The Reusable Coffee Cup System "Billie Cup" in a University Setting: A Pilot-Study

: 500 billion disposable cups are consumed every year and contribute to polluting the natural environment. Reusable cups offer a reasonable alternative, especially in work or study places with efficient and sustainable washing facilities. In one coffee bar at a university building, disposable cups were completely banished and a reusable polypropylene cup, the so-called “Billie Cup”, was introduced together with automated deposit and washing facilities. Quantitative and qualitative analyses were performed to measure financial differences, waste reduction, and customer opinion. After introduction of the Billie Cup, we reduced approximately 2.5 kg of waste per week and did not report significant changes in weekly sales [median: 336 (interquartile range: 291 – 359) vs. 337 (297 – 349) drinks, respectively, P=1.000] or revenue [578 (492 – 612) vs. 576 (492 – 586) euro, respectively, P=0.833]. Furthermore, we reported significantly higher numbers of refilling a cup with a median of 21 (16 – 25) vs. 43 (38 – 59) drinks per week, respectively, P=0.017. Resulting from our questionnaires, we found that all respondents believed that disposable cups produce unnecessary waste on campus. Our pilot study demonstrates that a reusable coffee cup system along with banishing all disposable cups can be successfully implemented without decreasing monthly revenue or sales.


Introduction
Globally, over 500 billion disposable cups are consumed annually, of which between 250 and 300 billion are plastic-coated paper cups (Martin et al., 2018).As a result, plastic waste is steadily accumulating in landfills, and where solid waste management is inadequate, it ends up littering and polluting the natural environment, waterways and oceans.Single-use beverage cups are one of the top ten items found littered on beaches around the world (Ocean Conservancy Report, 2011).Fonteinis et al. showed that switching to a reusable plastic cup results in a 76% reduction in environmental footprint compared to the landfilling and recycling scenarios for paper cups respectively (Lewis et al., 2021).Therefore, reusable cups are particularly useful in regions where renewable electricity makes up a high proportion of the grid mix and recycling rates are low.
The "Billie Cup" is a reusable cup for catering services and comes along with automated deposit and washing facilities (www.billiecup.com).However, data on implementation of such completely reusable coffee cup systems in university settings are scarce and scientific evidence is needed.
Hence, we conducted a prospective analysis of financial differences and waste reduction after the introduction of the Billie Cup system.Furthermore, we explored and visualized customer opinions by means of qualitative questionnaires.

Hypothesis
We formulated the following hypothesis: The transition to an automated reusable coffee cup system Billie Cup along with banishing all disposable cups is possible and will not lead to significant differences in weekly revenue, sales figures, or customer satisfaction.

Literature review
A literature review regarding previous studies about reusable cups in a university setting was conducted using a search strategy.The literature research was conducted in Google Scholar using the following terms: "disposable coffee cup" OR "reusable coffee cup" AND "university" OR "campus".Selection process: all database: 546 articles; after abstract screening: 12 articles; after full text screening: 8 articles.
Eventually, eight articles were selected to describe the context of current literature.Two field studies initiated reusable mugs to sell and promoted its usage.The pilot program at Dalhousie University (Archibald et al., 2019) showed that only 5% of individuals consuming beverages at the Second Cup used mugs provided by the pilot program while the remaining used disposable cups (83%) and their personal reusable mugs (12%).Poortinga et al. conducted a field study in which reusable cups were promoted next to disposables at twelve university and business sites (Poortinga, Whitaker, 2018).The study found that, on average, hot drink sales with reusable cups increased from 3.3 to 7.6%.Furthermore, they found that only charges on disposables increased the use of reusable cups and discounts had no significant influence.
Multiple studies investigated the effect of awareness interventions including environmental messages such as posters, discounts for reusable cups and an event entitled the "No Disposable Cups Day" (Suksant, 2018, Lee, 2015, Cox, 2014, Finlayson-Buck et al. 2020, Rokka, Uusitalo, 2022, Horne, 2020).Most studies reported a relevant increase of reusable cup use up to 463%.One of the most encouraging interventions were discounts for drinks and environmental education (Suksant, 2018, Rokka, Uusitalo, 2022).The "No Disposable Cups Day" showed no significant change in the proportion of reusable mug users before and after the event (Finlayson-Buck et al. 2020).
Main barriers in reusable mug programs were difficulties to carry and return the mug, prohibition in the library or other institutions, forgetting the mug at home, awareness, hygiene, and costs (Suksant, 2018, Lee, 2015, Finlayson-Buck et al. 2020).One study reported that completely switching to reusable or glassware was not feasible because of the lack of accurate data and funding for a new dishwasher (Poirier, 2020).In a report on single-use plastic reduction at higher learning institutions in the United Kingdom a financial risk from gastronomy or catering services was described (University of Leeds, n.d.).Furthermore, questionnaires before any interventions revealed that more than half of the customers already owned a reusable coffee cup (Suksant, 2018).However, half of the students at the University of Guelph were not aware of the fact that coffee cups are not recyclable.This finding underlines the importance of environmental education.

