Due to the complexity of the food chain–that is, its multistage, complex organizational structure–the process of rational food flow management represents a significant challenge. As a result of errors, the rise in the volume of goods available to purchase, and the extension of distribution and logistics channels, the scale of food loss and food waste (FLW) is increasing globally. At the agricultural production stage, losses may arise due to, e.g., overproduction or grading because of quality standards. In food production and distribution, losses may result from excess stock. At the stage of consumers, losses may occur due to, e.g., consumer preferences or the preparation of oversized meals [1
The aim of this study is to identify leading concepts in food waste management research through an academic literature search and bibliometric analysis that employed keyword co-occurrence analysis.
As Martin-Rios et al. [3
] indicated, food waste is an ecological, economic, and social problem. Reducing food waste plays an important role in global food security [4
]. Food waste has a high carbon, water, and ecological footprint. The economic impact of food losses and waste on the food system depends on the level: consumers and businesses that spend large portions of their budgets on foods that will not be consumed (micro level) reduce the financial resources available to be used for investment in other areas (macro level) [5
There are currently no universally accepted definitions of the terms “food loss” (FL) and “food waste” (FW), either applied in a European or national legal framework, or found in publications. As the FAO [6
] definition indicates, food loss is the decrease in the quantity or quality of food resulting from decisions and actions by food suppliers in the chain. On the other hand, food waste refers to the decrease in the quantity or quality of food resulting from decisions and actions by retailers, food service establishments, and consumers.
According to the project “Technology options for feeding 10 billion people—Options for Cutting Food Waste”, FL means food produced for human consumption that for various reasons falls out of the supply chain [7
]. The EU Fusions project group established at the European Commission only uses the term “waste”, which refers to both edible and non-edible parts of food, such as bones and husks [8
The High Level Panel of Experts (HLPE) defined FL as “A decrease in the food chain, excluding consumers, in the mass of food that was originally intended for human consumption, regardless of the cause”. HLPE defined FW as “food appropriate for human consumption being discarded or left to spoil at consumer level—regardless of the cause” [5
Given that the majority of the definitions of the terms “food loss” and “food waste” are similar and place an emphasis on reducing the amount of food intended for human consumption, this understanding of the term was adopted for this article.
The FAO estimated FLW at one-third of the total food produced [9
]. The European Commission estimated that between one-third and one-half of all food produced in the world is lost or wasted. Eurostat estimated, based on data provided by the EU-27, that in 2006 approximately 89 million tons of food waste were generated [10
Inefficient management of raw materials and food products, which leads to a given batch of food no longer being suitable for human consumption, is at the same time a waste of the human labor input previously invested in its production and an irreversible consumption of natural resources. It also incurs financial costs, which are estimated at about USD $
936 billion [11
]. In addition to quantitative losses, inefficient use of food poses a threat to the environment, causes excessive consumption of natural resources (land, water, fertilizers, energy) [12
], affects global warming, and thus constitutes a barrier to the sustainability of the food sector at a global scale. It is estimated that in developed countries the food system is responsible for 15–28% of total greenhouse gas emissions [13
] and methane, which has a global warming potential 25 times higher than carbon dioxide [14
According to Zhao et al. [15
], FW has been assigned a key role in achieving Goal 12.3 of the United Nations Environment Programme. Currently, the management of food waste is segmented, but a holistic approach is needed [15
]. According to Närvänen et al. [16
], the change is needed at three different levels: actors, systems, and sociocultural and institutional structures. As Lipinski et al. [17
] indicate, it also requires changes in technologies, practices, behavior, and policy. Fiore et al. [18
] suggest that interventions should be taken by policy makers and social marketers to influence consumers’ choices related to purchasing and consuming food, such as changing their planning and shopping routines. Fiore et al. [19
] note a lack of messages promoting sustainable consumption.
