An Economically Sustainable Glass Recycling Business Model in Puerto Rico: A Conceptual Solution for Regions Without Government Recycling Programs

Abstract

In Puerto Rico, less than 5% of glass waste is recycled annually compared to a US national average of 25%. In regions like Puerto Rico, where government glass recycling programs are absent, glass presents a challenging waste stream to profitably recycle due to high transportation costs and low market prices, with few scalable models identified in the literature. This study emerged from a multi-year shared action learning partnership between Worcester Polytechnic Institute’s Puerto Rico Project Center and the Corporación del Proyecto ENLACE, a community development NGO serving the Caño Martín Peña communities in San Juan, Puerto Rico. Based on online research and interviews with 16 key stakeholders, we describe an economically sustainable glass recycling business model designed for the Caño Martín Peña communities that offers broader applicability for similar contexts. The business model achieves three goals: (1) it offers a free and convenient glass-collection service for the Caño Martín Peña communities; (2) it generates local employment opportunities in a low-income region; and (3) it operates in an economically sustainable manner. The viability of the glass-recycling business model is premised on strategic partnerships with government agencies, recycling companies, glass-sand markets, and local businesses.

1. Introduction

In 2018, an estimated 12.25 million tons of glass waste was generated in the US, only 3.06 million tons of which was recycled [1]. Glass waste presents an environmental hazard that can cause injuries when not properly collected, is non-biodegradable, and contributes to occupying landfill space all over the world [2]. Reusing glass waste offers a means to maintain natural resources, reduce landfill area, and save money and energy [3]. Low recycling rates have long been attributed to logistical challenges and low profitability in processing glass waste [4]. Clean, color-sorted glass cullet commands low prices on the market, coupled with the high cost of transporting heavy glass long distances to bottling plants that receive it as an input [5]. Most municipalities struggle to secure buyers for their mixed, broken glass, often resorting to using it as “alternative daily cover”, a substitute for the topsoil applied to landfills [6,7].

There has been clear evidence that container-deposit legislation, also known as bottle bills, offers the most effective means to sustainably manage glass waste [8]. These programs promote recycling and reduce litter by adding a refundable deposit fee to the product price of certain beverage containers that can be redeemed at authorized redemption centers, thus incentivizing consumers to return empty containers to designated collection points. On average, the 10 US states with bottle bills recycle approximately 65% of glass waste annually, whereas states without bottle bills recycle 30% of glass waste [9]. Moreover, total roadside litter has reduced by 30–64% in states with bottle bills [10].

Bottle bills have been implemented in many countries in the Global North to manage glass waste effectively. For example, Germany, Denmark, Finland, and Norway have national bottle bill systems that include glass containers. These programs have achieved high return rates, often exceeding 90%, demonstrating their effectiveness in promoting recycling and reducing litter [11]. A notable similarity among countries with successful bottle bills is the presence of strong governmental support and public participation. For instance, Germany’s system, established in 2003, mandates deposits on a wide range of beverage containers, including glass, and has significantly reduced litter and increased recycling rates [12]. Bottle bills are typically national policies in countries with smaller populations or more centralized governments, such as Norway and Finland. However, in larger countries with federal systems, such as the US, Canada, and Australia, bottle bills are implemented at the state or provincial level. This decentralized approach allows for tailored solutions that address specific regional needs and challenges [11]. Despite the success of bottle bills, many countries and regions around the world do not have such legislation. As of mid-2024, only 30 countries have implemented bottle bills [13]. This means that a significant portion of the global population, particularly in middle- and low-income countries without these programs, lacks the financial incentives to recycle beverage containers, leading to lower recycling rates and higher litter levels.

