EME 807
Technologies for Sustainability Systems

5.1 Waste management purpose and strategies

"In order for something to become clean, something else must become dirty…
But you can get everything dirty without getting anything clean." --Imbesi's Law of the Conservation of Filth with Freeman’s Extension (Dictionary of Proverbs, Ed. Kleiser, S.B.N. A.P.N. Publishing 2005)

The starting point for this lesson is a general overview of waste management industry. The following reading will introduce you to the main issues related to waste generation, disposal, recycling, and related problems.

Reading Assignment:

Solid Waste Technology & Management, Christensen, T., Ed., Wiley and Sons., 2011.
Chapter 1.1. Christensen, T.H., Introduction to Waste Management, pp. 3-16.
This book is available online through PSU Library system.

After this reading you should be able to answer the following questions:

  • What are the main problems and risks associated with waste? Why does it need to be treated?
  • What is the waste hierarchy? How is it related to sustainable thinking?
  • What are main types of solid waste, and what are the major ways to treat it?

So, how is the problem of waste disposal currently handled? There are a number of established technologies that help remove discarded materials out of our sight. Some of those discarded materials are reused in some form, but much larger amount is dumped or buried in the environment, which creates contained pollution. But is it really contained? And is that practice sustainable?

Watch the following video, which tours waste management facilities near San Francisco. That gives you an idea of scale of waste accumulation in urban areas and shows what it takes to treat it:

Click for transcript.

