ERS 285 Waste Audit of Renison College

By Greg Macdonald

Table of Contents

  1. Identification of the System
    1. Why it is important for sustainability
    2. Components of the system
    3. Criteria for evaluation
    4. What needs to be measured
  2. Methods
    1. Pre-audit
    2. Conducting the audit
  3. Results / Discussion
    1. Composting percentages
    2. Changes from day to day
    3. Composting feasibility
    4. Limitations of the data
  4. Recommendations

Identification of the System

For my ERS 285 project I have chosen to conduct a waste audit of the food services system at Renison College. Renison College is the Anglican church college affiliated with the University of Waterloo. During the fall and winter there are approximately 170 residents living there. 95 of them are women and 75 of them are men. These 170 residents eat all of their meals at the college. Breakfast, lunch, and dinner are offered Monday to Friday, while on the weekend a brunch and dinner occur. Renison college also offers degree programs in Social Development Studies, East Asian Studies, and a certificate of Social Work. Other courses offered at Renison include Religious Studies, Japanese, and English. Many residents chose to live at Renison because of their enrollment in one of the above programs. Many of the professors at Renison, administrative staff, and off-campus students also choose to eat meals at the college.

In the spring term at Renison college there are currently only seventeen full time residents. Renison likes to complement these students with conferences and summer courses over the term to bring more people to the college. Over this past term that has included an economic development conference, a Christian nurses conference, two mathematics conferences, English as a Second Languages courses, and spring summer students working on Social Work classes. When these part time residents live at the college they too eat their meals in the Renison cafeteria. However, for this project I am going to concentrate on the food services waste in the spring term.

The Renison college kitchen and cafeteria are open during the spring term. During this term there are only seventeen full time residents, making this the most opportune time to study patterns of waste from Renison's food services. By doing the audit in the summer it is very easy to find time to talk to the kitchen staff, to collect the waste, and most importantly, to least disrupt the daily routines of the kitchen staff for the benefit of my project. I intend to collect the waste coming from the kitchen waste, and from student plates to see patterns of waste disposal in terms of physical weight, type of waste being generated, patterns of waste from day to day, as well as the compostable organic content of the waste to help determine composting feasibility.

Why it is Important for Campus Sustainability

Before I can discuss why this particular project is beneficial for campus sustainability I must first give a broad definition of sustainability as I see it. I define sustainability as "An underlying system of values to ensure that those after you can have the same or better life". The most important aspect of this definition is the part that says "the same or better". With all of the environmental and social problems we are currently faced with it is not even fair to future generations to leave them with the same opportunities that we have. It has only been in the last 150 years that our environment has taken a drastic change for the worse. Since it was our fault that this has happened, it is our responsibility to do something about it. This is part of why my project is important for sustainability at the smaller level, the level of the campus.

Currently, the University of Waterloo, and Renison college have problems with their waste management systems. Budget cut backs have meant less staff and money to be able to study and enact action plans to reduce, reuse, and recycle (compost). That means that the easiest approach for the University and for Renison is to haul away organic waste to be thrown away at local landfills. Currently at Renison college all of the waste created by food services is thrown out. This is very unsustainable. The nature of landfills is that once waste is buried there is little air to reach it. That means that even organic waste can take years to break down. Opening new landfills is a costly procedure that costs millions of tax payer's money to find a suitable site. Even if the new site is deemed appropriate it is impossible to foresee all of the environmental consequences of it.

Another part of sustainablity is closing the loop. By sending our waste off campus it is keeping the system open. It is not sustainable to hope that we can continue to ship our waste elsewhere and assume that we can do this forever. The money that it costs to do this either directly in collection fees paid by Renison or by municipal taxes are all unnecessary if we can reduce that waste ourselves. The money saved can best be put to use supporting education and research, the two main functions of a University. That is why understanding where the waste is being generated, and how much of it is compostable is so important. Unless we have a good grasp on this data, any plan of action coming into place is doing so blind and destined for failure. There is no point enacting a program of waste management and have it stopped after only a short period of time due to inadequate knowledge about the system.

Components of the System

The Renison college food services system is divided into two interconnecting sub- systems. The first is the kitchen, and the second is the cafeteria. In the kitchen there are inputs of raw materials (fresh vegetables, meat, pre-packaged food, etc.), as well as the human inputs of the kitchen staff. In the kitchen the food is processed to prepare it for serving the students. During the processing stage waste is generated in the forms of vegetable and fruit peelings, discarding rotten food, coffee grinds, and packaging. This waste is all disposed of in a dumpster and taken to landfill. The students are the main input of the cafeteria. In the cafeteria there is an exchange of processed food from the kitchen to the students. This includes beverages, soup, salad, deserts, side dishes (usually potatoes or rice), and main dishes. The students then take this food into the dining hall for consumption. After eating the food the students take their trays to the dishwashing area, where the dishwasher scraps everything left on the plate into the garbage. This waste is also sent to the dumpster and then to the landfill.