Methods
This prospective pilot study took place at one coffee bar in the building of a university between January 10 and March 20, 2022.The new reusable Billie Cup was introduced on January 31.COVID-19 measures at the university did not change and classes were live on campus during this period.Data was extracted from the Point-of-Service-System of the coffee bar as weekly numbers.The primary outcome of our study is revenue (excluding taxes) and number of sold drinks per week, respectively.

The Billie Cup system
Billie Cup uses polypropylene (PP) as its material, which is a thermoplastic polymer (www.billiecup.com).It is a sturdy material which makes it suitable for frequent use and washing.Unlike other materials like bamboo, PP is recyclable, and unlike stainless steel it is cheap and efficient to produce.Eco-friendly washing facilities were used to clean redeemed Billie Cups.
All disposable cups were abolished on January 31, 2022.Customers could choose between the Billie Cup or a porcelain cup (not allowed for take away).For each Billie Cup, the customer paid 1-euro deposit and multiple options were given: (1) return the Billie Cup via the automated deposit system which gives a one-euro coin back, (2) redeem the old Billie Cup for a new one without additional costs, or (3) return the Billie Cup at the coffee bar and use it as one-euro discount on any purchase at the coffee bar.Customers were encouraged to keep the Billie Cup until they bought their next drink so that they did not need to pay the deposit again.

Questionnaires
The questionnaires consisted of five questions: 1. Do you believe that disposable cups produce unnecessary waste on campus?(yes/no), 2. Were you already interested in reusable cups before the Billie Cup? (yes/no), 3. How would you rate the Billie Cup from one to five? (

Statistical analysis
Continuous data were reported as median and interquartile range (IQR) due to the small sample size and non-normally distribution.Categorical data were reported as counts and percentages.Comparisons between data employed the Mann-Whitney-Wilcoxon test for continuous variables and the Fisher's exact test for categorical variables, respectively.All Statistical analyses were performed using SPSS Version 26 (IBM Corp., Armonk, NY) and figures were created using GraphPad Prism Version 8.0 (GraphPad Software, San Diego, CA, USA).

Results
The study period lasted ten weeks and the Billie Cup was introduced in the fourth week.Therefore, three weeks before the Billie Cup were compared to seven weeks after introduction of the Billie Cup.

Figure 1. Comparison of sales, finances, and refill behavior before and after the introduction of the Billie Cup
Measurements were presented as median and interquartile range.*per week

Waste reduction
Plastic-coated cups were completely abolished in the fourth week.Before the introduction of the Billie Cup, the median number of released plastic-coated cups per week was 311 (IQR: 275-338).One plasticcoated cup has the weight of 8 gram.Therefore, we reduced approximately 2.5 kg of waste per week by implementing the Billie Cup.
Furthermore, we compared the number of refilling a cup that has been used already.Compared with the weeks before the Billie Cup, those after the Billie Cup introduction had significantly higher numbers of refilling a cup with a median of 21 (IQR: 16-25) vs. 43 (IQR: 38-59) drinks per week, respectively, P=0.017.

