SUSTAINABLE WASTE MANAGEMENT IN SCHOOLS

A school district was interested in making sustainable changes in their cafeterias to lower their environmental impact. To determine their current state, weight and dimensions of their waste were taken, lunch observations and spaghetti diagrams were developed, and the purchasing process of lunch trays was determined. This was all used to create a current state map, a common industrial engineering tool used in lean manufacturing to display the flow of a system and label problem areas. From there, a life cycle assessment made with Umberto NXT LCA software was created for four lunch trays systems: disposable paper boats, compostable trays if sent to a composting facility, compostable trays if disposed of in a landfill, and reusable plastic trays. This was used to calculate the environmental impact and the results were compared for each tray. After this, a cost analysis was completed. One portion was developed to determine the expense or savings involved in switching to a different tray and/or dishwasher unit than what was already in place at each school level (elementary, middle, and high school). Another involved comparing the estimated amount of trash accumulated over a year with the annual volume of the dumpsters the schools were paying for. Lastly, a future state map was developed to lay out changes that could improve the system of the cafeterias. The current state showed some areas in need of improvement such as recycling behavior, cafeteria layout of the waste bins, and educational signage. In terms of the weight and volume data collected, the high school had the largest tray contribution to trash when comparing the total weight and volume of the trash with the trays. For the life cycle assessment, reusable trays had the lowest environmental impact based on the impact categories studied. The tray types with the highest impact were the compostable trays if sent to a landfill and the disposable trays. Once the cost analysis was completed, it was determined that while the reusable trays would be the best choice to lower environmental impact, it would be costly for any school level to switch to using them at that time. Switching to new dishwasher units, however, would save the schools money if the initial purchase could be covered. Finally, the future state map created incorporated changes that would resolve the problems noted in the current state map such as the positioning of waste bins and better signage.

• What is the current state of the cafeteria systems?
• What are the environmental, economic, and social impacts of the systems?
• What changes can be suggested that will lower environmental impact?
• How would these changes affect the school financially?

Significance & Scope
This problem was selected not only because of the needs of the schools and the community but because it provides an opportunity to exercise multiple methods from the industrial and systems engineering discipline and present this appropriately to others who do not have expertise in this area. At the end of this study, the findings were summarized and shown to the Superintendent, Chief Financial Officer, principals, as well as other members of the school district. Educating students on this topic and demonstrating sustainable behavior within schools is a growing concern among numerous school districts and this can be made into an example for others to follow. In other words, supporting sustainable habits in a school system can greatly impact the community over time in terms of positive environment related behaviors (GSA, n.d.). Collecting and working with data and observations as well as facilitating how changes can be made by people working in multiple levels of hierarchy is a critical role industrial and systems engineers must take on. Students spend a major portion of their developmental years in school and if they are educated about sustainability issues in the classrooms and the cafeterias, there is great potential that this will aid in extending the life of the landfill as well as maintaining these good habits in their community in the future. A value stream map is a process mapping tool often used in lean manufacturing to display how a system is currently run with problems labeled (current state map) and how it can appear should the problems be resolved (future state map) (EPA, 2016). The problems are pointed out with a label known as a Kaizen Burst which can be seen in Chapter 4. Kaizen, also known as continuous improvement, "focuses on eliminating waste, improving productivity, and achieving sustained continual improvement in targeted activities and processes of an organization" (EPA, 2019). In this case, these will be used in the form of what is known as a sustainable value stream map. This method focuses on pointing out areas that can be improved to benefit the environment and reduce waste (Faulkner & Badurdeen, 2014). For this study, the school cafeterias with sustainable changes have been labeled on the maps.
The recommended flow of the cafeteria systems that is shown in the future state map was designed in a way that considers sustainable routing.

