Value And Benefits Of Backyard Composting

weighing backyard composting materials in VancouverBioCycle October 2011, Vol. 52, No. 10, p. 35

Year-long data collection by 16 households in metropolitan Vancouver reveals that backyard composting is undervalued when considering boost to diversion rates and collection cost savings.

Elizabeth Leboe

The North Shore Recycling Program (NSRP) is a tri-municipal agency of the City of North Vancouver, the District of North Vancouver and the District of West Vancouver in British Columbia. The NSRP administers the residential curbside recycling program and recycling drop-off depot and provides a variety of community education programs that support residential waste reduction. This includes backyard composting, which has a large role to play in partially diverting organics, the heaviest and largest component of the residential waste stream. Thirty-seven percent of the garbage sent for disposal from North Shore single-family homes could be composted at home.
weighing backyard composting materials in Vancouver
In 2008, the NSRP made a first attempt to estimate the amount of material the average single-family household backyard composts without any training or assistance; the result of this work is considered a “baseline” against which future studies would be compared. The NSRP estimated the weight of organic waste composted by single-family North Shore households (38,132 in total) based on data from various phone surveys conducted by NSRP and other studies. It was determined that 61 percent of households use backyard composters; 7.1 gal/week was the average self-reported estimate of volume diverted by composting. A literature search on density conversion factors for food waste found two different conversions – of 1348 lbs/cubic yard and 600 lbs/cy for food waste – so the NSRP used the average, along with a conversion of 350 lbs/cy for yard trimmings. It was calculated that North Shore households (with no composting support) were keeping 915 lbs/hh/year off the curb, resulting in 10,580 tons removed from curbside collection annually. By comparison, Metro Vancouver, the intermunicipal governing body of the Greater Vancouver Regional District, estimates that each compost bin distributed within its region keeps 551 lbs/yr of organics off the curb.

In 2010, a year-long study was initiated to address municipal and regional data gaps in the calculation of organic waste diversion rates attributed to backyard composting and to calibrate earlier calculated composting estimates. The findings of that study and their implications for planning and implementation of single-family organics diversion programs going forward on the North Shore are described in this article. Our conclusions following four years of research, surveys, pilot programs and evaluations focused on the topic of single-family organic waste are that Metro Vancouver’s diversion rate attributed to composting may be an underestimate and that North Shore municipalities are undervaluing the role of backyard composting. With new residential organics initiatives on North Shore’s horizon, ranging from outreach to curbside collection, the NSRP needed to replace all its estimates with an accurate measure of actual – and maximum possible – diversion rates of household organics through backyard composting.

STUDY METHODS
The year-long study involved 16 composting households, representing 54 residents, from the North Shore. These households were recruited to weigh and track the organic waste that they backyard composted for an entire year.

Volunteer households were required to undergo two separate training sessions: Project Startup, to conduct a presurvey, provide needed measurement materials and introduce weighing methods; and Compost Coaching, a personalized in-yard training session to optimize composting practices (see sidebar). In addition to indoor and outdoor scales, compost containers and data recording kits, volunteer households received monthly e-newsletter updates, were provided with telephone or in-person support throughout the year and were encouraged to participate in waste-reduction-related field trips and events offered in appreciation for their commitment to the project.

The 16 households using traditional backyard composters weighed their organics destined for backyard composting that were generated from inside the home (including low-quality household papers like napkins and egg cartons). Of these 16 households, 10 also reliably weighed the organics they would backyard compost from the yard and garden. Measurements took place from February to December 2010.

At the project’s wrap-up, all participating households took part in a follow-up survey and submitted their completed data recording sheets. Using the pre- and post-training household surveys and the recorded data, the study generated the following information for an 11-month period: Composting practices, confidence levels and perceived changes in volumes composted and placed curbside for collection; Actual weekly curbside set outs of garbage and yard trimmings; and Actual weights of materials from both inside and outside the home composted in the backyard. The results of these year-long measurements were used to calibrate the original 2008 and 2009 Compost Coaching evaluation (see sidebar) calculated estimates and to compare to Metro Vancouver’s 551 lbs/bin estimate used in regional diversion calculations.

STUDY FINDINGS AND IMPLICATIONS
These 16 volunteer households diverted 5.8 tons of organic waste from curbside pickup in 2010. Using data recorded for complete months between February and December 2010, the average study household kept 996 pounds off the curb during the year. By calibrating the 2008 baseline estimate from households composting without any support or training, an estimate of 796 lbs/hh/year is derived. Even though study participants were already composting prior to their involvement in the research, 79 percent of participating households increased the amount of material they composted and reduced the amount of waste they put in the garbage after they had their Compost Coaching session.

