As a community, Denver recycled just 20 percent of its household waste in 2016, according to Charlotte Pitt, who heads up Denver Recycles, a division of Denver Public Works.

That means 80-percent of Denver’s collected waste went to the landfill. That’s a little bit better than 2015 when 82 percent of waste went to landfill. It breaks down like this: The average participating household recycled 507-pounds of materials and sent 2,354 pounds of trash to the landfill in 2015. The full 2016 audit has not yet been released.

We visited the Waste Management facility where an average of 200 trucks a day dump recyclable materials from Denver’s single-family homes, schools, and apartment buildings with seven or fewer units. Multi-family housing properties with eight units or more are not eligible for Denver’s single-stream curbside recycling program. Businesses have to pay to participate.

Have you ever wondered what happens to all that stuff after you throw it into the big purple bin? We got some answers.

How it works

Enrico Dominguez of Waste Management, the city’s subcontractor for recycling, was our tour guide at the Franklin Street Materials Recovery Facility (MRF), or “the Murf”, as he calls it. Dominguez walked us along the sorting line where teams of thirty people work in alternating 10-hour shifts around the clock, five, and sometimes six days a week when they need to play catch-up. The tools of their trade: conveyor belts, screens, magnets, air vacuums, infrared optical sensors, and gravity.

The belts are moving at a pretty good clip. The sorters move rapidly with their eyes trained to spot and separate out valuable recyclables, and contaminants. The most common contaminants are plastic bags, which can get caught in the gears and seize the machinery.

The sorters, or pickers as they’re sometimes called, are audited several times a day to “make sure that they’re being efficient, pulling the proper product and sorting them properly”, Dominguez says. At various stations along the line, the sorters are honing in on items they’ve been assigned to pluck out of the mound. Clear plastic goes to one area, cardboard, colored plastics, cans and paper to other stations.

Glass

Until this year, all those beer bottles and glass jars you’ve thrown into the purple bin over the years have not actually been recycled. While Denver Recycles has been accepting glass, it hasn’t sold glass to the secondary market since single-stream recycling was introduced in the city. It just didn’t make economic sense. Glass is the heaviest commodity and it’s costly to transport.

Instead, glass ends up in small pieces that fall to the bottom of the recycling piles. Dominguez says that for many years now, glass has been used to create a liner at the bottom of landfills. “It’s cheaper than hauling in sand and gravel to line the landfills”, Dominguez says.

Broken glass is often layered in as the landfill pile grows, serving as a filter to help protect groundwater. Some facilities use a robust layer of broken glass on top of a maxed-out landfill to help prevent methane gasses from leaking out as organic materials underneath decompose.

That all changed this year for Denver and surrounding cities that contract with Waste Management for recycling. Momentum Recycling just opened a glass recycling facility in Broomfield. Momentum buys all the broken glass, cleans it, separates it by color, and refines it into what is called cullet. Cullet is sold to Owens-Illinois and Rocky Mountain Bottling Company. They use it to make new beer bottles to fill exclusively with MillerCoors products like Coors Banquet, Miller High Life and Blue Moon.

Aluminum cans

It was a kick watching the soda cans go by on the conveyor belt. It was an example of the crafty low-tech workflow solutions that are implemented in the world of recycling. The aluminum cans are sorted out by magnets that work against each other, creating an eddy current. The current systematically flicks the cans off the conveyor belt and into an area where they’re crushed and compressed into 1,500-pound blocks for the secondary market.

Paper

Screens carry newspapers, cereal boxes, food packaging, junk mail, computer paper and other fiber materials over the conveyor belt. Various weights of paper are sorted by vacuums that suck the paper to the belt in some areas, and puffs of air that blow other types of paper into a designated area.

Newspaper and cardboard are in categories of their own. Newspapers are often recycled into compostable paper products, according to Wastecare Corporation. Greasy pizza boxes are eliminated and sent to the landfill. Cardboard boxes turn into more cardboard boxes once they’re recycled.

All other paper products are considered mixed paper which comprises the largest category of household recycling.

Mixed paper

Cereal boxes, magazines, gift boxes, toilet paper rolls, junk mail and other mixed paper materials are blended together and recycled. According to the Wastecare Corporation, the blend is reduced to a pulp that is used to make new cereal boxes, book covers, board games, and food packaging.

Other ways consumers can help the city reach its goal of a 34% recycling rate by the year 2020: