Introduction

Municipal solid waste (MSW) is rubbish generated in a city, which includes household solid waste (HSW), institutional, commercial, or small business waste, as well as construction and demolition waste [1,2,3], waste generated during sweeping, cleaning, and maintenance of public areas [4]. In 2016, it was reported that 2010 million tons of MSW were generated worldwide. An increase in generation of up to 3400 million is projected for 2050, which represents an increase of 70% [5]. The trend is the same in the Latin American and Caribbean (LAC) region. This region produced 231 million tons of MSW in 2016, but only 4.5% of it was recycled. This is even thought the region has 32% recycling potential. Added to this, 52% is food and yard waste, which also has the potential for biological treatment [5].

A situation similar to that of LAC occurs in Colombia. 84% of MSW is taken to authorized and unauthorized final disposal sites [5,6,7]. Generation of MSW is 0.76 kg per person per day [5], more than 36,000 tons per day [5, 7]. About 30% of the MSW generated in the country is produced in the three main cities of Colombia, which are Bogotá, Medellín, and Cali [5, 8,9,10,11,12]. This is mainly due to recent processes of urbanization and population growth, as well as migration from rural areas to large population centers [13]. Furthermore, approaches to municipal solid waste management (MSWM) are fragmented and uncoordinated in Colombia's cities. Final disposal in controlled sanitary landfills is the most used method, but it does not have a preventive or comprehensive approach [14, 15]. This greatly affects the economic strengthening of the implementation of the municipal solid waste management system (MSWMS) [16]. Governments have been investing resources in partial actions that do not provide a solution to the problem of solid waste generation without adequate planning and financing.

In Colombia, several studies have focused on analyzing the components of the MSWM. The present study focuses on the gaps and opportunities for informal recyclers within the framework of national regulations [17]. Colorado-Lopera et al. have identified that the major cities in Colombia possess the logistics essential for ensuring effective MSWM, whereas other cities encounter challenges in obtaining resources [18]. Another study has identified 15 factors that impact MSWM in Colombia, including technical capacity, regulatory implementation, and investment costs, among others [19]. These factors are connected to other strategies that can be used around MSWM internationally.

Wilson et al. designed qualitative and quantitative Wasteaware benchmark indicators to evaluate the performance of the MSWMS in cities [2]. This tool constitutes a management instrument for the different managers responsible for the MSW. The Wasteaware application has allowed preventive and well-directed decisions to be made. Furthermore, it allows comparisons between cities [20,21,22,23,24,25]. In the past 14 years, these indicators have been used in more than 70 cities around the world. 13 of these cities are in LAC (19%).

This research presents the adaptation of Wasteaware, to the regulatory framework and national policy of integrated management of solid waste in Colombia. Adaptation allowed for a refined analysis using criteria that were specific to the national context, without affecting the focus of the evaluation. Evaluation provides comparable results to those carried out with the original methodology. The adjustments proposed for in Colombian cities are expected to contribute to improving the MSWMS in the country and will also be easily adopted for evaluation in LAC cities. It could also serve as a reference for possible adaptations of the methodology according to the particular conditions of each country. Finally, it is important to note that the National Policy for the integrated management of solid waste in Colombia (2016–2030) is aimed at promoting the circular economy, sustainable development, and adaptation and mitigation to climate change.

The validation of the methodology was carried out with the information of the MSWMS for the city of Cali—Colombia. From the assigned scores for the different Wasteaware indicators, the overall score for the MSWM was determined. The matrix method proposed by Sharma et al. [21] was adapted for this research. This study presents a comprehensive and consolidated assessment of MSWM performance in a city in Latin America and the Caribbean. Continuous improvement strategies have been identified for the indicators that have the lowest performance. It is planned that the evaluation and monitoring method of the MSWM will become part of the integrated management of solid waste policy in the country. The authorities responsible for leading MSWM in Colombia are the Ministry of Environment and Sustainable Development and the Ministry of Housing, City, and Territory.