Criteria for Evaluation

For the evaluation of the food services system at Renison college I will be looking at a broad range of things. These include:

What Needs to be Measured

A waste audit uses the analysis of numbers to determine waste reduction strategies. In this case the numbers I will be collecting will be the weight of waste from kitchen compostables and kitchen non-compostables, and the weight of student compostables and student non-compostables. I will also be systematically recording the types of waste being thrown out. This is important to determine any abnormalities in the system and to see how that might affect the base data. Other things that need to be measured are the number of people eating at the cafeteria on the day of the audit. When I analyse the final results I will take the data for the spring term residents and extrapolate from that the amount of waste being generated by 170 people. It is important to look at what percentage of the total waste is coming from the kitchen and from the students, as well as what percentage of the waste of those sub-systems is compostable. Finally, I will use the data to look for patterns from a day to day basis (i.e. Monday to Thursday).


Conducting a waste audit is no measly task. It takes time, planing, and above all cooperation from people your audit would affect. For this audit I have had exceptional help. Please see my project definition for a thorough list of my contacts. A good method is important so future people can review the project and reproduce the results. For this audit I have divided up the tasks that I have completed in the audit into two categories. Those that must be done before the audit, and those that take place during the audit.


Once I had the idea of a waste audit at Renison college I decided to contact Patti Cook, the University of Waterloo's waste management coordinator. She was instrumental in explaining to me how to conduct an audit properly and efficiently. As well as give me documents about past audits on campus she instructed me on the use of a scale to weigh the waste. It works when you attach the bucket or bag you need to weigh to it. Following that, it is a simple matter of reading the results on the side of the instrument. The scale reads from 0 to 25 kg. While it was very important to have some background knowledge of waste audits that means nothing without permission from the kitchen staff. I approached the kitchen staff soon after talking to Patti Cook. Andy, the head cook at Renison, as well as the other staff of Cathy and Artemis were very excited about my idea. They agreed to do whatever they could to help me on my audit. The kitchen staff allowed me the use of large plastic bins to use in the collection of waste.

My goal in the audit was to get the kitchen staff to separate their waste into four sections: kitchen compostables, kitchen non-compostables, student compostables, and student non-compostables. This would be possible by placing a collection bin for compostables directly beside the kitchen garbage, and another directly besides the garbage student wastes are scrapped into. This would make final analysis much easier. It is also important to note that I wanted the kitchen staff to do the separation of waste, not myself. This is mainly because one of the criteria for evaluation is how well the staff separate the waste. To ensure that the kitchen staff understood what I wanted done I had to talk to each one individually about what is compostable and what is not. To aid this I composed two signs, one for the kitchen compostables, and one for the student compostables. Once the kitchen staff were properly trained I could commence with the waste audit.

View the kitchen compostable sign

View the student compostable sign

Conducting the Audit

For the waste audit I chose a sample time period of four weeks, with the collection of waste occurring twice a week. I also wanted to equally represent different days of the week, so the audit included two Monday collections, two Tuesday collections, two Wednesday collections, and two Thursday collections. However, due to staff vacations and Canada Day on a Monday the days of the audit over the four weeks were not evenly spaced out. The final days decided on were: June 25, 27; July 3, 4, 8, 10, 15,16. Each day the audit was run exactly the same. During the day the kitchen staff would put any vegetable peelings, fruit peelings, rotten fruit / veggies, coffee grinds, egg shells, etc. in the kitchen compostable bin instead of the garbage. Non-compostable kitchen waste would continue to be put into the garbage. As the dishwasher scrapped plates he/she would separate any compostable waste and place it in the appropriate bin and put the rest of the waste into the garbage. At the end of the day I would come and weigh all four sites and record the data on Renison College Waste Audit Information Sheets. After each day I would dispose of all the waste and clean out the compost bins for the next day of the audit.