Analysis of the available literature regarding current research on food waste is an important source of information not only for scientists, but also for governmental organizations and policymakers. With such a data set, it is possible to identify research gaps and on this basis plan further actions and research.
Enterprises for which sustainable development has become an important element of building competitive advantage will look for solutions, both organizational and technological, that will allow them to reduce the burden on the environment and to use resources more efficiently. One element of sustainable development for enterprises in the food industry is sustainable production, which is disturbed by food losses and food waste.
The overall impact of these issues is to make food waste one of the most important global topics of concern, not only for organizations engaged in food markets and for food policy [20
], but also for scientists [21
The results of food waste management research have been presented in the form of a knowledge map [22
]. Mapping of knowledge domains (MKDs) and creating knowledge maps is an important research technique in bibliometrics. It provides a visual perspective for researchers and helps them to clearly understand the general situations of particular research fields and identify, e.g., new research trends [24
]. The data for the current analysis was provided by the Scopus database, which stores the largest amount of information meeting the selection criteria adopted in this study (these criteria are indicated in the Materials and Methods section). Next, a keyword analysis was performed using the VOSviewer software, in which analysis of bibliographic data with the clustering technique is possible (specifically, the VOSviewer clustering technique) [26
]. This allowed us to obtain a network of interactions and to identify six groups of terms (clusters) with interrelated keywords related to issues of food waste management. The main methods used in preparing this article consist of an overview of the academic literature (especially in the Scopus database) and network analysis. This procedure made it possible to identify leading research in the area of food waste management.
In this study, the following research hypotheses were adopted:
Hypothesis 1 (H1).
There has been a meaningful increase in scientific studies (as measured by the number of publications) that analyze issues of food waste in the management research literature.
Hypothesis 2 (H2).
Bibliometric analysis of keywords (selected in relation to issues of food waste management) allows determination of groups (clusters) of interrelated keywords.
Hypothesis 3 (H3).
Analysis of the indicators (i.e., occurrence ratio and total link strength) in particular groups (clusters) makes it possible to identify the leading research trend or trends in the area of food waste management research.
3. Results and Discussion
Research activity on FLW in management research was assessed by the number of publications. This allowed us to verify the H1 hypothesis that there has been a meaningful increase in scientific research (as measured by the number of publications) on issues of food waste management. By plotting the quantity of literature over time and conducting multivariate statistical analysis, one can understand the level of research and the future development trend in a certain field.
In the first stage of the research, the number of publications related to the terms “food loss” and “food waste” was analyzed (Figure 2
) in management research. The results regarding the occurrences of the term “food loss” in scientific publications in both databases used for the analysis show that these publications are few in number and did not exceed 50 per year, with a total number of 192 for the analyzed period in the Scopus database and only 73 in the WoS database. Moreover, the analysis of keyword groups of these publications indicates that the issues related to “food loss” are, in the majority of cases, analyzed in management research in relation to the term “food waste”. With this in mind, publications related to the topic of “food waste” + “management” were finally selected for the analysis of keyword co-occurrence.
The breakdown of the number of publications is presented in Figure 2
(second stage of research) shows that the number of publications related to the term “food waste” in “management” research (topic “food waste” + “management”) is similar in both databases, but generally more publications were collected in Scopus.
The quantity of documents relating to food waste management research has progressed through three stages—“initial”, “primary”, and “fast-growing”—which are explained below:
Initial stage (1991–2000)—from the first article regarding food waste management studies published in 1991 to the 2000s, there were few related research results in this field, and the maximum annual number of published papers was only 10 (Scopus database), which means a complete document system had not yet been formed. (The first publication indexed in the WoS database is Wilson and Huang [31
]. The first publication indexed in the Scopus database is Eckenfelder [32
Primary stage (2001–2013)—the number of documents in this stage started to rise meaningfully, with an average annual growth of eight articles. It can be considered that the research field of food waste management research was initially formed and growing systematically during this period.
