Comprehensive Utilization of Avocado in Biorefinery: A Bibliometric and Co-Occurrence Approach 2003–2023

Abstract

In recent years, the consumption of avocado, both fresh and processed, has experienced a significant worldwide increase due to its recognized nutritional value and beneficial health effects. However, this industrial processing generates a substantial amount of underutilized byproducts, primarily the peel and seed, leading to significant environmental and economic challenges. Fortunately, these residues are rich in bioactive phytochemicals, making their recovery an excellent opportunity to enhance the sustainability and profitability of the modern avocado industry. This bibliometric analysis utilizes data from the Scopus platform to explore the comprehensive utilization of avocado waste. By employing a biorefinery approach and computational tools, the study aims to identify and extract value-added compounds with potential applications in the food, pharmaceutical, chemical, and cosmetic industries. The results highlight that the most relevant research topics are currently focused on sustainable and comprehensive biotransformation of avocado byproducts. Additionally, there is a growing emphasis on methods for extracting valuable products, characterizing their properties, and identifying potentially exploitable active compounds. Furthermore, research is increasingly exploring the environmental and economic factors associated with new research advancements, such as emerging environmental regulations, certifications, substitutes, and technological applications. One key gap identified in recent research advancements is the lack of a sustainable diagnostic framework for avocado utilization processes in a cascade system (multiple high-value consumer products and by-products such as bioplastic). This suggests a crucial area for future research efforts.

1. Introduction

1.1. Generalities of Avocado

The avocado, belonging to the Persea genus and Lauraceae family, is native to Mesoamerica and distributed between 0 and 2200 m above sea level [1]. It is a drupe fruit, meaning it has an outer skin, inner pulp, and a seed (Figure 1). The size, shape, color, and phytochemical content of the avocado depend on its genotype. The avocado’s skin may be light green, dark green, purple, or black and its texture can be smooth, rough, glossy, or dull. The weight of the avocado may vary between 100 and 3000 g [2]. It is a tropical fruit whose consumption has experienced a dramatic increase, reaching approximately 8.7 million tons annually [3]. This surge is driven by its numerous nutritional benefits [4], including a high content of oil (12–30%) as well as carbohydrates, proteins, vitamins, and minerals [5,6]. Avocados have the highest lipophilic antioxidant capacity among fruits, which may contribute to attenuating lipid peroxidation in serum and promoting vascular health [7].

In addition to lipids or oils (approximately 40%), avocados contain unsaturated fatty acids (80%). These fatty acids include oleic acid, linoleic acid, linolenic acid, palmitic acid, stearic acid, capric acid, and myristic acid [8,9,10]. Four exclusive compounds called acetogenins (avocatins, hydroxy fatty acids, persins, and pahuatines) have been identified in avocados. These acetogenins are thought to be promoters of bacterial biofilms and neurotoxin inhibitors [11,12]. The active compounds in avocados, such as unsaturated fatty acids and acetogenins, are important for their health benefits. Unsaturated fatty acids help maintain normal blood cholesterol levels [13,14,15]. While acetogenins have been shown to have anticancer, anti-inflammatory, and antioxidant properties [16,17,18,19].

To date, three subspecies or horticultural races have been recognized: the Mexican race (Persea americana var. drymifolia), the Guatemalan race (Persea americana var. guatemalensis), and the Antillean race (Persea americana var. americana) [20]. The genetic diversity among these races has allowed, through hybridization and anthropogenic selection, the development of modern commercial varieties that have adapted to specific areas with high yields [21].

Avocados, native to central Mexico and Peru, are now cultivated in over 50 countries with tropical and subtropical climates worldwide. Mexico leads the way with 2.4 million metric tons annually, while the Dominican Republic boasts the highest yields per area at 43.7 metric tons per hectare [22]. In Colombia, production is estimated to be 544,933 metric tons annually, with an average yield of 9.77 metric tons per hectare, placing it fifth in volume of production worldwide [23]. The departments of Antioquia, Bolívar, Caldas, Huila, Quindío, Risaralda, Santander, Tolima, and Valle del Cauca contribute more than 80% of national production [24].

Avocado cultivation in Colombia is diverse [25]. Traditionally, the propagation of avocado plants for cultivation in Colombia is carried out by grafting commercial materials (‘Hass’, ‘Lorena’, ‘Choquette’, ‘Fuerte’, ‘Reed’, and ‘Trinidad’, among others) onto rootstocks produced from sexual seed (not grafted) of criollo and ‘Hass’ trees [26]. The seeds are obtained from local markets, which generally do not know the origin of the material, or from production areas located in contrasting agroecological regions without clear selection criteria.

In the department of Bolívar and the Montes de María region, agriculture prevails with an estimated annual production of 35,000 tons of avocados of the criollo-Antillean variety [27,28]. However, in recent years, a problem has been identified in the region that leads to root deterioration and rot, which causes tree death [29]. This problem is attributed to the presence of fungi, the poor condition of access roads, and the lack of strategies for commercialization, standardization, and the implementation of better production practices in the area [27,30].

Due to the above, knowledge about the various ways to industrially exploit avocados has increased. Avocado fruit or pulp can be used to obtain several products, mainly by extracting oil, which can be done using various methods, such as mechanical, thermomechanical, enzymatic, or solvent extraction [31,32]. In the process of extracting avocado oil, various solvents can be used, such as hexane, ethanol, chloroform, ethyl acetate, supercritical fluids, among others, each with different oil extraction percentages and process conditions [33,34,35]. In addition, fruit and vegetable processing industries face the daily challenge of managing large quantities of agro-industrial waste and the negative effects associated with their improper handling. It is estimated that the industrial processing of avocados generates 2.42 million tonnes of by-products, mainly peels and seeds, which can comprise between 30% and 35% of the weight of the fruit (13% and 17%, respectively) depending of the variety [36,37]. furthermore, during agricultural and transport stages, around 49% of the avocado is regarded as rejected due to the ripening time and diseases (mostly middle-income countries) [38]. Therefore, it is necessary to develop integrated biorefinery alternatives for the valorization of these residues, as they contain high-value components such as carbohydrates, proteins, lipids, among others [39].

The comprehensive exploitation of avocados in an industrial scale biorefinery involves a number of critical parameters that determine the efficiency and profitability of the process. These parameters include the quality of the avocado (oil content, maturity, etc.), processing conditions (temperature, pressure, etc.), extraction efficiency, and waste management [4,40]. The optimization of these parameters can result in a higher recovery of valuable products such as avocado oil and protein, while minimizing waste generation [41,42]. This not only improves the sustainability of the process, but it can also increase its profitability by maximizing the value obtained from each processed avocado. Therefore, the understanding and control of these parameters are essential for the success of an industrial-scale avocado biorefinery.

1.2. Biorefinery Concept Relevance for Avocado Utilization

A biorefinery is an installation in which various thermochemical, biochemical, combustion, and microbial growth conversion technologies are integrated to efficiently produce sustainable bio-based product streams such as biofuels, biochemicals, bioenergy, and other high-value bioproducts [43]. The biorefinery concept has recently been designed and used to process various biomass feedstocks, such as lignocelluloses, algae, and various types of waste [44,45].

Avocado biorefinery is a concept still in development. In this approach, all the components of the avocado are used, not only the pulp but also the seeds and peels, which are often discarded, to obtain value-added products. That is, a variety of bio-compound products can be produced, including food, chemicals, raw materials, and bioenergy [46]. The size of the avocado fruit is determined by the number of cells in the fruit, but it can be affected by several factors such as the age of the cultivar, the fruit load, light, nutrition, pests, and water availability [47]. Small avocados are often rejected as waste due to their low economic value [48]. Using these smaller avocados and their byproducts in refining applications could contribute to sustainable practices in avocado production, which could also contribute to the circular economy.

In this sense, second-generation (2G) biorefineries are gaining relevance as a key component of bioeconomic development around the world. While traditional biorefineries focus on the production of biofuels, the evolving market requires integrated systems that value all co-products. Therefore, the lignocellulosic fraction can be converted into oligomers with applications in the pharmaceutical industry, food additives, fuels, chemicals, and bioplastics [49,50].

