Keeping Compostables Out Of The Trash

Research study tests three different outreach strategies to reduce amount of food scraps and food-soiled paper in residential trash bins.

K. Phelps, L. Large, W. Schultz and J. Ettlinger
BioCycle  November 2017, Vol. 58, No. 10, p. 16

Figure 1. City of Fremont (Alameda County, CA) residential trash characterization, 2016 Nationwide, approximately one-third of trash is compostable. Even in cities that offer residential curbside organics collection, many residents continue to put compostable material in the trash bin. For example, Fremont, a suburban city of about 230,000 people in Alameda County, California, has offered residential curbside organics collection since 2003. However, food scraps and other compostable material still make up 33 percent of Fremont’s residential trash (Figure 1).

In 2016, StopWaste, a public agency responsible for increasing recycling and reducing waste in Alameda County, partnered with the City of Fremont’s sustainability staff and Action Research (a social marketing firm) on a pilot project to identify outreach strategies that would improve participation in curbside organics collection. This two-phase project consisted of a mail survey followed by testing of three outreach strategies.

Mail Survey

In the first phase, Action Research conducted a countywide mail survey to learn why residents were not placing all of their food scraps and compostable materials in the green curbside organics bin. The goal was to understand the deterrents (barriers) and motivators (benefits) for program participation. The survey was mailed to households that had received a waste audit of their trash in the previous year, which allowed mail survey data to be matched with their actual behavior.

Figure 2. Barriers to participation in curbside organics collection, on scale from 0 to 10The survey included measures of attitudes, barriers, benefits, and self-reported behaviors related to curbside organics collection. Respondents felt that participating was important and not difficult. Respondents rated a list of common reasons for not recycling all household food scraps and food-soiled paper using a scale from 0 to 10 where 0 was “not a reason” and 10 was “a big reason” (Figure 2). On average, all of the reasons were rated below a 3.5 on the 0 to 10 scale, suggesting that most respondents did not experience significant barriers.

More than half of respondents reported that they usually put all types of organic materials in the curbside green bin. Many reported having a kitchen container for food scraps, and those respondents were more likely to state that they put more than half of their household’s compostable material in the green bin. However, when analyses were conducted using waste audit data, there was no meaningful difference between people who self-reported recycling all of their compostable material and people who self-reported recycling none. This suggests that a significant number of those who reported recycling everything still had compostable material in their trash bin.

Outreach Strategies

Using the survey results as a foundation, the team designed and tested three different outreach programs in the City of Fremont. The outreach went beyond providing knowledge about how to participate and incorporated social science strategies to inspire behavior change. The three outreach strategies were: a mailed report on the rates of residential organics recycling for their neighborhood, compared to eight other nearby neighborhoods; a hangtag left on trash bins; and a kitchen counter food scraps pail along with educational materials delivered to households.

Program 1: Composting Program Participation Report
A composting report (Figure 3) was produced by Zerocycle and mailed to households encouraging them to put compostable food scraps into the green bin. The report included a “composting meter” showing the composting rate of their neighborhood compared to other neighborhoods in the city. The composting meter was meant to create cognitive dissonance by showing that, in contrast to their belief, their neighborhood — and likely their household as well — still had a fair amount of food scraps in their trash. It drew on social norms by comparing the composting rate to other nearby neighborhoods and including a testimonial from a local resident. The report also provided instructions and graphics to demonstrate sorting of food scraps.

Figure 3. Composting report

Figure 4. Hangtag exampleProgram 2: Hangtags
A hangtag was placed on household trash bins once in each of two successive weeks. The two hangtags (Figure 4) had printed messages encouraging households to put their food scraps and food soiled paper into the curbside green bin, along with instructional information about specific compostable materials typically found in the trash. The hangtags were intended to serve as a prompt to remind residents about participation.

Program 3: Kitchen Counter Pail
A new kitchen counter pail, a roll of 30 compostable bags, a card with instructional information, and a sticker about specific compostable materials typically found in the trash were delivered to each household’s doorstep. The card and sticker (Figure 5) both served as prompts to participate.

Figure 5. StickerPilot Program

In the summer of 2016, five waste routes in Fremont were selected for the pilot. Three were assigned an outreach condition and two were assigned as control conditions. To evaluate the strategies, approximately 100 pre- and post-outreach waste audits of trash bins were conducted for each treatment. In addition, route-level tonnage data was collected for all routes and a post-pilot survey was sent to 1,200 households, including all households that had received an audit.

The evaluation was conducted over a four-week period, two to three weeks following delivery of the outreach. Overall, all three of the outreach strategies produced significant reductions in the overall trash weight (between 13%–35%), the weight of compostable materials in the trash (24%–42%, Figure 6), and the weight of food scraps found in the trash (41%–45%, Figure 7).

Combined, the conditions reduced the average trash bin weight by 3.50 pounds, and specifically, reduced the compostable material by 1.81 pounds/trash bin. Most of the reduction in compostable material was due to a decrease in food scraps in the trash bin, an average of 1.36 pounds/bin.

Figure 6. Percentage change in compostable material in the trash binFinally, the post-pilot mail survey showed no significant differences between the three different outreach strategies, but did indicate that most households had seen the materials and they were well received.


Pre- and post-pilot waste audits of trash bins revealed that all three outreach strategies produced significant reductions in the overall trash weight, the weight of compostable materials in the trash, and the amount of food scraps in the trash compared to the control. From the survey and audit results, Action Research and StopWaste distilled four key tactics for successful outreach:

Go Beyond Concern And General Difficulty
Respondents across the board reported that participating in green bin recycling was important to them and not difficult. However, despite these attitudes, there were significant differences in their green bin recycling behaviors. While reinforcing the importance and ease of curbside green bin recycling in messaging seems intuitive, the results from the current study highlight the need for messaging that goes beyond these values and addresses other structural and motivational barriers.

Figure 7. Percentage change infood scraps in trash binMany Different Avenues To Success
All three outreach strategies significantly improved participation rates, reinforcing that there are multiple routes to success. Each showed a significant decrease in organic material in the trash, with hangtags having the highest percentage drop (while also having the most compostable material in their trash at the starting point). Importantly, each of these interventions has a different cost to produce and deliver, including differences in the need for “boots on the ground” or reliance on the postal system. We recommend that program managers carefully consider their available resources, knowing that each of these interventions has had demonstrable success.

Use Communication Best Practices
Communication best practices such as keeping the messaging positive, using images, employing simple nontechnical language, and incorporating humor, led to positive results. Residents liked the interventions and found them helpful, and no single intervention was rated significantly better than others. We recommend future messaging utilize these same practices.

Bin Audit Data — Strong Evaluation Metric
While bin audits require time and resources, particularly to track the homes that had previously received an audit to then audit them a second time, these data provided a better indicator of whether the outreach strategies are successful than route level data (i.e., data obtained by the waste hauler about materials collected across the whole route). Route level data, while important to collect for other purposes, is often not detailed enough to show success. Moreover, once an intervention has been in place for a sustained period, bin audits can reveal if continued issues stem from particular materials, a small segment of homes, or other specific target behaviors or audiences. We recommend that bin audits continue to be used as an evaluation metric.

Kaitlin Phelps and Lori Large are with Action Research, a social marketing firm based in Oceanside, California ( Wesley Schultz is with the California State University, San Marcos. Judi Ettlinger is with StopWaste (

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