How Mexico City has turned garbage into fuel

A year after Mexico City closed one of the world’s largest landfills, Bordo Poniente, the Mexican government has just announced that BMLMX Power Company has been awarded the international tender to build a biogas plant on the site of the landfill. Nick Michell looks behind the project to see how it is helping the city reach the emission reduction goals established in its Climate Action Program.

It did not take long from its opening in 1985 for Bordo Poniente to become the sole sanitary landfill for Mexico City. As the city’s population grew and occupied all areas with the potential to house a similar facility, the garbage concentration at the site progressively took over the available storage space. Twenty-five years after its launch, Bordo Poniente had grown to 370 hectares with over 70 million tonnes of garbage piled 17 metres deep. It had become one of the world’s biggest rubbish dumps and the city government decided enough was enough.

On November 22, 2010, the Mexico City Government signed an agreement with the Federal Government for the closure of Bordo Poniente, which has transformed the waste management practices of the city.

Under the agreement, the Mexico City Government committed to conduct an environmentally appropriate and definitive closure, with the engineering project having to meet the environmental technical standard for landfill closure. The city was authorised to produce electricity from the landfill biogas, to help recover some of the significant investments that its closure, biogas control and nature restoration would require. Perhaps of most significance, the city was obliged to introduce a dynamic recycling, composting and waste for energy programme to reduce the need for landfill.

“The landfill closure and biogas utilisation of Bordo Poniente are the main climate control actions of Mayor Ebrard’s present administration,” says Fernando Menéndez-Garza, General Coordinator of Mexico City’s Comprehensive Solid Waste Management Commission, Mexico City Government. “This project is expected to reduce 19.8 million tonnes of CO2e during its 25-year lifespan or 20 percent of Mexico City Government’s total greenhouse gas contribution.”

The origins of the closure go back to 2007 when the city’s mayor Marcelo Ebrard had meetings, as part of its membership of the C40 group of cities, with President Bill Clinton and New York City Mayor, Michael Bloomberg. Identifying Bordo Poniente landfill as one of the biggest sources of greenhouse gas emissions in the city, C40 in partnership with the Clinton Climate Initiative opened an office in Mexico City and started to work with city government officials on the development and implementation of strategies for the management of solid waste.

“Closing Mexico City’s Bordo Poniente Landfill is one of the most important environmental actions for the entire country,” says Marcelo Ebrard. “When there is a very high level of complexity but a common objective and a successful outcome, we build confidence in our ability to take on other important objectives.”

Managing the transition

The closing of such a large landfill was always going to provide the city government with a number of challenges, not least finding alternative ways of processing and disposing of its garbage. Before the Bordo Poniente landfill was shut down, the city launched a comprehensive programme to separate organic and inorganic waste in order to increase recycling to produce compost for gardens and parks, and to reduce the amount of daily waste, which needed to be sent to landfill.

Every day, 3,750 tonnes of waste is now separated for recycling with glass, cardboard, paper, tin, plastics and polyethylene terephthalate (PET), among other materials being collected by garbage truck crews, street cleaners and private collection companies, who then separate approximately 3,000 tonnes per day of inorganic solid waste for recycling. A second stream goes to three city-owned Material Recovery Facilities where approximately 750 tonnes per day are recovered for recycling.

Mexico City generates 12,500 metric tonnes of municipal solid waste per day and it has reduced the amount going to landfill to 5,500 tonnes, through the recycling programme and by diverting 1,023 tonnes of waste into energy and converting 507 tonnes into compost.

Another major factor in the reduction in waste going to landfill is the Mexico City Government’s agreement with CEMEX, one of the world’s largest building materials suppliers and cement producers, to deliver up to 3,000 tonnes a day of solid waste inorganic fraction (SWIF) for use as fuel in their kilns. The SWIF, having been separated from materials suitable for immediate recycling (like PET, aluminium, glass and metals), would end up in landfills if it were not sent for co-processing.

“Once all the materials suitable for immediate recycling have been separated, the remaining material is processed through a mechanical separator, where the organic and inorganic fractions are split apart, sending the organic portion for biogas generation, compost production and/or landfilling, while the inorganic fraction is sent to be co-processed as alternative fuel in cement kilns,” says Eduardo González, Sustainability Director for CEMEX México.

Before leaving the separating facility, the inorganic fraction is pressed and bagged in impermeable plastic.This increases its density, allowing for efficient transport, as well as avoiding unwanted water and pests. “Once in CEMEX, the SWIF (Solid Waste Inorganic Fraction) is ground to a size that makes it possible for transport by lorries, and it is then dosed into the cement kiln,” explains González.

The solid waste inorganic fraction processing by CEMEX decreases the amount of material going into landfills, extending the life span of existing landfills and reducing the necessity for new ones. The environmental impact from the fuel used for transport of the SWIF to CEMEX’s cement plants is also far lower than the impact if these materials were sent to landfill.

Teething problems

In the immediate aftermath of the closure, the city government came in for a significant amount of criticism. Waste pickers, who had spent their lives sifting through the waste for valuable materials, claimed the closure had destroyed their livelihoods and even their communities. And with waste being diverted to private landfills outside of Mexico City, trucks were having to drive two to three hours out of the city centre, increasing travel costs and countering the potential reductions in emissions from the closing of the landfill.

Fernando Menéndez-Garza is quick to dispel these criticisms and says the city government were simply encountering teething problems.

“After the shutdown of the landfill, the city experienced a period of adaptation to the new circumstances where the waste collection and transfer to other landfills failed to operate in certain parts of the city,” says Menéndez-Garza. “With regard to the informal pickers, Bordo Poniente has Material Recovery Facilities within its premises, where all valuable materials are selected, and sent to recycling industries. This project provides jobs and income to a union of former scavengers and that has continued operating after the landfill shut down.”

While admitting that refuse trucks have to travel longer distances now to transport solid waste to other landfills–on average refuse trucks travel 29 kilometres every day to deposit waste in landfills– Menéndez-Garza says there have been other efficiencies in the transport system: “Some of the routes are driven on toll highways, which in fact reduce the travel times to less than before.”

Biogas to light the streets

The latest phase in the development of Bordo Poniente has been the announcement this month that the Mexico City Government has awarded the international tender for the closure of Bordo Poniente and biogas utilisation to BMLMX Power Company Sapi SA de CV. The consortium, consisting of two Spanish and two Mexican companies, has signed a 25-year contract for the utilisation of the biogas, which includes the construction of an electric power generating plant that will sell power to the local government for public lighting at lower prices than those currently offered by the Federal Electricity Commission.

The project will not only provide the city government with significant energy savings but will also decrease the amount of carbon dioxide equivalent released each year. “It is estimated that a reduction of around 1.4 to 2 million tonnes of greenhouse gas emissions can be achieved during the first year of biogas utilisation,” says Menéndez-Garza.

The winning consortium will invest over US$2 billion in the project, financing the decommissioning of the landfill and the construction and operation of the biogas plant, which will generate electricity to light the streets of Mexico City for the next 25 years.

While Mayor Ebrard’s tenure will last only a few more weeks, his administration has left a long-term legacy not only for Mexico City but also for other cities. As the mayor himself says: “If it can be done here, it can be replicated elsewhere even if the solution is a complex one.”