Sustainable Routing:
This has previously been used as a tool for manufacturing facilities. The process of sustainable routing is to send manufactured parts through the system to determine which path leads to lowering environmental impact and costs by reducing the amount of usage in areas such as water and electricity. In terms of the schools,  (Brundtland, 1987, p.41). This report was a source of inspiration for the Triple Bottom Line (TBL), which was terminology defined by John Elkington, (Elkington, 1998). It is a theory often used in businesses to assess its performance. The term "bottom line" is often used to describe profit as a measure of success. While profit is important, it is not the only area that should be considered, as Elkington points out. The TBL is divided into three sections. These are economic, environment, and social equity which are elaborated on in the Brundtland report and necessary in order to be considered sustainable. This is also known as the three pillars of sustainability. The economic or profit section represents the financial portion as in the original "bottom line" term. Environment, or planet, is focused on how a company or organization impacts the environment such as a carbon footprint. Lastly, social equity or people is regarding how fair or well the community is treated such as when education or healthcare are considered (Elkington, 1998). In terms of a school district, economic restrictions exist as there is a limited budget provided. Concerns regarding the environment must be a focus when educating children that will become the next generation of citizens. Finally, social issues impact the school as there is not always agreement on the level of importance of sustainability among such a large body of people.

Life Cycle Assessment:
A life cycle assessment (LCA) is used to determine the total environmental impact of a product throughout its lifetime from raw materials to a complete design that will eventually be disposed. The main steps to complete an LCA include the definition of the goal and scope, an inventory analysis, and an impact assessment which will be elaborated on in Chapter 3. These steps are also outlined in Figure 1.
Within an LCA, there is a functional unit, which is the measure used to compare products and list the inputs and outputs as well as system boundaries which define the processes that will be accounted for in measuring impact. (Baumann & Tillman, 2014). In this study, the goal was to provide the schools with the most sustainable and economical tray option. A comparative LCA has been completed with the functional unit being one tray for the disposable, compostable, and reusable option. Once this was complete, the trays were compared for both the lowest environmental impact in all categories and the cost. As there was only one high school (HS) in this study, it did not have a letter associated with its name.

Outline
The outline of the following chapters begins with Chapter 2 which is a review of literature related to this study. Chapter 3 covers the methodology to gather the information used and Chapter 4 includes the results using these methods. Chapter 5 is an analysis of the results followed by Chapter 6, which discusses conclusions and the associated risks, assumptions, and final thoughts.

Environmental Impact
The United Nations developed an action plan titled "Transforming Our World: the 2030 Agenda for Sustainable Development". This agenda laid out seventeen main goals toward sustainable development designed for people, planet and prosperity.
These goals are listed in Table 1 below (United Nations, 2015). A number of these goals relate to the issue of sustainability in school districts. For example, Goal 4 (quality education) and Goal 12 (responsible consumption and production) are related to the objective of educating students and staff on proper trash and recycling habits. School sustainability also supports Goal 11 on sustainable cities and communities as schools are an essential element of local government. Finally Goal 13 regards climate action and environmental impacts within a cafeteria setting can have positive effects on reducing carbon footprint. One prevalent topic which has shown impacts on climate change is the treatment of organic waste. Food waste, for instance, has been a concern for many years due to its negative effects on the environment. A study completed by the Food and Agriculture Organization of the United Nations looked into the global impact of food waste in terms of carbon footprint, water and land biodiversity. Globally, food waste is estimated to produce a total of 3.3 gigatons of carbon dioxide equivalent per year without including the greenhouse gas emissions from the land usage. It also depletes surface and groundwater resources by an annual estimate of 250 cubic kilometers (FAO, 2013). While it is not ideal to have any unnecessary organic waste, there must be a decision made on how to handle any such waste that is generated.
Some examples of waste in this category include the composting of food in schools as well as the use of compostable trays.
A similar study has been completed on three Florida schools. Waste audits were made at each cafeteria location to determine the highest contribution of the waste streams. This resulted in the average student generating over one hundred grams of waste per day with food waste making up roughly fifty one percent of this. With other organic waste included such as paper added, this amounted to about eighty one percent of the overall waste daily. Given this information, the recommendation was to find a way to properly recycle and compost to reduce their environmental impact (Wilkie, Graunke, & Cornejo, 2015).
There has been skepticism over whether composting is a better method than landfilling this type of waste. When organic matter is placed in a landfill, it goes through a process of anaerobic decomposition. In other words, this waste is deprived of oxygen and produces what is known as methane. Should this same waste be composted, it goes through an aerobic decomposition process which produces carbon dioxide rather than methane (EPA, 2020). Neither of these emissions are beneficial to the environment, however, composting has a much lower environmental impact.
Methane is a type of greenhouse gas. It makes up about fifty percent of the landfill gasses that are produced. Over one hundred years, it traps heat in the atmosphere about twenty-eight to thirty-six times more effectively than carbon dioxide (IPCC, 2014). Figure 2 represents the pathways for greenhouse gas emissions from a landfill with carbon dioxide represented as CO2 and methane represented as CH4 (Bogner et al., 2007). The methane gas could be used as an energy source should it be captured and treated properly (see the gas well in Figure 2) which would reduce the environmental impact.