Another way to exploit avocado biomass is by extracting antioxidants and bioactive compounds such as polyphenols, flavonoids, and carotenoids using techniques such as microwave-assisted extraction, ultrasound-assisted extraction, and supercritical fluid extraction [51,52]. These compounds have potential applications in the food and cosmetic industries due to their antioxidant, antimicrobial, and anti-inflammatory properties. In addition, the production of animal feed [53,54], is considered, due to its high protein and fiber content. In addition, bioplastics [55,56], starch, and biofuels (bioethanol, biodiesel, biomethane, and biogas) [57,58,59,60] are also alternatives for the valorization of avocado waste. All these techniques offer diverse opportunities for the valorization of avocado waste and contribute to sustainable waste management practices and the bioeconomy.

The potential opportunities that biorefineries could achieve for leading producers like Colombia need to be study thoroughly. From that, this study proposes a novel method that combines bibliometric analysis, co-occurrence analysis with word connections and trends over time, and in-depth analysis to examine research trends in bioprocesses, and in this case, in avocado byproducts biorefineries, considering the local context in Colombia. The aim of the study is to identify the most relevant and emerging topics in bioprocesses and biorefineries, with a special emphasis on the use of avocado. Moreover, the study aims to detect underexplored areas or those with high potential for future research, allowing the development of new strategies and technologies to optimize the use of avocado.

2. Materials and Methods

2.1. Bibliometric and Co-Occurrence Assessment

This section describes the procedure for developing the bibliometric study of the integral use of avocado for the production of value-added products under a biorefinery perspective, using data obtained from the SCOPUS platform. The procedure developed is shown in Figure 2.

A bibliometric analysis was carried out by initially collecting data from the SCOPUS database related to the integral use of avocado under the concept of biorefinery and Process Systems Engineering (PSE). The aim of this search was to contextualize the implementation of PSE for the design, evaluation, control, and optimization of the production process, involving an exploratory search of existing research on the relationship between avocado and process simulation. A systematic search was carried out in SCOPUS, focusing on the terms within the title, abstract, and keywords of the articles using the terms “avocado” and “biorefinery”. The selected time interval was from 2003 to 2023, considering that 2024 is still in progress.

With the information obtained in SCOPUS, the number of research documents, including research articles, conference proceedings, books, book chapters, and review articles per year, were obtained and analyzed. The distribution of documents published by type was then obtained to identify the priority of original research and findings in publication trends, as well as the role of conferences and professional meetings in the dissemination of knowledge related to avocado waste valorization under a biorefinery scheme. Subsequently, the 15 countries that produced the most documents, and the number of publications from each country from 2003 to 2023, were obtained and analyzed, comparing the results with the leading avocado-producing and consuming countries and examining trends by continent. A more detailed analysis was carried out for the case of South America, showing the five countries that produced the most documents to observe regional impacts and trends. Additionally, the number of research articles and review articles per year was obtained and compared with the number of citations over the past 15 years to identify correlations in the variation of both indicators.

2.2. Relevant Publications Analysis

A comprehensive analysis was carried out to gain a deep understanding of the most relevant and innovative work developed in the field, following the co-occurrence analysis and prioritization of word clusters. To do this, the documents within the prioritized clusters were reviewed, summarized, and key aspects were highlighted, such as findings, methods, conclusions, and future work presented by the authors. In this stage, relevant documents from the current year (2024) were also incorporated to ensure that the analysis captured the most recent developments in the field. The results obtained from this comprehensive analysis were then grouped into categories based on the objective and scope of the studies, taking into account the contributions made in several aspects related to the integral biotransformation of avocado under the concept of biorefinery, evaluation of the avocado utilization process under sustainability criteria, extraction methods, characterization, and identification of bioactive compounds present in avocado, and value-added products obtained from avocado. Also, qualitative and quantitative analysis was carried out to initiate the discussion of results, indicate future directions, and draw conclusions. The results and/or conclusions obtained were interpreted and discussed according to levels of relevance, for the gaps found in the topics of interest and future research.

3. Results and Discussion

3.1. “Avocado” and “Biorefinery” Bibliometric Study

Based on the information presented in Figure 3, it is observed that the number of documents published is relatively low in the early years, with only three documents published in the first four years; however, the number of documents published begins to gradually increase from 2014, with four documents published in that year and a significant increase in the following years, with 2023 showing the highest number of documents published, with 368 documents published on these topics. In general, these data suggest that interest and research on the topics of avocado and biorefineries have been increasing over time. The increase in the number of documents published indicates a growing interest in these topics and a greater understanding of them. Additionally, this increase in the number of documents can lead to greater innovation and development in these fields.

There is evidence of an increase in the production of documents since 2020, which can be attributed to a greater awareness of the need for sustainability. This is due to the need to find sustainable solutions to address global environmental problems, especially after the COVID-19 pandemic. The integral use of avocado under the concept of biorefinery is aligned with this reality, as it is related to the production of renewable and sustainable products. This has increased interest in online research and development, as well as the need to find innovative solutions.

Based on the information in Figure 4, it is evident that scientific articles are the most common, with a total of 558 documents. This suggests that most research in this area is published in scientific journals. Thus, scientific articles are an effective way to share new findings, experiments, results, and research conclusions with other researchers. This is especially important considering that the research line on the integral use of avocado under the concept of biorefineries using computer-aided process engineering is growing fast and has found its peak in the last three years, considering the public policies of the fruit-producing countries. Additionally, a key finding is that the literature on avocado and biorefineries includes a significant number of reviews. This is expected, given the research limitations imposed by the COVID-19 pandemic, such as restrictions on experimental testing.

Figure 5 shows the top 20 countries with the highest number of publications on avocado and biorefinery for the period 2003–2023. India, China, and Spain lead the list with 140, 114, and 99 documents, respectively, suggesting that these countries have a strong interest in research on avocado and biorefinery.

It can be observed that the leading avocado producers, Mexico and Colombia, are in fifth and seventh place, respectively, in terms of document generation, indicating that research on this crop is a relevant topic in these countries. This may be since these countries are more focused on the production and marketing of this fruit, while other countries may be concentrated on the study of alternative uses of avocado, including under the concept of biorefinery.

That can be seen with the first three countries, India, China, and Spain, which lead the figure in terms of document generation, are not a significant avocado producer globally, with exception of Spain, which produces 95% of avocado production of Europe (still far from the leading producers). In the case of India and China, both countries are important consumers of this fruit with imports an increasing yearly. For example, in China, avocado consumption have risen 460%, from 154 tons in 2012 to 41,000 tons in 2022 [61]. In India, some estimates put the consumption around 4000 tons per year. This high volume of consumption leaves behind important rich food waste that could be used [62]. Also, the benefits from the potential compounds extracted from avocado by-products in health have led the attention of both nations’ drug and pharma sectors. At the same time, the same happen to the potential use of the fruit as bio-source for energy and fuels [63,64]. One the other hand, the allocation of resources in research and development of both countries are higher than most of the countries in the graph (2.6% and 0.3% of their GDP according to the world bank) [65]. Furthermore, both countries have started to study the feasibility of the cultivation of their own avocado variety [66], which could increase the type of waste available from food waste to agricultural. The United States, which is the biggest importer and consumer of this fruit, is the sixth country with the highest number of publications in the last 20 years, which could be due to the investment of these countries in science and research, in order to take advantage of the fruit and its waste in alternative uses [67].

Figure 6 shows that Brazil is the country with the highest production of documents on avocado and biorefinery with 91, followed by Mexico with 89, and Colombia with 67. These results are unexpected due to Brazil being the seventh largest producer of avocado in Latin America, below Mexico and Colombia (first and second, respectively) [68]. Nonetheless, Brazil’s larger agro-industrial sector could explain its leadership in research in this area. However, it is important to note that investment in science and research can also be a key factor in the number of documents generated, Brazil being also leader in this aspect (1.17% of its GDP). Chile, Ecuador, Peru, Argentina, and Uruguay have a much smaller number of documents, which could be since these countries are not the main producers of avocado in the region.

