It's trash day in Palo Alto. Time to load up your four crates of recycling, two cans of garbage and green compost bin before Palo Alto Sanitation Co. workers whisk it all away.

Ever give much thought to where it ends up?

These days, the journey of Palo Alto's garbage is a hot topic.

A controversial plan to build a 19-acre facility on the baylands east of Highway 101 -- possibly handling everything from compost to recycling to trash sorting -- is alarming environmentalists and baylands enthusiasts who want to see the city stick to its plan to turn the hilly landfill into parkland.

As the city council continues its discussion tonight on what to do with Palo Alto's trash, we offer a primer on how the baylands, Sunnyvale and trash bills all play a part in what comes next.

Q What's at the baylands now?

A The 1,940-acre Baylands Preserve includes bicycle and jogging trails, the Lucy Evans Baylands Nature Interpretive Center, an art park in Byxbee Park, the Emily Renzel Wetlands, the Baylands Athletic Center and the Palo Alto Golf Course. There also is a 140-acre landfill -- that still accepts construction debris -- and a 16-acre recycling center and composting facility.

Q What came first: the dump or the park?

A The dump was started during the 1930s, more than 30 years before the park dedication.

Q Why is the city considering a new waste facility in the baylands?

A Glenn Roberts, the city's public works director, has said a new waste center would allow the city to control its garbage and recycling programs after its landfill closes in 2011. Another crucial date is 2021 -- the end of the contract with the Sunnyvale Smart Station -- which processes and transfers waste from Palo Alto, Mountain View and Sunnyvale. 2021 also is the end of the contract with the Kirby Canyon Landfill in South San Jose, where Palo Alto's garbage ends up.

Q What would be the major changes if Palo Alto built a 19-acre center on the baylands?

A After 2021, city crews would sort garbage at the baylands, then have it hauled to Kirby Canyon in South San Jose or another landfill, removing Sunnyvale from the equation. The city also would build a recycling center there, which would allow recyclables to be sorted after they arrive mixed together in what's known as a ``single stream.'' That means residents won't have to sort recyclables at home, and the city wouldn't have to rely on other cities.

Q What would Palo Alto give up if the city went with a proposal for a 6.2-acre center instead?

A The composting area would not be included, among other things. The city might pay the Palo Alto Sanitation Co. to deliver yard waste to Sunnyvale.

Q What did Palo Alto do with its trash before the Sunnyvale station opened in 1993?

A Ever see those hills at Byxbee Park? There's about 48 feet of trash buried below. But don't go digging for artifacts. The final layer of dirt, clay and top soil is six feet deep. Some areas have as much as 60 feet of garbage buried below.

Q Is the buried trash harmful to the park's wildlife or the bay?

A Depends on whom you ask. Landfill supervisor John Connelly says no. The landfill follows state and county regulations to safeguard the atmosphere and bay, he said. Leachate, an inky black liquid formed when rainwater seeps through garbage, is pumped out and processed at the city's nearby water quality control plant. Methane gas, another byproduct of decomposing garbage, is burned off. The site is sealed with a clay soil barrier. Baylands supporters say any development -- especially of a decades-old landfill -- is bad for the bay.

Q Why are some park advocates and environmentalists against this project?

A Baylands advocates such as former city council member Emily Renzel have urged the council to follow the city's plan to return the landfill site to parkland when it reaches its capacity and is closed. Renzel argues that the city should continue to use Sunnyvale as a garbage transfer station and take a regional approach to waste disposal.

Q Does the city make any money off residents' recycling efforts?

A Yes. It nets about $1 million a year from selling its recyclables. That money helps offset the cost of garbage collection, which lowers residents' garbage bills. If Palo Alto shipped its recyclables to Sunnyvale, the city would lose about 93 percent of its recycling revenue, Roberts said. If the city created its own facility, there could be additional costs.

Q Will any of these decisions affect residents' rates?

A They could. Roberts says the 19-acre plan is the most cost-effective in the long term, although City Auditor Sharon Erickson released a report earlier this month that said building and operating the Environmental Services Center would cost the city $1.6 million a year more than continuing to haul garbage to the Sunnyvale facility.

Q Does this affect Palo Alto's recycling?

A It may in the long run. Starting this summer, the city plans to allow residents to mix all their recyclables together. But council members are having second thoughts about the expense of that added convenience, and may decide at a council meeting tonight that it's too costly.