For Mexico City, a Repurposed Landfill In developing countries, closing a landfill often means just that: locking the gate and walking away. But when Mexico City's government shut down the giant Bordo Poniente landfill last December, officials announced that they had a full-blown plan for the site. As I wrote on Friday in The New York Times, the city aims to capture the methane gas produced by the landfill to fuel a power plant that could supply electricity to as many as 35,000 homes. If all the pieces fall into place, Mexico City could be a model for other large cities in the developing world that are studying ways to manage their landfills effectively, said Karen Luken, the global waste director for the C40 Clinton Climate Initiative, a joint program of Bill Clinton and Mayor Michael R. Bloomberg of New York. "When you talk to a place like Jakarta, they can't even put their arms around it," she said of the Indonesian capital. Some 79 million tons of garbage have been dumped on the 927-acre site of the so-called fourth stage of Bordo Poniente since it opened in 1994. The earlier stages have long been shut down. As organic waste in a landfill breaks down, it produces landfill gas, a mix of methane, carbon dioxide and water vapor. Methane is over 20 times more effective in trapping heat in the atmosphere than carbon dioxide is over the course of a century, so action to reduce such emissions can have a significant impact on greenhouse gases over all. In Mexico City, officials estimate that Bordo Poniente produces as much as 20 percent of the city's heat-trapping emissions. Converting its methane to fuel a power plant will reduce annual emissions in the initial years by the equivalent of two million tons of carbon dioxide, Mayor Marcelo Ebrard said. The energy from the power plant will help cover the costs of shutting down Bordo Poniente, which will cost $100 million to $200 million, said Ms. Luken, who advised Mexico City on the project. Not only will the energy project generate revenue through electricity sales, but it will be eligible to receive carbon credits as a result of the emissions reduction. The Mexican federal government, which pushed the city to shut down Bordo Poniente, has also allocated money for the project. Still, the details may prove a challenge In the United States, where there are more than 550 different kinds of projects to use landfill gas, the supply of gas is more constant. Typically, operators build cells for a landfill, close them and then move on to the next one, Ms. Luken. said. But because the entire Bordo Poniente landfill was closed at once, methane production is expected to peak after three years and then drop off gradually. "It was never designed for landfill gas management," she said. The plant will have a generating capacity of 35.6 megawatts during the first five years of operation and supply power for up to 35,000 households at its peak before falling off. Even though the plant has limited output, "every indication is that it should make economic sense," Ms. Luken said. At times, forging a consensus among the city's government's competing authorities has been complicated, with someone always wanting to have the last word, said Ms. Luken, who worked with the city for three years. "You have to have a garbage czar," she said.