Sustainable Changes in Schools
The Center for Green Schools at the US Green Building Council provided what is known as the "Whole-School Sustainability Framework". The aim of the framework was to demonstrate how sustainable practices could be integrated in a school organization. A diagram of the three main components is shown in Figure 3.
The component, Organizational Culture, is defined as the "the shared values, social norms, and practices within an organization" (Barr, Cross, & Dunbar, 2014). This framework has also been used by other groups in the support of sustainable changes in schools. One example is the organization, Green School Alliance, which guides school communities to implement sustainable changes through programs for students, school professionals and district professionals. For instance, they host what is known as a Green Cup Challenge which has students win points for recycling properly over the span of four weeks (Green Cup Challenge, 2017). To implement lasting change in a school system it is imperative to find ways to empower the members of the community.
Figure 3 -The Whole-School Sustainability Framework (Barr, Cross, & Dunbar, 2014) A study done at an elementary school aimed to minimize the amount of waste produced with initiatives geared towards educating the children on proper recycling/composting behaviors. To display the issue of mismanaged waste, a trash audit was completed in the cafeteria on three garbage bins chosen at random. The results included that of every item placed in the trash, 93% was either recyclable or compostable and that recyclable milk/juice cartons as well as Styrofoam trays contributed most to garbage consumption (James, 2017). This was helpful to lay out this problem area within the school.

Life Cycle Assessment
The International Organization for Standardization (ISO), formed in 1947, "brings together experts to share knowledge and develop voluntary, consensus-based, market relevant International Standards that support innovation and provide solutions to global challenges" with 23,126 international standards defined (ISO, 2020). Within this, the ISO has a series of standards designed for Life Cycle Analysis, or LCA.
These standards are defined in the ISO 14000 Family, titled "Environmental Management" (ISO, 2020). Specifically, these standards can be found in ISO 14040 to ISO 14044. More details about the specific steps and model building using these standards are in Methodology section 3.2.
One example of an LCA that followed the ISO standards was completed on multiple crockery types used in the United States. The three scenarios considered were non-patient meals in hospital cafeterias, school lunches, and breakfasts for hotel guests. The two systems observed and evaluated for potential ecological impacts in each scenario were reusable and disposable crockery. Their audience was intended for experts along with responsible decision makers working in the commercial kitchen field. Their functional unit was defined as "Provision of dishes for the hygienic delivery of X portions of food a day within a year in a stationary out-of-home cafeteria in the USA" (Antony & Gensch, 2017, p. 23). The impact categories considered were ozone depletion, global warming, fossil depletion, acidification and terrestrial acidification, eutrophication, photochemical oxidation, agricultural land occupation, natural land transformation, cumulative energy demand, and water depletion. The software tool, Umberto NXT LCA, was used to carry out their assessment.
The results of Antony & Gensch (2017) showed that for most of the impact categories tested, reusable crockery had a lower impact than disposable. For the disposable crockery, the production and disposal contributed most to the environmental impacts in all scenarios. For reusable crockery, the use of washing the dishes contributed the most to the overall environmental impact. Given these results even with a higher water demand for the reusable system, the conclusion for all three scenarios after completing the life cycle assessment was that reusable crockery would have the lowest environmental burdens and should be used over disposable for this reason. This being stated, to improve upon this analysis, it would be beneficial to consider the costs of each system.

