The Solid Waste Association of North America’s (SWANA) Applied Research Foundation (ARF) was created in 2000 to support SWANA’s mission through leveraging research dollars to conduct collectively-funded and defined applied research projects that address pressing solid waste issues. ARF has four research groups: Collection; Recycling; Waste-to-Energy; and Landfill Disposal. Research topics are submitted by ARF subscribers to the research groups.

Last year, the City of Charlotte, North Carolina submitted a topic for research to the Collection Group about curbside collection of yard trimmings: “Interested in exploring options other than routed weekly collection with no limits [for yard waste]. Are there any examples of this as a call-in service during certain times of the year and routed during peak times? How do different options for limiting yard waste work for others — time limits, limits on piles or number of bags work? How are resources best maximized year-round, while sufficient to cover demands of peak periods/seasons? What are others doing? How is it working? Pros and cons?”

ARF’s Collection Group decided to target this topic for investigation during Fiscal 2017 (July 2016-June 2017). The final report — “Service Options for The Curbside Collection Of Residential Yard Waste” (August 2018) — presents the results of background research conducted for this project with input and guidance provided by the ARF Collection Group Subscribers. This article is excerpted from the full report.

Background

The city of Charlotte is the largest city in North Carolina and the county seat of Mecklenburg County. In 2017, the U.S. Census Bureau estimated the population to be 859,035, making it the 17th most populous city in the United States. The City’s Solid Waste Services Department provides collection of bulky waste, garbage, recycling and yard waste to its 218,000 single-family residences.

Yard waste generated by single-family residences is collected on a weekly basis by city crews throughout the year on the same day as garbage collection. Residents provide their own containers for yard waste collection and are instructed — when using rigid containers — to use uncovered containers less than 32 gallons in size. Households can utilize plastic bags for grass clippings, leaves and weeds. Solid Waste Services recommends — but does not require — use of paper bags for collection preparation. Paper bags can be purchased from local retailers.

In FY2017, 34 yard trimmings collection crews serviced about 216,000 single-family residences on a weekly basis. Each two-person crew consists of a driver and a laborer that utilize rear-load compactor collection vehicles. In Charlotte, leaves and grass clippings set out in bags by the resident are subsequently debagged at the curb as part of the regular yard waste service and placed into the rear-load collection vehicles for transport to the yard waste processing facility that is owned and operated by Mecklenburg County. The primary reason for debagging leaves and other yard waste at the curb is to avoid significant issues with respect to the quality of the compost produced at the county’s facility.

During the fall, the city hires temporary collection personnel to aid in debagging of the leaves. If the city collection crews cannot debag all the leaves during periods of heavy setouts, the county allows the city to unload bagged leaves at the yard waste facility. However, the city must pay the county an additional fee for unloading bagged yard waste and must provide temporary labor at the facility to debag the leaves and other yard waste before they are processed.

The operational costs incurred by the city of Charlotte to provide residential yard waste collection services in FY2017 totaled $7.2 million. That included almost $5 million in labor costs (permanent and temporary) and fringe benefits. Operating costs, equipment maintenance and fuel comprise the remaining cost. When equipment capital costs, indirect and overhead costs associated with city government and processing costs are factored in, the total is $11.7 million, which equates to $4.53/household/month or $211/ton.

Seasonal tonnage data for the city of Charlotte’s yard waste collection services for FY2008-FY2013 are illustrated in Figures 1 and 2. There are significant variations in the seasonal generation of yard waste tonnages with monthly quantities in the fall being 25 percent higher than the average monthly generation rate, and spring quantities being 15 percent higher than the average. Winter and summer generation rates are roughly the same and are about 80 percent below the monthly average of 11,896 tons/month. On a volumetric basis (assuming bulk densities of 108 lbs/cubic yard (cy) for mixed yard waste and 73 lbs/cy for dry leaves), fall yard waste volumes (assumed to mainly consist of dry leaves) are 60 percent higher than the average. Charlotte residents on average generate 30 gallons/week of dry leaves for collection or 391 gallons for the entire fall season.

Alternative Options

The SWANA ARF’s Collection Group identified a variety of alternative options to research for collecting yard waste. These included:
• Requiring use of compostable bags
• Establishing setout limits
• Switching to seasonal biweekly collection
• Switching to a call-in service during seasons of low demand
• Converting to automated yard waste collection

Compostable Bags

A significant number of municipalities require residents to use compostable bags when setting out their yard waste for collection. These include kraft paper bags as well as biodegradable plastic bags. In some communities, the latter are not accepted. The major advantages associated with use of compostable bags are the fact that yard waste does not have to be debagged at the curb by collection personnel and plastic bag contamination of the resulting compost is reduced or eliminated.