Despite its effectiveness, container-deposit legislation has been met with resistance. Industry stakeholders have raised concerns regarding the additional costs and administrative burden associated with implementing such legislation [14]. Coordinating and standardizing bottle bill systems across jurisdictions and stakeholders presents additional logistical and administrative complexities for governments. Moreover, glass is an inert material that does not contribute to pollution in landfills or incinerators [15], leading some to question whether glass recycling should be prioritized and economically subsidized over other waste streams [6]. Thus, in the absence of supportive legislation, glass recycling has primarily been led by dedicated citizens, environmental organizations, and private recyclers operating with thin margins—with few sustainable success stories and an absence of information sharing to inspire and support new initiatives.

Recent research has explored the economic feasibility of valorizing various post-consumer waste streams, demonstrating a growing interest in sustainable and profitable waste management solutions. These studies have focused on diverse waste types, including food waste [16], textile waste [17], plastic waste [18], poultry litter [19], and industrial waste [20], among others. The feasibility assessments typically employ a range of economic assessment tools and methodologies to evaluate the viability of different waste valorization projects. Common approaches include techno-economic analysis, which combines technical performance data with economic indicators to assess overall feasibility. Researchers frequently utilize financial metrics such as Net Present Value (NPV), Internal Rate of Return (IRR), Payback Period, and Return on Investment (ROI) to quantify the potential profitability of proposed waste valorization processes. Many studies also incorporate sensitivity analyses to account for market fluctuations and uncertainties in input costs or product prices. Additionally, life cycle assessment (LCA) is often integrated into these feasibility studies to evaluate environmental impacts alongside economic considerations, providing a more comprehensive view of sustainability [21]. Some researchers have also explored the concept of circular economy benefits, assessing how waste valorization projects can contribute to closed-loop systems and resource efficiency [22]. However, despite this diverse range of waste valorization feasibility studies, there appears to be a notable absence of research specifically addressing the economic feasibility of glass waste valorization in contexts without effective container-deposit legislation.

Current glass recycling technology has advanced substantially, enabling efficient collection, processing, and repurposing of glass waste. Modern recycling facilities utilize sophisticated machinery such as optical sorters, which use visible light and X-rays to scan and sort glass by color and type, ensuring high purity levels in the recycled material [23]. This technology produces high-quality cullet, which can be melted down and reused indefinitely without losing its properties [24]. Additionally, innovations like dryer systems and conveyor belt sorters enhance the efficiency of the recycling process [25]. However, these modern recycling facilities tend to only be economically sustainable when supported by government-subsidized programs.

There are a few small-scale efforts to collect and repurpose glass waste profitably, without government support, that have shown promise but also face significant challenges. For instance, Glass Half Full in New Orleans repurposes collected glass into sand and gravel for coastal restoration and construction, addressing both waste management and environmental restoration. Similarly, the Green Glass Recycling Initiative in South Africa transforms glass waste into decorative items and construction materials, providing local employment and promoting sustainability. In Australia, BottleCycler equips businesses with glass-crushing machines, enabling efficient on-site waste management and reducing environmental impact [26]. These initiatives often rely on community engagement and partnerships with local businesses [27]. For example, small businesses or community groups can gather glass waste from residents and local establishments, and then convert it into products such as glass sand for construction or decorative items [28]. This approach can create local employment opportunities and reduce the environmental impact of glass waste. However, the profitability and, thus, long-term sustainability of small-scale glass recycling is limited by several factors. The high cost of transportation and processing equipment can be a significant barrier, especially for operations without substantial financial backing. These initiatives tend to rely on volunteer support, charitable contributions, and consumer willingness to pay for glass-recycling services. Thus, most examples service higher-income populations. Despite these limitations, small-scale efforts can be successful with strategic planning, community support, and innovative business models that find niche markets for recycled glass products [29]. These initiatives highlight the potential for grassroots solutions to contribute to sustainable waste management, even in the absence of government-funded programs; however, there has been an absence of academic studies that explore scalable, economically sustainable glass recycling models that serve low-income communities.