Customer opinions
In total, 24 customers filled in questionnaires.All respondents believed that disposable cups produce unnecessary waste on campus (Figure 2A) and 79% were already interested in using reusable cups before the Billie Cup pilot (Figure 2B).Furthermore, the majority of respondents (50%) rated the Billie Cup with a 4 out of 5 (Figure 2C).

Results were presented as percentages
Customers have been asked about what they did not like about the Billie Cup (Figure 3).48% percent did not know before our explanation that there was a lid for the Billie Cup and mentioned that it is necessary to take a coffee to the library.13% of the respondents mentioned that they do not want to receive coins when they return a Billie Cup in the automated washing facilities.An "ugly and cheap" design, "getting no discount", or "nothing to complain" was mentioned by 9% of the respondents.

Figure 3. Pie chart projecting critique on the Billie Cup
In the last open question, customers were asked if they have new ideas for the Billie Cup system (Figure 4) and 42% replied that they would not change anything.The three most frequent ideas were discounts, full digital payment when returning a cup, and a better design from 11% of the respondents, respectively.

Discussion
Unnecessary use of disposable cups contributes to polluting the natural environment, waterways and oceans.However, alternative systems for reusable coffee cups exist and can tackle this issue.Our hypothesis was confirmed and the transition to an automated reusable coffee cup system Billie Cup along with banishing all disposable cups was possible and did not lead to significant differences in weekly revenue, sales figures, or customer satisfaction.
Previous studies about reusable coffee cups in a university setting were summarized in the literature review section.In comparison to our study, there are notable differences in the intervention strategy of reusable cups.Firstly, no study conducted a complete ban of disposable cups which is important because companies or catering services may fear financial losses from such an intervention (University of Leeds, n.d.).To the best of our knowledge, we are the first to report a successful implementation and no decrease in monthly revenue or sales.Therefore, this study should encourage more stakeholders to only offer a reusable cup option as most people continue using disposable cups if they are available (Archibald et al, 2019, Poortinga, Whitaker, 2018).
Regarding disadvantages and barriers of reusable cups, our strategy offered multiple solutions to the reported problems.Customers did not need to remember and conduct cleaning because it was managed by automatic washing machines that gave back the deposit.Furthermore, these machines are more energy and water efficient than hand washing.Forgetting mugs and transportation were mentioned in the surveys, however, the Billie Cup offered multiple returning points and flexible options.
Important lessons from our questionnaires are that a clear explanation of the system to all customers is difficult.For instance, a high proportion of customers did not know about the lid which was necessary to take a coffee to the library and some people did not know about the Billie Cup at all.We only used a small card (DIN A4) at the checkout to introduce and explain the Billie Cup.Furthermore, some baristas could not speak English well and we have a high proportion of international students who do not know Dutch.
Although our results add novel data to the implementation of coffee cup systems, the present study has some limitations.The study period lasted only ten weeks and long term effects were not measured.Only 21 customers filled in our questionnaires and this may not be representative for all customers.All coffee cups were abolished in this coffee bar, however, there were two other coffee points nearby in the same university building and weekly sales could have been lower or even higher.

Conclusions
Our pilot study demonstrates that a reusable coffee cup system along with banishing all disposable cups can be successfully implemented as we could prevent the generation of 2.5kg waste per week without decreasing monthly revenue or sales.Furthermore, significantly more customers refilled the same cup and overall customer satisfaction was positive.
The findings are highly relevant because disposable cups produce high amounts of plastic waste in university institutions.In previous intervention and promotion studies on reusable cups/mugs, the majority of people continued using disposable cups if they are available.Therefore, we conclude that a complete ban of disposables is necessary and our study demonstrated that a transition is possible without financial losses, if customer-friendly reusable cup systems are implemented.

Figure 4 .
Figure 4. Pie chart projecting new ideas for the Billie Cup 1, 2, 3, 4, 5), 4. What do you not like about the Billie Cup? (open), and 5. Do you have new ideas for reusable cups and/or motivate people?(open).