1. Introduction
According to Jakimiuk et al. [1], sustainable waste management (WM) is becoming more common worldwide. Universities and other Higher Education Institutions (HEIs) are advancing the “zero waste” approach, following or leading the trend in WM in cities and countries. Sustainable WM must also follow the United Nations Sustainable Development Goals 2030 (SDGs) and the three pillars of sustainability (environmental, economic and social aspects). Several SDGs are related to waste production and management practices. Directly related are SDG 11.6 “sustainable communities: management of municipal waste” and SDG 12.5 “responsible production and consumption: significantly reduce the generation of waste through activities of prevention, reduction, recycling and reuse” [2].
In this sense, HEIs can be considered “small cities” [3]. Sustainable campuses can make a major contribution to improving sustainability in partner cities, mitigating environmental impact and promoting healthy and sustainable lifestyles on campus [1]. People on campus, including students, see their teaching, learning and research opportunities strengthened through the creation of so-called living labs [4]. The campuses are thus an opportunity to learn, experience and consolidate real examples of a more sustainable and circular economy. According to Jakimiuk et al. [1], implementing a closed-loop WM system through the principles of reduce, reuse, recycle and recover (4R) is the essential basis for advancing circular economy models on campuses.
Amaral et al. [3] reviewed the implementation of sustainability actions and initiatives on university campuses. Scientific reports of sustainability initiatives in HEIs are scarce, as only 8% of HEIs in the United States of America (USA) and 3% over the world registered scientific or technical publications over the last decade [3]. Waste-related initiatives were also led by USA HEIs but appeared more evenly distributed, with examples in 22 countries and more than half of them in developing countries [3]. The total of 424 initiatives described by Amaral et al. [3] were distributed as follows: 28% energy, 27% buildings, 15% waste, 10% water, 9% bicycling and transportation, 6% green spaces and biodiversity and 5% others. Thus, decreasing total energy consumption and increasing the share of renewable energy on campus, together with the area of other building-related actions, present the greatest number and diversity in initiatives. The third area receiving attention was WM with a total of 64 initiatives [3]. Waste-related initiatives included 24 initiatives on waste separation for recycling and recycling campaigns, 9 on solid WM, 9 on the treatment of organic waste, 7 on sustainable purchasing, 6 on waste audits, 6 on waste-to-energy and, finally, 3 initiatives related to hazardous waste treatment.
As pointed out by Amaral et al. [3], several initiatives are interrelated, so a holistic and global approach is beneficial. An example is the use of native plants on campus, which contributes to CO2 capture, conservation of local biodiversity and saving irrigation water. Another example is the treatment of bio-waste from university canteens, which is used as a fertilizer for green spaces and vegetable gardens on the campus [4].
Casarejos et al. [5] described sustainability actions implemented in several United States HEIs. Ten among the forty identified actions corresponded to the operational field, which included the following one related to waste generation and management: “Measure and report the materials used and waste generated on the campus (paper, chemicals, packaging, organic matter, etc.) with the goal of use reduction, calling attention to any overly consumptive patterns of abuse, and diverting materials from landfills and incinerators, thereby conserving resources through recycling, repurposing and composting”.
Waste diversion is the most widely used concept in terms of WM improvement and means reducing the sending of waste to disposal (i.e., landfill and incineration or even littering). Another concept is zero waste (ZW), with a similar meaning to waste minimization. Both waste minimization and ZW goals should be achieved by preventing waste generation, reusing goods and preparing waste for recycling, which requires separation at source. The reuse, treatment and recovery of resources can be achieved on campus by the HEI itself or elsewhere by participating in municipal or local programs.
Sustainable waste initiatives have begun in some developed countries. For example, according to a review carried out by Anacio [6], the following achievements and objectives corresponded to several HEIs, mainly from the USA: (i) Waste diversion or recycling reached 53% at Harvard University, 33% at Boston University, 44% at Princeton University, 40% at Appalachian State University, 67% at Rutgers University and 25% at Arizona State University; (ii) waste reduction reached 34% at Princeton University and 70% at the Chinese University of Hong Kong. In terms of goals, Appalachian State University set a 90% waste diversion goal by 2022, while Harvard University’s waste reduction goal was 50%, and Princeton University’s was 40%. Arizona State University and Swansea University have also set ZW goals. Reuse and recycling dominate waste management initiatives. Six out of ten universities reviewed by Anacio [6] have implemented composting systems on campus, and three have water refill stations with the aim of reducing plastic bottle waste. Bahçelioğlu et al. [7] reported diversion rates ranging from 34% to 86% for higher-performing HEIs in the USA.
Characterizing, analyzing and understanding the composition of generated waste streams is a critical first step toward developing successful and effective WM and sustainability strategies across university campuses [8,9,10,11,12]. However, studies at universities are very limited compared with similar research at the urban level [3,12). In some cases, only information received from waste management contractors is available, with global data by flow but without the characterization by type of material for each flow collected [13].
The aim of this study is to review waste generation rates, waste composition and WM practices in HEIs around the world, reporting on current management practices, waste diversion initiatives and ZW approaches in both developed countries and developing countries. This article is structured as follows: First, in Section 2, the methodology used in the literature search and the process followed for its analysis are presented. Next, in Section 3, some waste characterization concepts and approaches used by the reviewing authors to determine waste generation rates, waste composition and classification on recyclability and recovery potential are briefly described. In Section 4 and Section 5, the results obtained for waste generation rates and their composition are presented and discussed, including their statistical variability, according to the quantitative data of a set of 48 studies. Section 6 describes good practices for waste prevention in HEIs, as well as waste minimization methodologies and zero-waste programs. Section 7 deals with waste separation models at source and the factors that influence the behavior of the HEI community in waste separation. Finally, the conclusions of the review are summarized in Section 8.
2. Literature Search and Analysis
The literature review was carried out focusing exclusively on scientific documents collected by searching the Scopus database on the following topics for campuses and HEIs: (i) waste generation and composition (WG&C), (ii) composting, (iii) food waste (FW) and (iv) edible food waste (EFW). The keywords used and the results in the number of articles are shown in Figure 1. A total of 293 publications were retrieved, of which the majority were journal articles. Only 5.1% of the articles corresponded to the period 1977–2003, while 30.0% came from the period 2004–2016, and the remaining 64.8% came from the period 2017–2023 and the first two months of 2024. This distribution is representative of the recent attention given to WM in HEIs. First, attention was paid to the composting of organic waste on campus, which was also the subject of more reports in any time period, with the following distribution of the total number of articles: 62 WG&C, 145 composting, 68 FW and 18 EFW. These articles also included the topics of ZW and waste minimization strategies, which are addressed in this review. Some of the most recent articles included the topics of circular economy and carbon footprints in relation to WM, although these topics are not addressed in the present review in terms of specific content.
For the selection of the articles finally included in the review, the list of articles obtained in the “Composting search” (Figure 1) was limited to those from 2014 and later years (97 articles), keeping the full list for the other topics. Screening was then carried out based on the content of the abstracts, discarding all those that did not have a clear relationship to the specified content. For example, those articles that used waste obtained on campus, usually as a source of food waste, for studies with a purpose other than WM on campus or in the university center were discarded. As a result, a total of 104 different articles remained. After analyzing the content of interest in this set of articles, their classification by their main topics was as follows: 63 WG&C (48 of them with quantitative data on per capita waste generation rate and/or waste composition), 16 composting, 18 FW and 7 EFW. Furthermore, several of these articles (n = 11) also addressed circular economy approaches. Their geographical distribution covered all continents. Considering the 48 articles with quantitative data, their distribution by geographical area was as follows: Central, East and South Asia (16 articles), Middle East (8), Africa (9), South and Central America (6), North America (5), Europe (3) and Oceania (1). Thus, developing countries were well represented, bringing together many of the quantitative studies on waste generation and composition, but there were also numerous studies carried out in developed countries.