The diversion rate of household organics through backyard composting has now been accurately determined. Study results and their implications suggest that some changes are warranted to the North Shore’s municipal and Metro Vancouver’s regional assumptions and to the NSRP’s budget and programming priorities. Both the baseline calibration and the measurements with Compost Coaching significantly exceed the 551 lbs/bin/ year estimate used by Metro Vancouver to calculate regional diversion rates.

The next step was to apply the study’s findings to the potential impact on curbside organics collection. Compared to the 2008 North Shore average (from a statistically significant, randomized telephone survey), study participants decreased what they placed at the curb by half a can of yard trimmings and a full can of garbage each week. Extrapolated to all known composting households on the North Shore, residents compost 9,257 to 11,690 tons that the municipalities never need to handle or pay to tip each year; this is equivalent to approximately 1,500 truck trips and is almost the same quantity (11,726 tons) as the current yard trimmings collection service, which costs $1.5 million in fleet and salary-related collection expenses and $600,000 in tipping fees each year.
volunteers in backyard composting study
The North Shore does not currently include backyard composting in its municipal diversion rate calculation of 59.5 percent (2010). When composting is factored in using the measurements obtained in this study, the North Shore’s diversion rate is actually 67.2 percent. The single-family diversion rate is higher than has been reported to municipal staff, and approaches Metro Vancouver’s regional goal of 70 percent diversion by 2015.

AVOIDED TIP FEES

Two-thirds of the total garbage and yard trimmings annual collection service costs on the North Shore are in the form of tipping fees (charges levied to a municipality for dropping off collected materials – whether for disposal or composting – at regional transfer stations operated by Metro Vancouver). Each curbside collection stream taken to the transfer station has a different tipping fee set by Metro Vancouver. In 2011, yard trimmings cost $57.15/ton and garbage cost $88/ton.

At 2011 rates, each study household saves the municipality $35.44 in tipping fees each year. Although this does not seem like much per individual household, the extrapolated total avoided tipping fee costs for the North Shore’s population of composting households totals $874,227 annually. Tipping fee savings have the additional benefit of being cumulative as long as a composting household maintains its composting behavior. Over the past five years on the North Shore, the NSRP has invested approximately $16,100 in bin subsidies and backyard composting has resulted in avoided tipping fees of approximately $3.5 million.

This backyard composting study’s results suggest interesting implications for the municipal and regional management of solid waste. First, the NSRP’s study indicates that backyard composting is undervalued and is far more important than previously thought in terms of source reduction. In summary, on-site composting is an extremely cost-effective method to divert very significant tonnages without requiring intensive municipal services. However, residents who choose to compost instead of using the curbside collection services they’ve paid for through their taxes are not receiving anywhere near the level of support (through municipal program investment) as their noncomposting neighbors. It would be a prudent step to begin providing support, such as personal coaching, to those households wishing to further reduce their waste through backyard composting.

Elizabeth Leboe is a Community Programs Coordinator at the North Shore Recycling Program. She tends a large garden and composts for three families in North Vancouver, BC. For North Shore’s complete study report, please visit www.northshorerecycling.ca and click on ‘Composting.’

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PERSONALIZED COMPOST COACHING
THE North Shore Recycling Program evaluated the benefits of personalized Compost Coaching methods for backyard composters in an in-yard, personalized compost support pilot program completed in 2009. It estimated that 1,146 lbs/ household/year could be diverted to backyard composting. Because it was highly successful, this kind of training was provided to all households participating in the 2010 study measuring actual quantities of organics composted at home. Although not the main intent of this measurement and diversion calibration study, some conclusions may be drawn about the Compost Coaching service provided to study participants.

Compared to their habits prior to Compost Coaching, supported study participants increased their diversion of low-quality household papers from the garbage to the compost, kept more leaves for on-site use, used alternative recycling depots for non-curbside collected materials and altered buying habits to reduce waste at source. With training, the NSRP found that households compost almost 220 pounds more each year than unsupported households. “We only made 2.5 kilograms of garbage in the last two months and almost 50 kgs of compost,” says Melanie Solheim, one of the NSRP’s study participants and member of a four-person household. When contrasted with its low cost of delivery, personalized Compost Coaching services provide immeasurable social and environmental value beyond the direct tipping fee savings and decreased curbside collection requirements.

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