Additionally, leading producers like Mexico and Colombia has opted to intensify their efforts to implement a more circular economy based on biomass (like avocado) processing [69]. Specifically, in Colombia, there are several public policies that seek to encourage avocado production by supporting producers, promoting the product in national and international markets, and improving infrastructure and technology related to avocado production [70]. As a result, greater research interest is derived from them, especially for the solution of problems related to the use of avocado.

Based on Figure 7, it can be said that the number of published documents has increased significantly since 2008, with a peak in 2022 with 278 published documents. Similarly, the number of citations has also increased significantly since 2008, with a peak in 2022 with 4,806 citations received. The years with the fewest documents and citations were 2007, 2009, 2010, and 2011. The years 2012 to 2015 had a gradual increase in the number of documents and citations. The years 2016 to 2023 showed an accelerated increase in the number of documents and citations.

In Scopus, more than 240 journals were found in which articles on avocado and biorefinery were published.

Table 1. Number of publications and citations about avocado and biorefinery of the top 20 journals between 2007–2023.

Source	TD 1	Percentage	TC 2	Editorial	PC 3	SJR 4	SNIP 5	h-Index	JIF 6	JCI 7
Biomass Conversion and Biorefinery	61	9.80	5808	Elsevier	6.6	3.158	3.396	162	4.05	4.00
Molecules	23	3.32	184,529	Multidisciplinary Digital Publishing Institute (MDPI)	6.7	0.704	1.167	199	4.60	4.60
Foods	22	2.66	56,352	Multidisciplinary Digital Publishing Institute (MDPI)	5.8	0.771	1.302	73	5.20	5.20
Industrial Crops and Products	22	2.66	43,674	Elsevier	9.7	0.897	1.567	158	5.90	5.90
Bioresource Technology	21	2.99	128,275	Elsevier	19	2.47	2.016	341	11.40	11.40
Journal of Cleaner Production	17	2.66	351,758	Elsevier	18.5	1.981	2.379	268	11.90	11.10
Sustainability (Switzerland)	17	1.66	281,274	Multidisciplinary Digital Publishing Institute (MDPI)	5.8	0.664	1.198	136	3.90	3.90
Antioxidants	15	1.99	55,568	Multidisciplinary Digital Publishing Institute (MDPI)	8.8	1.084	1.541	83	7.00	7.00
Renewable and Sustainable Energy Reviews	13	1.99	93,763	Elsevier	26.3	3.232	3.631	378	15.90	0.10
Applied Sciences (Switzerland)	12	1.50	176,120	Multidisciplinary Digital Publishing Institute (MDPI)	25.2	0.492	0.974	378	2.70	2.70
Processes	11	1.50	35,451	Multidisciplinary Digital Publishing Institute (MDPI)	4.7	0.529	0.979	54	3.50	3.50
Journal of Supercritical Fluids	10	1.33	7818	Elsevier	8.3	0.751	1.132	126	3.90	3.90
Trends in Food Science and Technology	10	1.66	37,308	Elsevier	25.2	2.522	3.335	231	15.30	0.10
Chemical Engineering Journal	9	1.33	376,280	Elsevier	21.5	2.803	2.176	280	15.10	15.10
Chemical Engineering Transactions	9	1.33	4831	AIDIC-Italian Association of Chemical Engineering	1.5	0.242	0.397	43	0.97	0.10
Energies	9	1.33	161,755	Multidisciplinary Digital Publishing Institute (MDPI)	5.5	0.632	1.025	132	3.20	3.20
Environmental Science and Pollution Research	9	1.16	141,408	Springer Nature	6.9	0.944	1.214	179	5.4	7.9
Critical Reviews in Food Science and Nutrition	8	1.16	28,142	Taylor and Francis	14.9	1.862	2.751	215	10.2	23.6
Food Research International	8	1.16	47,214	Elsevier	12	1.36	1.821	195	8.10	8.10
Plants	8	1.16	47,082	Multidisciplinary Digital Publishing Institute (MDPI)	5.4	0.79	1.277	67	4.50	4.50

¹ Total documents, ² Total citations, ³ Percentage of citations, ⁴ Ranking SCImago, ⁵ Source Normalized Impact per Paper 2022, ⁶ Journal Impact Factor 2022, ⁷ Journal Citations Indicator 2022.

highlights the top 20 journals. The journal with the most documents published was “Biomass Conversion and Biorefinery” (61), followed by “Molecules” (23), “Foods” (22), “Industrial Crops and Products” (22), “Bioresource Technology” (21), “Journal of Cleaner Production” (17), “Sustainability” (17), “Antioxidants” (15), “Renewable and Sustainable Energy Reviews” (13), and “Applied Sciences“ (12). The titles between positions 11 and 20 published between 9 and 8 documents each.

The documents have been published in important journals with a focus on chemical processing and transformation of material like “Chemical Engineering Journal”, which portrays the highest total number of citations, with 376,280. The same conclusion can be found when more traditional journals focus on the application of biomass in the food industry. Fewer documents have been published in journals like “Foods”, with a relatively low number of citations. This change could suggest the documents published in this journal have not been as influential in the scientific community. In general, this table points out that there is a great deal of interest in research on avocado and biorefinery and that documents are being published in a variety of journals from different research areas, including biotechnology, renewable energy, and food technology.

Figure 8 shows the authors who have produced the most documents on avocado and biorefinery. It can be observed that Cardona-Alzate, C.A. is the author with the most documents in this area with a total of 19 publications, followed by Ruiz, H. A. and Solarte-Toro, J. C. with 11 publications each. This evidences that there is a shared interest and effort in this area of research.

Table 2. Top cited articles.

Authors	Title	Year	Cites	Cites/y	Journal
Araújo, R. G., Rodriguez-Jasso, R. M., Ruiz, H. A., Pintado, M. M. E., y Aguilar, C. N. [71]	Avocado by-products: Nutritional and functional properties	2018	276	16.24	Trends in Food Science & Technology
Ruiz H.A., Conrad M., Sun S.-N., Sanchez A., Rocha G.J.M., Romaní A., Castro E., Torres A., Rodríguez-Jasso R.M., Andrade L.P., Smirnova I., Sun R.-C., y Meyer A.S. [72]	Engineering aspects of hydrothermal pretreatment: From batch to continuous operation, scale-up, and pilot reactor under biorefinery concept	2020	249	14.65	Bioresource Technology
Mora-Sandí, A., Ramírez-González, A., Castillo-Henríquez, L., Lopretti-Correa, M., y Vega-Baudrit, J. R. [73]	Valorization of byproducts from tropical fruits: Extraction methodologies, applications, environmental, and economic assessment: A review (Part 1: General overview of the byproducts, traditional biorefinery practices, and possible applications)	2020	91	5.35	Comprehensive Reviews in Food Science and Food Safety
Dávila, J. A., Rosenberg, M., Castro, E., y Cardona, C. A. [74]	A model biorefinery for avocado (Persea americana mill.) processing	2017	83	4.88	Bioresource technology
Solarte-Toro, J. C., y Alzate, C. A. C. [75]	Biorefineries as the base for accomplishing the sustainable development goals (SDGs) and the transition to bioeconomy: Technical aspects, challenges and perspectives	2021	57	3.35	Bioresource Technology
Villacís-Chiriboga, J., Elst, K., Van Camp, J., Vera, E., y Ruales, J. [76]	Avocado-derived biomass as a source of bioenergy and bioproducts	2020	54	3.18	Applied Sciences
Paramos, P. R., Granjo, J. F., Corazza, M. L., y Matos, H. A. [40]	Extraction of high value products from avocado waste biomass	2020	45	2.65	The Journal of Supercritical Fluids
Lara-Flores, A. A., Araújo, R. G., Rodríguez-Jasso, R. M., Aguedo, M., Aguilar, C. N., Trajano, H. L., & Ruiz, H. A. [49]	Bioeconomy and biorefinery: valorization of hemicellulose from lignocellulosic biomass and potential use of avocado residues as a promising resource of bioproducts	2018	34	2.00	Waste to Wealth
Del Castillo-Llamosas, A., del Río, P. G., Pérez-Pérez, A., Yáñez, R., Garrote, G., y Gullón, B. [39]	Recent advances to recover value-added compounds from avocado by-products following a biorefinery approach	2021	26	1.53	Current Opinion in Green and Sustainable Chemistry
Solarte-Toro, J. C., Ortiz-Sanchez, M., Restrepo-Serna, D. L., Piñeres, P. P., Cordero, A. P., y Alzate, C. A. C [23]	Influence of products portfolio and process contextualization on the economic performance of small-and large-scale avocado biorefineries	2021	14	0.82	Bioresource Technology