From the implementation of the Wasteaware adaptation in Colombian cities, those providing urban cleaning service (authorities and other companies) will have consolidated information on the evaluation for the development of continuous improvement projects. The monitoring of the MSWM in LAC cities certainly contributes to the reduction of gaps in the components of the urban sanitation services. In Latin American, countries such as Brazil, Argentina, Bolivia, Chile, Mexico, and others can strengthen the MSWM based on the evaluation of the Wasteaware methodology adapted in this research considering that the political, economic, and social conditions are similar. This study can serve as an example and motivation to close the gaps identified in other LAC cities.

Materials and methods

Study area

The Wasteaware benchmark indicators were modified and aligned with the legal framework and national policy in Colombia. Colombia is a LAC country that is in the low to middle-income category [26]. It is located in the northwest of South America and has an area of 1,141,748 km2 distributed in 32 regions or departments [27]. It is divided into 1,123 cities [28]. It is the second-highest biodiverse country in the world [29]. For 2019, a population of 49,395,678 was projected, of which 76% are located in urban areas and the remaining 24% are located in rural areas [7].

The adaptation of Wasteaware was carried out to evaluate the performance of the MSWMS. It was taken as a case study on Cali, located in the Valle del Cauca region of southwestern Colombia (Fig. 1). The population of Cali was 2,470,852 inhabitants in 2019, of which 98.5% were in the urban area. The area of Cali was 120.9 km2, distributed in 22 districts [30]. Table 1 provides an overview of the components of the MSWM in Cali. These components are later analyzed using the adapted methodology.

Fig. 1
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Study area—Urban area Cali, Colombia

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Table 1 Relevant aspects of the MSWM in Cali
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State of the art of Wasteaware benchmark indicators

Wasteaware benchmark indicators are intended to perform a standardized evaluation of a cities MSWMS under the concepts of integrality and sustainability. Wasteaware allows city decision-makers to understand the performance of the urban sanitation service, prioritize MSWM programs to improve the service, identify strengths and weaknesses, and monitor changes over time [2, 20, 31]. Wasteaware is composed of 12 indicators, 7 corresponding to the physical components of the system and 5 to the governance aspects. The indicators that evaluate the physical components of the system, such as coverage, collection quality, and recycling rate, are made up of four quantitative and three qualitative indicators. Governance aspects look at financial stability and include stakeholders based on quality indicators.

The quantitative indicators, such as the tons of municipal solid waste that are ultimately disposed of in sanitary landfills, are calculated based on numerical data generated during the provision of urban sanitation services. Qualitative indicators are composed of five or more criteria that address issues associated with the indicator.

All criteria are evaluated on a scale of 0 to 20. An assignment of zero represents a negative evaluation of the criterion due to noncompliance. The other assignments determine the degree of compliance: 5 low compliance, 10 medium compliance, 15 medium–high compliance, and 20 high. The score is then normalized to obtain the indicator's value in percentage. The following Eq. (1) summarizes the methodology for calculating qualitative indicators.

$$OIS=\frac{\sum SC}{20\times NC}\times 100,$$
(1)

where OIS = Overall indicator score (%)SC = Score assigned to each criterion (0, 5, 10, 15, or 20)NC = Number of criteria applicable in the indicator (#)

The methodology establishes a traffic light color code, with 5 levels with a percentage range for each indicator (low: red, low/medium: orange, medium: yellow, medium/high: light green, and high: dark green) [2]. It is important to emphasize that the Wasteaware methodology focuses on solid waste from municipal origin.

Table 2 presents an average analysis of the results from Wasteaware benchmarks indicators by continent. A significant trend in the use of the methodology is observed in Asia, with 30 cities evaluated in the past 14 years. Africa, Latin America, Europe, and North America are followed by regions with 14, 13, 9, and 4, respectively. In LAC, there are experiences of application in cities in Brazil [20, 32], Argentina [2, 32, 33], Chile [32], Mexico [31] and Bolivia [34].

