Australia sends upwards of 21.5 million tonnes of waste to landfill each year. That’s almost a whole tonne of landfill per person per year!
At some level, most of us agree we should try to avoid sending stuff to landfills.
The word landfill conjures up images of vast, foul smelling open tips, strewn with garbage, teeming with scavenger birds and flies.
“Of course we don’t want that!”, we tell ourselves.
But on another level, it’s hard to imagine a world where we don’t put stuff in the general waste (landfill) bin. We’ve all grown up relying on landfills. It’s just normal, after all. Humans have relied on landfills since the stone age and it doesn’t seem to have done us any harm.
What’s more, modern landfills eventually end up covered with grass and trees in the developed world.
So what’s the deal with landfill? Is it really so bad?
Modern Australian Landfill
In Australia we have approximately 160 major landfill sites.
Modern landfill sites are carefully constructed out of large cells lined with compacted clay, a thick layer of plastic and several further layers of geotextile. The cell floor is typically sloped to allow water to drain down to collection points. A single cell is normally the size of several football fields.
The cell walls and lining are designed to prevent contaminated water and other fluids from seeping out into the ground and gas from escaping into the atmosphere.
Waste is compacted into the cells using heavy machinery before being capped with a top layer of plastic and compacted clay.
Why so much care to contain the landfill in cells? Because the bi-products of landfill are pure poison.
Toxins
Landfill contains vast quantities of substances that are harmful to the environment. Plastics such as PVC and other materials leach toxic chemicals as they break down.
E-waste is the fastest growing waste segment in the developed world. Even though it’s the most toxic everyday waste stream of all, most of it ends up in landfill. E-waste is loaded with heavy metals, solvents, and acids.
Leachate
It takes a year or more to fill each cell, during which time the contents are exposed to rainfall. Rainwater filtering through the landfill dissolves and flushes 5-7 percent of the toxins with it to create a foul smelling liquor, known as leachate, which contains ammonia and various toxic salts.
Depending on rainfall, a single landfill site can easily produce several Olympic sized swimming pools of leachate each year. Leachate is carefully collected and recirculated into the landfill cells to prevent contamination of land, groundwater and waterways. Some leachate is reabsorbed when passed back into landfill, but the rest filters through again, picking up more toxins with each pass.
Landfill Gas
Greenhouse gas production is perhaps the biggest environmental threat posed by landfills.
Landfill gas comprises 35-55% methane and 30-44% carbon dioxide. Methane is produced when food, plant matter, and organic materials such as wood, paper and cardboard decompose in the absence of oxygen. Natural gas and shale gas are both mostly methane.
As a greenhouse gas, methane is many times more potent than carbon dioxide. We commonly hear that it’s 20 - 23 times more potent, but this figure doesn’t tell the full story. It’s effect is only 20-23 times more potent when averaged out over 100 years.
Within the first 20 years of emission, methane’s greenhouse effect is far worse—somewhere between 84 and 100 times more potent than carbon dioxide. And when it comes to moving the needle on greenhouse gas emissions, what really counts is what happens over the next 10 - 20 years.
So how much methane is produced by a typical landfill site? An awful lot. Enough to fuel a power station, in fact.
For example the Wollert Landfill in Victoria, which serves a population of half a million, generates nearly 1.7 million cubic metres of methane each month. 85% of this gas is captured and fires a generator which provides electricity to 10,000 homes.
While plant operators and governments often choose to describe landfill gas power as renewable energy generation, it’s certainly not a sustainable, or environmentally friendly form of generation. When burned, methane produces carbon dioxide - just like oil and coal.
Conclusion
In theory, barring earthquakes, underground methane gas explosions and human error, well constructed and managed landfill sites may be able to contain toxic chemical and leachate byproducts for hundreds of years. But the vast quantities of landfill gasses from landfills cannot be so contained.
Remember, before any methane is burned, landfills produce almost as much raw carbon dioxide as methane. And after taking into account burned off methane, a typical landfill site produces thousands of tonnes of carbon dioxide per month.
In striving to make our organisations and waste management more sustainable then, we should be doing everything in our power to eliminate landfill waste.
