Cambridge Recycling Contamination Rate Drops to Record Low of 4%. Recycle Right Campaign Efforts Save the City of Cambridge $100,000 in 2020

The City of Cambridge is pleased to announce that it has successfully reduced its recycling contamination from 11% in 2018 to 4% in 2020. This reduction not only saved the city more than $100,000 in 2020, it also made Cambridge’s recycling program more resilient.

This coordinated effort to reduce recycling contamination started in 2018, when Cambridge and cities across the world were informed that China’s National Sword policy would drastically impact the recycling industry indefinitely. Recycling markets were shifting rapidly and the costs to recycle were increasing. There wasn’t much cities could do other than reducing contamination in recycling. 

In June 2018, the city launched Recycle Right, a comprehensive and ongoing community outreach campaign with a goal of reducing contamination to below 7%. Items such as plastic bags, clothing, electronics, and other items not accepted in curbside recycling are considered contamination. Achieving this contamination reduction goal didn’t happen overnight. The city collaborated with dozens of building managers, residents, and other community members to increase awareness about the importance of reducing contamination in recycling.

“Lower contamination rates help make our recycling program more resilient," said Cambridge City Manager Louis A. DePasquale. “I want to thank our residents, building managers, and other community members for helping us reach this very important milestone.  I also want to commend our Public Works staff who worked so hard to achieve this goal."

About the Data Collection Process

The City of Cambridge serves approximately 44,500 households with free curbside recycling. A significant amount of data collection was needed to determine how to best reduce contamination. The city started by gathering data from Casella, the city's recycling processing contractor. Casella provided monthly contamination rate data tracked by truck route and collection day. Next, the city conducted audits of more than 1,000 recycling carts, to determine precisely which materials were the most frequent offenders in Cambridge recycling (see table below). It also helped in tailoring community outreach messages. Finally, this data was instrumental in an advanced analytics project between the City of Cambridge and the Center for Government Excellence at Johns Hopkins University. That study illuminated recycling trends that will help the city craft more effective outreach campaigns in future years.


Plastic Films, Wrappers

Plastic Bagged Recycle

Paper Towel, Napkin

Food & Liquid

Paper take-out containers, plates

Clothing & Textiles

Tanglers(Cords, Hoses)

Wood, Metal, E-waste

% of carts **









** Percent is more than 100% because many carts had more than 1 contaminant.

Recycle Right Campaign

With all of this data gathered, the City of Cambridge could implement direct outreach components of the Recycle Right campaign. First, the city started monitoring and tagging recycling carts on collection day. Over several months, more than 5,000 carts were inspected in each neighborhood of Cambridge. As a result, more than 1,500 carts were tagged with a friendly “Oops” message because the cart had “medium” or “high” contamination. The goal of these tags was to gently nudge and remind residents about how to recycle properly. For buildings with major contamination issues, postcards were also sent to each of the 4,000 households that had reports of high contamination.

Next, the city conducted a large rebranding and outreach campaign to promote the importance of reducing contamination. With the assistance from the Massachusetts Department of Environmental Protection, the city created new signage to simplify and clarify what’s recyclable. City staff collaborated with landlords, property managers, and other residents to help spread the word about contamination issues. Campaign highlights included:

  • December 2018: Advertisements on BlueBike Stations, MBTA bus shelters, and A-frame sandwich boards
  • June 2019: New stickers created for lids of all recycling carts. New flyers also created
  • October 2019: Citywide mailer about waste services, including how to recycle properly

Lastly, the city worked with its curbside collection contractor to reject more bins for having contamination. After a building received a rejection sticker, city staff would work with the building manager and tenants to reduce contamination, by providing new signage, helpful tips, and other technical assistance.

Although the markets for recycling have shifted in the last three years, there have only been minimal changes to the city’s recycling program. The most notable change is that paper cartons used to contain liquids (milk, juice, soup, ice cream, etc.) are no longer accepted.

For more information or resources to reduce waste, visit

Page was posted on 1/29/2021 10:51 AM
Page was last modified on 10/14/2021 11:21 AM
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