The major disadvantage is that additional costs must be incurred — generally by the resident. An analysis of current prices indicates a unit price of about $0.10 for a 33-gallon, plastic bag compared to a unit price of about $0.40 for a 30-gallon compostable paper bag.

Setout Limits

While the city of Charlotte does not limit the number of bags that residents can set out for yard waste collection, many — if not most — municipalities have limits. The number of plastic bags or bundles of yard waste that can be set out on a given collection day is generally used as the limiting factor. Typical limits are fifteen to twenty, 30-33-gallon plastic bags or bundles of yard waste per setout.

The major advantage of establishing setout limits is they protect service providers from excessive yard waste setouts by commercial landscapers and/or residents. Major disadvantages include the difficulty and expense associated with enforcing the limits and the minimal impact that the limits are likely to have on overall [collection] productivity.

Biweekly Manual Yard Waste Collection

As noted, there are large variations in the weights and volumes of yard waste set out by residents in the city of Charlotte, with significantly more set out for collection in the spring and fall compared to the summer and winter seasons. By switching to a biweekly collection service, the setout volumes during these lower-volume months would be in the range of 26 to 28 gallons/household/every-other-week — about the same volume that is set out on average by residents during the fall season.

During this research project, no examples were identified of municipalities that offered biweekly collection during seasons of low demand and weekly collection service during high-demand seasons. Numerous examples were identified, however, of municipalities that offered biweekly yard waste collection throughout the year or during the spring, summer and fall seasons.

Advantages of manually collecting yard waste on a biweekly basis throughout the year include significant reductions in personnel and equipment requirements, which translate into lower service costs. Other advantages include reduced wear and tear of local streets and reduced air pollution and noise from collection vehicles. The major disadvantage is that it exacerbates the issue of debagging yard waste at the curb since more waste must be debagged per collection stop.

Call-in Service During Low Demand

One of the service delivery options identified in the research topic submittal was provision of yard waste collection as a call-in service during seasons of low demand while offering it as a regularly scheduled service during high-demand seasons. Unfortunately, no examples of this service delivery option were identified during this research.

Automated Yard Waste Collection

Collecting yard waste using automated collection trucks and large, lidded rollout containers is a fairly common practice that has been used for many years by municipalities across North America. A fully automated system involves the mechanical collection and dumping of a specialized container. The crew, normally one person, rarely leaves the vehicle during collection so solid waste containers must be placed where they are accessible to the lifting device.

Automated collection vehicles usually have a large capacity ranging from 20 to 40 cubic yards to take advantage of the speed of operation. Automated collection containers are typically 90 to 96 gallon, lidded, rollout containers. Major advantages include the increase in operator safety since the operator does not have to leave the truck cab to service the household. Another advantage is the potential reduction in injuries since the collector does not have to manually lift the yard waste into the truck hopper and then cut and/or tear open and remove the bags. Also, fleet backup costs can be reduced if automated collection trucks are used for other collection services such as refuse and/or recyclables collection.

Major disadvantages associated with automated collection of yard waste are higher capital and maintenance costs associated with these vehicles and the fact that an automated collection container — which costs on the order of $50 — must be provided to each residence. Another significant disadvantage is the lack of setout flexibility in the automated collection system. The resident is limited to setting out yard waste equivalent to the volume of the automated yard waste container, which is typically 96 gallons. If residents set out the average of 391 gallons of leaves during the fall season, they would have to bag their leaves and subsequently unbag them and place them in the automated container over multiple weeks for them to be collected.

Another option for municipalities is to provide an automated yard waste collection service on a biweekly basis. The rationale is that the rollout container used for automated collection is large enough to contain setout volumes even if the collection frequency is reduced. For example, lowering the collection frequency to every other week in Charlotte would increase the average weekly setout volumes to 28 gallons in winter, 38 gallons in spring, 26 gallons in summer, and 60 gallons in fall.