This paper details a conceptual business model for an economically sustainable glass recycling initiative designed for the Caño Martín Peña communities in San Juan, Puerto Rico—a context with limited government recycling programs and funds to support environmental projects, a common feature in middle- and low-income country settings. The objectives of this research are to provide a free and convenient glass-collection service for the Caño Martín Peña communities, generate local employment opportunities, and ensure the model operates in an economically sustainable manner. The glass recycling conceptual business model described in this article offers broader relevance for regions with similar characteristics to our case study.

1.1. Glass Recycling in Puerto Rico

Puerto Rico has one of the lowest recycling rates in the US, which has strained its waste management system. The Puerto Rico Recycling Partnership estimates that 12–14% of all waste generated in Puerto Rico is recycled [30], compared to 32% in the mainland US [1]. Glass waste recycling is especially low. Based on industry expert interviews, Puerto Rico generated 100,000 tons of glass waste in 2000, of which only 3.8% was recycled through private initiatives [31]. Puerto Rico has 28 active waste disposal facilities that receive most of the island’s waste, which comprise 11 Environmental Protection Agency (EPA)-compliant landfills and 17 open dumpsites. Most waste disposal facilities have reached capacity, and the remainder are expected to be at capacity within a few years [32]. Thus, as a small archipelago, Puerto Rico requires significant waste reduction and waste recycling initiatives to sustainably manage its landfill capacity.

While recycling has been encouraged in government plans to divert waste materials from overburdened landfills, government-supported recycling programs have been patchy at best. In 1992, Law 70 set a recycling goal of 35% within three years and mandated recycling coordinators in each municipality. However, the Solid Waste Management Authority’s (SWMA) plan to expand solid waste management facilities was not fully realized, and the recycling goal was repeatedly postponed [33]. An estimated 30 of Puerto Rico’s 78 municipalities do not provide recycling services, while the remainder operate inconvenient and unstandardized systems [30]. Few municipalities offer curbside pick-up services, and there are insufficient drop-off centers, leading residents to dispose of recyclable materials in the trash or public spaces. Glass waste is generally not collected by municipal recycling programs and is only processed by a small handful of private companies that serve a niche, affluent, environmentalist clientele. For example, Reciclaje del Norte, a glass pulverizing company based in the municipality of Padilla, charges residents a collection fee of USD 0.25 per pound of glass, which is then pulverized and sold to cement manufacturers in Puerto Rico for USD 50/ton. Because government programs have been largely inadequate, the private sector accounts for approximately 80% of recycling in Puerto Rico [31]. Thus, in a context with inconvenient and underfunded municipal recycling programs coupled with expensive private recycling options, glass waste recycling is largely inaccessible to most of the Puerto Rican population.

1.2. The Caño Martín Peña Communities: Context for the Glass-Recycling Business Model

This study emerged from a multi-year shared action learning partnership between the Worcester Polytechnic Institute’s Puerto Rico Project Center and the Corporación del Proyecto ENLACE, a community development NGO serving the eight communities located along the Martín Peña channel that connects the San Juan Bay to the Laguna San Jose. This area became known as the “slum belt” and consists of over 11,000 people living in eight neighborhoods: Lan Monjas, Israel Bitumul, Barrio Obrero Oeste, Marina, Buena Vista Hato Rey, Barrio Obrero San Ciprian, Buena Vista Santurce, and Parada 27. The Martín Peña communities have been historically marginalized, as mass migration from 1920 to 1940 led to impoverished rural Puerto Ricans settling in government-owned land previously deemed unfit for residential or commercial use [34]. Currently, these communities face significant economic challenges, with over 60% of residents living below the poverty line and average incomes being half of the national average [35].

The Caño Martín Peña communities are overcrowded, with inadequate urban planning, leading to significant environmental and public health consequences. The once steadily flowing waterway that weaves through the communities and is home to a thriving ecosystem is now clogged with waste and debris. The channel has decreased significantly in width and depth over the past century from an original 200–400 feet in width to a maximum of 100 feet in 2018 as a result of excessive development and pollution [36]. The channel now stands stagnant, is prone to flooding, and is blooming with bacteria and pathogens [37].