Table 2 Trend in the evaluation of the performance of the MSWMS by continent.
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In China, an adaptation of Wasteaware was made [35]. The adaptation incorporated aspects of the MSWM in this country, including technological advances and strategies related to sustainable development goals, specifically those related to cities and communities. This adaptation made minor changes to the Wasteaware methodology, increasing the level of demand in the measurement scale of some indicators. It was aligned with the initiative of the Asian country for climate change mitigation and its relationship to the proper management of MSW [35].

Based on a review of the regulatory framework and integrated solid waste management policy for Colombia, this study adapts Wasteaware to the context of a Latin American country (Colombia). Furthermore, it presents the results of the performance evaluation of the MSWMS for the city of Cali.

Calculation of the overall MSWM score using the matrix method

Different authors have used a matrix method to calculate the overall score of the Wasteaware benchmarks indicators, from 0 to 100%. This evaluation of performance allows us to compare two or more cities, as well as identify activities that should be strengthened in MSWM [21, 22, 36, 37]. An analysis of the results of the evaluation of the Wasteaware indicators adapted will be done by calculating the overall score (Eq. 2).

$$OS=\frac{\sum \left(RWI\times SI\right)}{5},$$
(2)

where OS = Overall score (%)RWI = Relative weight of the indicator (%)SI = Score of the indicator obtained by the matrix method (value between 1 and 5)

The Wasteaware adaptation for the calculation of the overall score categorized the indicators according to their importance and relevance. The indicators were grouped into three sets. Type I indicators, which could lead to a health emergency due to inadequate MSWM, were assigned a higher relative weight (12.5%). Type II indicators, of medium importance, contribute to strengthening and improving the MSWM (8.3%). Lastly, the desirable type III indicators (4.2%). The classification of the indicators and relative weights proposed for the evaluation of the MSWMS in Colombia are presented Table 3.

Table 3 The weighting of indicators for the evaluation of the MSWMS
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In this study, information from the MSWMS of the city of Cali was used for the evaluation with the adapted Wasteaware benchmarks indicators. To compare performance with other LAC cities, an adjusted matrix method was applied to recalculate the overall global scores and compared with the score obtained for the evaluation in Cali.

The application of the Wasteaware methodology adapted allows the calculation of a score for each indicator, in one of the five defined categories: 1 is low, 2 is medium/low, 3 is medium, 4 is medium/high and 5 is high. The overall score in a city is determined by the rating of each of the indicators (1 to 5) [21]. The value of each indicator is multiplied by its respective weight (12.5%, 8.3% or 4.2%), and the values obtained are added. The overall score of the Wasteaware assessment was calculated using Eq. 2.

Data collection

The evaluation of MSWM in the city of Cali was based on official data. These data were gathered from the different actors involved in the system (municipal administration, cleaning service companies, recycling companies). Occasionally, the actors themselves shared their experiences with each evaluated criterion. The information was collected using a mixed methodology, with data published in the Single Information System for residential public services and other official sources. Additionally, interviews were conducted with the main actors (public cleaning service companies, recycler associations, experts in health and safety at work, and planning experts from the MSWM).

Similarly, qualitative, and quantitative information was collected from reports prepared by the Superintendence of Public Services, the Special Administrative Unit of Public Services, the Administrative Department of Environmental Management, and MSWM plans. Furthermore, an exhaustive review of the Colombian integrated solid waste management policy, laws, decrees, and resolutions related to MSWM was conducted.

The year 2019 was used as the base year for the application of the adapted Wasteaware methodology. The analyzed data reflected a typical year for the city of Cali before the COVID-19 epidemic. Furthermore, it serves as a starting point for monitoring and controlling the indicators in the following years.

Results

Adaptation of Wasteaware benchmarks indicators

The review of 18 standards and regulations related to MSWM in Colombia was conducted. It was investigated that each indicator and criterion of the Wasteaware methodology was articulated with the technical and environmental requirements of Colombian standards. It was sought that the adaptation could be applied to any city located in the national territory. Several aspects that are not mandatory in Colombia or that represent high technical standards for MSWMS in the country were not included in the adaptation. Additional demands or requirements for representative standards were identified, including aspects that were not being evaluated by any indicator or criteria in the original Wasteaware methodology. It was therefore possible to adjust the definition or measurement scale of existing criteria, and additional criteria were added.

