As oil companies search for untapped reservoirs and engineers struggle to develop cheaper renewable energy, usable natural gas seeps daily from the world’s landfills. Now, after a heavily debated decision by the Palo Alto City Council, landfill gas from Bay Area facilities could power local homes.

In a 5-4 vote last Monday, the council approved two contracts with Ameresco, a company that plans to generate electricity using gas produced during the breakdown of refuse in landfills. Deep wells in the hills of waste will literally vacuum up the gas and send it to an internal combustion engine.

“It’s important to use the methane because otherwise it will enter the atmosphere and contribute to global warming,” said civil and environmental engineering Prof. Craig Criddle Ph.D. ’89, who studies green energy.

He explained that methane acts as a greenhouse gas 24 times more powerful than carbon dioxide.

“This is a low-hanging fruit of climate change mitigation,” he said. “But globally, 90 percent of landfills do not capture their gas.”

Landfills in the United States are required by law to carefully monitor and limit gas emissions, according to Michael Carroll, a senior engineer at a San Joaquin landfill where Ameresco will harvest some of its gas. In the San Joaquin Valley, captured gas is currently disposed of through combustion. This process, called “flaring,” reduces greenhouse gas impact by 90 percent and smog by 92 percent, but produces no energy.

“With the landfill-gas-to-energy project, we’re using a fuel that is already being collected, and we’re glad it can be used as energy,” Carroll said.

Based on the amount collected each day, he predicted the wasted gas could consistently power around 4,000 homes.

Several council members said the newly approved commitment posed a financial and environmental risk to the city. Council member Greg Schmid worried that the council embraced this opportunity without fully investigating the potential indirect environmental impacts of the process.

“It appeared to me as a non-scientist that more research needed to be done,” he said.

Carroll said the electricity production does release slightly more nitrous oxides than flaring. Nitrous oxides are important components of smog.

Mayor Pat Burt and council member Karen Holman had other trepidations.

“Environmentally, I was concerned that the particular landfills involved do not have the best practices,” Burt said.

San Joaquin Valley landfills still accept some recyclable and compostable materials. Carroll said most of these items are removed before they even reach the landfill, but more rigorous sorting is not economically feasible.

“San Joaquin Valley waste management is funded almost entirely by our clients, so every decision is an economic decision,” Carroll said.

The landfill gas project is only possible because towns like Palo Alto are willing to pay for it, Carroll said.

According to Schmid, landfill gas energy is currently the cheapest option for expanding Palo Alto’s alternative energy portfolio.

“As a leading city we want to be out there grabbing the best deals,” Schmid said.

With the contribution of landfill gas, Palo Alto is expected to receive 28 percent of its energy from “green” sources.  The city hopes to reach 33 percent by 2015. But Burt says there are better ways to reach this goal.

“I want to see us put a greater portion of our effort into reducing the purchase of polluting energy as opposed to buying more green energy,” Burt said. “We will always use a combination of increased renewables and increased efficiency. The question is how best to strike that balance.”