the Lystek International Limited plant in Fairfield, where it will undergo thermal and chemical treatment and get converted into an agricultural soil supplement.
Filseth noted that the environmental benefits aren't the only reason for retiring the incinerators. Another factor is the high cost and difficulty of maintaining the aged equipment.
"At 1,400 degrees Fahrenheit, we have no right to expect that these things lasted even 50 years," Filseth said. "It's such a harsh environment and they continue to work. So, it's a capital issue as well."
But even as he inaugurated the new haul-out facility, he also noted that the city has not yet abandoned its exploration of local solutions that would not require trucking.
"The ultimate plan is to have that additional processing done not in the Central Valley but here in Palo Alto," Filseth said. "So this is a bit of an intermediary step."