Proyecto ENLACE was founded in 2004 with the main goal of dredging the channel, but preventative measures to avoid future pollution post-dredging are insufficient. Recently, the dredging of the canal was approved by the US federal government, with implementation of the USD 215 million project expected to be completed within the next decade. However, there are currently over 3000 structures that dump their sewage and waste into what remains of the channel [38]. While glass waste represents a small portion of the total waste stream and a holistic waste management approach is required, there are currently no accessible recycling options for glass waste available for these communities. Thus, a glass recycling project offers an opportunity to address multiple issues simultaneously: it can provide much-needed jobs, reduce environmental pollution, and support sustainable waste management practices.

This paper describes an economically sustainable glass recycling business model designed for the Caño Martín Peña communities that offers broader applicability to analogous contexts—that is, regions that have no government-sponsored glass recycling program, a clear market for glass waste, and a sub-population willing to pay for glass-collection services. The business model sought to achieve three goals: (1) to offer a free and convenient glass collection service for the Caño Martín Peña communities; (2) to generate local employment opportunities; and (3) to operate in an economically sustainable manner. In what follows, we describe our multi-method approach to developing the glass recycling business model. Then, we discuss the key elements of the glass recycling business model, which include collection, pulverizing, and markets for glass cullet coupled with estimated establishment and operational costs and the important role of strategic partners. While this conceptual model was designed for the Caño Martín Peña communities, we expect that its main principles will offer broader relevance for similar contexts.

2. Materials and Methods

This study employs a mixed-methods approach comprised of interviews and online research to assess the feasibility of a glass recycling business model that primarily serves the Caño Martín Peña communities. Our approach aligns with methodologies commonly used in waste valorization feasibility studies. Similar to recent research on various waste streams, including food waste, textile waste, and plastic waste, our approach combines qualitative data collection through interviews with quantitative economic analysis [16,17,18,19,20]. This methodology is consistent with other feasibility studies that utilize techno-economic analysis, incorporating both technical performance data and economic indicators to evaluate project viability. While many studies focus on financial metrics such as Net Present Value (NPV) and Return on Investment (ROI), our research places additional emphasis on the practical aspects of business-model development, including collection methods, equipment needs, and a particular focus on synergistic partnerships with a variety of stakeholders [39]. Moreover, unlike many existing studies that focus on government-supported initiatives, our approach emphasizes a community-driven, market-based approach, highlighting the potential for grassroots solutions to substantially contribute to sustainable waste-management practices in regions lacking government support [34]. This comprehensive approach allows for a holistic assessment of the proposed glass-recycling initiative and pathways for broader adoption in other, similar contexts, considering both economic sustainability and operational feasibility.

We conducted six semi-structured key informant interviews with recycling companies in San Juan, Puerto Rico to determine a collection method for the Caño Martín Peña communities that maximized glass collection while minimizing operational costs to optimize profits, to determine the equipment needed for the glass recycling business, and to ascertain other relevant business-development information. One of the recycling companies had an existing glass recycling program, while the others did not. In addition, we conducted 10 informative interviews with potential partners and clients for the glass recycling business (i.e., restaurants, bars, hotels, glass waste industry representatives) to determine their willingness to pay for glass collection services, establish market rates for pulverized glass, and explore details of strategic partnerships. We estimated glass collection costs by developing a collection route in the Caño Martín Peña communities to calculate time and operational costs. Finally, we estimated the remaining establishment and operational costs of the glass recycling business model through interviews with representatives of Proyecto ENLACE and through a combination of online research and correspondence with sales representatives from relevant industries. These estimates enabled us to determine the establishment costs before operations could begin, which included the machinery, trucks, collection bins, warehouse construction, and shipping costs associated with materials and machinery, in addition to the operational costs, which included insurance for workers and machinery, maintenance of machinery and vehicles, workers’ wages, electricity, gas, and general warehouse maintenance. The determined estimates were intended to develop a conceptual model that is feasible and economically sustainable; however, we recognize that each cost estimate is subject to change. The relatively small sample size of interviewees and potential bias in self-reported information introduces an additional limitation of the study.