Lean Manufacturing Techniques
In lean manufacturing, the main goal is to eliminate wastes in a system. Waste is considered any process that does not add value. These wastes have been divided into specific categories. The first seven, known as the Seven Deadly Wastes were identified in the Toyota Production System. These include defects, overproduction, waiting, transportation, inventory, motion, and excess or extra-processing. The eighth waste, added later, is known as unused talent, or not using resources efficiently.
Defects refer to products that do not meet customer needs. Overproduction occurs when more is made than needed to meet the demand. Waiting is when time is spent not adding value to the system. Transportation refers to unnecessary movement from parts of the system such as the people or inventory. Inventory refers to having more than is needed of a product on hand that is taking up valuable space. Motion is the unnecessary movements done by people that can cause ergonomic issues. Excess processing is completing more than is needed in terms of work, equipment, or steps in a process. Lastly, not using resources efficiently refers to human or natural resources (The Lean Way, 2020).
In "The Lean and Environmental Toolkit" by the Environmental Protection Agency, some of these wastes are related to environmental impacts. For Defects, this can relate to raw material and energy consumption that goes into making the defective product as well as the disposal of the product. Overproduction requires more raw materials and energy than is needed to complete the task. A lunch period observation took place once at each school to determine how the system was run. Notes were taken on the layout of the cafeteria, including the location of the serving stations, tables for the students to eat, as well as the trash, recycling, and compost barrels. Additionally, sustainable behaviors of the students were tracked to assess their familiarity with the trash and recycling regulations of Rhode Island. The flow of the lunch period was determined by creating spaghetti diagrams of the students' processes to learn the functionality of the layout. After these observations, weight and dimension data of the trash and recycling was measured at the end of each of the lunch periods. A sample of the trays used at each level was collected, measured, and weighed to calculate how much the trays contribute to the cafeteria trash.
The bags of waste were weighed using a standard scale and the trays were weighed with an electronic food scale. This information was used to determine the estimated daily tray contribution to trash. All trash bags were weighed at each school after the lunch periods and added together for each level to make the estimated daily weight of trash. To determine the daily weight of the trays, the annual number of trays purchased was divided by the number of school days in a year (assumed to be 180 days) and multiplied by the unit weight of the tray for each level. The dimensions of the trash and trays were taken with a standard ruler and used to determine the volume.
The volume of each trash bag was calculated by assuming the shape was a cylinder.
After the volumes were determined, they were added together to make the daily volume of trash per level.
Like the trash, the different tray volumes were determined by volume calculations of shapes that were most similar to the trays. The compostable tray used the volume of a rectangular prism, the disposable tray used the volume of a trapezoidal prism (see Figure 12 for reference), and the styrofoam plate used the volume of a cylinder. An assumption was made that the trays were stacked before throwing them away so for all cases, when multiplying the number of trays needed per day by the volume of the tray, the height is calculated by adding together the height of one tray with the product of the thickness and number of trays needed per day to create a total height. The contribution the trays to the trash per day was calculated by taking its daily weight or volume and dividing it by the weight or volume of the trash. For the compostable trays, this scenario assumed that the trays were being thrown into the landfill which was occurring at the time of this study. This information was then used along with the price and frequency of the trash collection service to support the cost analysis of the current systems in place.

Environmental & Economic Comparison LCA
The following sections, 3.21 to 3.23, define the processes followed in the life cycle assessment which will be connected with this study in Chapter 4, the results section. The costs of all products mentioned will also be determined and further discussed in the next section, 3.3 -Options and Cost Analysis.