presents the 10 most cited documents on avocado for sustainable development. The most cited document, “Avocado by-products: Nutritional and functional properties” by Araújo et al. [71], received 276 citations. The review article presented an overview of the current production, export, and uses of avocado in Mexico, providing relevant information on the production, composition, and application of avocado, with an emphasis on its byproducts, focusing on the proper use of waste and the possibility of making them profitable for nutritional and environmental purposes. The second most cited document, with 249 citations, was by Ruíz et al. [72], entitled “Engineering aspects of hydrothermal pretreatment: From batch to continuous operation, scale-up and pilot reactor under biorefinery concept”. The review article is based on the fundamentals of hydrothermal pretreatment, the changes in the structure of biomass during this pretreatment, multi-product strategies in terms of biorefinery, reactor technology, and engineering aspects from batch operations to continuous operations. It should be noted that, in the two most cited articles, Ruíz H.A. is a co-author, being one of the authors with the highest number of published documents related to “avocado” and “biorefinery” (Figure 6).

The third most cited document, by Mora-Sandí et al. [73], addressed the state of research on the valorization of tropical fruits into value-added products, with an emphasis on the extraction of phenolic compounds and carotenoids. The article by Bhattarai et al. [74], entitled “A model biorefinery for avocado (Persea americana mill.) processing”, received 83 citations and was the fourth most cited document. The authors studied and diagnosed a biorefinery to process Hass avocado to produce microencapsulated phenolic compounds, ethanol, oil, and xylitol.

3.2. Co-Occurrence Study and Tendences

Based on the keywords extracted from SCOPUS and used in VOSviewer 1.619 to generate the map of connections and co-occurrences (Figure 9), the number of keywords that were to be displayed in the keyword co-occurrence graph was selected, quantitatively decreasing the number of words from the 510 that met the previous criteria. Subsequently, words were qualitatively eliminated by visualizing the keywords with the most occurrences. Relevance to the study topic was considered, and some words that were not in the context of the analysis that was to be developed were eliminated. For example, in this case, the words “Article” with 70 and “review” with 32 occurrences appeared. Although there were many, the words were very general and did not allow trends in research to be identified. Words that were outside the scope of the study could also appear, such as “nonhumans” and “humans”, which were also discarded, since our study was more focused on the computational part than on the effects on people.

The frequency of occurrence of keywords, the connections between them, and the word clusters were analyzed. It is observed that the most repeated are “biomass”, “fruit”, “extraction”, and “adsorption”; this allows us to infer that the use of avocado as lignocellulosic biomass is studied based on the compounds that can be extracted from the fruit and its potential use as a contaminant adsorbent material. Another frequent word and the first related to the trend we want to find is “sustainable development”, which indicates that research is being developed for the integral use of avocado, guaranteeing the balance between economic growth, environmental protection, and social well-being. Other terms of high frequency of interest are “bioactive compounds” and “biorefinery”, which indicates that studies focus on the efficient and sustainable use of avocado for the production of high-value-added products, through the extraction and purification of valuable bioactive compounds in their purest form, waste valorization, and process integration.

It can be observed that the word “biomass” is one of the most frequent in this analysis, as it has the highest number of links (112) and the highest link strength (1497). It is related to terms such as “waste management”, “environmental sustainability”, “sustainable development”, “biorefinery”, and “life cycle analysis”, which shows the orientation towards the use of biomass, even those considered waste, in a sustainable way, maximizing its value and contributing to sectors such as health, food, and industry. It is also linked to terms such as kinetics, water treatment, chemical composition, adsorption, biochar, antioxidants, and phenolic derivatives, among others, showing an evident interest in the production of high-value products and the comprehensive valorization of biomass. The life cycle analysis item is linked to the words “biorefineries”, which allows us to see the initiative to diagnose the environmental impacts generated by the avocado utilization process.

In terms of the segmentation of keywords into clusters, it is observed that they are divided into five groups, each represented by a specific color. The red cluster has 109 items and is related to the integral biotransformation of avocado, as it touches on aspects of bioenergy production, sustainability, agriculture, biomass utilization through biorefineries, life cycle, processing methods, and quality control within the process. On the other hand, the green cluster is associated with the study of extraction methodologies of active compounds and byproducts from the different parts of the avocado and their characterization; aspects such as circular economy, antioxidants, green extraction, microwave-assisted extraction, extraction with solvents and supercritical fluids, fractionation, additives, bioactive compounds, among others, were considered, with a total of (107 items).

The blue cluster encompasses keywords related to biological origin processes for the separation of active compounds such as carotenoids, with words such as “hydrolysis”, “packaging materials”, “bioreactor”, “avocado seed”, “bioremediation”, “biotechnology”, “fermentation”, “integrated biorefinery”, as well as “saccharification” for a total of (98) items. The yellow cluster focuses on the use of avocado by preparing adsorbents for their use in the removal of contaminants, “activated carbon”, “biochar”, “adsorption”, “isothermals”, “water treatment”, and “kinetics” are some of the words seen, and the number of items is 97. Finally, the smallest cluster, represented by the purple, shows several occurrences of 82 and contains words such as “biodiesel”, “biofuels”, “hydrothermal carbonization”, and “waste to energy”, among others. Based on this evaluation, it can be said that the research areas of our interest are: integral biotransformation processes of avocado, extraction methods, characterization and identification of active compounds in avocado, evaluation of the avocado utilization process under sustainability criteria, and value-added products obtained from avocado.

For the analysis of research trends over time (Figure 10) concerning the search equation used for the study, it is evident that work associated with the use of avocado under the biorefinery concept has been a topic of scientific interest in the last four years. The central axis of the research around the topic of interest is waste management, sustainable development, bioenergy, and biomass utilization, which corresponds to cluster 1. More recently, the main focus is based on waste utilization, production of bioenergy, synthesis of biosorbents for the removal of contaminants, preparation of bioplastics, extraction methods, and determination of biocompounds of interest, which helped to understand the possibility of obtaining value-added products. This trend highlights a growing concern about the environmental impact of plastic materials and the need for sustainable solutions. As a result, the research landscape is recent but has evolved significantly over time, reflecting both the changing priorities of the scientific community and the ongoing advances in the field.

3.3. Technological Advances and Future Path

In this section, we consider exclusively documents registered in the last seven years, including publications from 2024, and documents whose topics are the most recurrent keywords previously identified during the co-occurrence analysis. In addition, the removal of duplicates and of the smallest data groups or clusters of lower relevance was implemented. From the co-occurrence figures, three relevant topics were found: (i) extraction of the active compounds, (ii) process or methods to transform avocado by-products and potential products, and (iii) criteria related to sustainable development and circular economy.

3.3.1. Extraction Methods, Characterization, and Identification of Active Compounds in the Avocado Byproducts

For the extraction, characterization, and identification of active compounds in avocado-by products, novel methods and techniques have been proposed. Conventional techniques’ technical limitations, toxicity, and environmental impacts have provoked a shift into eco-friendly and efficient extraction processes. Studies focus on searching for alternatives that are faster, more selective, and automated, and able to preserve the quality of the extract [77].