Potential Cost Savings Of Various Options

To estimate the cost savings associated with each option, a cost estimate of the city of Charlotte’s current yard waste collection service was developed. This cost estimate is similar to the service costs presented above, with the following important differences:
• Direct labor, temporary labor, fuel, equipment maintenance and other operating expenses are actual FY2017 incurred costs.
• The indirect and overhead costs included in the service costs are not included.
• Yard waste processing costs at the county’s yard waste facility are not included.
• The equipment capital costs are estimated based on new truck purchases being amortized over a 7-year period and financed at a rate of 4.25 percent.

Development of this cost estimate for the city’s yard waste collection services in this manner facilitates the estimated cost savings that could be realized through implementation of one or more of the options discussed. Currently, the city’s cost to provide weekly yard waste collection services on a four-season basis using manual collection vehicles with collection personnel debagging the yard waste at the curb in FY2017 equates to $3.59/household/month. (These costs do not include yard waste processing costs or the indirect costs of city government.) Residents are not charged directly for the city’s yard waste collection services. Rather, the costs are paid out of the city’s general fund. Residents must, however, supply their own plastic bags. At $0.10/bag and 30 bags/year, each residence incurs a cost of about $3.00/year.

The options researched compare as follows:
• Requiring Use of Compostable Bags: If households set out 30, 33-gallon bags/year for pick up, at a $0.30/bag price differential for a 30-gallon kraft paper bag ($0.40 for paper bag vs. $0.10 for a plastic bag), residents would incur an additional annual cost of $9.00/year to use compostable paper bags. This equates to $0.75/household/month or about $1.96 million/year.

The city of Charlotte incurs costs of about $750,000/year to hire temporary labor to meet the debagging demands during the peak fall leaf collection season. By requiring use of compostable bags, it is likely that the city could avoid using temporary labor and its associated costs. Therefore, it appears that requiring use of compostable bags will result in a cost savings of about $750,000/year for the city but will require residents to incur additional costs of about $1.96 million/year.

• Switching to Biweekly Yard Waste Collection: In addition to the temporary labor hired in the fall, the city of Charlotte uses 34, two-person crews to provide yard waste collection services to 218,000 residences on a weekly basis. Switching to biweekly manual yard waste collection would enable the city to reduce year-round permanent collection personnel and equipment by 50 percent since one collection crew can serve twice as many households on a biweekly basis. However, it would also require the city to double the temporary labor hired for the fall season and hire similar numbers of temporary laborers for the winter, spring and summer seasons.

As noted, Charlotte residents set out an average of 19 gallons/week of yard waste, which can be contained in one, 33-gallon plastic or paper bag. Switching to biweekly collection during seasons of low demand (summer and winter) would increase the average setout volume to 38 gallons/week, which can be contained in two, 33-gallon bags. Based on these averages, it seems that providing a biweekly yard waste collection service on a seasonal basis would be feasible from a waste volume perspective.

Based on this cost analysis, it appears that the city could potentially save over $1.2 million/year by switching to a biweekly manual yard waste collection service. In addition to cost savings, the city would reap several other benefits including reduced air pollution (including greenhouse gases), reduced road wear and tear and reduced truck accident risks. A significant drawback for this option is that it would only exacerbate the problems associated with debagging of leaves at the curb.

• Converting to Automated Yard Waste Collection: A cost analysis of switching to automated yard waste collection, which includes the $50/household cost of supplying a cart, is estimated to cost the city of Charlotte about $9.7 million/year. This cost estimate is slightly higher than the current annual cost of $9.4 million/year that the city incurs using the manual collection approach. However, residents would not to have to purchase plastic bags ($3/year/household), which would save residents a combined total of approximately $650,000/year. The cost analysis for biweekly automated yard waste collection service — providing each residence with 10 compostable bags per year to cover overflow setout volumes during the fall leaf collection season — could potentially save the city almost $1.7 million/year. This option would also eliminate the need for the city’s collection personnel to debag yard waste at the curb.

Jeremy K. O’Brien is a solid waste research engineer and consultant with over 40 years of experience in the industry. Since 1999, he has served as the Director of Applied Research for the Solid Waste Association of North America (SWANA) — an organization of more than 10,000 public and private sector professionals committed to advancing from solid waste management to resource management through their shared emphasis on education, advocacy and research. Reports produced by SWANA’s Applied Research Foundation’s (ARF) research groups are available during the first year following publication only to ARF Subscribers. SWANA members can then obtain the reports free of charge. The full report includes detailed cost analyses as well as pros and cons and case examples associated with each option presented in this article.