PRESENTER: Each year, Joe Citizen discards more than half a ton of garbage, everything from empty pizza boxes and egg shells, to broken dishes, appliances, old tires, and the kitchen sink. Worldwide, that's almost a billion tons of stinking trash every year. And somehow all of it needs to be either recycled or otherwise disposed of. So how do they do it? It's 6:00 AM in the San Francisco Bay Area, and Mike Abate and his refuse wrangling colleague, John Fuston, are starting their weekly garbage collection round. For most of us, remembering to put out our trash bins is the end of the story. But in fact, it's just the beginning of an extraordinary epic journey. A few years ago, strong men had to wrangle your garbage into the back of their truck. These days a robot arm takes over that duty. One truck for recyclables, another for the truly trashy. Thanks to these robotic refuse collectors, Mike and John can empty 600 bins every trip. And once they're full of trash, the trucks head for a delightful spot known as the Davis Street Transfer Center. Trucks carrying waste for recycling deposit their load here. To you and me, it just looks like rubbish. But to the discerning eye, there's gold in them there hills. Each truckload is worth hundreds of dollars. But no one is going to pay for it in its present state. First, these vast mountains of trash need to be separated into the various components of paper, metals, plastics, and glass. Doing that by hand would require a small army. So it's a good thing they have George Atrestain and a friendly garbage monster known as the single stream recycling facility. GEORGE: It's pretty incredible. It's noisy. It's dirty. It's very unglamorous. But it's a fun place to be. PRESENTER: George's smelly monster is a state of the art garbage sorting machine. Housed in a building that's barely 300 feet long, it contains almost a mile of conveyor belts constantly fed by loaders. It can sort over 300 tons of waste every day and relies on George to keep the wheels turning. First, high power fans blast a jet of air through the trash, suspending lighter paper, metal, and plastic, leaving the heavier glass bottles to fall into a separate pile. Next, a steep conveyor bounces the garbage across a series of rubber wheels. This causes the light paper products to continue upwards, while heavier metals and plastics drop down onto yet another conveyor belt. Powerful electromagnets then whisk away anything made of metal, leaving behind the plastic and other materials. Unfortunately, that's where the machine runs out of tricks. The conveyor transports the remaining waste to a team of operatives who grade the plastic into various bins under George's eagle eye. GEORGE: This is our container aisle. And it's a fun, noisy, very unglamorous place to be. But most of our staff actually prefer to be up here, because the pace of work is brisk, and there's always a chance of finding someone else's nugget, something fun and exciting. PRESENTER: Once George and his team have finished having their fun, the waste must be prepared for sale and transportation. So it's fed into these high-powered baling machines, which turn everything into identically sized cubes. Each of these bales of paper is now worth around $200, while this bale of aluminum is worth almost 10 times as much. Thanks to their uniform shape, they can be easily lifted with standard forklifts and loaded onto trucks, which will carry them off to start a new life as a pizza box or a coffee cup. But of course, some garbage is just garbage. This stuff is no good to man or beast. So it's about to be sent down into a trashy hell from which nothing returns. This is what George and his chums call the pit. It's huge. It's noisy. And it stinks. It's as deep as a four story house and the size of a football field. Every week, this monstrous cavern swallows up the waste from over 1 million people. The garbage is heaped in at an extraordinary rate. But where does it go? Underneath the pit is a ending line of massive 18 wheeler trucks, which park beneath an opening, allowing a combination of bulldozers and grabbers to fill them up. No sooner has one truck been filled to the brim with stinking trash than another appears ready for loading. Each truck carries five times as much garbage as a dump truck. And once they've accepted their load, they head for the burial ground. 31 miles outside of San Francisco, the trucks finally arrive at the Altamont Landfill site. Right now, it's like the barren landscape of some cold, unfriendly planet. But today's landfill is tomorrow's golf course. Stuck underground in various parts of California sits 1.2 billion tons of waste. The massive basin currently being filled has been lined with clay and a huge impermeable membrane made from high-density polyethylene and geotextile. This lining means each basin acts a bit like a giant plastic container, preventing the waste from contaminating the surrounding soil and water table. Almost half of this waste is organic material like chicken legs and rotten tomatoes. And as it decomposes, it generates potentially explosive gases. What's more, any trapped air can cause potentially dangerous subsidence. So to remove the air and make the trash good to build on, it needs to be squashed. And that's a job for the lords of the landfill, a team of enormous bulldozers and compactors. With over 7,700 tons of waste arriving every day, they must work quickly. First up is the compactor. With a pressure of nearly 40 pounds per square inch, it's 50-ton wheels act like giant rolling pins, crushing the waste into solid mass. Next, it's the bulldozers' turn. They cover the waste with a layer of soil and recycled car upholstery known as auto fluff, which helps to seal in the smell and deter scavenging animals. Finally, everything is covered with a permanent layer of soil. But that's not quite the end of the story. Because even this buried waste is put to good use. As the rubbish rots, it gives off valuable methane gas, which is harvested by these wells, which are scattered across the site. The methane extracted feeds a gas turbine, which produces enough electricity to power over 6 and 1/2 thousand homes. What's more, there is also a pilot project to turn some of the methane into liquid natural gas, which will eventually fuel the city's fleet of refuse trucks. So next time you leave your bins outside of the house for collection, take a moment to ponder the incredible journey it's about to take. And remember, everything you throw away begin life underground. Thanks to landfill sites like Altamont, it all ends up back there. Ashes to ashes, dust to dust.

This is how numerous facilities around US currently operate. For the most part it is so-called cradle-to-grave scheme, when discarded products and waste are recycled to typically lower grade material (i.e., down-cycled) or packed in a landfill. According to EPA, more than 50% of generated solid waste in the US is discarded, i.e., disposed off in the landfill. The following material is an EPA document showing some concrete numbers, which demonstrate how developing recycling technologies help reverse the trend in waste generation.

Reading Assignment:

Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2012, US EPA 2012.

While reading, look to understand all the diagrams representing the data, and specifically look at the data in Table 1, which gives you an idea on the efficiency of recovery of certain types of waste materials.

Compare Figure 4 with data in the book chapter you read in the beginning of this section (diagram 1.1.5). How does USA rank by waste treatment ratio among European countries?

Answer the following question to check your learning of this section.

Check Your Understanding

What are the five levels of waste management hierarchy? (Input answers below.)


Click for answer.

1. Prevention
2. Reuse
3. Recycling
4. Recovery (materials and/or energy)
5. Landfill and burning

From 1 to 5, each next method is more energy and resource intensive and has more adverse environmental impact. The goal of sustainable technologies is to shift the emphasis towards the upper levels.
In the next section, we will overview different recycling approaches and how they fit in the sustainability framework.