An Excel file was created with an entry for each article’s data regarding the year of publication, size of the university community, daily amount of waste generated, per capita generation rate, composition in terms of principal components and potential for diversion of disposal through recycling and composting. If it was not expressly stated in the article, the percentage of waste for disposal was obtained as the difference between 100 and the sum of the percentages of composting plus recycling. When necessary, annual waste generation data were transformed into daily generation rates, considering 240 school days per year.
Regarding the waste generation data per capita, two alternative expressions were used, depending on whether the figure referred to (i) potential people (i.e., the size of the community of a HEI, campus or center) or (ii) the actual number of users counted or estimated (i.e., the number of people who actually use a service or facility during a defined time). The expressions used are (i) kg/d·person (or kg/d·student if the community refers only to students) and (ii) kg/d·user, respectively.
In relation to waste composition, when information was available, the content of the following materials was recorded: paper and cardboard (P&C), plastics, metals, glass, organic and food waste (O&FW), hazardous waste (HW), waste from electrical and electronic equipment (WEEE), yard and wood waste (Y&WW) and other types of materials (Other W). The last category, also defined as miscellaneous, may have included quantities of some of the other categories when separate data were not available in the study to consider. This occurred particularly for the less frequent materials.
Statistical analysis was performed using Excel statistical tools to obtain descriptors such as the mean and median, among others. Simple regression and one-way analysis of variance were also used. The coefficient of determination (R2) and probability (p) were used to assess the adequacy of the least-squares fit. Box and whisker plots were generated to analyze the statistical variability of the data. In these plots, the box includes values between the first (Q1) and third (Q3) quartiles, while the lower whisker corresponds to the value of Q1 minus 1.5 of the interquartile range (box width) and the upper whisker to the value of Q3 plus 1.5 of the box width. Although the whisker defines the statistical minimum and maximum, outliers may appear outside this limit.
3. Waste Characterization Concepts and Approaches
Several methods have been used to determine waste generation rates and waste composition, which can be performed in the same or different sampling operations. General municipal solid waste characterization methods include two major categories: (i) material flow and (ii) site-specific approaches [14]. The first one estimates the amount and composition of waste based on national production data. Consumption rates and waste generation factors have also been used to estimate the flow of materials and waste generation [13]. This approach has application for large geographical areas, such as the whole country or a region, having little utility in the case of HEI campuses. On the other hand, the site-specific approach involves sampling, sorting and measuring the respective components of a local waste stream. In this case, the sampling can be directed at the source or carried out on the load of vehicles that transport the waste. Vehicle load sampling is not always applicable, particularly if the same vehicle and route collects waste from several sources that must be differentiated. On the other hand, direct sampling at source implies the characterization of solid waste directly at the points of generation, allowing us to differentiate areas of the campus with very different generation rates and waste composition. Thus, direct sampling at source was the most used method, although, on some occasions, reference is also made to vehicle load sampling. Direct sampling at source allows the determination of weekly, seasonal and spatial variations in generation rates and composition, although this is labor intensive.
As an example, waste samples were collected from different locations and sources on the campus of the Imam Abdulrahman Bin Faisal University in Saudi Arabia, such as university buildings (mainly faculty classrooms and staff offices), administrative buildings and service buildings (e.g., the main library, photocopy center and canteen) at least once a week for a full academic term (January to May) [15]. In other cases, waste was sampled one or more discrete times, and the data obtained were extrapolated to obtain average daily and annual rates of generation and composition. The sampling campaigns must represent at least the ordinary period of activity or incorporate non-teaching periods.
Merchán-Sanmartin et al. [16] stated that there are successful examples in terms of waste characterization and waste reduction actions and cited the Universitat Jaume I in Spain, the University of Brasilia in Brazil, the Autonomous University of Baja California in Mexico, Harvard University in the USA, the Catholic University of Chile and the universities of British Columbia and Northern British Columbia in Canada. A minimum amount of waste (e.g., 100 kg of waste [12,17]) or a minimum period of generation time can be established as a reference in sampling campaigns [18,19]. Sampling points should cover different sources of generation. Composition studies proceed by identifying, separating and weighing the materials pertaining to different fractions, for example, food waste, plastic packaging, plastic bottles, paper, aluminum cans, other plastic packaging, tissue, construction waste, etc. [17,18]. However, the procedures and types of waste considered generally vary from study to study. Chemical waste is often the subject of separate management plans and programs. The total generation rate can be obtained without fractioning the materials. Data obtained from sampling campaigns are often completed with data from other sources, such as private waste contractors, municipal waste services, recycling operators and internal data on resource consumption, such as paper products [19].
Lim et al. [20] defined residual waste as non-recyclable waste, including tissue, diapers, sanitary waste, swept dust and contaminated components. On the other hand, food waste includes material from the processing, storage, preparation, cooking, handling or consumption of food. The recycling potential of waste varies depending not only on composition but also on local conditions. For example, the following three-level classification was established for the University of Lagos, Nigeria [21] and Mersin University, Turkey [22]:
1 =. Recyclables: waste with an existing recycling market, including metals, polythene bags, paper and plastic;
2 =. Potentially recyclables: recyclables with no existing market, including organic waste, e-waste, glass and leather;
3 =. Non-recyclable waste: sanitary waste, inert waste and others.
A different classification was used by Zhang et al. [23], who defined class 1 based on the existing local market and included in class 2 waste for which there is no local recycling market, but there is somewhere else in the country (China), while in the category of non-recyclable waste, they included materials such as plastic packaging bags, disposable plastic bags and food bags, as well as animal carcasses, which in other countries can be considered recyclable or compostable. Maçin et al. [24] defined organic waste, e-waste and textile waste as potentially recyclables since they have the potential to be recycled on the campus of the Istanbul Technical University but were currently not recycled. However, they included paper towels in the non-recyclable category. In this line, Al-Shatnawi et al. [25] reported waxed cardboard in the form of plates, hot drink cups and food containers as one of the main contributors to non-recyclable paper and cardboard waste.
The accounting of spatial effects made it possible to reduce the variation in the calculated waste generation rates, while the per user generation data decreased the daily variation and allowed extrapolation over time and space [26]. Regarding residential waste, spatial differences in the composition of waste streams were due to differences in the age of resident students and habits, such as meal plans and social patterns, and the presence of kitchens in residence buildings [9]. The presence of canteens and commercial areas is another factor that varies both the generation rates and the composition of waste in the campus space. Due to this variability, designing an efficient WM program requires an understanding of the mechanisms and behaviors responsible for waste generation.
4. Waste Generation Rates
The total number of articles with waste amounts and composition data included in the review was 48. However, for each individual parameter, the total number of data is somewhat lower, with 42 for per capita generation and 43–45 for the main components of waste (paper, plastic, organic and others). Full information about this database is available in the Supplementary Information (Tables S1 and S2). Most of the reviewed HEIs or HEI campuses have a population of between 5000 and 20,000 people, with an average of 16,717 people because of a few large cases (Figure 2). Thus, the reviewed data are representative of small and medium HEIs around the world.
The per capita waste generation rate ranged mainly between 0.045 and 0.293 kg/d·person (these are the values for the first and third quartiles, Q1 and Q3, respectively; Figure 2). Most HEIs reported low waste generation rates, as the median was 0.093 kg/d·person. However, the average value was higher, reaching 0.192 kg/d·person, due to some cases with very high generation rates. Total amounts of waste generated on campus ranged mainly between 373 (Q1) and 3457 (Q3) kg/d, within the complete range of 96 to 14,320 kg/d (Figure 2, excluding the outlier value of 32,000 kg/d corresponding to Lagos University (Table S1)).