At the same time, secondary metabolites can be extracted, from parts such as the peel, and seed [78,79,80], not only the pulp. These bioactive compounds, such as polyphenols and total flavonoids, have been quantified from these materials [81]. This is important due to these compounds’ wide range of health benefits, including antioxidant, anti-inflammatory, anticancer, anti-aging, anti-aggregative, antibacterial, and antifungal activity [82,83]. These benefits are due to the ability of these compounds to neutralize free radicals, reduce inflammation, inhibit the growth of cancer cells, delay aging, prevent the formation of blood clots, and fight bacteria and fungi [84,85].

Extraction of Active Compounds in Avocado by Products

Some the techniques used for the extraction of bioactive compounds from avocado peel, pulp, and seed include: supercritical fluid extraction [86,87], deep eutectic solvents [88], ultrasound [89,90], hydrothermal treatments [91,92], microwaves [93,94], supercritical fluids [40], among others [95,96]. Recent investigations have examined technical aspects like yield, operation conditions and others. At lab scale, Del-Castillo-Llamosas et al. [97] investigated the valorization of avocado seed (SA) using microwave-assisted auto-hydrolysis within a green biorefinery concept. They tested temperatures between 150 and 230 °C for 5 min, with the optimum at 220 °C, yielding 42.15 mg of gallic acid equivalent per gram (GAE/g) of phenolic compounds, 31.89 mg of retinol equivalent per gram (RE/g) of flavonoids, and 38.82 g/L of glucose + glucooligosaccharides. Ethyl acetate extraction preserved polysaccharides while recovering bioactive compounds, including 99.02 mg/g vanillin and various phenolic acids and flavonoids. Enzymatic hydrolysis of the solid and phenol-free liquor produced glucose at concentrations of 9.93 and 105 g/L, demonstrating a promising method for extracting fermentable sugars and antioxidant phenolics from avocado seeds. In a separate study, Del-Castillo-Llamosas et al. [98] explored deep eutectic solvents (DES) for extracting bioactive polyphenols and carbohydrates from avocado seeds. Their design varied temperature (40–60 °C), time (60–180 min), and water content (10–50% v/v) to optimize total phenolic content (TPC), flavonoid content (TFC), antioxidant capacity (ABTS, FRAP), and xylose yield. Using choline chloride and glycerol mix (1:1), they achieved significant results: 19.71 mg GAE/g TPC, 33.41 mg RE/g TFC, 20.91 mg TE/g ABTS, 15.59 mg TE/g FRAP, and 5.47 g/L xylose. HPLC-ESI identified eight phenolic compounds. Both delignification with DES and microwave-assisted autohydrolysis improved glucan susceptibility, producing nearly complete glucose yields. DES was identified as an eco-friendly, cost-effective alternative to traditional solvents for extracting phenolics and carbohydrates. Additionally, Del-Castillo-Llamosas et al. [99] used hydrothermal treatment at 150 °C on avocado peel, achieving a high recovery of antioxidant polyphenols (3.48 g GAE/100 g peel and 10.80 g TE/100 g peel, via ABTS assay) and 14.3 g of oligosaccharides/100 g peel. HPLC analysis identified 43 metabolites, including flavonoids, phenolic acids, organic acids, lignans, and fatty acids. These findings highlight effective methods for extracting valuable bioactive compounds from avocado byproducts. Limited works have explored the optimization of operational conditions of these emergent extraction methods. Statical analysis has showed to be an effective tool to find optimal conditions that maximizes bioactive compounds’ extraction. Araujo et al. [100] used ANOVA to optimize microwave assisted extraction, using ethanol and acetone as solvent. The statistical analysis used temperature, time, and ethanol concentration as variables to measure the extract. The optimal temperature and time was 71.64 °C by 14.69 min with 58.51% of ethanol. Similarly, Figueroa et al. used ANOVA to optimized microwave extraction, proposing solvent–sample ratio as new variable to study. The optimal MAE conditions were temperature of 130 °C, extraction time of 39 min, ethanol concentration of 36%, and solvent–sample ratio of 44 mL/g. Likewise, the analysis of feasibility parameters is lacking. Trujillo-Mayol et al. [101] assessed energy efficiency, material efficiency, and energy and raw material demand for ultrasound, microwave, and conventional maceration. These parameters was proposed to their effects in economic performance at higher scale. The microwave was found to be more effective in scenarios where energy costs are restrictive. The use of ultrasound and microwave were more advantageous than conventional maceration.

Characterization and Identification of Avocado Bioactive Compounds

Characterization methods are crucial for the identification and quantification of bioactive compounds from various parts of the avocado. The composition of the byproducts is affected by the cultivars analyzed, as well as other factors affecting growth, such as the region of avocado production, climate, altitude, and others [102]. Understanding the composition and properties of these compounds facilitates the development of new products and processes that maximize value from by-products. The identification of the compounds is carried out through methods like high-performance liquid chromatography (HPLC), mass spectrometry, among others. The antioxidant activity of an extracted fraction is measured using methods such as the ferric reducing ability of plasma (FRAP) and the inhibition of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical [51,103].

King-Loeza et al. [52] analyzed the compositional and bio functional compounds in avocados of different commercial qualities from southern Jalisco. They assessed edible, inedible, and oil fractions, focusing on fat content, moisture, dry matter, phenols, carotenoids, antioxidant capacity, and fatty acid profiles. Lower-quality fruits showed higher phenol and carotenoid levels, greater antioxidant capacity, and higher oleic acid content compared to higher-quality fruits. Discriminant analysis revealed that quality classification impacts bioactive compound content, suggesting lower-quality avocados could be beneficial for oil production, while peels could be incorporated into extraction processes.

Kupnik et al. [104] characterized biologically active compounds in avocado seeds using ultrasound (US), ethanol (EtOH), and supercritical carbon dioxide (scCO₂) extraction techniques. Yields ranged from 2.96% to 12.11%. scCO₂ samples had the highest total phenolic content (TPC) and proteins, while EtOH samples had the highest proanthocyanidin (PAC) levels. EtOH samples also showed the greatest antioxidant potential (67.49% DPPH). Antimicrobial activity was tested against 15 microorganisms, confirming potential for applications in the medical, pharmaceutical, and cosmetic industries. Additionally, the study showed the ultrasound method (with water) presented the highest yield (12%), but the selectivity was poor.

García-Vargas et al. [105] examined the chemical composition of avocado peel and seed, focusing on lignin, polymeric sugars, and aqueous extracts. They found significant antioxidant activity in the phenolic compounds within the peel extracts, confirming their bioactive potential. Abd Elkader et al. [106] studied polyphenol content and antioxidant activity in ethanolic extracts of avocado fruit and leaves. Leaf extracts had higher phenolic content (178.95 mg GAE/g) compared to fruit extracts (145.7 mg GAE/g). They identified 26 phytogenic compounds and demonstrated strong antioxidant activity in both extracts, with 95% DPPH elimination in fruit extract. The study also found higher α-amylase inhibitory activity in fruit extracts (92.13%) than in leaf extracts, highlighting their potential health benefits.

García-Ramón et al. [107] evaluated how ethanol concentration, temperature, and solvent ratio affected the extraction of bioactive compounds from avocado Hass peel at different maturity stages. They optimized conditions for maximum total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity. Unripe peel extracts using 40% ethanol, at 49.3 °C, and a 14.3 mL/g S/F ratio showed the highest TPC (44.24 mg GAE/g), TFC (786.08 mg QE/g), and antioxidant capacity. Vanillic acid and 4-hydroxyphenylacetic acid were identified as the primary phenolic compounds in these extracts. Also, the efficacy of the extract obtained by hydrothermal treatment against the activity of Gram-positive and Gram-negative bacteria Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, and Salmonella spp. was confirmed at different concentrations [108].

The methods described previously are potential alternatives to extract more value from avocado by-products. These techniques have been demonstrated to be more environmentally friendly while producing extracts with low toxicity, without compromising their antioxidant activity. At the same time, processes can be developed to produce metabolites from avocado by-products, with potential application in the food, pharmaceutical, or nutraceutical sectors. However, the extraction conditions and solvent choice are still a topic under study due to the variety of cultivars and their composition. Efficient and reliable methods to recuperate these valuable compounds are crucial to potential scalability and commercialization. The applications of these methods requires further research to simplify them and improve their accessibility; economic aspects of these advance extraction methods should be assessed.