A description of the measurement scale for each criterion was provided for the qualitative indicators. It aims to assign the score in an objective manner and as standardized as possible. The description of the indicators and criteria is presented in a manner that is easily understood by municipal officials of varying levels of education. The scope of some criteria was expanded to include the presentation of MSW at collection sites, compliance with technical standards for the transport of MSW, and a degree of control over the treatment and disposal of MSW. The following criteria were added: the quality of the transhipment and transfer station and the effectiveness of post-closure of open-air dumps or sanitary landfills.

In the calculation scheme for the qualitative indicators, the option 'does not apply—NA' was included. This is for criteria that are not viable or represent a very advanced level for small cities with different approaches or priorities than the average in Colombia. The indicator was calculated only using the criteria for which scores were assigned.

It is important to note that the adaptation of the Wasteaware methodology was done exclusively at the criteria level. This allows the results of the evaluation for cities in Colombia to be compared to other cities in the world where the original methodology has been applied.

Performance of the MSWMS of the city of Cali

For 2019, the performance of the MSWMS for Cali—Colombia was high (91%) and none of the indicators analyzed were below the average level (Fig. 2). The scores obtained for each of the quantitative indicators and the scores assigned to each of the qualitative indicators are shown in Table 4 (the complete qualification matrix of indicators is presented in supplementary material in Table S1).

Fig. 2
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Evaluation of the performance of the MSWMS for Cali—Colombia using adapted Wasteaware

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Table 4 Qualification matrix of indicators for the evaluation of the performance of the MSWMS of Cali in 2019
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MSW collection

The urban area of Cali has a population of 669,315 homes, of which 97% are users of the municipal cleaning service [30]. The evaluation of the performance in the MSW collection coverage in Cali is medium–high, that is, it indicates the quality in the provision of the cleaning service in this city.

The waste captured by the MSWMS in Cali was consolidated based on information from the Integrated Solid Waste Management Plan. The information was provided by the operators of the public sanitation service and the associations of formal recyclers for 2019. A total of 676,867 tons of MSW were collected [38], with a high degree of compliance with the indicator (100%). The municipal administration reports a per-person production of 0.44 kg/hab-day for the urban residential area of Cali. In addition, the MSW is made up of 55% by the HSW [39]. Considering that the population of the urban area in Cali for 2019 was 2,190,363 inhabitants [10], it was determined that the theoretical generation of MSW was 639,586 tons. It is evident that the collection of material waste exceeded the theoretical generation of material waste. The calculation methodology (MSW = HSW/55%) and the variability in the available information for the same data would lead to a score higher than 100%

In Cali, the quality of the waste collection and street cleaning service was in the medium/high range (72%). This score is mainly affected by the presence of critical points for temporary storage of solid waste and the early submission of collection times. MSW accumulation in sites that are managed as critical points is recurrent, only 28% could be eradicated [40]. The observed variation in the presentation of the MSW by citizens varies significantly depending on the area of Cali and socioeconomic status [41]. The accumulation of MSW in containers or public roads is often inadequate, mainly due to the presence of homeless people, subnormal settlements, and high-level generation of MSW in marketplaces [41]. However, if the municipal administration recognizes the economic value of the MSWM, sanitation operators can manage the situation and keep roads and public areas clean. During 2019, no open dumps were identified in Cali, but open burnings were identified in some sectors [41].

The Superintendence of Residential Public Services reviewed the status of the vehicles used for MSW collection for Cali and determined that they met the majority of the technical requirements [42,43,44,45]. It also verified the use of all the required personal protection elements and support procedures were implemented for the management of their health and safety at work [42,43,44,45]. Furthermore, it was analyzed the transfer of MSW, finding a high degree of compliance with the required requirements and efficient transshipment activities [46].