Fast growing stage (2014–2019)—the number of publications grew annually by 40 articles on average. This indicates that work on food waste management research grew intensively and entered a phase of rapid development.
It can be seen in Figure 2
a that during the entire period under consideration, more articles on the topic of food waste management were indexed in the Scopus database. The H1 hypothesis was thus verified. Moreover, as a result of the initial investigation of databases and evaluation of the number of publications (a database was considered ineligible for this study if there was too low a number of aspects of interest to the authors), as well as the number of duplicated articles (the WoS database), the Scopus database was identified as representative. Therefore, the Scopus database was selected for further analysis (third stage of research).
In next (fourth) stage of research, the main areas of investigation related to the topic of food waste management research were identified. The analysis was concluded in relation to this criterion, which involved the number of scientific articles in the top ten subject areas.
It can be seen in Figure 3
(fourth stage of research) that the nature of food waste management research by subject area has been quite concentrated. Researchers have worked in fields such as Environmental Science (37.4%) and Energy (11.2%).
Interesting information is also provided by the observation of the spatial distribution of the study authors (by country). This indicates that the authors who have investigated issues of food waste management in their publications are most often from the United States (362 articles—16.4%), China (268 articles—12.2%), the United Kingdom (214 articles—9.7%), and Italy (138 articles—6.3%), which collectively represent almost 40% of the total number of all studies in this field.
Keyword co-occurrence analysis is used to analyze the link strength between the co-occurrence of keywords by studying the relation of their co-occurrence in a large number of documents (in this case, 2202 research papers from the Scopus database regarding management). Its main aim is to describe the internal relationship and structure, as well as to reveal the research fronts of a particular academic discipline. Research front here refers to, inter alia, basic problems, as well as the rise or unexpected emergence of theoretical trends and new topics. The results of the keyword co-occurrence analysis of food waste management research (sixth stage of research) with the VOSviewer software are shown in Figure 4
. Data selection and research procedures using the VOSviewer application were adapted from studies by van Eck and Waltman [26
], Gudanowska [25
], and Xin et al. [22
]. The analysis of the co-occurrence of keywords was performed with the use of VOSviewer software following van Eck and Waltman [26
] and Xin et al. [22
]. The analysis was based on the keywords provided by the authors of the publications. As Xin et al. [22
] indicate, the keywords are an important indicator in bibliometrics. Keyword co-occurrence analysis is based on the statistics of the number of times a pair of keywords is cited in the same document; 13,137 keywords were identified in the course of the analysis. To present a clear visualization, this paper focuses on those expressions that appeared at least 10 times in a group of selected publications (this limited the group of keywords to 891).
presents the resulting map (a whole map of co-occurrence keywords) and Figure 5
presents the resulting maps of clusters detected over time. In Figure 4
, it can be seen that the topics of food waste in management studies form six clusters. The map includes the most frequently occurring keywords. The size (height of the element on the map) of the nodes [26
] representing each of the keywords, as well as the font size in which the name of a given node is written, correspond to the frequency of the occurrence of a given term.
The distance between items in the visualization approximately indicates their relatedness in the co-occurrence network. The distance is understood as the interval between the nodes. In the distance-based approach, the nodes in a bibliometric network are positioned in such a way that the distance between two nodes approximately indicates the relatedness of the nodes [29
]. Items are understood as objects of interest (e.g., publications, researchers, keywords, authors [24
]). In general, the closer the two items are located to each other, the stronger their relatedness in terms of occurrence links in the analyzed group of publications [24
]. This allowed us to verify the H2 hypothesis that bibliometric analysis of keywords (selected in relation to issues of food waste management) allows determination of groups (clusters) of interrelated keywords.
Additionally, the resulting connection network is quite compact and is characterized by numerous connections in selected parts of the map (occurrence ratio—OR, and total link strength—TLS).
