Palo Alto may still be years away from building a state-of-the-art facility to process local food waste and yard trimmings, but officials are preparing to pick up the pace when it comes to dealing with sewage sludge, the third stream in the city's complex waste flow.
The topic of waste management re-emerged at Monday's City Council meeting, where members heard a presentation and offered feedback on the three different proposals the city has received from the private sector in recent months in response to its request. The effort was prompted by the 2011 closure of the landfill in the Baylands, which also eliminated the city's composting facility and spurred debate in the environmental community about the merits of building a local waste-to-energy plant versus the value of preserving parkland.
In November 2011, proponents of a local facility won a battle when voters approved Measure E, which made 10 acres of Byxbee Park land available for a possible composting facility. A citizens task force that studied the subject recommended as its preferred technology "wet anaerobic digestion," which uses bacteria in an oxygen-deprived atmosphere to process organic waste and release methane, which is then converted to biogas. The idea was to have a facility that would accept food scraps, yard trimmings and the sewage sludge, also called "biosolids."
Now, city staff is urging the council to press ahead as soon as possible with a solution for the lattermost waste stream. Phil Bobel, assistant director of the Public Works Department, stressed the importance of retiring the city's sewage-burning incinerators, a long-standing blot on the city's green record. Phasing out the obsolete technology, he said, is now staff's top priority.
"We need another technology beside incineration," Bobel said.
The tentative proposal from staff is to first pursue a Biosolids Facility Plan and build a dewatering and truck off-load facility at the sewage plant site. This would both allow the city to decommission the incinerators and create a back-up system for sewage treatment.
The next priority on the list would be to pursue a wet anaerobic digester of the sort recommended by proponents of Measure E. Bobel said that the responses to the city's request for proposals confirmed for staff that wet anaerobic digestion is indeed the best technology for processing food scraps and sewage sludge, the same conclusion offered a specially appointed citizens task force in 2009. Staff also learned about thermal hydrolysis, a process in which cell walls in organic waste are broken down and which allows more energy to be released during anaerobic digestion.
Two of the three companies that offered services to the city Harvest Power and We Generation proposed using wet anaerobic digestion. We Generation offered to combine that with thermal hydrolysis. The third company offered to export all three waste streams, an option that no one voiced support for.
The final piece of the puzzle in staff's plans would be to find a new site for processing yard trimmings, according to a staff report.
Though Bobel said staff is still evaluating the proposals, he and others expressed reluctance about accepting either proposal outright. Unlike in the past, when officials were focused on signing a deal with a company that would design, build, own and operate the facility, they are now talking about having the city operate its own plant. The fact that wet anaerobic digestion is a well-used technology makes it a fairly low-risk proposal, he said. An option that Bobel and City Manager James Keene appeared to be leaning toward was nixing the requests-for-proposal process and pursuing a different procurement strategy that would treat the waste streams in phases. Keene said the city is "on track to make a recommendation for rejecting the proposals."
Representatives from both vendors attended the Monday meeting and made cases for their respective technologies. Paul Sellew, CEO of Harvest Power, stressed that his proposal is the only one that would treat yard trimmings locally, on a 3.8-acre piece that is part of the 10 acres undedicated in Measure E.
"We were the only responder that completely handled everything on site," Sellew said. "Greenhouse-gas reduction was a big issue, but doing it on site there was a big advantage."
Alvin Thomas, representing Cambi (a partner in We Generation), talked about the merits of his company's technology and said the proposal could include an option for transferring ownership to the city. It would, however, entail shipping of yard trimmings to Newby Island, near Milpitas.
"I really believe our proposal covers everything staff asked for -- it processes biosolids, it processes food waste, it deals with a dewatering facility and has a more-than-adequate alternative for yard waste."
Even so, staff concluded that "no one proposal has all the components that we wanted," Bobel said.
The council didn't take any votes on the item, which will return in March, but council members asked staff to consider various models of plant ownership before moving too far ahead with any decisions. Councilman Larry Klein requested that staff bring back three possible alternatives for owning and operating the plant. Councilwoman Gail Price suggested that one alternative could be a "hybrid" approach in which different vendors work together on a project. This might be complicated, she said, but it could prevent the launching of another lengthy request-for-proposal process.
"Complicated never seems to bother anyone in Palo Alto," Price said. "I think that would be useful."