MSW treatment and disposal

From the 676,867 tons of collected wastes in 2019, only 27,976 were recycled or reused, the rest being placed for final disposal in a controlled sanitary landfill.[47]. The information registered in the Single Information System corresponds only to companies or associations that comply with technical, administrative, and operational requirements that safeguard the environment. Therefore, it was assumed that 100% of the treatment and disposal was carried out in controlled facilities.

MSW is treated and disposed of with high levels of environmental protection (88%). The criterion for efficiency of energy generation and use was not included in this indicator since this treatment method was not used in Cali. The MSW is disposed of in the Colomba-Guabal sanitary landfill, where the reception is controlled by the operators and reports are generated that are audited by the environmental authority [46, 48]. The landfill personnel is continuously trained, they have a knowledge management model and use the required protection elements [48]. The current treatment of leachate from the Navarro dump, the former Cali disposal site, is in progress, but the other impacts are not being adequately compensated or mitigated [49, 50].

There is a record of the use of dry MSW in the urban area of Cali in that year. According to the single information system for residential public services (SUI) reports, the recycling rate for Cali was 24%. That represents an average performance relative to the total waste with potential for recycling (116,089 tons) [47]. Considering that there is no information on the use of MSW by the informal sector, the real rate could be higher. Some MSW managers are also legally constituted corporations or companies that are not required to report to the SUI.

The real rate could be higher since there is no information on the use of MSW by the informal sector. In addition, some MSW managers are legally constituted as corporations, limited liability companies, and simplified joint stock companies, and companies that are not supervised and cannot report their management in the SUI.

The quality of MSW reduction, reuse, and recycling in Cali is medium (56%). To evaluate this indicator, the environmental impacts associated with recycling were not considered, as recycled waste represents only 4% of the waste generated in Cali by 2019. The criterion of separation at the source of biowaste was not included either, since the city had not defined a differentiated treatment for that fraction.

The quality of separation at the source of dry recyclables is satisfactory, but it varies with socioeconomic status, type of housing, access to selective routes, and awareness-raising activities. The municipal administration and recycling managers developed awareness campaigns to promote the reduction, reuse, and recycling of MSW [41, 51].

The Municipal Mayor has made progress in incorporating waste picker associations into the formalization process, but street recyclers who are not associated are not recognized [49, 50, 52]. The use of personal protection elements by recyclable waste managers should be strengthened, as the operating personnel do not have a culture of self-care [53].

Inclusion of MSWM stakeholders

The user inclusion indicator for Cali is high (100%). In order to protect public health and the environment, all citizens of Cali have a continuous, quality MSW collection service [10]. The national legislative framework includes numerous laws, decrees, and resolutions governing the right of citizens to be attended by public or private sanitation service providers in Colombia. Superintendence of Residential Public Services engages in activities to promote social control, such as accountability, “Superservices to the neighborhood”, training to empower, citizen service fairs, and workshops for development and social control committees [54].

During the update of the Cali integrated solid waste management in 2019, different actors from the management chain participated. Furthermore, the municipal administration, the companies providing the public cleaning service, and the recycler associations have sufficient mechanisms to receive feedback from the public at the different stages of their management [55,56,57,58,59,60,61]. The Municipal Mayor of Cali developed activities related to information, education, and communication related to the MSWM [51, 62,63,64].

The inclusion of suppliers in Cali is in the high range (95%). In Colombia, there are regulations related to the characteristics, conditions, and obligations of different actors of the public sanitation service [65]. These regulations establish the characteristics that cleaning operators must have in their contracts [65]. The process of formalizing recycler organizations is also encouraged, through progressive strategies to include them in the system [66, 67].

The selection processes carried out by the Municipal Mayor of Cali for the execution of the projects, programs, and services required in the MSWM were open, responsible, and transparent [68]. Similarly, all service providers, or their representatives, were included in the decision processes of the MSWMS of Cali [69].