The interview data were analyzed with a systematic approach involving notetaking during interviews, audio-recording when permitted, and subsequent transcription of these recordings. This multi-step process allowed for thorough examination of the information gathered. Using a grounded-theory inductive coding procedure, we systematically coded the transcripts and notes, allowing themes to emerge organically from the interview content. We focused on themes such as logistical challenges, economic feasibility, community engagement, and potential partnerships that informed the glass recycling business model. To validate findings, we employed triangulation by cross-checking information from multiple interviews, comparing responses across different stakeholder groups, and corroborating interview data with online research and industry reports. This approach helped ensure the reliability and consistency of the information used to develop the business model.

3. Results: An Economically Sustainable Glass Recycling Model

Below, we describe the main component of an economically sustainable glass recycling business model that can operate in regions without government-sponsored recycling programs that have access to pulverized glass markets and sub-populations willing to pay for glass-collection services. The model is premised on a cross-subsidized glass collection system where residents in a low-income neighborhood receive free glass waste collection, which is subsidized by businesses that are motivated to pay for glass collection services. The second revenue stream is derived from the sale of pulverized glass to concrete manufacturing companies. Combined, the revenue from business glass collection and the sale of pulverized glass generates sufficient profits to sustain the glass recycling operation and provide free glass collection for the Caño Martín Peña communities. In what follows, we describe the conceptual business model based on our interviews and online research, beginning with the collection of glass, through the processing and sale of pulverized glass, the organizational structure of the glass recycling business, and the necessity of strategic partnerships.

3.1. Glass Waste Collection: A Cross-Subsidized Approach

Within the Caño Martín Peña communities, recycling services are primarily provided by a private entity, Martín Peña Recicla, which collects about 22 tons of plastic, cardboard, and paper per year free of charge. Glass waste is not collected due to its high weight and low profit. Within our glass recycling business model, collection becomes economically feasible through a cross-subsidized approach: free collection for the Caño Martín Peña communities and collection as a paid service for external entities. Free household collection is essential for residents to participate in an unsubsidized glass recycling program. Martín Peña Recicla has established a collection route populated by residential clients who fill recycling bins with recyclable materials for weekly collection. According to the owner of Martín Peña Recicla, these clients have expressed a desire for glass collection and would be the first adopters, receiving a 60-gallon bin for weekly collection, with opportunities to expand to include new residential and business clients incrementally (see Figure 1). Residents can also deliver glass waste directly to the glass pulverizing center (described below). According to our projections, approximately 132 tons of glass waste would be removed from the Caño Martín Peña communities annually in the first year of operation based on an estimated 45 first adopters filling a 60-gallon bin weekly, with community participation expected to scale incrementally through word-of-mouth and strategic public awareness campaigns.

To offset the cost of operating free glass collection within the Martín Peña communities and supply a greater glass volume to maximize glass pulverization economies of scale, external entities such as hotels, bars, restaurants, and apartment complexes from the neighboring tourist-dense San Juan region would be secured as clientele. Interviews with these entities revealed a strong interest and willingness to pay for glass collection. Currently, businesses in San Juan dispose of glass with the general waste stream, with the nearest landfill charging USD 42 per ton for the tipping fee. Moreover, Reciclaje del Norte, a private glass recycling company in central Puerto Rico, has demonstrated success securing clients who pay USD 0.25 per pound of glass, which does not include collection service. Based on interviews with potential clients and market rates, we estimated acceptable glass collection rates for external entities to include a base fee of USD 30 per 95-gallon bin in addition to a transportation fee based on distance from the collection center. Interviewees shared that these costs would be similar to what they are currently paying for waste-disposal fees and were willing to incorporate the added logistics to support an environmentally beneficial recycling program. Clients would sign an annual contract, which would include 95-gallon bin(s) that an employee of the glass recycling business could load in a truck with a dump-bed. Within the first year of operation, the glass-recycling business would earn approximately USD 96,720 in collection fees from external entities based on collecting 62 bins per week, which is expected to increase in subsequent years.