3.3.2. Integral Avocado Transformation Process and Products

The avocado processing process, from its natural state to derived products, involves various stages. It all begins with the harvesting of avocados, selection, classification, and segregation (rejection) of the avocados. Then, techniques such as solvent extraction, cold pressing, or centrifugation are implemented to extract oils and bioactive compounds. Also, avocado pulp can be transformed into products such as guacamole, dressings, or dehydrated to make avocado powder. The residues of the pulp and seed can be used in several methods that includes thermochemical, physicochemical, and biological to transform them into biofuels or biomaterial used as intermediate or raw material for the production of consumer products [109,110].

Mass Based Transformation of Avocado by Products

Some proposed intermediates includes flour, as Di Stefano [111] transformed avocado peels and seeds from Sicily into flour as a reusable resource and evaluated its chemical properties. The byproducts were dried at 60 °C for 4 h and ground. The study found low enzymatic browning and high luminosity in the flour, with significant total phenolic content (386.80 mg GAE/100 g) and antioxidant activity (127.86 mmol TEAC/100 g) in the peels. The fatty acid profile of the peel flour included 9.5% saturated fatty acids (SFAs), 78.3% monounsaturated fatty acids (MUFAs), and 12.2% polyunsaturated fatty acids (PUFAs). Bioactive compounds identified using UHPLC-Orbitrap-MS included hydroxycinnamic acids, hydroxybenzoic acids, flavonoids, and tannins. This research highlights the potential of avocado byproducts for producing functional products with health and industrial benefits. Other research have proposed pectins, like Sivamani et al. [112], optimized the extraction of pectin from avocado peel by analyzing four variables: pH, solvent/substrate ratio (RSS), agitation time (TAG), and agitation speed (VAG). They compared two methods: Box-Behnken response surface design (DSRBB) and artificial neural network with a genetic algorithm (ANN-GA). ANN-GA provided more accurate predictions with optimal conditions of pH 1.9, RSS 16 mL/g, TAG 2.1 h, VAG 99 rpm, and a process yield (RP) of 90.59%, versus DSRBB’s 85.44%. Structural analysis confirmed the pectin’s high esterification and amorphous nature, with a melting point of 258.5 °C, similar to commercial pectin. SEM revealed a flaky and spherical structure, indicating potential use in food products. Starch has also been seen as alternative intermediate, Salazar-Irrazabal et al. [113] produced starch from avocado seed from three avocado seed varieties: Criolla, Fuerte, and Hass and compared their molecular, physicochemical, and digestibility. The starch extraction involved washing and sedimentation. The starch granules were oval and spherical, with Criolla having the largest average size (24.55 μm), followed by Hass (21.37 μm) and Fuerte. Fuerte starch exhibited the highest gelatinization enthalpy (8.55 J/g) and temperatures for gelatinization (75.28 °C) and pasta (75.57 °C). Hass starch had the highest viscosities, including maximum (836.27 mPa·s), final (1407.37 mPa·s), setback (588.78 mPa·s), and breakdown (17.68 mPa·s). Additionally, the starches had a high resistant starch content (60.06–68.90%). Additionally, emergent methods studied avocado by products as precursor for plastic production. Espinel Ríos et al. [113] used a Plackett-Burman design to evaluate the potential of avocado seed hydrolysate (ASH) to replace components of MRS medium for lactic acid production by Lactobacillus sp. Using 20 g/L of initial reducing sugars from ASH, they identified five MRS components that could be replaced, reducing medium costs by at least 17%. Casein peptone (10 g/L), meat extract (8 g/L), yeast extract (4 g/L), and sodium acetate (5 g/L) were retained. The highest lactic acid concentration, 5.7 ± 0.7 g/L, was achieved with 40.0 ± 2.0 g/L of reducing sugars in a stirred-tank bioreactor, despite some inhibitory effects on growth. This is the first study exploring lactic acid production from ASH.

Energy and Fuel Production from Avocado by Products

At the same time avocado by products are transformed into biomaterials as industrial feedstock, thermochemical processes have been studied as source of bio energy, as fuel or as a precursor of conventional fuels, from avocado biomass. Ankona et al. [114] conducted a kinetic study of avocado and lemon wood pyrolysis using thermogravimetric analysis (TGA). Weight loss was recorded in a nitrogen atmosphere with a heating rate of 10 °C/min between 30 °C and 700 °C. The thermal decomposition occurred in four stages: dehydration, initial decomposition, and both active and final decompositions. During active decomposition, gases were released between 255–355 °C for lemon wood and 246–340 °C for avocado wood. Gaseous products, including CO₂, CO, H₂O, CH₄, methanol, formic acid, acetic acid, and furfural, were identified using Fourier transform infrared spectroscopy (FTIR).

On the other hand, Paniagua et al. [115] analyzed the thermal properties of avocado crop residues, including seeds and pruning residues from the Hass and Bacon varieties, to evaluate their potential as fuel. The study also assessed the impact of fertilizers like cow manure and inorganic products. Thermogravimetric analysis (TGA) at heating rates of 10, 20, and 40 °C/min was used, with kinetic parameters estimated via the Friedman, FWO, and KAS methods. Pruning residues had a higher heating value (19.43 MJ/kg) compared to seeds (18.74 MJ/kg). Cow manure improved performance across all samples. Activation energies for wood (143.89–211.04 kJ/mol) were lower than for seeds (174.05–279.99 kJ/mol). TGA identified three mass loss stages—hemicellulose, cellulose, and lignin. Fertilizers and heating rates influenced thermal behavior, particularly in rapid gas release at different rates. Similarly, San José et al. [116] explored the feasibility of using avocado waste as fuel in a conical expanded bed reactor. This reactor promotes improved mass and heat transfer, enhancing energy exploitation. Heat transfer coefficients in avocado waste beds were measured to assess their biofuel potential. Combustion tests were conducted at 300–600 °C, and exhaust gases were monitored to calculate emission ratios. The study compared the combustion efficiencies of avocado seeds, peel, and their mixtures, analyzing the effects of temperature and bed composition on efficiency, using exhaust gas concentrations as a metric.

Vourdoubas [117] evaluated the potential of using avocado byproducts and residues in Chania, Crete, to produce valuable products and energy. Avocado production in Crete amounts to 6300 tons annually, generating 550 dry tons of byproducts. However, avocado biomass is small compared to Crete’s total agricultural biomass, which ranges between 82,555 and 123,172 tons annually, mainly from olives, citrus fruits, vineyards, and greenhouses. The energy content of avocado biomass is estimated at 2.43 × 10⁹ Kcal/year, a minimal portion of Crete’s total biomass energy. The study concluded that the best use for avocado residues is heat generation in rural areas or field disposal to enrich soil nutrients.

Sangaré et al. [118] investigated the reactivity and kinetics of slow pyrolysis in lignocellulosic biomass through numerical modeling. Using avocado stone (AS) and α-cellulose (CEL) as biomass, they conducted thermogravimetric analyzer (TGA) experiments in an inert atmosphere, exploring temperatures between 25 °C and 700 °C at heating rates of 10, 20, and 40 °C/min. The results indicated that CO and CO₂ are the primary gases released during devolatilization, while H₂ and CH₄ are produced in secondary reactions above 400 °C. The developed kinetic model had average relative errors below 6.90% for gas mass yields and 9.74% for biochar when compared to experimental data.

The processing of avocados and their byproducts has seen significant advancements. Avocado oil is no longer the only valuable product derived from the fruit; new products such as flour, starch, and energy have also been proposed. Recent studies, as mentioned in the previous section, showcase experimental methods to transform various avocado components, including seeds and peels. Most of these protocols focus on using either single or multiple feedstocks to generate a single product. However, few studies have explored experimental procedures that produce multiple products, moving beyond the extraction of biocompounds and intermediates to the creation of high-value items like plastics. The technical data from these studies provide valuable insights that could be applied in pilot-scale operations. Another emerging trend is the use of experimental data in simulation environments, where conceptual designs are developed to model production on a larger, industrial scale.