Financial stability

The financial stability of the MSWMS is high, with a score of 85%. Resolution CRA 720 of 2015 establishes the components of the MSWM to be included in the calculation of the public cleaning services rate [70]. From the analysis of the physical components evaluated, it is considered that the invested budget allowed for the service to be of high quality. It is important to note that the cleaning service rate is proportional to the income of citizens and is lower for low socioeconomic status [71]. During 2019, four initiatives were identified to ensure continuous improvement of the system. The organization of recyclers, selective routes, use of organics and the management of the sludge from the Navarro dump [72].

Adequacy of the national reference framework for the MSWM

The adequacy of the national framework of the MSWM is in the medium/high range (79%). Until 2019, various regulations were issued and implemented to regulate the MSWMS for Colombia, with objectives and goals for the actors involved. The responsibilities associated with the MSWMS are clearly defined, distributed, and supervised at the national and local levels [73,74,75]. It is recognized in the management reports of each agency that more than 90% of the budgeted activities could be executed [63, 76, 77].

Local institutional coherence

Cali has a high level of local institutional coherence (88%). Since 2004, an integrated solid waste management plan has been implemented. This plan is updated periodically when there is a change in local government or when there are significant changes in the MSWMS [10]. The responsibilities defined in the Integrated Solid Waste Management Plan fall mainly on the district planning agency. Other functions are dependent on the local environmental entity—DAGMA, the administrative unit of public services, and the local health entity [10]. Government agencies with responsibilities report a high level of compliance with the defined projects in the planning. Compliance was justified because they had sufficient resources [62, 64]. The final disposal of solid waste requires municipal cooperation with a regional operator [10, 78].

Due to the update of the integrated solid waste management plan, sufficient and high-quality information was consolidated for the evaluation of the MSWMS in 2019 [10]. However, it is not consolidated into one unit and the data may vary depending on the source of information.

Discussion

Wasteaware benchmarks indicators provide a general assessment of MSWMS performance in cities around the world [2]. However, many Latin American cities have unique technical, economic, and social characteristics. The Wasteaware adaptation methodology was proposed for Colombian cities, to include relevant aspects of the regulatory framework and the integrated solid waste management policy. Furthermore, different criteria were reviewed and adjusted to make them easier to understand, and the assignment of scores was not subject to interpretation. As previously mentioned, the 'Not applicable' option was included in the evaluation of the criteria for aspects that cannot be developed in a city specifically due to external factors. This decision allows the score of an indicator to be ignored if it does not apply to the city of interest.

A 91% score for the MSWMS of Cali indicates a high performance for the year of study (2019) at a global level. The evaluation of the Wasteaware benchmark indicators demonstrates that this city is an example of effective management and waste reduction practices. Limitations were presented for the assignment of the score in some criteria included in the evaluation of the MSWMS of Cali. The reason is that certain criteria require different sources of information. There are some subnormal settlements that are not counted, and the dynamics of the MSWMS in these sectors are formally unknown. Few users of the sanitation service in Cali have access to a selective route for achieving MSW. Some MSW collected is managed by actors who are not required to report to the SUI, such as private companies that are not constituted as public sanitation service companies, informal recyclers, and homeless people.

Table 5 provides a comparative analysis of the performance evaluation of the MSWM systems reported for different LAC cities. The following aspects stand out in the analysis of the MSWM in Latin American cities: medium, medium/low, and low performance of the recycling rate, and the quality of the 3Rs are common factors. The findings suggest that further enhancements may be required to enhance the degree of circularity of MSW. In general, MSW collection coverage had a medium/high to high performance, this is because this is a vital component to avoiding sanitary emergencies. The low scores achieved by several Latin American cities on several indicators may be attributed to a lack of formal data or official information.

Table 5 Comparative analysis of the performance evaluation of the MSWMS reported for LAC cities.
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The analysis shows that the indicators with the lowest performance in LAC cities are the recycling rate, quality of the 3Rs, and financial sustainability (Table 5). The low recycling rate in LAC is mainly due to informality [79,80,81], incipient integration between the formal and informal sectors and the lack of rigor in the implementation and supervision of policies. Furthermore, the benefits received by waste pickers are insufficient [82]. Another aspect to consider is the low demand for recycled raw materials by industry [83].