Results / Discussion

Renison College Waste Audit Results
Number of ResidentsKitchen Compostables (kg)Kitchen non-compostables (kg)Student compostables (kg)Student non-compostables (kg)
Tuesday, June 25/96175.
Thursday, June 27/96171.94.751.153.5
Wednesday, July 3/96171.
Thursday, July 4/96173.
Monday, July 8/96345.856.152.15.55
Wednesday, July 10/96344.
Monday, July 15/96343.314.42.25.2
Tuesday, July 16/96343.
The table above shows the results from all eight days of the audit. I will analyse these results in three sections. The first section will cover the patterns of waste. This includes how much of the waste coming from Renison is compostable, as well as whether that waste came from the kitchen or the students. The next section will be to look at how this waste changed from day to day. This includes a comparison of waste from Mondays with Tuesdays, etc. The last section will look at the extrapolation of how much waste 170 students would make, to determine the feasibility of composting. It is important to note here that the results have been broken down into a few categories as well. I have data for all 8 days of the audit. This information is used to look at overall percentages of waste from the kitchen, students, and what percentage is compostable. However, for the first four days of the audit there were only 17 students living at Renison. During the last four days of the audit there were double that number due to summer students, and English as a Second Language students. This means the overall data is still relevant when looking at percentages, but not when looking at actual weights of garbage since half of the dates had double the residents at the college. Whenever I use information about weights of garbage it will be specifically mentioned if there were 17 or 34 students eating at the college.

Composting Percentages

This section will deal with what percentage of the waste at Renison college is compostable and where that waste came from. I will start with discussing the waste coming from the kitchen of Renison college.

The graph above shows that 39% of the waste coming from Renison's kitchen is compostable, while 61% of the waste is non-compostable by weight. This data includes all eight sample days as actual weights are not what is being measured just composting percentages. These results are very interesting as 39% is a lot of waste that could be reduced by composting. The compostable waste is made up of vegetable peelings for the salad bar, soup, and vegetable side dishes, rotten fruit, eggshells, and coffee grinds and filters. The Renison salad bar is kept fully stocked with lettuce, cucumbers, tomatoes, potato salad, carrot and celery sticks, broccoli and cauliflower, spinach, brussel sprouts, and macaroni salads. These salads must be kept full and accordingly peelings are created every day. Renison also puts out an assortment of fresh fruit such as apples, oranges, and bananas. If any of this fruit is not taken before it goes bad it was dumped into the compost bins as well. Peelings for side dishes are not as regular as Renison may peel carrots on one day for the entire week. The potato peeling machine is also only cleaned out when it is full and thus this weight is only periodically reflected in the data.

The waste that is non-compostable from the kitchen was usually non-organic in nature. This included plastic milk containers, cereal containers, and napkins. Periodically, meat that could not be used again was also thrown into this garbage. I am very pleased with the results of the kitchen audit. There was no contamination of the kitchen compostable bin, any only once were compostables thrown out accidentally. The potato peelings were once thrown into the regular garbage and due to their mushiness could not of been transferred to the compost bin. It is important to note that the staff had no problems in separating the waste. Since the compost bin was located directly by the garbage where waste is normally put it took no extra time to separate it. Another factor involved in the high compost percentage is that most leftover meat is reused into stews. Leftover vegetables are also recycled into Andy's soup of the day, and stews.

This data is also very interesting in that the percentage of compostable waste has reduced dramatically when compared to the kitchen. Only 26% of student waste is compostable, with 74% being non-compostable. This is a 13% drop in compostables. I initially expected student compostables to be easier to compost and separate. For this site the staff scrap any compostables into the compost bin and the rest into the garbage. I believe the biggest reason for this drop in percentages is the avoidance of contamination. I was very explicit with the kitchen staff that any vegetables contaminated with gravy, oils, butter, or fats be thrown into the garbage. Despite the fact that many residents don't finish all of their vegetables most of the leftover vegetables such as cooked carrots, beans, or peas are usually contaminated with sauces from the main dish. While this may seem unfortunate it is much better to get an accurate account of what should actually be composted than artificially boost that number with contaminated vegetables that would attract pests to a composter.

The student compostables thus included mostly fruit peels from breakfast and lunch. It is very easy for the staff to put a half grapefruit rind or melon rinds in the bin than to separate contaminated from compostable cooked carrots. This means that almost without exception all of the student compostables is fruit from breakfast or lunch. Non- compostables are almost entirely organic in nature. This includes any meat scrapings, dairy products, desert leftovers, and used napkins. While this result may seem initially disappointing they may actually be advantageous. Due to the ease of collecting the fruit rinds I am inclined to forget about putting out composting bins at dinner, and only collect student waste at lunch and dinner when a composting program is initiated. This is important as the staff expressed worries about not having the time to separate student waste during the fall and winter as the number of students is so increased. I also don't feel the composter would be overrun with acidic fruit as the kitchen waste is primarily vegetable in nature.

When looking at the overall results of composting percentages it is found that 34% of the waste being generated from Renison's food services is compostable. A side note on that figure is that 60% of that compostable waste is from the kitchen while 40% of the compostable waste is from the students. Again, that is due to the high contamination rate of compostables from student plates.