The net amount of waste generated depended, to a greater extent, on the per capita generation rate (R2 = 0.380, n = 38) than on the size of the campus population (R2 = 0.294, n = 36), but it is clear that both factors affected it (p < 0.01). This suggests the existence of a certain minimization potential through the reduction of per capita generation. However, it should be considered that certain specific characteristics of each campus can play a determining role. This is the case, for example, in the existence of residences on campus and their relative sizes or dining services, etc.
Owojori et al. [27] reported that most of the generated waste came from the residence area at the University of Venda, South Africa. Studying waste generation at a university dormitory in Shanghai, Pan et al. [28] attributed the preference for online shopping to the generation of large amounts of packaging materials, which became unseparated residual waste. The average waste generation in the dormitory was 0.275 kg/d·user. Residual waste accounted for 64% of the total, followed by food waste (29%) and recyclables (7%). Restaurants and/or cafeterias also contributed significantly to the generation of waste, ranging from 21% to 50.4% of the total waste [19,29,30].
On the other hand, the total generation of waste, along with its composition, determines the quantities generated by each type of material, which can condition the viability of certain management options. For example, the amount of organic and food waste (O&FW) varied between 109 (Q1) and 1100 (Q3) kg/d per campus, with a median value of 329 kg/d. Although the amount of O&FW generated on a given campus does not affect the viability of aerobic composting on campus [4], the opposite may be true for anaerobic digestion or biorefinery options.
The per capita waste production on campus was lower than their country rates due to the limited presence in time and activities on the campus of most of the HEI population. Beyond this consideration, waste generation in HEIs has a different tendency than municipal waste and may not be directly explained by the income level [24]. However, Zhang et al. [23] concluded that annual gross domestic product per capita growth in recent years is an important factor influencing the increase in food waste on a university campus, whether in a low-income country or a high-income country.
Casarejos et al. [5] reported waste generation from a statistically representative sample of HEIs in the USA (n = 23), including private and public institutions, as well as distribution by country zones and HEI size. Waste generation for the entire sample reached an average of 1.22 kg per student and day (considering 240 teaching days per year). HEIs under public institutional control exhibited a lower per capita waste generation (1.02 kg/d·student) when compared with private institutions (1.81 kg/d·student). On the other hand, per capita waste generation was lower for medium- (0.52 kg/d·student) and small- (0.44 kg/d·student) sized HEIs than for large HEIs (1.34 kg/d·student). However, it should be noted that the per capita generation rates obtained from Casarejos et al. [5] for USA HEIs, as also reported by Bahçelioğlu et al. [7], are approximately an order of magnitude higher than the global median found in our literature review. On the other hand, lower values were indicated for Ibero-American universities [16].
5. Waste Composition
The total number of articles reviewed with waste composition data was 46 (Table S2). The results obtained for composition by type of material are shown in Figure 3. In general, these works detailed the waste content in various materials, mainly in P&C (n = 44), plastics (n = 44), metals (n = 34), glass (n = 34), O&FW (n = 45), HW (n = 9), WEEE (n = 14), Y&WW (n = 21) and Other W (n = 43).
HW was not the focus of most of the articles, which dealt with waste similar to municipal solid waste; however, the available data were included in this review. This is probably due to the differentiated character of hazardous chemical and biological waste and the fact that they follow differentiated and highly regulated management and treatment procedures. On the other hand, according to Stephan et al. [13], hazardous waste generated in university activities may have little potential to be considered in circular economy programs.
The reason for not differentiating the generation of WEEE in many studies does not appear specified. However, an increase over time can be observed in the percentage of studies that pay attention to the generation of WEEE. This went from 24% in the case of studies prior to 2018 (n = 21) to 33% in the last 5 years (n = 27). However, several recent studies (n = 4) have indicated zero generation of this type of waste. A different situation may be considered regarding yard waste because some campuses may not generate this type of waste. In other cases, waste generated by gardening services was managed by the service contractor and was not the subject of campus waste studies. On some occasions, garden waste could have been included in the O&FW category, with both organic and food waste considered biodegradable wet waste.
O&FW constituted the waste fraction that contributed the largest amount to the waste generated, reaching 30.1% on average (median 32.4%). The next materials in terms of quantity were P&C, with mean–median values of 23.1–26.6%, and plastics, with mean–median values of 17.9–17.5% (Figure 3). These three types of materials represented more than 70% of the waste generated in the HEIs. The minority material components differentiated in the studies were glass and metals, with mean and median values of approximately 3% each.
Figure 4 shows the statistical variability of the data on the percentage of different materials in the HEI waste. A large variation was observed between the HEIs in the percentage content of the main materials in the total waste (Figure 4). This also implies a large variation in the per capita generation rate of these materials (as can be obtained from Tables S1 and S2). The mean values of the percentage content were slightly above the median, in general, except in HW, glass and other waste, in which the differences were greater.
P&C waste ranged between 3.7% and 56.0% of the total waste generated on HEI campuses (Figure 4), while most of the data was in the range of 13% to 31% (Q1–Q3 intervals). Until recently, paper was considered the most specific material for education and research activities in HEIs, as well as for administrative tasks. As such, it has received early attention for separate collection and recycling, as well as prevention measures. However, neither the percentage of P&C of the total waste nor the per capita generation of P&C showed a significant correlation over time (R2 < 0.03). This could be because most of the articles reviewed correspond to a short period of time (the period of 2015–2023, with 34 data items out of 44, while only the remaining 10 data items correspond to the period 2000–2014).
A large variability in O&FW content in the total waste was also observed (Figure 4). The O&FW content ranged from 4.1% to 66.5%, with most data in the range of 17–41% (Q1–Q3 intervals). It was considered that O&FW are generated mainly in food service zones as well as in residences or dormitories. In this way, Lim et al. [20] found that food waste was 6.7% in the academic zone, 15.6% in the laboratory zone and 83.4% in the cafeteria zone of the total waste generated in each zone. However, the generation of food waste is more widespread, extending to all areas and centers of the campus. Felder et al. [26] reported that 21% of the total compostable waste on campus was generated in the offices, where food waste reached 41% of the total waste generated in those areas. Mbama et al. [31] reported that organic waste was a major component of waste in all areas of the University of Lagos, but the commercial area had the highest proportion (45%), followed by administrative (35%) and residential (36%) areas. Ugwu et al. [32] reported 34.3% organic waste, on average, at the Nsukka Campus of the University of Nigeria, while in academic and administrative areas, this was reduced to 13.5%. The presence of food leftover in management and education areas still reached 12 to 18% in the University of Venda, South Africa [27], while a higher organic content was found in residences and food service areas. Torrijos et al. [33] reported that the presence of bio-waste in the academic and administrative areas of the centers of the University of A Coruña has increased over time, going from 9.0% of the total waste in 2011 to 33.3% in 2021. Thus, these authors considered that the separate collection of O&FW should not be limited to canteens but should be extended to general areas of the centers.
Plastic was the third highest material present in the waste in terms of percentages. The plastic content ranged from 1.5% to 41.9%, with most data in the range of 10–24% (Q1–Q3 intervals). When data were available, we included all types of plastic materials in the plastic category, whether considered recyclable or not. Plastic waste is one of the most critical environmental problems [34]. Considering evolution over time, plastic waste was the only material for which a correlation was found between the percentage of total waste and the date of publication of the data. Although weak, this correlation shows that the plastic content has increased over time (R2 = 0.13, n = 44, and p = 0.016). In fact, the average values of plastic materials in the waste were 11.7% (±4.0%) for the period 2001–2014 (n = 10) and 19.7% (±11.5%) for the period 2015–2023 (n = 34), which shows significant differences between both periods at a p < 0.05 level.