The top 10 keywords with the highest occurrence ratio (OR) and total link strength (TLS) are as follows: food waste (OR = 1293; TLS = 26,847), waste management (OR = 1180; TLS = 24,101), food (OR = 495; TLS = 13,706), anaerobic digestion (OR = 465; TLS = 12,000), waste disposal (OR = 418; TLS = 10,759), recycling (OR = 331; TLS = 7249), waste treatment (OR = 328; TLS = 8540), municipal solid waste (OR = 304; TLS = 6934), solid waste (OR = 302; TLS = 8377), and refuse disposal (OR = 294; TLS = 8933). Details on the main keywords and their characteristics by co-occurrence and total link strength related to this map are presented in the analysis of individual clusters.
Cluster 1 (red) shows keywords of coexistence (10 keywords with the highest number of occurrences) namely, food waste, waste management, waste disposal, recycling, municipal solid waste, human, solid waste management, anaerobiosis, landfill, sustainable development.
The first cluster classified in VOSviewer (Cluster 1, Figure 4
and Figure 5
; Table 1
) is a group of issues related to food waste, waste management, and sustainable development, among others. This cluster is the most numerous among all of those classified, due to the number of links and their strength. The leading keyword in Cluster 1 is food waste. As the depicted links indicate, the issue of food waste is primarily considered in the context of sustainable development. The leading group of studies concerns the analysis of food waste due to issues of waste management, especially disposal, storage, and recycling (e.g., Iacovidou et al. [33
], Paritosh et al. [34
]). The research focuses on the issues of municipal waste and solid waste management. Examples of this research are Peng et al. [35
], Ng et al. [36
]. The problems observed in Cluster 1 are reflected both in the latest scientific literature, as well as in economic and political recommendations. For example, solid waste management is one of the key services every city government must provide with widely variable service levels, costs, and environmental impacts. One researcher who emphasizes this is Parry [37
], who analyzed selected sustainable food waste management alternatives (economic, environmental, social, and operational impacts), e.g., de-centralized composting, for a hypothetical community of 100,000 residents. In turn, Edwards et al. [38
] proposed in their study a specific approach determining the efficiency of a system to turn waste into a valuable resource. On the map of trends, food waste is clearly shifted toward the center of the map, which indicates its numerous stronger connections with a large number of other issues. In this cluster, we can find few relatively new elements (see Figure 5
Due to the links between the keywords over time, the analysis of the cluster shows that the problem of food waste is considered in the context of its environmental impact (the link between elements is quite strong). This kind of research is presented by Edwards et al. [38
] and Koido et al. [39
]. The most recent research trends in this area chiefly concern analyses in the context of supply chain management, problems related to food loss, food waste management, and changes in consumer behavior and consumption behavior. Examples of this are Pellegrini et al. [40
], who analyze the factors affecting consumer food waste behavior at a household level, and Bhatti et al. [41
], who investigate the factors that affect young consumers’ food waste behavior in the context of a developing country. Importantly, the most recent research concerns analyses in the context of the circular economy (this is discussed, e.g., in the study by Loizia et al. [42
]). It can be said that food waste in management research (especially in supply chain management) in these areas is a new trend. This is confirmed by research by Zhao et al. [43
], in which the authors also point to value chain models to reduce food waste and forecasting food waste as an area of current research inquiries.
Cluster 2 (green) shows keywords of coexistence (10 keywords with the highest number of occurrences), namely, food, anaerobic digestion, methane, controlled study, procedures, nonhuman, bioreactors, environmental impact, sewage, bioreactor.
