Solid waste disposal is a great environmental burden, often associated with hazardous gas emissions, water contamination, energy consumption, natural habitat degradation and biodegradation. In 1989 the U.S. Environmental Protection Agency (EPA) announced a national goal of reducing landfill use and all 50 states have passed legislation requiring cities to reduce the amount of trash buried in landfills. Curbside recycling programs are the most commonly implemented strategy in this quest. Recycling has the potential to divert thousands of tons of reusable materials away from landfills. However, many cities have found a ceiling to the effectiveness of their curbside recycling programs.

The study included 605 houses in suburban Los Angeles, all single-family dwellings, selected using 1990 census data to represent high, medium, and low socioeconomic status (SES) areas based on property value. The week prior to the intervention, most residents received a plea, a green door hanger placed on their front doorknob stating that, “Volunteers will be conducting a study on recycling. Your household has been selected as part of a larger sample of La Verne residents. … In order for La Verne to achieve the benefits of recycling, please try to recycle as much as possible.”

Houses then received one of three series of green door hangers over the next four weeks:

• Individual written feedback – Residents received feedback about their recycling behaviors, including the amount of each material collected at their house the previous week, the amount of each material collected the current week, and the total amount of each material collected for the duration of the study. The information was written onto preprinted hangers and delivered within 2 to 4 hours after the observations were made.
• Group written feedback – Residents received feedback about their residential area, including the amount of each material collected the previous week, the amount of each material collected the current week, the total amount of each material collected for the duration of the study, and the percentage of households that participated that week. Feedback on weekly amounts and participation was in the form of average participation behavior.
• Information – Each week had a different type of information: (1) information about which materials were recyclable in the current La Verne recycling program; (2) information about non-recyclable materials and frequent contaminants; (3) the recycling process from collection to reuse of materials; (4) information about energy and landfill conservation that results from recycling.

Houses were randomly assigned into one of five groups of about 120 each: 1) plea door hanger only, 2) plea plus 4-weeks of individual feedback hangers, 3) plea plus 4-weeks of group feedback hangers, 4) plea plus 4-weeks of information hangers, and 5) no door hangers at all. Researchers observed the recycling participation, amount of recyclables collected, and quality of recyclables collected from each household over an 8-week period prior to the intervention, during the 4-week intervention period, and for another 4-week period after the interventions were discontinued.

The randomized trial found that both individual and group feedback hangers significantly increased the amount of material recycled as well as the frequency of recycling participation. Individual feedback increased the amount of recycled material by 23% and group feedback increased recycled material by 19%. The recycling participation of both individual and group feedback households differed significantly (p<.01) in the post-intervention period compared to baseline, to 49% from 43%, and to 50% from 42%, respectively. The information hangers or plea hanger alone did not result in significant changes.

Inspired to implement this design in your own work? Here are some things to think about before you get started:

• Are the behavioral drivers to the problem you are trying to solve similar to the ones described in the challenge section of this project?
• Is it feasible to adapt the design to address your problem?
• Could there be structural barriers at play that might keep the design from having the desired effect?
• Finally, we encourage you to make sure you monitor, test and take steps to iterate on designs often when either adapting them to a new context or scaling up to make sure they’re effective.

Additionally, consider the following insights from the design’s researchers:

• Motivation is believed to be a powerful determinant of recycling behavior. One potential source of motivation is social norms—sets of beliefs about the behavior of others. Descriptive norms are beliefs about what other people are doing. Personal norms are feelings of obligation to act in a particular manner in specific situations. A substantial body of research suggests that norms help to determine behavior, particularly when they are activated. Activation involves making the norms salient in a particular setting. One of the most particular approaches for the activation of norms is feedback. Feedback interventions are defined as “actions taken by (an) external agent(s) to provide information regarding some aspect(s) of one’s task performance.”
• Households were selected using 1990 census data to represent high, medium, and low socioeconomic status (SES) areas based on property value. No significant differences were found among households of different social status.
• Households were grouped by small contiguous areas ranging in size from 5 to 16 houses. This procedure grouped households geographically so that discussion between residents in different conditions would be minimized (to reduce the possible diffusion of different interventions).
• Costs of the intervention include materials (door hangers), labor (observation and dissemination), and planning (organization and scheduling). The door hangers cost approximately $2.50 each, including both the material and printing costs. Labor time to distribute the interventions required approximately 1.5 hours for each 100 households. The weekly observations required approximately 1.5 hours per 100 households. Preparation of intervention materials required approximately 1 hour per 100 households for the personal feedback, and 0.5 hour per 100 households for the group feedback.
• Labor costs would differ substantially with the individual feedback condition requiring approximately 40 hours of labor per 1,000 households, 35 hours for group feedback, 15 hours for information, and 15 hours for plea only. Estimating labor costs at minimum wage ($5/hour in 1999) generates weekly labor costs per 1,000 households of $200 for the individual feedback condition, $175 for group feedback, $75 for information, and $75 for plea only. The interventions could be less costly if less labor intensive dissemination procedures were developed.
• Though the feedback interventions significantly increased the frequency of participation and amount of material recycled, none of the interventions successfully reduced the amount of contamination (any material placed in the recycling crates other than those listed – newspapers, glass, and plastics, and metal cans).