The Y&WW content in Figure 4 was higher than in Figure 3 because Figure 3 considers all HEIs with “zero” for the YWW content in the residues when the presence of these residues was not indicated or accounted for separately in the reference study. On the contrary, Y&WW in Figure 4 refers to the statistical data only of the set of HEIs with data on the generation of this type of material (n = 21). With a variability similar to that of other materials (Figure 4), the Y&WW content in the total waste of the HEIs ranged between 0.7% and 45.0%, with most of the data in the range of 5–22% (Q1–Q3 intervals) and a mean value of 15.5% (median 11.8%). Usually, the Y&WW fraction corresponded mainly to garden waste, with wood waste being mentioned on rare occasions. Y&WW was considered biodegradable waste and recommended as a complementary material for composting processes.
Minor components of HEI waste, such as metals, HW and WEEE, showed less variability than the major components, with the exception of glass (Figure 4). Although the glass content in the generated waste showed limited mean and median values (3.1% and 2.0%, respectively), some HEIs reported higher percentages of glass waste that were in the range of 5 to 11% (Q4).
The variability in the percentage content of the majority of materials in waste was mainly due to the specific waste generation profiles of each HEI analyzed, which indicates that the mean or median values cannot be extrapolated. For example, as reported by Ramamoorthy et al. [35] for the Puducherry region in India, the garden waste generation rate was the highest in rural schools and lowest in urban schools in which land to support gardening practices was scarce. The relative size of residences and dining services on campus also determine the relative amounts of some types of waste. Therefore, specific characterization studies must be performed for a given HEI to determine waste composition and generation rates. The percentage of paper in generated waste and the rate of paper waste generation may also be affected by the unofficial sale of paper and other recyclable materials, as reported by Mbama et al. [31] for the University of Lagos. This practice was also present in other HEIs [21,23,32].
6. Waste Reduction and Waste Minimization Programs
Table 1 presents a summary of selected waste reduction programs and measures in selected HEIs, including general WM programs and prevention measures targeting specific product/waste categories. A university stakeholders’ commitment to prevention and sustainable WM policies requires effective communication, performance incentives, sustainable technology and feedback, including collaborative research work [21]. Separate collection at source of the O&FW fraction from the rest of the waste is considered a basic requirement for sustainable WM. Education is needed to stimulate the habit of proper food waste separation from the source, both for the operators of cafeteria centers and the users of residential apartments [21], as well as the whole community in general [33].
Next, this section describes measures to reduce the generation of various types of waste (paper, packaging, food waste, etc.) and examples of good practices recommended in HEIs around the world. It then moves on to the analysis and discussion of methodologies for the minimization of waste.
6.1. Main Measures to Reduce Paper and Packaging Waste
Promotion of the use of water dispensers in all campus centers, including cafeterias, commercial areas and academic areas, has been shown to be an important action to reduce the generation of plastic waste and indirect CO2 emissions [17,21,23,24,25,34]. Thousands of polythene bags or polyethylene terephthalate (PET) bottles are sold daily in a medium-sized or large university. Water dispensers also give access to water at a lower cost, so the sensitivity of students and staff to savings will encourage the adoption of this practice compared to the purchase of single-use containers. A 90% reduction in plastic waste from PET bottles after the adoption of sustainable drinking water solutions was reported by Saleem et al. [36]. Uehara and Ynacay-Nye [34] found that students would be willing to pay to install water bottle refill stations at their university and cover the project costs. The study indicated that 58.8% of students stated that they would be willing to use a refill system, saving 45,191 disposable plastic bottles and reducing 10.8 tons of related CO2 emissions every year. However, it has also been found that it may not be enough to have the option of a water dispenser. In Ireland, a tax of 53 euro cents on the consumption of drinks in plastic containers has reduced their use by 90%.
Adeniran et al. [21] stated that the low volume of paper waste disposed (15%) at the University of Lagos may be associated with the effort placed in establishing a paperless policy, both in administrative, research, and teaching and learning activities. Electronic and online procedures in general HEI activity clearly reduce the generation of printing paper waste [17,25,36]. Combining several measures, paper consumption was reduced by 50% between 2009 and 2013 at the Universiti Teknologi Malaysia [17]. Revising policies related to printing (e.g., adopting double-sided printing) also led to a considerable reduction in paper waste [36]. However, a large amount of paper and cardboard waste fraction corresponded to packaging that was affected by online procedures to a lesser extent. An increase in the generation of packaging was even detected due to online shopping [28].
Al-Shatnawi et al. [25] developed a list of solid WM practices based on the UI Green Metrics ranking indicator system to be applied at the University Al-Ahliyya Amman in Jordan. Among them, these practices include a fee for the use of disposable cups and plates, as well as the reduction of paper documents through digitization and double-sided printing, the introduction of water fountains on the university campus and reuse as a management strategy for books, computers and furniture. However, the authors recognize that UI Green Metrics works exclusively on the WM system, which does not fully comply with the concept of ZW. The latter would require working on the production system, which would allow waste to be reduced.
6.2. Food Waste Prevention and Management
Food waste generates about 8% of global greenhouse gas emissions and environmental impacts affecting SDG No. 1, 2, 6, 12 and 13 [39]. Identifying the specific causes of food waste and taking action to reduce it is urgent, which also involves promoting awareness in the campus community and achieving changes in the eating habits of students [40].
Aiming to analyze the State of the Art about actions to reduce food waste at universities, Leal Filho et al. [40] identified four priorities: (i) planning and awareness, (ii) food preparation and storage, (iii) services related to healthier food options, adequate portion sizes and personal behavior and (iv) direct food waste reuse and recycling. Minimizing waste from prepared edible food can be achieved through prevention or via reuse or redistribution of food to those in need (e.g., food banks) [15,41]. Recycling inedible and unavoidable food waste conserves energy and nutrients and can be implemented in various ways, such as through its use as animal feed [32,41,42] or to produce compost. However, carbon mitigation potential through FW recycling is insignificant compared to the reduction/prevention of FW at the food supply and consuming stage [43].
Studies on food waste generation and prevention were carried out recently at several HEIs [15,37,38]. Students identified the following potential factors to reduce food wastage on campus ordered by decreasing importance [38]: improving taste, improving food quality, tasting food before filling plate/purchasing, purchasing plated food (a la carte) instead of buffet and increasing cost. Food quality and a tiered cost system based on food quantity were identified as the main solutions to prevent food wastage. Abdelaal et al. [38] highlight the need for not only educating the consumer but also food providers, given that on campus, operators believed that full food display cabinets led to more sales, meaning that display waste was the most significant contributor to waste.
6.3. Zero-Waste Strategy at Istanbul Technical University
Maçin et al. [24] carried out a detailed study to determine the waste characterization and recycling potential of the Ayazağa campus of Istanbul Technical University (Turkey) before and after the implementation of a zero-WM strategy. The characterization of the waste differentiated the following materials: glass (transparent and colorful), aluminum cans, other metals, PET bottles, plastic bags, other plastics, electronic waste, cardboard paper, organic waste (raw), organic waste (cooked), textiles, inert waste, toilet paper/paper towels, “tetra pak” and other waste [24]. Furthermore, they divided the campus into four distinctive areas: (i) academic, (ii) administrative, (iii) dormitory and (iv) cafeteria. Per capita waste generation was lower in academic and administrative areas (0.011–0.140 kg/d·user) and higher in dormitories and cafeterias (0.083–0.190 kg/d·user).