Goal & Scope
In

Inventory Analysis
An inventory analysis involves a flowchart of the process, data collection of the product and associated processes, as well as the results of the environmental loads.
The collection of data is laid out to show what was determined and what sources were used as well as how it is represented in the results. This includes sections such as the product name, the quantity, material type, dimensions, environmental loads in relation to the functional unit, and mass (Baumann & Tillman 2014). Once this is determined, an impact assessment on the results can be completed.

Impact Assessment
The impact assessment includes three mandatory elements. The first involves defining the impact category. This includes the selection of impact categories, category indicators, and characterization models. The next element is classification, where the results based on impact categories are listed. The last element is characterization. This is where the environmental impact per product or category is determined (ISO, 2016).

Options and Cost Analysis
The information gathered from the current state and life cycle assessment allowed for many options to be considered and an engineering economic analysis to be are labeled with circles with "T" being trash, "R" being recycling, and "C" being compost.
In the elementary schools, in most cases for the lower grades, students lined up to throw away their waste. The upper grades were able to use the bins as needed.
There were several observations of students that hesitated at the bins unsure which was the correct one to dispose of their waste and many ended up using the incorrect bin. To help with this, a few of the schools had signs educating the students on the proper rules of recycling and compost. Two of the schools had bins that were color coded (trash was grey, recycling was blue, compost was red) to also help in this situation. In addition, at the end of the lunches, most schools had the trays stacked to save space before they were thrown away. The middle school and high school students were able to use the bins whenever needed. There were a large amount of milk and water bottles thrown in the trash. The paper boats and styrofoam plates were not stacked before disposal. After observing lunches and taking note of the layouts and processes in each school, a current state map was created as shown in Figure 11. The beginning of the process occurred when the purchasing department ordered lunch trays from a supplier, labeled as Cafeteria Supplier. The information on how the trays were ordered came directly from the purchasing department of the school. Next, the delivery truck dropped off the trays to each school. The teal triangle labeled "Trays Delivered" is known as an inventory symbol to show the trays sitting in the cafeteria for an amount of time before they were provided to the students. The student then ate their lunch and walked over to the waste bins to either throw away, recycle, or compost what was left.
Composting was only an option for some of the elementary schools at this time, with pickups which occurred once a week by volunteers from the community. Recycling was picked up once a week in every school. Trash for the landfill was picked up three times per week at each building. The first kaizen burst (the blue pointed icon) is labeled for when the student walked to the waste bins titled "Transportation" referring to the unnecessary distance traveled to reach the locations of certain waste bins. The next is at the point of disposal with a "Waste" label due to improper throwing away of trash or recycling and therefore materials sent to a landfill that could have been recycled. The last kaizen burst is located where there are trucks symbolizing the delivery of waste to its appropriate destination labeled "Emissions" referring to the emissions required to transport the waste to its disposal location when alternatives might provide less travel. The calculations for the volumes of the trays are shown in Table 2. Table 3 shows the tray contribution to trash by level for both weight and volume. Figure 13 and 14 show a graph of the tray contribution by weight and volume as a percentage of the trash, respectively. Based on weight, the high school lunch trays contributed to 42.910% of cafeteria trash. The middle school trays were 10.539% and the elementary schools were 20.756% of the trash weight. Based on volume, the high school trays made up to 6.915% of the trash, the middle school trays were 1.687% and the elementary school trays were 21.821% of the trash.  The research question associated with this LCA was: What are the effects of changing the material of the tray currently being used in the school in terms of the impact categories and expenses? The intended audience was the school district being studied but could also be an example for other schools to follow. In addition, the LCA was designed for locations in the United States alone as this was where all data was retrieved.
As for the functional unit, this assessment had a functional unit of one tray.
This is in terms of one reusable tray that is washed in a dishwasher, one compostable tray sent to a composting plant, one compostable tray sent to a landfill, and one disposable paper boat sent to a landfill. These are considered the four main systems of the LCA study. The reason for the types of trays chosen is because of what was being used in the schools. The elementary schools served lunch on compostable trays, whereas the middle schools and high schools served lunch on disposable paper boats.
The high school also served lunch on styrofoam plates which were not included in the LCA portion of the study. As for the two versions of a compostable tray, at the time of the study, the trays were disposed of in the trash and sent to the landfill, however there were options being investigated for composting these trays. Therefore, an LCA was completed considering all possible outcomes.
After speaking with various members of the school district, it was apparent that the majority believed disposable trays would have the most harmful environmental impact but were unsure whether reusable or compostable trays was the best choice in terms of the environment. For these reasons, all tray types were tested to determine the outcome. Along with this, the school district needed to be able to afford any changes made so a cost analysis on these trays was also completed in section 4.3. The impact categories are shown in Table 4, Listing the Life Cycle Inventory Analysis (LCIA) databases used, impact category, unit and unit description for each category as well as the source of the data which was derived from Umberto ("Umberto NXT LCA",2016).

