Landfill 101: What to do with waste
All the trash that we take out has to go somewhere. Some things can be sorted out and recycled, but for the rest, it usually ends up in a landfill. It can be incinerated first, to take up less space, or it can be thrown right in and buried.
It doesn't just sit there forever. Trash decomposes and rots, producing gases like methane and a nasty liquid called leachate, which seeps out of the landfill.
Landfills are engineered to be as minimally environmentally harmful as dumping trash underground can be. This involves placing a layer of 5mm polyethylene (thin plastic sheet) down before stacking alternating layers of garbage and soil. This prevents the leachate from seeping into the ground below the landfill and contaminating drinking water. Pumps move leachate out from the bottom of the landfill so it doesn't accumulate too much. This leachate is then stored and treated. Some landfills also have vertical pipes installed throughout the pit to collect gases produced by the rotting garbage. This gas, which is composed of roughly 50% methane, can be used as a source of power to generate electricity. (In fact, the campus of UNH uses landfill methane to generate much of its power!)
However, the generators and associated equipment is fairly expensive, so the technology hasn't really been shown to pay for itself yet. Still, even if the methane isn't used for electricity generation, it is beneficial to the environment if the gas is collected and burned, as methane is a greenhouse gas 10-20 times more potent than CO2, so landfills with uncaptured methane can actually contribute to climate change.
The other method to generate electricity from trash is through incineration. If you're trash is energy dense enough, you can just burn it and get power immediately, then bury the heavy ash after. One benefit is that is reduces the volume of the trash about 90%, one major downside is that is can produce light ash in the air.
The Sao Joao landfill to the east of Sao Paulo was opened in 1992, and by 2004 was nearly filled with garbage from Sao Paulo, (SP produces 15,000 tons of trash/day). There was a growing call for a solution to the methane problem, so a company came in and set up a power plant there, which has been operational since 2008, burning the methane biogas and producing around 20MW of power on average.
This is considered a renewable energy source, as there will always be a fresh supply of trash. The idea doesn't work quite as well in the U.S. and other European countries, because we have a higher proportion of packaging in our trash, compared with Brazil's more compostable rotten-produce-like waste.
First off, it was a cold morning. We've had quite a cold, wet week here, after the first 2 were really nice. I woke up and instantly knew I was going to bring my blanket on the bus with me. Almost everyone else did too, so we all looked so cold and pathetic carrying around our little green blankies. It was so hillarious.
As soon as we got off the bus we were assaulted with a putrid, vomit smell that was so strong we had to cover our noses up or face retching.
Hayley and Harrison's faces say it all. We thought the cold would keep the smell down better than if it was a hot summer day, but the lady who gave us a brief overview of the landfill said that its usually worse on wet rainy days. Like this one. Either way, you couldn't pay me enough to work there!
To smile would be deceitful
There's roads that curl around the landfill for company trucks. The pool in the bottom right of the photo is for storing leachate.
So there was actually 2 companies working at this complex. EcoUrbis, who gave us the presentation, is responsible for one site, they just collect the gas and burn it on site without producing power. BioGas, responsible for the other site on the complex, has invested in a power plant to generate electricity from methane gas. So we started at one, and then drove a few minutes on the bus to the generation facility of BioGas.
Gustavo translating for an employee in the control room
Cold and smelly, some of us had really checked out.
This behemoth is one generator. There must have been around 20 of these things lined up through the facility.
Some seemed to be out of order, however.
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