The pilot study on ZW management included the following actions [24]: (i) continued education and training on ZW for students, academic and administrative staff and cleaning staff (2019–2022), including questionnaires to understand their willingness to contribute to new ZW management activities; (ii) implementation of almost 4000 new bins with ZW reminders/posters placed across campus, with blue and gray bins used to collect recyclable (packaging) and non-recyclable waste, respectively, while green glass waste bins were also placed on the first floor of each building; and (iii) carrying out field studies for the characterization of waste before (2019) and after (2022) the ZW management strategy.
No significant differences were found between the waste composition of blue and gray bins in 2019, indicating that staff and students were not complying with the university’s waste disposal policy at that time [24]. Meanwhile, the actual landfill diversion rate increased from 16.3 to 21.3 percent between 2019 and 2022, indicating little overall improvement. However, the quality of segregation at source clearly improved in some areas after the implementation of the ZW strategy. The blue containers increased the content of own materials (recyclables) from 67% to 82% in the academic areas and from 41% to 86% in the dormitories, while the presence of recyclables in the gray containers in these areas was reduced from 42% to 33–35%. On the other hand, the blue containers maintained a high quality of compliance in the cafeterias (with more than 97% of proper materials), and the newly implemented green containers for glass waste were filled with more than 90% of proper materials in administrative and dormitory areas.
The performance results were considered promising, and the authors [24] made the following suggestions toward the goal of ZW on campus: increase public participation and awareness as a general requirement, improve waste reduction by supporting green purchasing and other processes, such as e-learning and channels of electronic presentation or double-sided printing, improve reuse opportunities, place water-filling stations and establish policies to create clean waste flow since separation at source is one of the most critical stages for recycling.
6.4. Best Practices Recommended for Mid-Sized US Universities
Ebrahimi and North [44] reviewed best practices at several top-level and benchmark US universities to obtain recommendations for application to many medium-sized US universities with limited resources for WM. Examples of benchmark universities included Appalachian State University, Arizona State University and Michigan State University. Appalachian State University manages more than 3200 tons of waste annually through reuse, recycling, composting or landfilling. The per capita waste generation exceeded 0.71 kg/d·person. In 2012, this university committed to a zero-waste campus, with a goal of diverting 90% of waste from landfill by 2022. Arizona State University has achieved an estimated 31% diversion rate by implementing a commingled blue bin recycling program, while packaging has been reduced by 50% through the implementation of a sustainable purchasing policy. Michigan State University reduced waste by 10% in 2013, achieved a 57% diversion from landfill in 2014 and planned to reach a 70% waste diversion rate by 2017.
The conclusions obtained by Ebrahimi and North [44] and recommendations for medium-sized universities with limited resources include the following:
−. There is a direct correlation between monetary and personal investment in WM programs and waste diversion achievements;
−. However, there are several low-cost initiatives that can make a positive contribution to reducing waste generation;
−. Bins and advertisements are the main unavoidable investments;
−. Publish a WM plan with a timeline for becoming a zero-waste campus, establish clear timeframes for awareness and behavior change programs and provide infrastructure needs;
−. It is essential to start by signing a commitment to carry out environmental stewardship actions, especially sustainable purchasing policies;
−. All programs must be evaluated and updated regularly;
−. The entire campus community should be the target of behavior change campaigns;
−. Ensure that all stakeholders in WM, direct and indirect, are identified and involved;
−. Carry out comprehensive audits of waste regularly, involving the participation of students, which reduces monetary costs;
−. Adopt sustainable procurement policies, particularly in the food service sector.
It is worth noting that both the zero-waste strategy of Maçin et al. [24] and Ebrahimi and North’s [44] set of recommendations include the general steps of the PDCA (Plan, Do, Check and Act/Adjust) cycle identified by Fagnani et al. [18] in their proposal for “Cycle of continuous improvement”. However, in the application of the PDCA cycle strategy, systematic and sufficient attention to all steps is very important as it can influence the results. On the other hand, when attention is focused on best practices, there is a tendency to adopt some of them individually rather than the overall procedure, which puts overall efficiency at risk. Thus, the sustainable WM programs in the universities have obtained very different results depending on each case.
6.5. Methodologies for Waste Minimization
Zen et al. [17] formulated waste minimization in a framework of institutional sustainability that adopts the concept of a living lab, integrating campus operations, curriculum, learning by doing and research. This requires a participatory-based approach, involves the decentralization of WM and establishes knowledge co-production, co-implementation and effective monitoring. Combining a top-down and bottom-up approach is a necessary integrative process that must reach the entire organizational system of the HEI, which, being focused on the governance of people, can be carried out through a series of dialogues, implementation of measures, monitoring and re-assessment of the integration process. Sustainability action involves campus-wide co-management and participation, including shared responsibility for building institutional capacity, trust and social capital [17].
The organization of WM for waste minimization implies the participation of several structures, such as the green office, the green managers at the centers, the cleaner service, the campus community, and other internal (e.g., the sustainable energy management group, the directors of centers, etc.) and external (the collector and/or recycling company) stakeholders [17]. A WM group is a core stakeholder, including practitioners from management and members of the academic or researcher staff, acting as a group of experts for social, technological and economic issues of WM [17]. Waste minimization works on the integration process of the three basic communities on campus, that is, those related to research, teaching and learning, and campus operations. Among the basic initiatives, Zen et al. [17] highlighted saving paper and energy, recycling, sustainability in meetings, biodegradable packaging, and green e-waste, while a separate program dealt with organic waste from the canteen. The following complementary strategies and tools were identified [17]: written policies, implementation of procedures, formation of working groups, external sources of funding, student volunteers led by researchers, support from departments and communication platforms.
WM in HEIs is considered a complex task that requires multidisciplinary and experienced managers. For developing countries, Fagnani et al. [18] proposed a high-efficiency and low-cost methodology named the “Continuous Improvement Cycle” by the authors. This methodology was based on the experience acquired by the School of Civil Engineering, Architecture and Urban Design at UNICAMP (State University of Campinas, São Paulo, Brazil; [18]). The continuous improvement cycle proposed followed the classic PDCA cycle, also known as the Deming Cycle. The cycle steps were adapted as follows: The first step is the diagnosis of the situation. The second step consists of the development of the selective collection of all generated waste and the promotion of the first actions for people’s environmental awareness. The third step is the implementation of the program and measures, and the fourth step involves a critical assessment of the gathered data. The process must listen to the impressions and expectations of the community, while suggestions can be made, including dialogue and knowledge sharing between managers and other stakeholders, to start a new cycle. Periodic awareness campaigns with an attractive visual identity are needed to keep people involved.
Fagnani et al. [18] reported very good results for this continuous improvement cycle program. After the implementation of the first cycle of the program, a decrease of 22% in total waste generation was observed, as well as a 25% decrease in recyclable waste. The percentage of recyclable material in waste sent to disposal decreased from 60.0% to 23.2% before and after the implementation of the plan, decreasing further to 15.3% after the waste minimization awareness campaign.
Following the analyzed literature and incorporating the experience of the authors at the University of A Coruña, an integrative methodology was proposed for the sustainable management of waste in HEIs (Figure 5), which also took the PDCA cycle as a reference. The process requires the direction and management of a core unit, such as the green office or sustainability office, which incorporates the participation of stakeholders, including the university community. The process starts from an expert diagnosis, initially external to the improvement cycle, which can be global for the entire institution or partially limited to one or several centers or sectors of the institution. The latter is a frequent situation in many HEIs, and the applied methodology must take advantage of the experience gained in those partial spaces. Thus, it is possible that the first PDCA cycle reaches only a part of the HEI, with the ultimate goal of reaching the entire HEI. After diagnosis, the PDCA cycle begins (Plan, Do/Implement, Check/Study and Act/Adjust), according to the content indicated in Figure 5. The review of the results by stakeholders and managers and the approval of the new measures and actions (phase A) allow the core unit to rework the plan, starting a new cycle.