Inventory Analysis
For all systems studied, reusable trays, compostable trays, and disposable paper boats, the flowchart shown in Figure 15 displays the simplified process from "cradle" to "grave" (or start to end) of the life of the products. The functional unit for each system is listed in Table 5 along with the dimensions and weight. The weight was used in the LCA throughout the models in Umberto. The disposable and compostable trays were measured with a ruler and food scale and the data on the reusable tray was retrieved ("School Trays: Cambro"). The two scenarios for each system modeled in

Umberto were the Use to End-of-Life Phases and the Raw Materials to End-of-Life
Phases. The process, description, and source of these are shown in Tables 6 and 7, respectively. The source listed as "ecoinvent 3 v3" is pulled directly from the software and the created sources were made using materials created of the functional units with the weight data included (GmbH, 2016). The compostable tray system includes the two additional scenarios should the trays be sent to a landfill.

Impact Assessment
The impact results of the LCA for both scenarios of the use to end-of-life phases as well as the raw materials to end-of-life phases are displayed in Tables 8 and   9, respectively. In each table, the LCIA data source/group, category of impact assessment, results by system, and unit of impact category are listed. The four systems were listed as Disposable -disposable paper boats, Compostable -sent to a composting plant, Compostable (Landfilled) -sent to a landfill, and Reusable. Once the results were calculated, the carbon footprint of each system was determined for each scenario. Figure 24 shows the carbon footprint results of each system from use to end-of-life phases. Figure 25 shows the carbon footprint results for the same four systems, extended to show the raw material extraction to end-of-life phases. The reusable systems, in Tables 13 and 17, for all scenarios differ when determining the annual impact per category as the first year requires an initial purchase of the tray followed by smaller replacement purchases the years following.
To estimate the impact for this, the percentage of trays needing replacement was shown for ten percent, twenty percent, and thirty percent of the original purchase amount. Originally, the amount of thirty percent was given by the schools from the foodservice providers as their estimation of loss or theft. The ten and twenty percent replacement rates were also shown in the event that the schools would be able to reduce this. All of these were calculated by multiplying the original purchase amount (estimated number of functional units for the initial year) by the percentage. This number was then multiplied by the results per functional unit for each category.   In addition to the impact categories, the results for annual impact were also determined by carbon footprint in kilograms of carbon dioxide. Table 20 and Table 22 show the Reusable System based on the initial purchase (year 1) and all subsequent years, respectively, for all scenarios. The carbon footprint for the first year was calculated by multiplying the carbon footprint results per functional unit by the number of functional units needed in the first year (estimated by the number of trays purchased the year before as mentioned earlier). Table 21 and Table 23 show the annual carbon footprint calculations which were completed by multiplying the carbon footprint per functional unit by the estimated annual quantity. As done previously, the reusable trays display calculations based on a ten, twenty, and thirty percent annual replacement by multiplying the percentage by the number needed in the initial year and the carbon footprint per functional unit.   Finally, the high school tray expenses are shown in Table 39. An energy audit was completed, and the dishwasher information was incorporated into the analysis.
According to the schools and contracted food service provider, the high school would not require additional labor for the switch to reusable trays. The cost estimates for the disposable tray (the system in place) versus the compostable tray are shown in Table   40     After all the results were gathered, a future state map of the cafeteria process was completed, as shown in Figure 28      Another school had a built-in stand for the bins to be placed underneath, color coded for the students to use. The stand was not in use during the observation, however, due to its large height and the younger students having difficulty seeing above it, so a shorter version would be preferred. This was also an issue for the liquid drain stations at some of the schools where students drain excess liquids such as milk out of the cartons before recycling. Outside of the elementary schools, there were no other liquid drain stations observed; however, some locations allowed the draining to be done in the garbage bins. While this was a possibility, it was not often observed, and many recyclable containers were noticed to be thrown in the trash bins half full.
Another noted problem in some schools involved the placement of the trash and recycling bins. In Elementary School C, the lower grades had a trash bin that was moved from its location in the spaghetti diagram to the center in between the tables.
While this made it easier for these younger students to get to, the recycling bins were not being used at all for this lunch period. Every piece of waste was observed to be thrown into the trash, recyclable products included. As seen in the spaghetti diagram for Middle School B, there is only one recycling bin which is placed away from the entry and exit doors in the back of the cafeteria. This resulted in a great deal of recyclable items being thrown in the trash. Those that did use the recycling bin appeared to be sitting closer towards the back of the room near its location. As for the other schools, the spaghetti diagrams depicted an expected path that students would take during lunch and all of these aided in the development of the current state map.