3.2. Glass Pulverization and Markets

The market for glass waste is diverse and extends beyond traditional recycling into several specialized applications. Recycled glass can be used to produce containers and bottles, which remain a significant market segment. Additionally, glass waste is utilized in the production of foam glass, a lightweight and insulating material used in construction. Liquid glass, another application, is used in coatings and sealants due to its protective properties. Fiberglass production also heavily relies on recycled glass, providing materials for insulation and various industrial applications. Other markets include highway beads for road markings, abrasives for cleaning and finishing processes, and fillers in construction materials. These diverse applications highlight the broad potential for recycled glass, making it a valuable resource in multiple industries.

While there are a variety of glass waste processing mechanisms and product outputs, glass pulverization offers a versatile and profitable processing option in Puerto Rico. Pulverized glass offers value when added to concrete mixtures to replace typical sand materials. When pulverized glass of 20 μm accounts for 20% of a cement mixture, the strength and rigidity of the cement are optimized [40]. In Puerto Rico, concrete manufacturer Bloques Caribe owns a glass pulverizer and uses glass sand in its concrete mix. There are over 20 concrete manufacturers in Puerto Rico that could incorporate pulverized glass into their mixtures. Based on information from Reciclaje del Norte, the market rate for pulverized glass in Puerto Rico is approximately USD 50 per ton, which would generate a maximum of USD 78,000 annually based on full capacity throughput for a mini glass pulverizer of 1560 tons per year. In addition, fine glass sand can be sold for use in applications such as sandblasting, backfilling, and coral restoration, whereas larger pulverized glass offers a secondary product suitable for landscaping and garden decoration. Thus, the glass recycling business model can depend on the sale of pulverized glass at USD 50 per ton to concrete manufacturers while exploring alternative, potentially more lucrative, options for pulverized glass for different markets.

3.3. Economic Considerations and Organizational Structure

The glass recycling methodology involves several key stages to ensure efficient processing and high-quality output. Initially, glass waste is collected from both residential and commercial sources, then transported to the recycling facility. Upon arrival, the glass is sorted to remove contaminants and non-glass materials using a combination of manual sorting and automated systems, such as optical sorters and magnets. The sorted glass is then crushed into smaller pieces and fed into a pulverizer, which grinds the glass into fine sand-like particles. This pulverized glass is subsequently cleaned and screened to achieve the desired particle size and purity. The final product can then be packaged and sold to various markets, including concrete manufacturers, construction companies, and other industries that utilize recycled glass. This comprehensive methodology ensures that the glass recycling process is both economically viable and environmentally sustainable, providing a valuable resource for multiple applications.

The glass recycling business requires USD 324,300 to finance establishment costs and first year operation costs, which can be funded through a grant or low-interest loan. The establishment costs are estimated at USD 242,800, which include warehouse construction and machinery, a glass pulverizer, two pick-up trucks with a dump-bed, recycling bins, and office supplies. Notably, land for the glass pulverizing center will be provided by the Caño Martín Peña Community Land Trust in a non-residential area, minimizing noise pollution and public health risks (see Figure 1). Annual operating costs for the first year are estimated at USD 81,500 and increase to USD 142,900 per year as the business scales up to full operation (see

Table 1. This table shows the establishment costs, annual operating costs for the first year and subsequent years, and anticipated annual profit for the glass waste recycling business (Data sources that inform the cost estimations can be accessed here: https://digital.wpi.edu/concern/student_works/3t945v39g?locale=en, accessed on 1 October 2024).

