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Tapping (Mountains of) Trash for Landfill Gas

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Apple cores, pumpkins, Christmas trees and the crusts your mom cut off your sandwich 27 years ago. They all ended up at Cloverbar landfill in Edmonton and as that material breaks down it releases methane.

While the landfill isn't accepting new waste that methane (which we know from our biogas episode is a valuable resource) can be collected and burned for electricity. It's called landfill gas recovery and in this case the methane powers a 4.8-megawatt power plant, generating enough electricity to power 4,600 homes.

Neil Burkhard was our very enthusiastic host as we toured Edmonton's waste management facility, a place that sports a very spiffy landfill diversion rate of 60 per cent. It was 21 years ago in 1992 when Edmonton started sucking landfill gas out of its landfill.

Today there are 60 active wells in the old landfill site and a star-like pattern radiates out from each well to collect the methane. These pipes are 20 metres under the surface and they all feed into a network of pipes that ring the perimeter of the landfill.

What's collected in those pipes is typically a mixture of methane, carbon dioxide and water vapour. It's collected by massive vacuum pumps, cleaned up and burned in three different 20 cylinder converted diesel engines.

They collect a lot of gas, enough to fill the equivalent of 8,000 hot air balloons per day. What doesn't get burned for electricity is flared. The operator who was showing me around mentioned that this is done for carbon credits. It was curious -- how is burning methane a positive for the environment?

It turns out that methane is 21 times more potent a greenhouse gas than carbon dioxide. Venting it directly to the atmosphere is far worse than even just burning it off as the flaring process converts the methane into plain old CO2.

Landfills produce a lot of greenhouse gases, in 2010 they produced 27 megatonnes of CO2 equivalent. Through landfill gas recovery techniques they were able to capture seven megatonnes of that bringing their total down to 20 megatonnes of CO2 equivalent. For scale the total emissions from Canada in 2010 were 692 megatonnes with the biggest single sector being transportation.

"In an energy hungry world and a world concerned about climate change it would make a lot of sense to take all of these landfills across our country and take that methane and turn that into a source of energy to meet that demand," says Burkard. He's a fount of information during our tour pointing out that Edmonton was the first in Alberta to get a landfill gas recovery operation and trooping down to some exposed pipe on a cold winter day to show us how it all works.

The whole facility treats waste as a tremendous resource and all it takes is a slight shift in how you see the world to realize it along with them. It's a theme we've covered over and over again on Green Energy Futures.

There are 64 landfill gas recovery sites in Canada right now and while not all of them burn the methane for electricity there will be lots of opportunities as carbon markets and carbon pricing develops.

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Waste to biofuels

Twenty years in, creating electricity from landfill gas still isn't that common, but Edmonton is not resting on its laurels. A new biofuels plant under construction will convert 100,000 tonnes of undiverted trash into 38 million litres of biofuels annually.

"It's quite a complex process - we create a feedstock initially where we take the garbage and shred it up into something the size of a corn flake or a potato chip," says Burkhard.

"That waste will then be fed into what is called a bio-refinery, that will raise the temperature of that material to 750 degrees Celsius and crack the bonds of the garbage." That cracking process creates syngas, which is a mix of carbon monoxide and hydrogen. Through another process called catalytic synthesis the whole mix is turned into methanol.

"The methanol has all kinds of uses. It can be refined further into ethanol for ethanol-blended gasolines. Raw methanol can be used for making windshield wiper fluid, glycol and a whole series of other chemicals that are used in the petrochemical industry."

With Edmonton currently trucking 70 loads of garbage a day one hour southeast to a dump in the small town of Ryley, getting that diversion number up as high as possible means cash savings.

90 per cent waste diversion rate

Other municipalities are catching up with Edmonton's 60 per cent landfill diversion rate. Toronto diverts as much as 67 per cent, while Vancouver diverts 55 per cent and Winnipeg only diverts 17 per of its waste from the landfill. Edmonton does it with a massive composting complex, an army of workers working conveyor belts picking out recyclables and new initiatives that partner with companies to find the value in old electronics and waste paper and old clothes. Edmonton's new biofuels operation will get waste diversion rates to 90 per cent by 2015.

"Landfills aren't obsolete just yet, but we're getting very, very close," says Burkhard.