CSM
As described earlier, the current state map (CSM) shows the process of the lunch trays being ordered and the cafeteria process during a lunch period. The first kaizen burst, transportation, was noted due to the problem with certain bin locations mentioned above. The trash bin located in the center of the tables or the recycling bin in the back of the room required students to travel much farther to reach the required bin which resulted in improper recycling or trash disposal due to inconvenience. The next kaizen burst, waste, is often used when resources are not being used properly or there is a decision being made that impacts the environment. In this case, the waste refers to the improper disposal of the trash, recycling, or compost that was occasionally noticed as well as the use of disposable trays and plates in the secondary schools when they could switch to more eco-friendly trays. Once the impact result for each system per functional unit of one tray was calculated, the projection of impact accumulated over ten years was created considering the number of trays that would be required for purchase every year. The purpose of this was to have a more accurate representation when comparing the systems with one another. For example, the impact appears to be high for the reusable system when comparing it with the other systems based on the impact of one tray, however, one must consider that these trays are purchased significantly less often than the other types of tray systems.
In both scenarios of Use to End-of-Life Phases and Raw Materials to End-of-Life Phases, the reusable tray with a ten percent replacement rate due to loss or theft had the lowest environmental impact results in every category. This was mainly due to the fact that it required the least amount of purchases of trays over the ten years. In addition, all impact results of the reusable trays for any of the three replacement rates showed a significantly lower impact than the other systems involving disposable or compostable trays.
For the Use to End-of-Life scenario, the disposable system had the highest impact for total human toxicity and ecotoxicity.

Dumpsters
When looking at the estimated amount of trash and recycling accumulated over the year in terms of the volume compared with the annual volume of dumpster pickups in (Table 49), the results show that for all cases, the cafeteria waste contributes to less than ten percent of total school waste. The trash accumulation in the cafeterias for every level was calculated to be under three percent of the annual dumpster volume and the recycling was under five percent. The total annual contribution of cafeteria waste to dumpsters was 2.698% for trash and 4.266% for recycling. While there are other factors that contribute to filling these dumpsters in the schools such as classroom waste, it is very possible that the schools were paying for more pick-ups than was necessary.

Future State
The future state map is similar to the current state map but with additions or slight changes with the goal of resolving the kaizen bursts. The bins are suggested to be repositioned closer to entry/exit points where there were previously no bins in place for some schools. For the elementary schools, suggestions were made to add new bin stands and liquid drain stations that would be easier for the students to reach. In addition, the coloration of the bins as well as the posters with familiar examples of trash/recycling/compost would assist the students in knowing the proper bin to use.
For all other schools, adding compost bins would be better for the environment and lower the amount of waste going into the trash which may save the schools money.
Also, if throwing liquid waste such as coffee or milk in the trash is acceptable, adding signage may assist or remind the students to do so and recycle more.