	Variable	Amount (USD)
Establishment Costs	Powered dump dolly	4000
	Small articulated loader	38,200
	Truck with dump-bed	45,000
	Pulverizer	39,500
	Warehouse construction	90,000
	Concrete storage	9600
	Garage door	5000
	95-gallon recycling bins	10,000
	Office equipment	1500
Total		242,800
Year 1 Operational Costs and Revenue
Costs	Maintenance and insurance	2000
	Labor	81,500
Revenue	Collection fees	96,720
Gross Profit		13,220
Year 2+ Operational Costs and Revenue
Costs	Maintenance and insurance	18,500
	Labor	112,400
	Warehouse operations	12,000
Revenue	Collection fees	96,720
	Product sales	78,000
Gross Profit		31,820

). The glass recycling business will incrementally scale up operations to minimize operational costs while building organizational infrastructure and ensuring sufficient glass waste quantities to maximize glass pulverizing economies of scale.

The first-year establishment costs to finance the glass recycling business can be funded by government, philanthropic, or private entities through one of two mechanisms: grant funding or a low-interest loan. The preferred grant-funding option would enable a projected gross profit of USD 13,220 in the first year, followed by USD 31,820 annually in subsequent years, which can be reinvested to provide additional glass collection services for neighboring communities as the operation scales. Alternatively, through a low-interest loan, profits can be reallocated to loan repayments over a 20-year period.

The glass recycling business would initially employ three residents and be structured as a social enterprise non-profit organization. The social enterprise structure would provide tax-advantaged benefits, increase employee satisfaction, and generate opportunities for strategic partnerships with funders, clients, and allied partners. In the start-up phase, the social enterprise would be supported by Proyecto ENLACE’s economic development branch to build capacity toward independent operation.

4. Discussion

The Caño Martín Peña glass recycling business model offers an economically sustainable pathway to recycle glass waste in a context where government recycling programs are absent. Yet the economic sustainability of the model demands several strategic partnerships. Within our business plan, Proyecto ENLACE committed to initial and ongoing capacity building for the glass recycling business and employees, the Caño Martín Peña Community Land Trust provided land for the glass pulverizing center, Martín Peña Recicla offered access to their clients, concrete manufacturers must shift concrete mixtures to include glass sand, businesses must pay for glass waste collection, and a financial backer must offer a grant or favorable low-interest loan. Each of these partner commitments embeds risk in the viability of the model and demonstrates the necessity for strategic partnerships to facilitate an economically self-sustaining approach to recycling glass waste in the absence of a government-supported bottle bill. Even with these partnerships, the modest annual profits can induce organizational stress and limit growth opportunities.

Additional mutually beneficial partnerships with government entities and corporations offer pathways to expand glass collection capacity and reduce organizational risk. The San Juan municipality and the Puerto Rican government stand to benefit from the glass recycling program. Glass recycling reduces litter in public spaces, saves landfilling costs, and supports island-wide recycling targets. For example, within the Caño Martín Peña communities alone, if 430 tons of waste were diverted from landfill annually, it would save the government approximately USD 10,500 in landfill costs and modestly extend the lifespan of existing landfills [30]. Additional savings through subsidies per ton of glass waste recycled and tax waivers can offer low-to-no-cost financial incentives that governments can provide to support environmental management. For example, the San Juan Municipality currently subsidizes Martín Peña Recicla with USD 3500 per month to support their recycling efforts; a similar arrangement could be made for glass recycling. In other contexts, government partnerships may offer long-term low-cost leases for land to construct a glass pulverizing center. Glass bottle producers offer another strategic partnership opportunity as corporations face increasing pressure to operate sustainably. In contexts where glass recycling is inaccessible to the public, opportunities to remove labeled bottles from public spaces and advertise environmental responsibility can produce mutually beneficial partnerships. In Puerto Rico, alcohol companies Barcardi, Don Q, and Medalla have modest environmental sustainability programs in place and have supported small-scale projects without economic sustainability potential [41]. Because glass waste offers a challenging waste stream to develop an economically sustainable recycling program, such strategic partnerships become necessary for the long-term sustainability and impact of the glass recycling business model.

