| LOS ANGELES
LOS ANGELES About 45 minutes north of downtown Los Angeles, a machine the size of a small truck flattens tons of food scraps, paper towels and other household trash into the side of a growing 300-foot pile.
To Waste Management, which operates the landfill, this is more than just a mountain of garbage. Pipes tunneled deep into the mound extract gas from the rotting waste and send it to a plant that turns it into electricity.
Apart from the huge-wheeled compactor driving over garbage on its surface, it looks like an ordinary hillside. And it doesn't even smell. Yet it produces enough energy to power 2,500 homes in Southern California.
Trash, rubbish, whatever you call it, the 1.6 billion tonnes of stuff the world throws away each year -- 250 kilograms per person -- is being touted as a big potential source of clean energy.
As concerns about climate change escalate and prices on fossil fuels like oil and natural gas soar to record levels, more companies are investing in ways to use methane gas to power homes and vehicles.
Around the world, landfills where municipal waste is collected and buried are one of the biggest producers of methane, a gas whose greenhouse effect is 21 times worse than carbon dioxide. If instead that gas is collected and burned to generate electricity, proponents say the resulting emissions of carbon dioxide are less harmful to the environment than the original methane.
In the United States, trash haulers like Waste Management and Allied Waste Industries Inc are rapidly expanding the number of gas-to-energy projects at their landfills, while start-up companies are developing the latest technologies to transform garbage into ethanol, gas and electricity.
"We are able to take that resource and turn it into real value financially for us. In a very basic sense it helps improve our earnings," said Ted Neura, senior director of renewable energy development for Phoenix-based Allied Waste, which is turning waste into energy at 54 of its 169 U.S. landfills, with 16 more projects in the works.
The "green" credentials that go along with the waste-to-energy projects are an added benefit, Neura said.
"You begin to look at landfills a little differently when you couple them with a renewable energy project," he said.
Environmentalists aren't quite as enthusiastic. Nathanael Greene, director of renewable energy policy for the Natural Resources Defense Council, said touting the benefits of landfills was akin to putting "lipstick on a pig." Instead, we should be trying harder to reduce waste.
BIOGAS AROUND THE GLOBE
Biogas, another name for methane produced from waste, manure or other organic matter, is most developed in Europe, where Germany has 70 percent of the global market. In Britain, landfill gas makes up a quarter of the country's renewable energy, giving electricity to some 900,000 homes.
Waste-to-energy projects are also being expanded in the developing world, where rapid economic growth has led to a surge in municipal waste, but efforts to collect the methane emitted by rotting garbage have been slower.
Last year, the World Bank announced a deal to install a gas collection and electricity generation system at a landfill in Tianjin, China, saying the opportunities for other such projects in the world's most populous nation was enormous.
In less developed countries than China, however, a waste infrastructure needs to be installed before energy projects from landfills or garbage incinerators will make sense.
"Some of the developing countries are fascinated by the possibilities of introducing incineration," said Henrik Harjula, principal administrator for the Organization for Economic Cooperation and Development. "The problem is normally that it is like putting a modern facility in the jungle. There is nobody to take care of the maintenance."
In the United States, technology to produce electricity from waste has existed since the 1970s, according to Waste Management's vice president of renewable energy, Paul Pabor, who said federal tax incentives introduced in 2005 and state mandates to produce a percentage of their power from renewable sources has fueled the recent growth in such projects.
Environmentalists recognize that turning methane into power is preferable to releasing it into the air, but quibble with the characterization of landfill gas as renewable.
"This is an environmentally preferable option, but it's not renewable in the sense that it's not something we can do forever," said the NRDC's Greene. "Before we go adding incentives for energy production from garbage, we need to first get the incentives right so that we are maximizing the amount of recycling we do."
RUBBISH TO REVENUE
Despite the arguments about how "green" landfill gas really is, Waste Management and Allied Waste are benefiting from their growing new revenue streams. Allied Waste's Neura said the company generates less than 5 percent of its revenue from sales of electricity, but is evaluating all of its landfills to determine how best to develop them.
Landfill energy projects are much smaller than gas or coal-fired power plants, producing about 5 megawatts (MW) of electricity each, on average, Neura said. That's about enough power for 4,000 homes.
Houston-based Waste Management, which already produces energy at 100 of its 280 U.S. landfills, plans to spend $400 million over the next five years to build an additional 60 landfill gas-to-energy plants.
To produce enough gas to make a power plant financially viable, landfills must contain a large amount of organic waste and have been in operation for several years, Pabor said. At the moment, they also have to be located in states where power prices are high enough that electricity from the landfill will be competitive with energy from the grid. Finally, they also need to be close enough to transmission lines that the interconnection costs do not get out of hand.
"As a public company, of course, we've got to invest our fund in projects that do make a return for the investors," Pabor said in an interview. He declined to say how much of the company's revenue comes from its energy projects.
TRASH TO TRUCKS
In its latest effort, Waste Management last month joined a growing number of companies that are using waste to power vehicles. In California, the company is building the largest-ever facility to turn landfill gas into liquefied natural gas to fuel its heavy-duty garbage collection trucks.
But big, established companies aren't the only ones using waste to replace fossil fuels.
One start-up company, Boston-based Ze-gen Inc, is creating what it says is a zero-emissions process for producing electricity from construction waste that it is diverting from landfills. Ze-gen, which is backed by venture capital firms Pinnacle Ventures LLC, Flagship Ventures and VantagePoint Venture Partners, through a gasification project turns waste into syngas, a combination of hydrogen and carbon monoxide.
Bill Davis, the company's chief executive, said Ze-gen's syngas is able to produce more energy than competing gases without the waste having to be buried. Ze-gen hopes to attract industrial customers that will be able to power their factories with both their own waste and Ze-gen's technology.
"We are talking to large companies who are really worried about the escalating price of oil or natural gas," Davis said.
General Electric Co is also working to adapt its gasification technology, which today is used to burn coal more cleanly, to turn municipal waste into a cleaner-burning gas.
Solena Group, which is backed by Spanish conglomerate Acciona SA, is developing a facility in California to make renewable jet fuel from municipal waste, and BlueFire Ethanol Fuels Inc is building its first cellulosic ethanol plant adjacent to a landfill in Lancaster, California, so it can use municipal waste as its feedstock.
"It was the lowest risk feedstock," said Arnold Klann, president and chief executive of BlueFire Ethanol. "By putting this inside the landfill we totally avoid the creation of a new infrastructure, because the infrastructure already exists to bring (waste) into the landfill every day and bury it. We are taking the material that society values the least and converting it into a transportation fuel."
(For more coverage on the business of waste, click here)
(Reporting by Nichola Groom; Editing by Eddie Evans)