Alternative Case Scenario
The alternative case scenarios allowed for the possibility of a combination of the tray in place and the reusable trays without adding labor costs. Based on the results in Figures 27 and 29 This being said, the expense of making this change would increase to a minimum of almost two thousand dollars.

Environmental Perspective
One of the main reasons this study was completed with the school district was due to their high interest in lowering their impact on the environment. Some areas of improvement that were determined include updating the signage to better educate the students on proper waste handling as well as positioning the bins so that it is more convenient to not only dispose of trash but also to recycle or compost. Based on the life cycle assessment, reusable trays had the lowest environmental impact in all scenarios and therefore was the best option to cause the least amount of harm to the environment. In addition, switching to reusable trays would lower emissions caused by the delivery of waste to a disposal site as this would occur less often unlike the other options which was an issue pointed out in the current state map. After this, compostable trays would be the next best choice. That being said, this is only the case if the compostable trays are composted and not sent to a landfill. In many cases, the landfilled compostable trays resulted in a higher environmental impact than disposable trays. As for the alternative case scenarios of mixing reusable trays with the trays in place for the elementary and middle schools, in all cases, the environmental impact would be lowered in terms of the carbon footprint.

Cost Perspective
Based on the cost analysis, it was determined that making the switch to entirely reusable trays would be too costly of a decision for any school to make. This being said, if money could be raised or grants could be used towards the initial purchase of the trays and new dishwasher, the high school would be able to not only afford this option, but save money doing so. Compostable trays would end up costing the middle and high schools more money than the disposable options each year, however, this amount is significantly less than the reusable trays. Based on the dishwasher information, if the schools switched to the newer versions that were listed, the money saved could be put towards either reusable or compostable trays. As for the alternative case scenarios, if the elementary schools are able to add fifty reusable trays to each school, they would save money doing so.

Risks, Assumptions, & Final Thoughts
To complete this study, there were assumptions that were made in the calculations. One assumption was that the school year was considered to be 180 days.
Another assumption was that the weight and dimensions of the trash and recycling would be the same every day based on the measurements taken, which could have a great deal of variability. Also, the calculated volumes were completed based on the three-dimensional shapes that most resembled that object. For example, the compostable tray was rectangular, so a rectangular prism volume calculation was made. For the LCA, each tray included the use of the ecoinvent 3 database to assume the process of its life cycle, as shown in the inventory analysis.
Not every company or organization considers the environment to be a necessary concern and this school district's desire to improve made this study possible.
One area that is crucial to focus on is educating the students from the early ages into adulthood. This would continuously engage them in this subject to better understand the impact they have on the environment. In addition, the more they learn, the less likely they would be to make mistakes such as throwing trash in the recycling bin.

Future Work
Based on the results of this study, future work and recommendations have been made that can improve the school cafeterias' sustainability. In terms of the waste bins, it is recommended that every type of bin be positioned in more convenient locations based on the flow of traffic. Additionally, all schools should investigate adding compostable bins that do not yet have this in place, so the food is not going into the landfill and contributing to the volume and cost of trash. Based on the low volumes of cafeteria trash to the dumpsters, a trash audit should be completed daily for several weeks of normal school activity to see if these dumpsters are full three times per week.
This would allow the schools to determine if they could lower the amount of trash pickups occurring at each location which would save money.
As reusable trays would be the best option from an environmental perspective, a time study should be done to determine if the added labor hours required at each level is lower than estimated as this was one of the largest contributors to reusable tray expenses. It would also be beneficial to determine how many trays can fit within the loads that are currently being run. This way, the schools could at least have some number of reusable trays in place without requiring added labor. In terms of the reusable tray replacement rate of thirty percent provided by the schools and cafeteria suppliers, one suggestion that may be able to reduce this would be labelling the trays