This proposal takes into account flexibility and potential adaptation to any situation, considering the diversity of sustainability approaches in HEIs and the type of highly participatory methodologies, including learning by doing, service learning and action research. These methodologies are particularly relevant in the phases Do and Check, including the participation of staff and students, in general, and of specific researchers, both through curricular actions and volunteering. In addition, from the core unit, the necessary basic and complementary actions will be carried out or contracted.
In addition to the role of the core unit, the participation of stakeholders is important in the Plan and Act phases. The approval of the waste management program can take place at different stages of the process and occur at different levels, such as the agreement to carry out a pilot project in a specific area or the implementation of the process in a center or area of the campus. However, we must not lose sight of the objective of the plan to reach the entire HEI and all types of waste; thus, it must be finally approved in the Plan phase by the highest authority in the institution (Figure 5). In addition to incorporating legal requirements (Plan phase) and non-conformity identification and addressing (Act and Plan phases), approval by the senior management/rector is a key milestone. Following the principles of environmental management systems, such as ISO 14001 [47] and the EMAS (Eco-Management and Audit Scheme), waste management decisions in HEIs should not be limited to the executive body (usually the green office) but must have explicit approval, authority and resources granted by senior management. This is of great importance for the effective and co-responsible participation and involvement of the stakeholders.
7. Waste Separation at Source
7.1. Need for Waste Separation at Source and Used Models
Separation at source is mandatory in many developed countries. For example, the European Union (EU) has agreed on the goal of recycling 65% of municipal waste by 2035, after it is collected separately at source by type of material [48]. With a percentage of 34%, bio-waste is the main component of urban waste in the EU. Similar rates were reported in the previous sections for HEI campus waste (Figure 3 and Figure 4). Recycling bio-waste is key to meeting the EU target of recycling 65% of municipal waste by 2035. The production of compost of sufficient quality for use in soils requires separate collection at the source of bio-waste and with a low level of impurities. Municipal bio-waste in the EU-28 comes from food waste at 60% and vegetable waste from gardens at 35%, leaving 5% from other sources. In 2017, 43% of urban bio-waste was collected separately, while the remaining 57% was lost from recycling as it was mixed with other materials. In addition, separate collection rates varied widely at between 10% and 80% depending on the country [48].
Regarding HEI campuses, there are situations in which the separation at source exceeds the average in the country, and there are cases of the opposite [33,49,50]. However, already at an early stage, universities were more likely to have composting programs than the cities in which they were located [51]. Providing source separation facilities right at the point of waste generation is one of the important points of waste minimization [17,24]. However, separation of waste at source is not currently practiced on many campuses. It can also happen that there is separation, but the waste is subsequently mixed due to the requirements of the evacuation and transport service [42].
Table 2 presents a summary of waste collection systems in various HEIs. Separate collection models are not always described in detail in the referred studies nor are the results obtained in terms of recovery rates and quality. In general, the model and number of containers for selective collection at source must be adapted to the recycling objectives, the legal requirements of WM in the country and the particularities of the area considered, including the level of awareness and willingness to participate of the campus community. Malakahmad et al. [52] proposed the separate collection of waste in three fractions in academic buildings: (1) all paper and cardboard in the first container, (2) all plastic, glass, tin cans, aluminum and any other metals (commingled recyclables) in the second container, and (3) food waste in the third container. A limited number of sets of three indoor recycling bins were also distributed in the first phase of the Universiti Teknologi Malaysia recycling program [17].
Limited access to recycling bins is often cited as a factor hindering participation in recycling [17,51,52], while the convenience of sorting facilities has been identified as a major factor favoring participation in recycling [53,54,55,56]. Although the results of a survey showed that 80% of students and staff expressed their interest in participating in recycling activities, only 53% practiced it, the main reason being the inadequacy or insufficiency of recycling bins [52]. Putting the recyclable items into the wrong recycling bins is an important issue, which may reflect a low level of awareness of pro-environmental behavior, which must be addressed through teaching and learning initiatives in the context of the living lab [17].
Table 2Summary of waste collection systems in several Higher Education Institutions (HEIs).
| Reference | HEI and Place | Separate Collection Model (SCS) | Main Results | Highlighted Actions |
|---|---|---|---|---|
| [52] | University Technology PETRONAS (academic buildings) | SCS with three fractions:
| Recyclable items in wrong bins. | Need for sufficient recycling bins. |
| [51] | University of Northern British Columbia | SCS poorly described: | No recycling policy. | More than 70% could have been diverted through waste reduction, recycling and composting. |
| [9] | Furman University (residential buildings) | SCS with three fractions b:
| Recycling rate: 25% current and 61% potential. | Need to understand the mechanisms and behaviors behind waste generation. |
| [18] | State University of Campinas (São Paulo, Brazil) | SCS with two fractions a:
| About 23% of improper material in both bins. | Need for awareness campaign. |
| [57] | University of Malaya | SCS including:
| Landfill diversion of 15% reached in 2017 | Promote stakeholder participation. |
| [33] | University of A Coruña (all center areas) | SCS with three fractions d:
| Correct content in bins > 85%. Total waste collected for recycling around 70%. | Organic fraction in the general areas of centers > 25%. |
| [24] | Istanbul Technical University (Ayazağa campus, Turkey) | SCS with two main fractions c:
| Good results in some campus areas. | Need for increased participation and awareness. |
P&C: Paper and cardboard. a Organic waste; 4.1% of total waste; considered non-recyclable. b Limited composting system for canteen food waste. c Glass waste bins and diverse fractions only at the main entrance of each building. d Organic matter, although defined as potentially recyclable, was intended to be the non-recyclable fraction. e Intelligent recycling center where university communities can send their source-separated recyclables and obtain various products in return.
Fagnani et al. [18] proposed the segregation of solid waste into recyclable and non-recyclable waste, i.e., only two streams, which was considered the best strategy under the local circumstances for a center of the State University of Campinas (São Paulo, Brazil). However, Fagnani et al. [18] also reported that non-recyclable waste represented 23.7% by weight of the content of the containers for recyclable waste, while the initial target was only 10%. On the other hand, the bins for non-recyclable solid waste contained 23.2% of recyclables. A waste minimization awareness campaign was required to improve these results [18].
At Furman University, students must sort recyclables into two categories: (1) mixed paper, including white and colored paper, newspaper and cardboard, and (2) commingled recyclables, including aluminum and two classes of plastics, while other plastics and glass are not included in the recovering program [9]. Furman University also has a successful on-campus composting program for pre-consumer vegetable waste, with the produced compost being used in the campus organic garden.
Zhang et al. [53] reported recycling rates of up to 72% of all waste generated at the University of Southampton (Southern England) using commingled recyclables collection where all dry recyclables were placed in a single container or bag. This system was considered more convenient than source-separated schemes in terms of the time and effort that people must devote to recycling.
The University of Malaya has developed a campaign since 2011 to achieve a zero-waste campus, including the living laboratory concept for waste characterization, food waste segregation, composting and anaerobic digestion processes and separate collection of used clothing, wood waste, electronic waste and other recyclables [57]. ZW objectives included achieving 15% landfill diversion by the year 2020, 30% by the year 2030 and 60% by the year 2040. The 15% landfill diversion was already reached in 2017, with 200 tons of recovered materials, including 60 tons of food waste, 50 tons of recyclables, 50 tons of wood, 20 tons of green waste and 20 tons of textiles. Yusoff [57] highlighted multi-stakeholder participation, support from top management and industrial collaboration as the key factors for the success of the model.