Value-Added Products Obtained from Avocado

Due to the multiple bioactive compounds present in avocado and its health benefits, it has become a key ingredient in the production of value-added products. These products, ranging from food and beverages to cosmetics and pharmaceutical products, take advantage of the nutritional and medicinal properties of avocado. The bioactive compounds present in avocado, such as monounsaturated fatty acids, vitamins, and antioxidants, are used to improve the quality and nutritional value of food, as well as to develop innovative cosmetic and pharmaceutical products. In addition, the use of all parts of the avocado, including the pulp, peel, and seed, in the production of these products contributes to sustainability and the circular economy.

Among the products obtained from avocado peels and seeds are antioxidant bioplastic films for use as food packaging and coatings. For this purpose, Merino et al. [56] prepared the films by the casting method, after acid hydrolysis, plasticization, and mixing with pectin polymers at 25 and 50% by weight. A better performance was found for the bioplastics prepared with the mixture of peel and seeds, and the combination of plasticization and mixing with pectin is essential to obtain materials with competitive mechanical properties, optical clarity, excellent oxygen barrier properties, high antioxidant activity, biodegradability, and migration of components in TENAX suitable for food contact applications. On the other hand, Yokokura et al. [119] synthesized an anode from carbon obtained from avocado seeds with a cycle stability of 100 cycles, and a storage capacity of around 315 mAh/g, with a current density of 100 mA/g. Recently, Gnaim et al. [80], produced poly(3-hydroxybutyrate) (PHB) by using avocado seed waste (ASW) as a substrate, in a microbial cultivation of Cobetia amphilecti using acid hydrolysate of ASW. A chemical analysis of the ASW shows high content of carbohydrates (464.7 ± 21.4 g kg⁻¹) and proteins (37.2 ± 1.5 g kg⁻¹). The extraction of the PHB was done by ethyl levulinate as a sustainable extractant, achieving a high recovery yield (97.4%) and purity (100%) of PHB, along with uniform molecular weight compared to traditional extraction methods using chloroform.

By leveraging the full potential of avocado, it has been obtained: bioethanol from seed starch using fermentation with Saccharomyces cerevisiae [120,121], bioplastic [122], biofilms fortified with seed starch [123,124], biogas [125]; biofilms made from peel fiber [126], increased protein and fatty acid content in chicken meat [53], seed-derived charcoal, biodiesel from peel oil [127], carbon anodes for energy storage [128], pulp-based snacks [129], and even polyethylene biocomposites from avocado pruning waste [130]. Additionally, various adsorbent materials have been developed for contaminant treatment, including: Cu nanoparticles [131], matrices functionalized with La, Ce, and Ca [132]; nanoscale seeds [133], and activated carbon [134,135,136,137,138]. This diverse range of value-added products demonstrates the potential of avocado, harnessing its properties and characteristics attributed to the presence of bioactive compounds and its lignocellulosic nature.

3.3.3. Assessment of the Avocado Utilization Process Under Sustainability Criteria

The concept of biorefinery presents a promising approach to the valorization of avocado waste components, including the seed, peel, and pulp residues, from food loss in agricultural production and fruit processing [139,140]. The valorization of these compounds has the potential to contribute to the compliance of several sustainable development goals (SDGs) as it provides a sustainable solution for waste management and can lead to the creation of value-added products. Some challenges that need to be addressed before potential biorefinery projects include logistics for small producers, scale-up, and potential environmental impacts. Currently, some of these issues are being analyzed through computer-aided tools to develop feasible and sustainable designs [37,141].

Recently, modeling and simulation of avocado biorefinery topologies have turned relevant. The data from conventional processing is abundant and can be used to build chemical processes to transform avocados and their by-products into valuable products like biofuels [142]. These process schemes serve as a basic basis for diagnosing the process from a technical standpoint and evaluating the stages and their impacts. Different variants of avocado have been analyzed for use as feedstock from Hass to variants that are more regional or indigenous [143]. For the design of conceptual schemes, hierarchical methods have been used based on experimental data, such as Herrera-Rodríguez et al. [144] used Aspen Plus software (V.12.0) to simulate avocado oil production in northern Colombia, modeling the extraction process using hexane. The simulation detailed flows, stream compositions, operating conditions, and extraction efficiency (65.19%). Also, heuristics methods have been used to find the most optimal process that maximizes economic performance and yield, considering the composition of the feedstock, like Poveda-Giraldo et al. [145] used a method that maximizes valorization by isolating more biomass fractions or removing unwanted compounds of sequential pretreatment for lignocellulosic feedstock.

Additionally, sustainability analyses have been applied to study the effects of these chemical processes on social, economic, and environmental dimensions. The economic aspect is the most studied of the three, analyses evaluated processes for one product or multiple. Some work combines this analysis with a simulated flowsheet or analyzes the criteria alone like Herrera Herrera-Rodríguez et al. [146] assessed the economic feasibility of extracting oil from residual Creole-Antillan avocado in northern Colombia. The analysis revealed good economic performance with a significantly favorable cost–benefit ratio. The total capital investment (ITC) was approximately $6,433,363 with an investment recovery after the seventh year from the start of the project. Furthermore, the study highlighted that equipment costs are a crucial factor in determining the total capital investment. Also, Herrera-Rodríguez et al. [147] evaluated the production of oil and biochar from avocado pulp and seed, respectively. The total capital investment required was $7,699,270.14, with an estimated investment recovery in 6.67 years. In addition, a cost–benefit ratio of more than one (1) was achieved, indicating that the project should be considered, as the benefits exceed the costs. These works highlight the effect of multiple products in a biorefinery; if more products are desired to produce, then capital and operation costs are increased (more complexity), but at the same time, higher earnings could be gained. Another scenario studied recently is a combined multiple feedstocks biorefinery, like the one studied by Piedrahita-Rodríguez et al. [148], who conducted a technical–economic study on a multi-feedstock biorefinery utilizing banana and avocado residues to produce biogas, avocado seed oil, and ethanol. They employed Aspen Plus V.9.0 for mass and energy balances and the Aspen Process Economic Analyzer for economic evaluation. The study highlighted the potential of integrating avocado and banana residues (0.103 t/h) to enhance the biorefinery’s overall efficiency by increasing the volume and the content of the feedstock. Achieving an annual profit margin of $3.56 million and a positive net present value (NPV) in under two years. In the same idea, emerging advanced extracting techniques’ economic feasibility has been studied, like the work of Restrepo-Serna et al. [149], where they examined avocado peel extracts from two varieties (Lorena and Hass) using solvent extraction, ultrasound, and supercritical fluid methods in a simulation environment. The conventional solvent extraction presented the highest recovery of catechins. While supercritical fluid extraction increased yields, it reduced catechin concentration in one variety, and ultrasound extraction proved beneficial for catechin recovery in the other. Economically, solvent extraction is preferred for catechin extraction due to its higher yields, with a minimum production cost of $8.21/kg, whereas ultrasound, although technically promising, is not as economically favorable for extracting flavonoids like catechins from avocado peels. (technical analysis of extraction methods). Similarly also, Restrepo-Serna et al. [150] compared the valorization of avocado residues (peel and seed) under a biorefinery scheme and to a standalone supercritical fluid extraction (SFE) process. The biorefinery showed profit margins of 47.41% and 43.05%, respectively, significantly higher than the 21.40% and 21.14%, margins from SFE. The biorefinery has lower production costs for the extract’s retrieval of $5.26/kg and $3.99/kg, respectively—which contrast sharply with SFE costs of $7.86/kg and $5.52/kg. These studies show that differences in composition significantly impact the choice of solvent, affecting the yield and the quality of the active constituents and their antioxidant capacity. Additionally, these findings proved that comprehensive valorization not only reduces production costs but also enhances profit margins for avocado residues.

