Collection Programs For Kitchen Organics: Impacts of Program Design Decisions on The Material Diverted
Many cities and communities in the U.S. and Canada have set residential waste diversion targets of 50 percent and higher. A good curbside collection program for recyclables and leaf and yard waste can achieve a diversion rate of 35 percent or higher. However, to get to a value of 50 percent, it is essential to divert food waste, which makes up as much as 25 percent of the residential waste stream.
Source Separated Organics
Residential collection of source separated organics (SSO) (mostly kitchen organics consisting of food waste and kitchen papers) is increasing rapidly across the U.S. and Canada. Implementation of residential SSO programs requires many decisions: what materials to collect, how they should be stored in the home and collected at the curb, the processing approach used (composting or anaerobic digestion), policies which could increase participation and capture in residential SSO programs, and the most appropriate end markets for finished compost. One of the program design decisions is which type of kitchen catcher bag (paper, plastic, biodegradable plastic or certified compostable plastic) to allow for set out of SSO in curbside bins.
SSO Program Performance
The impacts of different bag choices (paper, plastic, biodegradable plastic or certified compostable plastic) were examined as to what effect they had on SSO program performance.1 Operating data were collected from SSO programs across Canada, predominantly in the provinces of Ontario and Nova Scotia. The information collected included:
Year that the SSO program was implemented
SSO tonnage collected annually since the program was initiated
Type of bags permitted in SSO bins (paper only, compostable plastic, biodegradable plastic or plastic)
Frequency of garbage collection (weekly or bi-weekly)
Other curbside or other policies which would impact on participation (bag limits, PAYT programs, etc)
Location where SSO was processed
Residue rates at the processing operation
The conclusion of the analysis was that many factors impact the performance of the SSO program. Some key factors are:
Age of the program (number of years in operation)—Participation in SSO programs generally increases and the amount of SSO collected generally increases over time as residents become used to the program requirements, and adapt their behaviors to suit the set-out requirements of the new program., as long as a consistent promotion and eduction program is maintained. The highest collection rates were measured in Southgate, ON, Halifax, NS and Ottawa Valley, ON—all of these programs have been in place for a number of years
Frequency of garbage collection—Participation in SSO programs (measured as the percent of all households who set out the Green Bin once per week or at least twice per month) and capture of SSO (measured as pounds per household per year collected in a source separated state) are both higher in communities which only collect garbage every other week. Less frequent garbage collection service encourages people to use the Green Bin more
Curbside policies—SSO program performance is better in communities with lower garbage bag/container set out limits and in communities where extra bags or containers of garbage cost extra (through a tag system)
Size of curbside Green Bin containers provided, and extent to which leaf and yard waste are collected in the Green Bin—Some communities chose small 46 litre Green Bin containers which collect kitchen waste only whereas other communities chose a larger Green Bin container, and allow some leaf and yard waste in the green bin. Bin sizes in the programs studied included: 46, 80, 120, 140 and 240 liters. The community decision on the bin size is generally related to optimizing the collection system design. It also impacts on processing options chosen.
The research found that the choice of a particular type of kitchen catcher bag (paper, plastic, certified compostable plastic or biodegradable plastic) did not significantly impact on participation or capture rates in the programs examined—there were generally a number of other factors at play (including the list of the materials collected, the age of the program, frequency of garbage collection, curbside policies and size of Green Bin) which influenced participation rates and capture rates. Figure 1 presents collection values (in kg per household per year) for programs which allow the use of paper bags and certified compostable plastic bags in “kitchen catchers” (countertop kitchen bins). Capture levels are low for Kingston and Waterloo, ON as the programs are new—both were launched in 2009 and 2010.
Composting facility operators contacted for the study preferred paper bags, as these compost readily in existing systems, and result in residue rates of “virtually zero”. All facility operators noted that certified compostable plastic bags compost more slowly than paper bags, and they experience higher residue rates from programs that use plastic bags, including biodegradable and certified compostable bags. Operators commented that a well run composting operation should be able to achieve a residue rate of below 5 percent.
Green Bin programs are being implemented across North America. A number of years ago communities were faced with making decisions without significant information on what impacts the design decisions might have on program performance. There is now significant operational experience to draw on to help program designers choose a system which suits the needs of their community. Well performing programs include a blend of policies and practices which best meet community needs and diversion targets, while integrating collection decisions with the broader integrated waste management system, and taking account of the implications of program design decisions on the organics processing operation.
Maria Kelleher is Principal at Kelleher Environmental, an environmental consulting company based in Toronto, ON. Maria has over 25 years of experience in researching and evaluating waste diversion and renewable energy policies and programs For more information or to obtain a copy of the full report, e-mail [email protected] or visit www.kelleherenvironmental.com.
Bag to Earth, a manufacturer of kraft paper kitchen catcher, Green Bin and leaf and yards waste bags, commissioned Kelleher Environmental to perform the study.
Annual collection of SSO from select Canadian communities, 2009 and 2010.
Figure courtesy of Kelleher Environmental based on information in the Waste Diversion Ontario Municipal Datacall (www.wdo.ca).