The poor quality of the 3Rs in LAC is mainly associated with the prevalence of a linear MSMW model [81]. The presentation of mixed waste and the deterioration of recovered materials hinders utilization. Other aspects to consider include the use of rapidly disposable products, the collection of mixed waste by sanitation operators, and the poor self-care culture of sanitation workers. [81, 84, 85]. Lastly, the limited budget and the lack of cooperation between actors make it difficult to implement strategies oriented toward a circular economy. [85].

The financial sustainability indicators performance demonstrates a medium to low behavior for the cities analyzed. The variation of the score is related to the economic situation of the country and the availability of resources for the MSWM [86]. Generally, the budget allocated for MSWM competes with investments in health, drinking water, and infrastructure [81], which makes it difficult to plan new capital investments [85]. Sometimes, direct and indirect costs of MSWM are not accounted for [81], so the budget does not meet 100% of the real needs. The lack of coordination between the national government and the cities regarding financial plans makes it difficult to use and monitor the resource at the local level [85]. Furthermore, in many Latin American countries, revenues are not sufficient to pay for the service provided to users, and other funds are used to bridge these economic gaps. [85].

In Cali, the overall score achievement for solid waste was underestimated. The available information does not include formal companies that are not obliged to generate utilization reports. The consolidation of recycling information is considered to be a first improvement strategy for the completeness of data. It includes the use made by private managers, with monitoring strategies and follow-up to informal recycling in the city. It is recommended that companies or associations that collect, classify and sell recyclable MSW implement a health and safety system at work. The lack of information provided in evaluations regarding improvement strategies necessitates the pursuit of research that provides additional insight into the subject matter.

It is important to focus efforts on improving the rate of solid waste utilization and the quality of the 3Rs—Reduce, Reuse, Recycle in the city of Cali. Diverse authors worldwide have developed strategies or tools that can be implemented in LAC cities, such as the machines where people deposit recyclable waste and receive discount coupons in return. [87]. A viable model system could also be implemented to recognize waste recyclers in different systems, levels, and responsibilities of the waste management activity [88].

Other strategies proposed including the implementation of geographic information systems combined with tree methods of optimization of the collection routes, in the same time encouraging the eco-design and reverse logistics of packaging in the industrial sector [89]. It would be beneficial to use machine learning methods to understand the generation and composition of solid waste in the industrial sector, to plan and encourage the reuse and recycling of materials and products [86].

Successful strategies have been implemented in several Latin American countries, which could be incorporated in Cali to achieve significant enhancement of its most crucial indicators. Brazil utilized machine learning techniques to establish connections between waste pickers and waste generation sources, thereby facilitating the provision of collection services [90]. Different strategies are being implemented in Mexico to improve community understanding of the importance of separating waste at source. These strategies include visiting each household. Furthermore, an exchange of recyclable waste for transportation vouchers or fresh food has been carried out, which encourages community participation. These measures have proven to be effective in encouraging more sustainable practices [84, 85]. A program in El Salvador that involves informal recyclers has been established. They are responsible for collecting recyclable waste weekly in previously selected locations. Generators who produce more than 5 kg of waste are rewarded with a bag and a green bonus as a form of incentive. Users with four green bonuses receive a 20% discount on the payment of the sanitation service [91].

Cali has implemented strategies that have enabled it to attain the highest score in three indicators. The excellent performance of the indicator of waste collection by the system is because the waste service operators and formal recyclers in the city report collection data on a digital platform. A sampling of municipal solid waste generation was also conducted in 2019. Both of these strategies have enabled us to monitor MSWM collection in Cali and implement the necessary measures to meet the goals. Operators that report the amount of MSW collected on the digital platform only receive payment for their services to the extent that they are endorsed by the supervisory bodies. Therefore, an economic strategy is employed to ensure that the treatment or final disposal is carried out in a controlled manner. These can be implemented in several LAC cities, mainly in those that scored the lowest on this indicator such as Cigres (Brazil), Belorizonte (Brazil), Managua (Nicaragua), Payogasta (Argentina), Cañete (Chile), and Cachi (Argentina).

