Divide And Conquer Curbside CollectionsDivide And Conquer Curbside Collections
January 1, 1997
Michael J. Engelbart and Steven D. Brachman
You can plan, you can pilot, but when you're the first to experiment with new collection ideas, you're destined to make adjustments throughout the process.
When Milwaukee began its curbside recycling collection program in 1989, it already had studied a variety of models to determine which system would work the best.
Although Milwaukee couldn't benchmark collection practices against similar cities - few others had extensive curbside experience - it determined that a commingled, weekly collection would be most effective.
The next year, as part of its study, a variety of vehicles and collection containers were evaluated. They found that an over-the-top semi-automated vehicle, coupled with a 20-gallon set-out bin was the most efficient on the route. As a result, the city expanded its commingled bin program to 60,000 households by 1991. However, it did not anticipate the health and worker safety problems spurred by the change.
Milwaukee had switched to semi-automated cart trash collection in 1981, reducing the amount of manual lifting by collectors. Now, bin recycling collection threatened to increase workers comp claims because the new physical requirements were resulting in back and shoulder injuries.
In some cases, the injury on bin routes was 50 percent greater than on semi-automated routes. To compound matters, residents complained that their bins were too small to hold an entire week's recyclables. Collectors also found the bins to be impractical since the materials would blow out of the coverless bin or would be-come wet in rain.
In late 1991, the city began a pilot program to evaluate a more automated cart-recycling collection system. It found that carts:
* reduced collection frequency;
* increased residential participation;
* were more efficient than bins;
* eliminated unproductive drive-bys;
* reduced the need for a second cart;
* reduced back injuries;
* discouraged scavenging; and
* allowed for drier, more saleable recyclables.
The city also had to consider a few negative aspects of the cart system. Carts would:
* increase time spent on backyard collection;
* carry a higher initial cost; and
* hinder content screening by the collectors.
What cinched the decision to switch to a split-cart recycling collection system were the results of an independent public opinion survey in Jan-uary 1995, in which 87 percent of residents expressed a preference for using carts rather than bins.
The Drawing Board The split-cart collection system has three main components:
* a 25-yard, split-body rearload collection packer;
* divided 95-gallon carts; and
* an adjustable lifter capable of tipping recyclables in three different positions ensuring the segregation of paper from mixed recyclables.
Although each of these three components had been used independently before, their combination was unique and required extensive testing and refinement.
A rear-loading truck with two separate compacting compartments was developed to maintain the paper fiber quality. The body has a paper side with 15 cubic yards' capacity, while the mixed containers' side has 10 cubic yards' capacity.
Mounting this body on a low entry, dual-side drive chassis helped to maximize the work radius while allowing for optimum compaction rates.
With payloads of up to 15,000 pounds, these trucks rarely tipped at the material recovery facility (MRF) more than once a day.
These vehicles also can be used on garbage routes, for special collections and spec'ed to plow snow. Garbage and recycling trucks are the backbone of the city's snow plow force. The size, weight and tandem rear axle make these trucks effective plows.
The two-load compartments on each truck have independent compaction hydraulics. During the pilot program, the city found that payloads could be optimized by using maximum compaction (approximately 6-to-1) on the paper side and by using this packing blade on a continuous basis. Conversely, compaction on the container compartment is lowered to 111/42-to-1, and the packing blade is pushed and released intermittently during the workday to reduce glass breakage.
The lifter is another important system component. The sliding, automated tipper keeps the co-mingled containers separate from the paper stream during collections by using a vertical fin which joins the divided cart during tipping. This fin is located between the two compartments on a pneumatic arm. The slide lifter also can collect single commodities from undivided carts in multi-unit housing and self-help stations.
Based upon the pilot program's results, Milwaukee expanded its cart recycling system to an additional 130,000 households, and reduced the total number of recycling routes from 45 to 35.
In addition, worker injury has been reduced, though not as much as an-ticipated: While back and shoulder in-juries have deceased 25 percent with cart routes, leg injuries have in-creased since the monthly collected recycling carts are heavier than be-fore.
Educational Materials Milwaukee used a show-and-tell approach to educate the public about the new system. A die-cut replica of the cart with a fold-up lid was created to show the compartments for particular items (see page 56). In addition, the promotion piece included recyclable preparation directions and recycling tips. It is attached to each cart as it is delivered along with a recycled plastic litter bag and a refrigerator magnet.