Changes from Day to Day

In this section I will very briefly look at how the composting percentages of waste at Renison change from day to day. Here I must also point out that these figures are averages from all 8 periods. The actual weights of the garbage is inadmissible in this section as some of the days of collection were done with 17 students and some with 34 students. For example, both Tuesday's fell on days with 17 students, both Mondays fell on days with 34 students, while one Thursday collection had 17 students, the other 34 students.

The graph above shows the wave pattern of compostables day to day. The results roughly show the cyclical pattern of more compostables on Tuesday and Thursday, and less compostables on Monday and Wednesday. There are many possible explanations for that change. I can hypothesis that the kitchen staff peel enough vegetables for the salad bar and side dishes for two days. That is shown in the data as I noticed an exceptional amount of vegetable peelings in the kitchen compostable bins on Thursdays. Another possible explanation is that there may of been simply less non-compostable waste on those days. This however is harder to provide reasons for as most non-compostable waste is generated randomly (i.e. whenever the milk runs out the bag is thrown out). Even patterns of the menu could affect this data. If watermelon was put out on those two days that would result in an increase of compostables in the student area. All in all there are so few sample days and so many possibilities that it is hard to pin point concrete explanations for these results.

Composting Feasibility

This analysis is the most important as it will show how much waste is being generated per day by 17 students and then extrapolated into 170 students for the fall and winter. It was found that an average of 19kg of waste was produced per day by 34 students. Again, overall weights could not be used as that reflected a mix of student populations. 19kg / 34 residents / day ( 5) = 95kg / 170 residents / day. This information assumes a constant increase of 19kg for each increase of 34 people. However the data showed that the increase from 17 residents / day to 34 residents / day did not show a doubling of waste but an increase of 33% (17 residents made 12.8kg / day, while 34 residents made 19kg / day). Using the law of exponential growth I can calculate that for 170 students there would be 128kg / day. 12.8kg (.33) = x, 12.8 + x = y (.33) etc.... Do this nine times and you get 128kg. This is higher than the first method because it assumes a 33% increase for each time 17 more students are added.

I don't believe that either method is totally valid. I don't think it can be assumed that waste increases at a constant rate because there is a base amount of waste that is created just for keeping the salad bar stocked and that would not be reflected for each increase of 34 students. The law of exponential growth is also not exact as with only four sample periods at both 17 and 34 residents there is too much room for error. An example here is that preliminary comparisons before the last two audit days were complete showed only an increase of 15% as you go from 17 to 34 students, not 33% as indicated above.

Either way, some base conclusions can be made from the data. Using 95kg /day/ 170 residents results in 32.3kg of compostables per day (95 x .34). Using 128kg / day /170 residents results in 43.52kg of compostables per day (128 x .34). For the composting program I have planned at Renison, a 3-bin turning unit is the most appropriate choice. This type of composter is the fastest and largest of the backyard styles. It can handle up to 20kg of compostables per day. Using the results of the audit, I predict that Renison would produce more than that amount. However the data above does not reflect that approximately 30% less students eat at Renison on Fridays and on the weekend. That would result in a noticeable decrease of the average daily compostables.

Limitations of the Data

The first and foremost limitation in the data I have collected is the limited statistical validity of it as well as my non existent statistical knowledge. It is impossible to accurately predict exactly how much waste would be produced by 170 students, using a sample size of only 17 student. Having only eight sample periods is also very low. This is compounded with the problem that in half of them there were 17 students, and in the other half there were 34 students. Another limitation is that I only used one weighing instrument. If this scale was wrong than all of my data would reflect that. There may of been further limitations in the use of the staff to separate the waste. I only noticed one case of staff error, however I did not dig through every compost bin and garbage pail looking for more. A cursory visual inspection was all I did. One of the biggest limitations is the time of day I weighed the waste. Since I conducted the audit by myself I had to find the time to do all of the weighing. Usually this was done at the end of the day. However, in the summer the kitchen staff like to leave early, this means I had to conduct the audit before everyone in the dining hall had returned their trays, thus that waste was not reflected in the data.


Certain core recommendations can be made about the data despite all of the limitations. Primarily I recommend that a compost program commence despite the problem of too much waste being generated. I hypothesis that Renison would generate about 10kg more compostables than a 3-bin turning unit could accommodate. However there are many ways of still making a compost program a success. Firstly, Renison could simply just compost waste either from the kitchen or the students, whatever is easier. This would reduce the amount being composted by 60 or 40% respectively. Another option is to limit the waste being collected to certain types, say salad bar peelings only. Using these methods and having the same cooperation of the kitchen staff that I had during the audit would help make composting a success at Renison college.
Greg Macdonald (