Other criteria have also been analyzed using computer-aided tools like environmental, safety, and social, for single stages of the biorefinery process or expanding the scope to include other stages of the value chain using methodologies such as the Waste Avoidance Algorithm (WAR) and Life Cycle Assessment (LCA), among others. For safety, Herrera et al. [151] evaluated the oil production process from a safety perspective, using the Intrinsic Safety Index (ISI). An ISI of 17 points was obtained, which indicates that the process is safe despite working with substances such as hexane and sodium hypochlorite and using equipment such as ovens and distillation columns. However, for environmental analyses, most relevant works have considered a localized plant on a specific scale of production. Localization of a biorefinery scheme has several key factors that need to be examined: the proximity to raw material, proximity to market, availability of utilities, infrastructure, and labor, as stated by Tesfaye et al. [152], who analyzed both the process and plant location to extract starch from residual avocado seeds using techno-economic and environmental analysis. The study concluded that starch extraction is economically and environmentally viable, with a two-year investment recovery period. Recently, analyses have started to incorporate criteria or considerations associated with the socioeconomic context of leading producers’ countries (like Colombia). The analyses study the impacts of the implementation of biorefineries in rural areas, taking advantage of locations where the avocado is cultivated with the aim to industrialize the countryside. Works such as Cardona et al. [153], analyzed the sustainability of agricultural waste biorefineries designed to promote rural economic development in Colombia. It was found that biorefinery implementation in rural areas is feasible, the production of oil and biogas from peel and seed has low carbon emissions, and low cost of raw materials, especially in poor rural areas. Despite that, Piedrahita-Rodríguez et al. [154] showed that distances between distribution centers and the biorefinery can incur significant CO₂ emissions, with 2.67 tons of CO₂ eq/kg of avocado seed oil. This is a study of geolocation of a biorefinery from avocado and banana residues using Life Cycle Assessment. The effect of the biorefinery scale can be seen in Poveda-Giraldo et al. [155], who examined the processing of Eucalyptus spp. Chips, avocado seeds, and banana pseudo stems across five biorefinery scenarios under economic and environmental (LCA) criteria. It was found that economic viability increases due to a higher processing flow. On the contrary, the environmental impact is disadvantaged due to the increase in scale and its different chemical and energy requirements. A similar conclusion was reached by Solarte-Toro et al. [59] when comparing the environmental and social performance of two small-scale avocado biorefineries (B1, B2) in a rural area of northern Colombia. The more complex B1 presented higher carbon and water footprints with 8.99 kg CO₂-eq/kg of 6.63 m³/kg, respectively, while B2’s footprints were 0.72 kg CO₂-eq/kg and 1.38 m³/kg. In the same publication, the social analysis showed positive impacts on the community stakeholders by creating jobs and increasing the minimum living wage for workers. These findings are in line with the results obtained by García-Vallejo et al. [38], where positive impacts are perceived by workers and community stakeholders. In this work, four schemes were assessed with different complexities. The best scheme for the rural location studied was the least complex with just guacamole production, it generated a modest economic return with low capital and operative expenditures. But on the contrary more complex schemes prove to be more economically beneficial due to more valuable products generated.

Furthermore, the complexity of sustainable aspects assessed to identify optimal biorefinery schemes leads to disconnected assessments, where the effects of other dimensions are not properly discussed. This highlighted the need to establish a multidimensional strategy for designing sustainable biorefineries. Solarte-Toro et al. [156] proposed a sustainable index as a straightforward tool for stakeholders and decision-makers to evaluate and understand sustainability in biorefinery projects. Moreover, the authors described a methodology for designing biorefinery schemes considering various factors such as country-specific variables, scale definition, product selection, economic constraints for viability, the sustainability index calculation, and alternative assessments. The study found the index for a biorefinery producing avocado oil, animal feed, biogas, and electricity was approximately 54%, indicating a need for improvements in processing lines and the development of new products. On the other hand, novel works studying integration and optimization techniques have started to appear. Sousa et al. [157] showed the potential benefits of heat integration and optimization of a biorefinery that produces phenolic compounds, bioethanol, xylitol, syngas, and electricity from avocado seed and peel. A simulation was done in Aspen Plus, and Aspen Process Economy Analyzer and Aspen Energy Analyzer were used for economic and heat integration analysis. The optimization aimed at maximizing gross profit. The optimized biorefinery increased its gross profit from approximately 30 million USD/year to 37 million USD/year, while the heat integration contributed an additional 0.77 million USD/year by reducing utility consumption.

The studies mentioned provide important insights for potential biorefinery projects, including the optimal sequence and capacity of units, ideal extraction methods, suitable products for both rural and urban settings (near cities), and the potential environmental and social impacts. Additionally, they help identify resource optimization objectives. The studies show that conventional methods are still preferred, as they are more reliable and cost-effective than emerging extraction technologies. These alternative extraction processes should be integrated into the conceptual design of biorefineries and be analyzed within the biorefinery framework, even if further refinement is required. More work is essential to understand the optimal process design, particularly given the high variability of material composition and its effects on both economic and technical feasibility. The localization of biorefineries requires considering numerous variables and parameters, such as material availability and environmental restrictions. A significant number of biorefinery proposals have been aimed at rural areas. These schemes typically operate on a small scale and have low to medium technological complexity. This scenario proves that, even though existing conditions are ideal for biorefinery implementation, the demands of rural areas differ from what the market may require. More biorefinery projects need to be assessed, not only at small scales, as has been done, but also at more conventional (industrial) scales. Industrial biorefineries should be characterized by larger processing capacities and greater technological complexity. A direct comparison between small- and large-scale biorefineries would help to identify the most suitable schemes that generate the greatest socio-economic benefits. Additionally, there is a lack of biorefinery proposals that include the integral transformation of avocados, such as converting intermediates (starch, pectin, flour, and bioactive compounds) into consumer products like plastics, pharmaceuticals, pigments, and more. Including these processes would contribute to creating a more efficient industrial processing infrastructure and maximizing economic value. Finally, comprehensive and integrated analyses should be conducted to accurately assess potential designs and their socio–economic and environmental benefits or drawbacks. As these processes are scaled up, material and energy consumption must be minimized. Integration techniques offer promising advantages for addressing resource management challenges, yet there are few studies fully exploring potential savings in avocado biorefineries. This knowledge will become more accessible as more large-scale biorefinery models are developed.

4. Conclusions

This article aimed to conduct a concise and detailed bibliometric and co-occurrence review of the relevant aspects or topics related to the application of the biorefinery concept to avocado utilization. The methodology used allowed us to analyze the behavior over the years of research, the types of documents used, and the involvement of different countries and authors, among other aspects. The results of the bibliometric analysis reveal a growing interest in the comprehensive utilization of avocado biomass, which contributes to sustainable practices in avocado production and can also contribute to the circular economy. In addition, it is highlighted that scientific articles continue to be one of the most effective means of communicating information to the research community. The co-occurrence analysis allowed researchers to quantify the research areas that present gaps and those that have been widely explored. The tendency to relate keywords that are frequently used in these areas over time has also been identified. For example, the terms “avocado” and “biomass” are highly relevant, considering their link strength. A great interest was identified in studying the coupling of different avocado utilization technologies in a single production process, as well as the multiple potential products with high value due to their chemical composition and health benefits. The application of Process Systems Engineering (PSE) allowed researchers to diagnose and confirm the feasibility of implementing avocado biorefineries at small and large scales, by scaling the process from experimental data using specialized software and process simulation. From an economic point of view, the evaluated processes proved to be profitable due to the implementation of the circular economy and waste management. The environmental criterion was the most studied using the life cycle assessment (LCA) methodology, taking into account the concern about process emissions, especially attributed to the planting, harvesting, and transportation of both fruit and the products. Finally, it is crucial to evaluate the sustainability of avocado biorefineries using exergy criteria, technoeconomic analysis, technoeconomic resilience assessment, environmental risk assessment (ERA), impact assessment, and safety assessment, among others. This is to establish possible social impacts, evaluate economic viability and the response to changes in the economic environment of the process, and measure the overall sustainability performance of the evaluated technologies. They can also guide the development of new technologies and process improvements in line with environmental, energy, social, and economic objectives.