Smyth et al. [51] reported that WM at the University of Northern British Columbia (UNBC) was described by the absence of a formal recycling policy and the small number of recycling bins, which were poorly labeled and unevenly distributed on campus. Although 79% of the waste generated at the Universidad Iberoamericana (IBERO, Mexico DF) was recyclable, only 26% was recovered at that time [58]. Recycling included 100% of garden waste but only 1% of food waste, 21% of paper and 3% of beverage containers.
The income potentially attributable to the sale of recyclable materials or the recovered energy was estimated by several authors under the respective local conditions [22,59]. However, fluctuations in the recyclables market challenge recycling programs. This fact highlights the importance of local markets for recyclable waste as well as the commitment of recycling companies to support recycling programs by accepting materials recovered on campus [8,17,60].
7.2. Surveys: Understanding the Factors That Influence Waste Separation Behavior
The behavior of the university community regarding the separation of waste depends on several factors, which are essential to analyze and understand with the aim of improving WM [55]. Surveys through questionnaires were applied to the community to evaluate the reach of the environmental awareness programs. In addition to diagnostic responses, the questionnaires reinforced environmental awareness. As pointed out by Fagnani et al. [18], by conducting surveys, staff routines are broken to reflect for a few minutes on their environmental behavior. The importance of communication and information campaigns to encourage pro-environmental behavior was also highlighted by Uehara and Ynacay-Nye [34], who found a statistically significant increase in the willingness to pay for and use water bottle refill stations as they introduced more and more information about pro-environmental behaviors to students. In this way, surveys play an important role in various stages of the PDCA cycle, particularly in the Plan and Check stages (Figure 5).
Zhang et al. [48] conducted a survey at 10 university campuses in Beijing to collect information on students’ behavior regarding waste separation at source and its influencing factors. The results showed that 47% of university students mixed all waste materials at source, a figure much higher than that of their parents at home (27%). Regarding knowledge about proper waste separation, almost 90% of those surveyed can carry out a correct separation of food waste, but the ability to separate drug waste (76%), textile waste (73%), battery waste (69%) and electronic waste (54%) was much lower. The main influencing factors that make students more likely to actively participate in the separation of waste at source were the following: gender, with greater female participation than male participation; awareness of the consequences of damage caused by waste; better knowledge about proper waste classification; having friends around who separate waste at source; and improved perceptions of both the appropriateness of waste separation systems and university WM processes [48]. The results made it possible to formulate recommendations to improve the behavior of students regarding the separation of waste at source. A similar trend in relation to gender and knowledge was reported by Eskandari et al. [12]. Yang et al. [54] found that Chinese university students know how to identify and classify perishable organic waste but show difficulty in distinguishing recyclable and non-recyclable waste. The convenience of waste separation, ease of understanding of bin labels and the level of publicity and education about WM at the center were considered important factors.
This suggests that the source separation model should be as simple as possible, based on the compatibility of the components collected in the same collector (which can be easily separated at the destination and with high efficiency) and remain in time without being conditioned to variations in the stability of the recyclables market. Thus, as already noted, the separation between wet and putrescible organic waste (wet fraction) from the rest of the waste (dry fraction) becomes a determining factor. Since it is not easy to explain to people why some types of plastic are recyclable and others are not, which is also the case within other categories of materials, the existence or not of local markets for different products of the same type of material should not have a determining weight in the definition of the model, at least when there are facilities capable of separating compatible materials at the destination. This is the counterpoint to what was stated at the end of Section 7.1 in relation to the importance of local recycling markets, so it is necessary to reach a solution with the best compromise.
Along the same line, Zhou et al. [56] found that student behavior resulted from the combined effect of several factors, such as the convenience of sorting and recycling facilities and related advertising and education. Thus, it was considered necessary to strengthen the publicity of the knowledge of waste classification on campus to improve the willingness of students to actively participate. Colleges should keep the students informed of country policies and implement them on campus. However, Chinese campuses suffer from problems of individual conscience, living habits and recycling facilities, so waste separation on campuses will be a long-lasting battle [56].
On the other hand, Zhou et al. [56] emphasized the important role of university students as promoters of the separation of household waste. The authors address the contribution that sustainability on campus can bring to the home and city. However, it is necessary to motivate university students to participate in the separation of household waste and, above all, to encourage university students to transfer waste separation habits from campus to families and society. This would have a great effect on spreading waste collection throughout society.
Similar results for the factors that determine people’s participation in waste sorting were reported by Hu et al. [55], indicating that greater participation in the separation of waste at source by a group of international students can be mainly attributed to factors such as the environmental knowledge of individuals, clear community guidelines and the convenience of sorting facilities (or the degree of ease to separate the waste). Chao et al. [61] added, apart from motivation, interpersonal altruism and place attachment (i.e., the affective bond that people feel toward their place of residence) as factors that have significant positive effects on recycling behavior.
Dixon and Parker [50] investigated student perceptions of recycling to determine whether a university’s strategy helped or hindered student recycling behavior in residence halls. It was considered that student recycling rates were even lower than the average of 45.2% reached in the country, England. The results showed that students’ recycling behaviors were limited by a lack of perceived ability, lack of facilities and unconfident knowledge. The authors recommended a holistic approach that includes peer influence, education and information for improving attitudes and motivations, along with improving physical recycling structures.
8. Final Remarks and Conclusions
Sustainability researchers and managers are paying more and more attention to the management of waste generated on university campuses, with a strong increase in scientific articles being recorded in the last 6 years. The research carried out on this topic was formulated with very varied objectives and methodologies. Part of the research reviewed was carried out with the central aim of analyzing and providing the most advanced and sustainable waste management models for HEIs. However, other research has responded to needs more related to the functions of HEIs, such as research and teaching. Thus, some studies on campus waste are part of active learning methodologies, such as learning by doing, service learning and action research. In some cases, the campus, the center or the university community was considered a laboratory for research, the so-called living lab. The scientific relevance of the reviewed research focuses on the analysis of measures designed to promote environmentally friendly behaviors, with the aim of preventing the generation of waste and improving separation at source, as well as the development of on-site technologies and management models appropriate to the campus scale. The identification of campuses as small cities and the leading role that HEIs must have in solving problems such as the environmental crisis confers a high potential for the transfer of the results of that research to society. The present review can help launch and guide new studies and research in this field.
Early research attention was paid to the composting of organic waste on campus, as well as to the study of waste composition. In recent years, the issues of zero-waste and waste minimization strategies have gained attention, while consideration of the circular economy and carbon footprints in relation to waste management is incipient. While we consider it necessary to incorporate indicators of circularity and carbon footprints in the future relating to different aspects of campus sustainability, we must point out that waste management currently lacks these and other recognized indicators beyond the disposal deviation rate.
Characterizing and understanding the composition of generated waste streams is the first step to a successful and sustainable WM strategy on a university campus. This review gathered and analyzed the results of a total of 48 articles with quantitative data, either on the generation rates or the composition of the waste generated. The variability in waste generation rates (mean 0.19 ± 0.21 kg/d·person and median 0.093 kg/d·person) and composition (30 ± 19% organic waste, 23 ± 13% paper and cardboard, 18 ± 11% plastics, 3 ± 3% metals and 3 ± 3% glass, on average) was mainly due to the specific profiles of each HEI, indicating that the mean or median values cannot be extrapolated. For example, the per capita waste generation rate mainly ranged from 0.045 to 0.293 kg/d·person (quartiles Q1 and Q3, respectively), while the full statistical range of variation (excluding outliers) was from 0.013 to 0.59 kg/d·person, with the figures differentiated by a factor of 45. The specific characteristics of each campus, such as the existence of residences and dining services on campus and their relative sizes, play a determining role. However, the per capita generation rate is another factor to consider, suggesting distinctive waste minimization potential between campuses.