This study offers an economically sustainable business model to collect and process glass waste in a context where government-supported glass recycling is absent. By collecting glass waste from community members, pulverizing the glass, and then delivering the glass sand to concrete manufacturers, glass pollution can be reduced, helping prevent the clogging of the channel in the Caño Martín Peña communities while providing employment opportunities in a low-income region. Moreover, producing glass sand reduces the need in concrete manufacturing processes for natural sand, which is a non-renewable resource with a steadily rising price due to lack of supply, while other sand substitutes such as silica sand carry long-term health risks such as silicosis and lung cancer [42]. Within the described glass recycling business model, glass waste will be reduced by up to 430 tons per year, saving space in landfills, and by extension saving the municipality money.

Comparing our model to other community-based glass-recycling efforts previously discussed provides valuable insights. For instance, the Glass Half Full initiative in New Orleans successfully repurposes glass into sand for coastal restoration, demonstrating the importance of aligning recycling efforts with local environmental needs. Similarly, the Green Glass Recycling Initiative in South Africa highlights the potential for creating local employment through the production of decorative items and construction materials from recycled glass. However, these initiatives also face challenges such as high transportation costs and reliance on volunteer support, which underscores the need for strategic partnerships and sustainable funding models. By learning from these successes and limitations, our model aims to create a scalable and economically sustainable solution tailored to the unique context of the Caño Martín Peña communities.

The economically sustainable glass recycling model that we present in this article has broader applicability in other regions, particularly given that only 30 countries worldwide have implemented bottle bills, leaving the majority without government-supported glass-recycling programs [13]. This underscores the need for market-based solutions to manage glass waste effectively. Suitable regions for exploring this model must have certain characteristics: low-income communities that would benefit from the program and are located near affluent businesses or residents willing to pay for glass recycling services; proximity to concrete manufacturers or other outlets who can purchase and utilize pulverized glass; and opportunities for strategic partnerships with local businesses, NGOs, and government entities. For instance, regions in Southeast Asia, where urban centers are surrounded by economically disadvantaged areas, or certain African cities with burgeoning construction industries, could benefit from adapting this model [43]. Additionally, cities in Latin America, which face similar waste management challenges and have active community organizations, might find this approach particularly effective [44]. By leveraging local resources and fostering community engagement, these adaptations can substantially contribute to sustainable waste management practices in diverse global contexts.

Despite the promising findings, this study has several limitations worth considering. The relatively small sample size and specific context of the Caño Martín Peña communities may limit the generalizability of the results. Additionally, the reliance on self-reported data from interviews introduces potential biases, such as social desirability bias. The economic feasibility of the business model is based on certain assumptions about market conditions, costs, and revenues, which may change over time. Long-term sustainability poses another challenge, as maintaining strategic partnerships and securing ongoing funding are critical for the model’s success. Finally, implementation requires significant financial investments for the initial establishment costs, a complex coordination system to manage the logistics of collecting, transporting, and processing glass waste, and sustained community engagement from residents and participating businesses.

While container-deposit programs offer the most effective means to manage glass waste, many regions have been unable to pass legislation necessitating creative business models to profitably recycle glass waste. Glass presents a challenging waste stream to profitably recycle due to high transportation costs and low market prices, with few scalable models identified in the literature. In this article we offer an adaptable concept for an economically sustainable glass recycling business model designed for the Caño Martín Peña communities, although we believe there are opportunities to expand this model to other settings with similar circumstances; for example, low-income communities located near affluent, tourist-dense areas offer possibilities to cross-subsidize glass collection costs. Additional strategic partnerships with government agencies, pre-existing recycling operations, and glass sand markets are necessary to ensure economic viability.