Minnesotans are sending about a third less recyclable material to landfills than they were a decade ago, but plastic bags are nonetheless being trashed in growing numbers.

Those are among the trends revealed in meticulous garbage data maintained by the Minnesota Pollution Control Agency, analyzed by the Star Tribune ahead of Earth Day. The state's data is among the most comprehensive in the country.

Despite their light weight, plastic film materials like bags and wrap accounted for nearly 382 million pounds of what entered Minnesota’s landfills and incinerators last year. That's a whopping 70 pounds per Minnesotan, more than any other material. Back in 1996, the first year of available data, 48 pounds per person of plastic film went into landfills.

Wayne Gjerde of the MPCA says just under half of that plastic film is retail bags. Much of the remainder is plastic that had been used to wrap bulk items for distribution, or used at construction sites.

Plastic bags cannot be tossed in most residential recycling bins, since they gum up the sorting machines. But just about every grocery store has a place to recycle them (find locations and learn more about plastic film recycling here). In addition to plastic grocery bags, you can also recycle the plastic wrap that comes on things like toilet paper packages; the plastic sleeve that your newspaper sometimes comes in; bread bags and resealable bags; dry cleaning bags; and even the air cushion bags protecting the items you had delivered to your house from an online retailer (just release the air first). Companies like Trex turn plastic film into decking and outdoor fences.

“So we could do a much better job on that,” Gjerde said.

The good news is that the recycling rate for plastic film has risen dramatically, though we still landfill and incinerate more than 23 times what we recycle.

Other recyclable items that end up in the trash more now than in the past include plastic containers such as milk jugs, shampoo bottles and the ubiquitous water and soda bottles. But recycling rates for these materials have increased. Gjerde said that may be because there are simply more of those materials, potentially due to companies switching from aluminum to plastic packaging.

Most other items are showing up less in the trash, although it isn't always because they are being recycled more. Sometimes, it's just because we have less of it.

Since 1996, the amount of newsprint that has ended up in the trash has dropped by more than two-thirds. And the amount recycled has dropped from about 82 pounds per person to 59 pounds. Interestingly, it's only recently that more magazines have been recycled than were thrown in the trash.

“There’s less newspaper out there, less magazines,” Gjerde said.

The trend line is a bit different for corrugated cardboard, which is getting recycled at increasing rates and trashed less. The full effect of the online shopping bonanza may not have shown up in the 2013 numbers, which is the most recent data available. “With the online shopping, there’s a lot more boxes out there,” Gjerde said.

Data on what's been recycled shows a steady rise since 1996 in the amount of materials per person, about an 18 percent increase. The bulk of that increase comes from plastics. We now recycle about 26 pounds per person, up from 15 pounds in 1996. All types of paper, which includes office paper and newsprint, makes up more than half of all recycled materials.

Within all that recycling data we found another big loser: Phone books. The state doesn't track how many of those end up in the landfills, but recycling data shows that the amount being recycled has dropped dramatically.

So how do we get all this data? For trash, the state conducts periodic "waste composition" studies at landfills and incinerators looking for materials that should have been recycled. (Yes, this is as disgusting a job as you might imagine).

In the case of recycled materials, processors report annually on the composition of what they receive.

“This data we have here is probably the best in the country in terms of what’s in the waste stream and in terms of amounts,” Gjerde said.

Definitions of some materials you'll find listed in the data visualizations above:

PET = Includes water and soda bottles
HDPE = Includes milk jugs, shampoo bottles
Uncoated old corrugated containers = cardboard boxes
Paper boxboard = Includes cereal boxes
Plastic film = Includes plastic grocery bags, garbage bags, plastic wrapping

Data Drop is a weekly feature that uses data analysis and visualizations to explain, surprise, inform and entertain readers on topics relevant to Minnesotans. Do you have an idea you'd like us to explore? Contact MaryJo Webster