The second cluster classified in VOSviewer (Cluster 2, Figure 4
and Figure 5
, Table 2
) is a group of issues related to wastewater management in the anaerobic co-digestion context (digestion, fermentation, growth, metabolism, process, reactor, treatments, among others). The most frequent and the most interrelated components in the cluster were food and anaerobic digestion. These components were presented, for example, by Loizia et al. [42
], Nguyen et al. [44
], and Singlitico et al. [45
In this cluster, we can find relatively new elements (see Figure 5
). This may indicate that research on, e.g., food waste in the anaerobic co-digestion context is at a rapid growth stage (the link between elements is quite strong). This cluster, like the first, is relatively more numerous, due to the number of links and their strength, among all those classified. The leading keywords in Cluster 2 are food and anaerobic digestion. As the illustrated links indicate, these issues are considered primarily in the context of wastewater management. This issue has been studied, for example, in work by Maalouf and El-Fadel [46
]. This study explores the economic dimension of introducing a food waste disposer (FWD) policy in the context of its implications for solid waste and wastewater management. As the authors indicate [46
], the sensitivity analyses on processes with a wide range of costs showed an equivalent economic impact, thus emphasizing that the viability of an FWD policy although the variation in the cost of sludge management exhibited a meaningful impact on savings.
The leading group of studies concerns analyses related to anaerobic co-digestion, particularly the role of microbial methanogenic bacterium in pollutant removal. On the trend map, food waste is clearly shifted toward the center of the cluster, which indicates its numerous stronger connections with a large number of other issues. In this cluster, we can find few relatively new elements (see Figure 5
This is confirmed by the cluster analysis due to the links between the keywords over time (the link between elements is quite strong). The most recent research trends in this area chiefly concern analyses in the context of issues in wastewater management in relation to such topics as biofuels, methanogenesis, and pollutant removal (biodiesel, methanogenesis).
It can be said that food waste in management research (especially in wastewater management) in these areas is a new trend. Food waste is increasingly viewed as a resource that should be diverted from landfills. For example, Beckeret al. [47
] used life cycle assessment to compare co-management of food waste and domestic wastewater using an anaerobic membrane bioreactor versus conventional activated sludge and high-rate activated sludge with three disposal options for food waste: landfilling, anaerobic digestion, and composting.
Cluster 3 (blue) shows keywords of coexistence (10 keywords with the highest number of occurrences), namely, composting, anaerobic growth, chemical oxygen demand, incineration, chemistry, greenhouse gases, life cycle analysis, supply chains, waste incineration, land fill.
The third cluster (Cluster 3, Figure 4
and Figure 5
; Table 3
) is generally associated with the chemical processes related to composting, greenhouse gases, and waste incineration. This cluster is also relatively numerous, but in comparison to Clusters 1 and 2, it groups just over 100 keywords. The leading keywords in the third cluster are composting and issues concerning anaerobic processes (including co-digestion, fermentation, metabolism, and other anaerobic treatments). These issues are a continuation of the trends outlined in Cluster 2. As the depicted links indicate, the issue of composting is considered primarily in the context of municipal solid waste management. The leading research group also concerns analysis in the area of waste management, in particular, problems of waste disposal facilities, for example, Iacovidou et al. [33
]. The research focuses on the problems of municipal waste and solid waste management. On the trend map, municipal solid waste is clearly shifted toward the center of the cluster, which indicates its numerous stronger connections with a large number of other issues. In this cluster, we can find few relatively new elements (see Figure 5
Cluster analysis due to keyword linkages over time shows that the issue of municipal solid waste is considered in the context of its link to the greenhouse effect and electricity (the link between elements is quite strong). The keyword groups observed in this cluster develop the research areas indicated in the previous clusters, further elaborating these issues. For example, identification of the decisive factors for greenhouse gas emissions in comparative life cycle assessments of food waste management was made by Bernstad et al. [48
] and Bernstad et al. [49
It can be said that research in these areas presents a grounded stable trend, but municipal solid waste in the management research (especially the greenhouse effect) is a relatively new trend.
Cluster 4 (yellow) shows keywords of coexistence (10 keywords with the highest number of occurrences), namely, waste treatment, solid waste, refuse disposal, waste, biogas, organic waste, carbon, garbage, humans, wastes.
