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How to Improve Bottle Recycling and Measurement at Sports Venues

RAPID RESPONSE QUESTION: In trying to develop best practices for tracking our recycling efforts, we are wondering how to get an accurate count of beverage containers recycled during sports events at Ford Field. We were hoping to be able to weigh the outgoing collected containers and convert these to a number of bottles. How can we overcome some obstacles that may give us inaccurate measurements?

Request by: Lydia Camel, Capital Development | Ford Field



Concourse vendors at Ford Field sell pre-packaged beverages in different plastic bottles, and some beers (from a large sponsor) in aluminum bottles. The field’s main restaurant sells beverages on tap, in compostable cups. (The restaurant also uses compostable utensils, bowls, plates and beverage cups, and operates a compost collection program.)

These pre-packaged aluminum and plastic beverage containers, after use by the customer, are co-collected in bags and sent to Waste Management, Inc. for sorting and processing. After processing, Waste Management Inc. weighs the bottles.

Due to contaminants of this collected stream, the unknown ration of plastic to aluminum bottles, and the unknown amount of liquid residuals remaining in any of the bottles, there is no reliable means of determining the number of bottles based on the weight of the collected material. Typical contaminants, aside from residual liquids, could include: caps, wrappers or other materials that consumers stuff inside the bottle, and other waste incidentally thrown into the recycling bins.

The venue had considered trying to eliminate the aluminum bottles from this waste stream, by switching to tap beers served in compostable cups. This would leave only plastic bottles (single-stream) in the collected recyclable stream. While this might help in distinguishing between plastic and aluminum, the challenge of determining the amount of contaminants and liquids would not be resolved. This option is probably not viable at the current time anyway, due to the nature of the sponsorship.


Findings and Possible Suggestions for Improving Bottle Collection Measurement  

If a bottle count is the desired metric, the first and likely most accurate method would be to find out the sorting and weighing process undertaken by the recycling/waste management company or hauler or processor after picking up the collected material. If the processor is sorting and decontaminating before weighing the material, it is a simple matter of dividing that final weight by the individual unit weight of a single item.

For an accurate estimate, the venue needs to know if the hauler is draining liquids, removing lids and/or labels, segregating different materials (e.g., aluminum vs. PET plastic), and sorting other contaminants prior to weighing. If the hauler is not segregating by different materials, and/or is weighing the materials with residuals and contaminants, a bottle count (as determined by the total weight reported by the hualer, divided by the weight of one bottle), the metric will not be accurate.

If the hauler is weighing the sorted, decontaminated material streams, and these single streams consist of one size or type of beverage container, the number of bottles is easy to calculate by determining the weight of an individual bottle. Divide the total weight of the reported material by that value.

If this method is used, ensure the individual unit item(s) (e.g., a plastic bottle) to be weighed for the calculation, is in the same state as when hauler weighs it. For instance, if the hauler removes any labeling or sleeves on the plastic bottle, the individual unit you are weighing to calculate a bottle count, must also have the sleeve removed.

If the hauler is not segregating materials into single-stream before weighing, and/or weighing with any contaminants or residuals, it may be difficult to establish an accurate numerical count of the bottles. A few suggestions are offered below for the venue to improve measurement, including: counting by inventory of bottles sold, sampling, reverse vending machines, and providing liquid-catch receptacles for emptying liquids prior to disposal.

Note: Any of these suggestions would be more accurate with increased and “fool-proof” signage and fan/staff outreach to further reduce contaminants in the bottle stream.

Inventory Sold: The number of bottles sold at each event can be tracked from an inventory perspective using barcoding or manually count in stock at the start of the event, and the number of remaining bottles in inventory after each event. An assumption would have to be determined from sampling, to determine the typical percentage diversion to recycle receptacles to account for consumers that put bottles in regular trash.

Determining a percentage of aluminum to plastic typically sold could also be helpful in estimating a conversion ratio in a representative sampling scenario mentioned below.

Representative Sampling: The venue could conduct a representative sampling of collected materials after an event, including mixed bottles with contamination, directly from the recycling receptacles.   After weighing this material, a sort and clean-up of the material could yield a percentage of the bottle weight relative to the initial collected weight.

Depending on the desired measurement, the collected bottles could be further sorted by plastic or aluminum to typical percentage of aluminum vs. plastic.

A relatively large sample from different receptacles throughout the venue may yield a more representative estimates. Additionally, samples collected over the course of a few different events with varying audiences may show differences in recycling efforts.

This exercise should be repeated and updated over time, to check for changes in diversion as a diversion program gains more momentum, or as menu items or bottling types change in the concourse.


reverse vending machineReverse Vending Machines (RVM): Many grocery stores in states with bottle deposits, install reverse vending machines that accept bottles and dispense the deposit amount (e.g., five cents), or a chance to win a token or award, for returned bottles.

Waste management companies and/or sponsors (that can advertise on surface of the machine) might be interested in partnering with venues for this opportunity for collecting bottles. However, these are probably only viable in bottle deposit states, and there may be some complications with their use in stadiums or sporting venues.

The Houston Astros installed an earlier-technology version of these in ~ 2008, built by Tomra. They initially resulted in an increase in diversion, but the Astros ultimately eliminated them for various reasons, including misuse (non-bottle materials), and long lines of fans waiting to put bottles in the machines.

Newer and more sophisticated technology RVMs ensure that unwanted materials are rejected by the machine.

If an RVM is of potential interest, other considerations are the capital expense, and maintenance by site staff to empty collected bottles and liquid residuals, and maintenance as needed by the manufacturer or a licensed repair entity. Repair companies are reportedly reside only (or mostly) in bottle deposit states, making it less convenient for RVMs that would be installed in non-bottle deposit states.

Liquid-Catch Receptacles at Recycling Stations: Install receptacles for consumers to empty liquids and remove caps from bottles before placing in the recycling container. This would only be useful if the site wanted to get a more accurate collected material weight before sending these recycled streams to the recycler. This suggestion would be labor-intensive to say the least, and may also pose the problem of potentially long lines as fans wait to empty out their bottles before recycling.


Related Information

At Safeco Field in Seattle, Washington, concessioners remove caps for ALL beverages sold in bottles, before giving them to the customer. This eliminates bottle caps in the recycling collection receptacles, and means less caps to clean and sweep up at the end of an event. If collected recyclable materials are to be sorted or weighed in-house prior to sending to a recycler, this reduces another variable when weighing collected bottles.

Volume to weight conversion calculators are available from several sources. Volumes may not provide a consistent conversion to a bottle count either, due to contaminants, and not knowing how many bottles or cans were flattened by consumers before disposal in the recycling receptacle. In addition, the aluminum bottles of beer, sold at Ford Field, are less common than aluminum cans, and no volume to weight calculators were found for them. Examples:

Greenhouse gas reduction calculators for recycling are available for venues interested in this number. EPA’s Waste Reduction Model (WARM).


Disclaimer: PPRC does not endorse any particular vendor, material, or process, and provides any commercial links as examples only.


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