Waste separation at source is a general condition for the recovery and recycling of urban waste and is currently mandatory in many countries. On campuses, separate collection models are not always described in detail in the studies reviewed, nor are the results obtained in terms of recovery rates and quality of materials. Although the separation of the wet organic fraction should be at the basis of a comprehensive model for the recovery of all waste fractions, this is often not the case. In some cases, the models focus on specific fractions, such as paper and cardboard, some types of plastic or other types of waste, when there are local recycling markets for such fractions. Thus, local conditions also determine, to a large extent, the objectives pursued and the measures adopted. Figures for total recycling achieved are rarely given clearly in the studies. Figures of results in prevention and recycling, which are generally variable and often not updated, can be consulted on the websites of some HEIs, but there is a lack of impartial studies in this regard.
What is common to studies is that the quality of separate collections is determined in the end by the participation of the university community, which depends not only on the means put into play but also on environmental awareness and confidence in the institutional goals. Thus, analyzing and understanding the factors that influence waste separation behavior is critical to improving WM. With this objective, surveys are carried out through questionnaires to collect information on the behavior of the university community in relation to the separation of waste at source and its influencing factors. The convenience of waste separation, ease of understanding of waste separation rules and labels, and the level of publicity and education about WM at the center are important factors. Furthermore, progress in separate collection and recycling rates on campuses requires the persistence of specific practices over a long period of time. Finally, it should be noted that the success of university waste separation programs can translate into a greater diffusion of waste collection throughout society.
Sustainable waste management in HEIs is considered a complex and multidisciplinary activity, which requires experienced managers, stakeholder engagement, effective communication and collaborative research work. Regarding the separation of waste at source, waste prevention measures, such as green shopping, electronic learning and communication channels, double-sided printing, reuse opportunities, water-filling stations to avoid single-use packaging, prevention of wastage of food and food packaging waste, etc., also require community acceptance and participation. Waste minimization programs can be implemented within the framework of institutional sustainability and adopt the living lab concept that integrates campus operations, curriculum, learning by doing and action research, formulated as a continuous improvement cycle. The waste prevention methodology was reviewed and an integrative model of sustainable waste management in HEIs was formulated, which can be followed by both advanced and beginner HEIs. There is a great opportunity for HEIs with fewer resources to make progress in sustainability without incurring the costly programs and actions that some institutions have in place.
Conceptualization, M.-J.R.-G. and M.S.; methodology, M.S.; validation, M.-J.R.-G. and V.T.; investigation, M.-J.R.-G. and V.T.; data curation, M.-J.R.-G. and V.T.; writing—original draft preparation, M.-J.R.-G. and M.S.; writing—review and editing, M.-J.R.-G., V.T. and M.S.; supervision, M.S. All authors have read and agreed to the published version of the manuscript.
The original contributions presented in this study are included in the article/
The authors declare no conflicts of interest.
Footnotes
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Summary of selected waste reduction measures in Higher Education Institutions (HEIs).
| Reference | HEI | Reduction Measure | Results | Highlighted Actions |
|---|---|---|---|---|
| [ | Universiti Teknologi Malaysia | Waste minimization in the framework of the living lab concept, integrating campus operations, curriculum, learning by doing and research | Participants: green office, center green managers, cleaner service, campus community and internal and external stakeholders | The process contributed to sustainable consumption and behavioral changes in the campus society |
| [ | Universiti Teknologi Malaysia | Save paper campaign combining measures a | Paper consumption was reduced by 50% in 4 years | The economic dimension of reducing paper consumption |
| [ | State University of Campinas (School of Civil Engineering, Architecture and Urban Design, São Paulo, Brazil) | “Continuous Improvement Cycle” as a low-cost methodology for sustainable waste management | Waste generation was reduced by 22%. Recyclables in disposed waste reduced from 60.0% to 15.3% | Listen to the impressions and expectations of the community and stakeholders. |
| [ | Japanese university | Option of water bottle refill stations | Potential saving of 45,191 disposable plastic bottles | The study found that 58.8% of students were willing to pay to use the bottle refill stations |
| [ | Imam Abdulrahman Bin Faisal University (College of Engineering, Saudi Arabia) | Sustainable drinking water solution (reusable drinking containers instead of water bottles) | Reduction of PET bottle waste by 90% | Including drinking water purification and incentives for student participation |
| [ | University Al-Ahliyya Amman in Jordan | Combination of measures identified b | After reduction, paper and metal recycling had the greatest impact on sustainability | Zero-waste goal requires attention to the production system |
| [ | Several HEIs | Recent studies on the generation and prevention of food waste were carried out | Food quality and tiered cost system based on food quantity was identified as the main solutions to prevent food wastage | The potential for carbon mitigation by preventing food waste is much greater than recycling it |
a Sustainable meeting, monitoring paper consumption, avoiding unnecessary printing, encouraging double-sided printing, using different containers for reusable and recyclable paper next to the printing machine, etc. b Including fee for disposable cups and plates, digitization, double-sided printing, water fountains and reuse of books, computers and furniture.
Supplementary Materials
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References
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Abstract
This article reviews waste generation rates, waste composition and waste management practices in Higher Education Institutions (HEIs) around the world, reporting on current management practices, waste prevention and diversion initiatives, separate collection at source and zero-waste approaches. The average waste generation rate was 0.19 ± 0.21 kg/d·person (median 0.093 kg/d·person). On average, organic waste reached 30 ± 19% of total waste, followed by paper and cardboard (23 ± 13%) and plastics (18 ± 11%). Common minority material components included glass and metals, with 3 ± 3% each. Yard waste, hazardous waste and electronics were only reported for some cases. The applied methodologies for the minimization of waste and the valorization of resources for a more circular campus were discussed. Key measures to reduce paper, packaging and food waste were reviewed, as well as examples of recommended good practices. Waste management in HEIs is considered a complex task, which requires multidisciplinary and experienced managers, stakeholder engagement, effective communication and collaborative research work. Collection at source of the organic, wet fraction separated from the rest of the waste is considered a basic and imperative requirement, while the separate collection of other materials will depend on the particular case, but the participation and awareness of the entire HEI community appears to be essential. Prevention measures also require acceptance by the community. Following the analyzed literature, a methodology was proposed for the sustainable management of waste in HEIs, taking as a reference the PDCA cycle (Plan, Do, Check/Analyze and Act/Adjust).
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Neither ProQuest nor its licensors make any representations or warranties with respect to the translations. The translations are automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. PROQUEST AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the translations is subject to all use restrictions contained in your Electronic Products License Agreement and by using the translation functionality you agree to forgo any and all claims against ProQuest or its licensors for your use of the translation functionality and any output derived there from. Hide full disclaimer
Details
; Torrijos, Verónica 2 ; Soto, Manuel 3
1 Department of Chemistry, Polytechnic School of Engineering, Campus Esteiro, 15403 Ferrol, Galiza, Spain;
2 Sustainability Office (Former Office for the Environment), Ed. Xoana Capdevielle, Campus de Elviña, 15071 A Coruña, Galiza, Spain;
3 Department of Chemistry, Faculty of Sciences & CICA, University of A Coruña, 15071 A Coruña, Galiza, Spain