The fourth cluster classified (Cluster 4, Figure 4
and Figure 5
, Table 4
) is a group of issues associated with waste treatment in the context of solid waste, garbage (especially refuse disposal), biogas, organic waste, and carbonization processes, among others. This cluster is also relatively numerous, but in comparison to Clusters 1 and 2, it groups just over 100 keywords. The leading keyword in the fourth cluster is waste treatment. These issues are a continuation of the trends outlined in Clusters 2 and 3. On the trend map, the keywords “carbon” and “soil” are clearly shifted toward the center of the cluster, which indicates their numerous stronger connections with a large number of other issues. In this cluster, we can find relatively few new elements (see Figure 5
Cluster analysis of keyword linkages over time shows that the issue of municipal solid waste is considered in the context of its link to the carbonization process (the link between elements is quite strong). This trend is, for example, outlined in the studies by Eriksson et al. [50
] and Eriksson and Spångberg [51
] examining the carbon footprint and energy use of food waste management options for fresh fruit and vegetables in supermarkets, or in studies by Maaloufand El-Fadel [52
], who analyze the carbon footprint of integrated waste management systems with implications for food waste diversion into wastewater streams.
It can be said that carbonization issues (especially in waste treatment) represent a new research trend.
Cluster 5 (violet) shows keywords of coexistence (10 keywords with the highest number of occurrences) namely, animals, waste composition, chemical water pollutants, heating, consumption behavior, pollution, biological oxygen demand analysis, renewable energy resources, effluent treatment, emission.
The last two clusters classified are relatively low in number relative to Clusters 1–4. The topics taken up in the fifth cluster (Cluster 5, Figure 4
and Figure 5
; Table 5
) are focused on research regarding animals. The location of Cluster 5 is clearly shifted towards the center of the whole map of keyword co-occurrence, which indicates it having some quite strong connections with other issues of food waste. Additionally, from a food waste perspective, this research is at a rather early stage (Figure 5
). This research is presented by Shahariar and Rooney [53
]. Despite the numerically small group of keywords, their inclusion in the clustering technique indicates their close connection. The emergence of the issue of food waste in the research of animals is signaled by research of Salemdeebi et al. [54
], who conducted a comparative analysis of food waste management options in relation to the environmental and health impacts of using food waste as animal feed.
Cluster 6 (light blue) shows keywords of coexistence (10 keywords with the highest number of occurrences), namely, food processing, industrial waste, unclassified drug, meat, physical chemistry, developing world, waste to energy, volatile organic compound, resource recovery, natural resources management.
Finally, the sixth classified cluster (Cluster 6, Figure 4
and Figure 5
; Table 6
) is a group of issues associated with the general aspects of natural resources management, particularly in food processing, industrial waste, and waste in the energy context, among others. Cluster 6 is clearly shifted out of the center of the whole map of keywords co-occurrence, which indicates it having some, albeit weaker, connections with other issues.
Analysis of changes in keyword linkages over time shows that the most recent research in the area of food waste regards food processing (especially in the fruit and vegetable industry). This research from the food waste management perspective is at a rather early stage (e.g., Martin-Rios et al. [3
], Otles et al. [55
], Ounsaneha et al. [56
], and Thamagasorn and Pharino [57
]). It can be said that research in these areas is a quite new trend.
Cluster trends identified in this cluster can be found, among others, in research by Kosseva [58
] regarding food waste management techniques and processing technologies, or by Garcia-Garcia et al. [59
], who describe a novel decision-support tool to enable food manufacturers to evaluate a range of waste management options and identify the most sustainable solution.
The bibliometric analysis of the co-occurrence of keywords in research on food waste in the management research indicates research gaps resulting from current trends in management science. This allowed us to verify the H3 hypothesis that analysis of the indicators (i.e., occurrence ratio and total link strength) in particular groups (clusters) makes it possible to identify the leading research trend or trends in food waste management research.