Environmentalists cheer as Palo Alto retires incinerators | News | Palo Alto Online |


Environmentalists cheer as Palo Alto retires incinerators

City makes the switch from burning sludge to shipping and treating it

Visitors to Palo Alto's new sludge dewatering building view informative graphics and photos showing how sewage is processed during a ceremony to retire the incinerators and open the new facility on June 5, 2019. Photo by Veronica Weber.

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been in use since 1972, marks a significant milestone in Palo Alto's plan to address climate change and upgrade its outdated waste-treatment system.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."

Related content:

A journey of 9,500 miles. Why recyclables are heading overseas to Asia.


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Like this comment
Posted by Curmudgeon
a resident of Downtown North
on Jun 7, 2019 at 4:16 pm

That incinerator had architectural merit. It's replacement has all the design verve of a Soviet-era dewatering plant.

Like this comment
Posted by John
a resident of Midtown
on Jun 10, 2019 at 12:14 pm

Have our local authorities looked at the full picture of energy invested in disposing of the sludge? This would include the electrical energy to run the de-watering process, the fuel to truck the sludge, additional energy inputs to process and distribute the sludge.

Like this comment
Posted by file under 'D'
a resident of Green Acres
on Jun 10, 2019 at 12:49 pm

> Have our local authorities looked at the full picture of energy invested in disposing of the sludge?


Like this comment
Posted by John
a resident of Midtown
on Jun 10, 2019 at 6:04 pm

Where can this energy expenditure data be found? Also, has the toxics burden of the sludge been considered? Will it be spread on agricultural land?

Like this comment
Posted by John
a resident of Midtown
on Jun 12, 2019 at 11:35 am

Since we are trucking our sludge to Synagro, which is controversial among the organic farming communities, are we willing to spread Synagro on our own park and school lawns? I just feel like we have taken the path of exporting our problems to someone else.

Like this comment
Posted by file under 'D'
a resident of Green Acres
on Jun 12, 2019 at 12:10 pm

> controversial among the organic farming communities

Controversial? It's not considered 'organic'. No controversy about that. Am I missing something?

Or are you positing PA park/school care should be non-toxic, certified organic only?

Like this comment
Posted by John
a resident of Midtown
on Jun 12, 2019 at 1:06 pm

Synagro markets itself as organic, but organic farmers refuse to use it, and they resist its use near their properties (odor, leaching into streams). Yes, the build up of toxics is a concern. In order to overcome public resistance to human sewage sludge as a fertilizer, a contest was held to call it something else...the winner was "biosolids".

Instead of exporting our (literal) crap onto others, why don't we act locally to solve the problem? Wasn't that the original idea? I personally would like to truck it to a regional refuse station and mixed with plastics and other garbage and subjected to gasification to produce net electricity.

Like this comment
Posted by file under 'D'
a resident of Green Acres
on Jun 12, 2019 at 1:17 pm

Synagro tries to blur the lines, frequently (honestly) using the word 'organic' in proper context ("Synagro recycled fertilizer compost replenishes organic matter...") but as I see it, never fully claims that it is what is traditionally thought of as a 'certified' organic product.

The 'blurry' claims: "Synagro’s organic recycled fertilizer pellets..."

Uh, no.

I don't see the advantages of gasification over eventual composting.

Like this comment
Posted by John
a resident of Midtown
on Jun 12, 2019 at 1:52 pm

Gasification destroys the organic toxins; inorganics (e.g. heavy metals) are isolated and embedded into slag. It allows a solution to sludge, plastics, tires, landfill, etc. And it produces net electricity.

Palo Alto was embarrassed about using natural gas to combust our sludge. Shouldn't it also be embarrassed about dumping our problem on others (usually in less privileged areas)?

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