Other strategies have also been implemented in the MSWM of Cali to encourage the inclusion of users. The providers of the public cleaning service are required to keep the common areas of the city clean, so that potential users can present their waste in common areas. In Colombia, there are laws, decrees, and resolutions that guarantee citizens the right to be heard by public or private companies that provide public services. Moreover, the community is motivated to exercise social control through accountability sessions, training to empower citizens, citizen service fairs, and workshops for development committees. The Municipal Mayor's Office of Cali developed activities related to information, education, and communication on issues related to MSW management. This included the use of social networks, the development of citizen projects for environmental education, and home visits. These programs can be implemented in several LAC cities, mainly those that obtained the lowest score for this indicator (Payogasta (Argentina), Cachi (Argentina), Buenos Aires (Argentina), La Paz (Bolivia), Mexico City (Mexico), Guadalajara (Mexico), Macae (Brazil), and Managua (Nicaragua)).

During this investigation, a web application was developed that utilizes the Wasteaware methodology adapted to evaluate the MSWMS in Colombian cities. It contains information about the Comprehensive Municipal Solid Waste Management System (ProSIGRSM, by its Spanish acronym). This digital tool is intended to be an additional instrument for planning and monitoring over time of solid waste management, and it can also be replicated in other Latin American cities. Therefore, it will be possible for the authorities responsible for MSWM to prioritize the allocation of resources toward strategic indicators. ProSIGRSM is designed to generate MSWM databases in a city and identify opportunities for improvement.

Conclusions

The original Wasteaware methodology was designed to be applied to any city in the world, regardless of its socioeconomic conditions. The adaptation for Colombian cities, however, serves as an efficient, effective, and useful instrument based on the rules and regulations of the MSWM. A precedent that justifies this adaptation are the adjustments made to the Wasteaware methodology in China in 2019.

The indicators and criteria of the original Wasteaware methodology, in general, are in line with the standards and the MSWM policy in Colombia. The adaptation allowed for the inclusion of new criteria, such as effectiveness post-closure of open dumps or landfills, and quality of the transshipment and transfer station. It is important to note that the results of the adapted Wasteaware methodology are fully comparable to those of the original version.

The application of the Wasteaware methodology adapted yielded very favorable results. The performance of the MSWMS of the city of Cali achieved an overall score of 91%, placing it within the high range of the rating scale for the year 2019. Cali was found to have the highest MSWMS performance among LAC cities that have used this methodology. The comparative analysis was conducted with 13 other regional cities that utilized the original methodology.

The MSWM of Cali had several strengths, such as a high degree of control over the treatment and disposal of waste materials, the presence of formal actors in the collection of waste materials, and the inclusion of users. The opportunities identified for improvement were the rate and quality of recycling. The other indicators indicated a range of performance between medium and high. Cali's MSWMS should be strengthened, specifically in the recycling component.

The informal nature of many municipal services contributes to the lack of measurement of service indicators. One way to strengthen the MSWM and improve future applications of the adapted Wasteaware methodology in LAC cities is to improve the quality and quantity of available information related to MSW. It is recommended to establish a policy for the generation of MSWM databases in cities. A digital tool is proposed for reporting the information on different actors in a mandatory manner. This will be the responsibility of the municipal administration or a delegated authority. The initiative aims to improve the management and consolidation of information and recommend measures for improving service provision. Future research could focus on developing this platform into a web tool, where all MSWMS actors report the information that corresponds to them semi-annually. This information will be consolidated by the city and reported at the national level.

This study establishes the foundations for the transfer of experiences between LAC cities in favor of the integral management of MSW. It was possible to identify common factors between cities in the region and opportunities for improvement with the Wasteaware application. This approach allows rulers to identify cities with similar contexts, which leads to success stories in low performance indicators. Therefore, international cooperation is essential between LAC countries to ensure the common use of the methodology adapted in this research and the transfer of knowledge about strategies implemented to achieve the integrality of the MSWM.