Palo Alto voters will be asked to wrestle with incomplete and possible contradictory data in November when they hit the voting booths to consider whether the city should be allowed to build a waste-to-energy plant on parkland in the Baylands.

The anaerobic digestion plant, which would process local yard trimmings and food waste and convert them into electricity, has become a topic of fierce debate between environmentalists who say the city should take care of its own waste and conservationists who argue that public parkland is no place for a new waste facility. Members of the City Council acknowledged Monday that a lack of conclusive information about the plant's potential costs will make the voters' decision particularly challenging and susceptible to the clashing arguments from the two green camps.

Public Works staff and consultants have been scrambling in recent months to gather information about the projected costs of the new plant, which would occupy a roughly 9-acre site in Byxbee Park. They have already provided projections on how much the city would have to pay if it were to build a local plant and if it were to export its food scraps and yard waste to San Jose and Gilroy, respectively.

But given the complexity of the topic, the inherent uncertainty of adopting new technology and the deep split both on the council and in the community, each answer has only spawned further questions and requests for more analysis. Despite months of crunching numbers and researching other facilities, Palo Alto officials are no closer than they were a year ago to figuring out what to do when the city's existing landfill closes this summer, bringing the city's composting operation to an end.

Some of the most crucial questions are far too broad and complicated to be answered before the November election, staff said Monday. These include a suggestion to process sewage waste and food scraps together in a "wet anaerobic digester"; a proposal to integrate the compost study with the city's ongoing analysis of the Regional Water Quality Control Plant; and consideration of composting technologies other than anaerobic digestion.

The shortage of information means voters will have to rely on partial analyses, campaign literature and their own instincts when they step inside the voting booths in November, council members said.

Public Works staff and the consulting firm Alternatives Resources, Inc., (ARI) have been fielding comments from both sides of the debate since late January, when the city released the preliminary cost estimates for the proposed facility. The estimates compare the per-ton cost of keeping waste operations local and shipping yard waste and food scraps to Gilroy and San Jose, respectively.

Early results indicate that building a local facility would be substantially more expensive than shipping it elsewhere in the short term. The difference, however, would narrow over time.

Proponents of a local plant, including former Mayor Peter Drekmeier, are asking the consultants to modify their analysis to include such things as "carbon adders" (putting a price on carbon emissions) and the costs of replacing the city's sewage-burning incinerators. Drekmeier is also lobbying the city to consider a wet anaerobic digester that would process both food waste and sewage sludge. Such a facility, he argues, would allow the city to retire its polluting incinerators -- a source of shame for the notoriously green community.

Others have urged the consultant to consider the rent value of the land, the costs of mitigating the new plant's potential environmental impact and "contingency" costs for the exporting options.

"It's getting a little politicized -- some people want higher rent, some want carbon adders," Councilman Greg Scharff said Monday. "What I want to see is real numbers that allow us to look at this in a thoughtful manner."

Some of these questions will be at least partially answered in June, when staff returns with additional information about such things as carbon adders, land-rent value and the potential for replacing the incinerators with a wet anaerobic digester. Others, however, will remain unanswered even by November, said Phil Bobel, the city's manager for environmental compliance.

"It's just too late to get started on new options, either at the (water quality control) plant or the 9-acre site," Bobel said.

Drekmeier's group last month submitted more than enough signatures to put the land-use issue -- whether or not to "undedicate" the parkland and make it eligible for a new plant -- on the November ballot. The council and staff concluded on Monday night that this does not give the city enough time to answer all the major questions about the proposed facility.

"We have to live in the real world and the information the public will have will be what it is," Councilman Larry Klein said. "Frequently, the public is asked to vote on things without having 100 percent of the information."

Despite this limitation, Klein said he believes the public will be able to "vote knowledgeably and intelligently -- as Palo Alto voters normally do."

Mayor Sid Espinosa said at the end of Monday's discussion that even after staff comes back with more information in June, neither the council nor the community would likely have all the information they need to make a decision on the highly divisive topic.

"I suspect we'll end up in a place where whatever limited information we have -- the proponent and opponent side will tweak it to their benefit and will say if its financially feasible or not," Espinosa said.

Councilwoman Karen Holman called the lack of definitive information "an unfortunate situation." She joined Espinosa and Klein in voting to direct staff to come back with more information, and a "manageable list of scenarios," in June.

"The voters need as good information as we can provide," Holman said.

Councilman Greg Schmid, the sole dissenter in the council's 7-1 vote (Pat Burt was absent), continued to call for staff to consider other technologies besides anaerobic digestion. He pointed to other communities, including Santa Barbara and Salinas, which are struggling with similar problems and which are considering "plasma arc gasification" -- a process that uses intense heat to convert waste into energy.

"I think the issue is not around the difference between adding a carbon adder or grant or rent," Schmid said. "It's really the basic question, 'Are we making investment in the right technology in the right place?'"

While the November ballot measure would make the land available for a composting facility, it does not specify which technology the city should use. Scharff pointed out that the council will have plenty of time, even after the election, to examine its waste-management options fully before making its final decision.

"My sense is that when we go to the voters, if they choose not to undedicate, the discussion ends," Scharff said. "If they do, that's the beginning of the discussion, frankly."

But some, including Emily Renzel, think the city has already done more than enough analysis. Renzel, a leading opponent of the new plant, argued Monday that existing data clearly shows that the proposed plant would not be financially feasible when compared with the export options. The new facility, she claimed, would lead to years of steep rate increases to residents' garbage bills.

"You can have ARI tinker with a lot of numbers, but unless they are REAL numbers, sooner or later Refuse Rate payers will have to pay the difference," Renzel wrote in a letter to the council, which she read Monday night.