The slogan "Do the Blue" was used in all types of media, from billboards to home mailers.
Also, a "Do the Blue" rap video with a segment from the mayor was produced and distributed door-to-door in neighborhoods with low participation.
The city's recycling program was presented to the Milwaukee Public School system, and, as a result, recycling was offered as a facet of the School to Work program.
In addition, an Environmental Education Resource and Tour Center was established with Keep Greater Milwaukee Beautiful (KGMB); they also staff the facility which provides tours of the MRF, hands-on exhibits, and a library of resources on all aspects of recycling and pollution prevention.
The sanitation division mails a bi-annual update to participants in the spring and autumn. This four-sided, foldout includes topics like leaf collection, a focus on individual commodities and their proper recycling preparation, drop-off site operation hours and a reminder of what is recyclable.
To help correct problems with individual cart use, the collector attaches a bright red tag to the container which explains what the resident did incorrectly and then suggests ways to remedy the situation.
Back To Reality Despite the cart system's successes, Milwaukee could not implement it universally throughout the city. For example, the recycling carts were frequently contaminated with garbage in highly transient, low income neighborhoods. Only collected once a month, these garbage-filled carts were being left behind for up to six weeks and posed a possible health threat. In addition, these same neighborhoods produced much lower recycling tonnages and didn't seem to merit a 95-gallon container.
In 1995, as a result of meetings with aldermen and neighborhood groups, the city replaced carts with 20-gallon bins in 24,000 households, leaving approximately 32,000 residences with bin collection. Also, the city began collecting weekly in this area, which reduced scavenging and left it cleaner.
Participation also increased from about eight to 15 percent, either be-cause of a specific educational campaign, a designated collection day, or less contamination and scavenging.
These changes saved approximately $300,000 annually, which allowed for increased bulky collection. The city also used the reclaimed containers to convert the remainder of the city to cart collection in two years as op-posed to the four years originally planned.
Trends Milwaukee has developed a flexible, yet efficient, curbside collection system. By using state-of-the-art trucks and an innovative cart and lifter design, the collection system produces good results in a number of different types of neighborhoods.
In addition, its flexibility allows for the equipment's alternate uses and can accommodate changes in waste collection methods.
The current monthly collection frequency is pushing cart capacity to the limit. Interestingly, while the volume of recyclables is increasing, tonnages collected are staying the same, or even dropping slightly.
This is due to the increased use of recyclable packing plus the "light-weighting" of these containers, which further highlights the benefits of load compaction.
Milwaukee's sanitation staff currently is discussing increased collection frequency with a designated set-out day and is weighing the impact of adding additional carts.
Michael J. Engelbart is the Resource Recovery Manager at the Sanitation Division, in Milwaukee. Steven D. Brachman is the Waste Reduction and Management Specialist at the University of Wisconsin-Extension Solid and Hazardous Waste Education Center.
1. Refuse trucks: 38 G&H bodies mounted on low-entry, dual-side drive, crane carrier chassis (new trucks will come on Oshkosh)
2. Types of containers/lifters: 95-gallon Otto carts, semi-automated A.R.E. lifters
3. Number/type of customers: 170,000 cart households; 30,000 bin households. No apartment or commercial collection.
4. Employees: 1 per crew.
5. Service area: All residences in buildings of 4 units or less. City government offices.
6. Local tipping fees: $29/ton.
7. Most interesting collected item: An abundance of bowling balls.
Milwaukee used a variety of objective criteria to evaluate the performance of a wide variety of vehicles, including capacity, ergonomics and driveability. However, because recycling collection has its own set of demands, other factors often enter into a decision as to what type of vehicle to use.
For example, prior to the recycling truck evaluation, the city had tested several vehicles with front-wheel drive. These vehicles suffered from poor driveability in snow and ice conditions. This prior history influenced the selection of rear-drive vehicles.
Similarly, Milwaukee utilizes its fleet of rear-load garbage packers as part of its regular snow plowing fleet. Permanent plow hitches are mounted to heavy-duty chassis to provide a durable and serviceable plow vehicle.