The zero-waste concept emerged in the 1970s in response to the rising global population and associated consumption patterns with the early efforts of Paul Palmer who begun the zero-waste movement in the chemical industry. Since then, initiatives, such as the Urban Ore, No Waste by 2010, Zero Waste USA and the Zero Waste Conference have gradually refined the concept (Mohajan 2025). The Zero Waste International Alliance has defined zero waste as: the conservation of all resources by means of responsible production, consumption, reuse, and recovery of all products, packaging, and materials without burning them and with no discharges to land, water, and air that threaten the environment and human health (ZWIA 2018). Zaman and Ahsan (2019) also describe the aim of zero waste as eliminating waste generation by ensuring that all materials are fully utilized, leaving nothing to be landfilled or incinerated.

However, these definitions present a practice-based limitation. Recent studies interpret the concept as a performance-based objective/ target rather than a literal elimination of all waste. The definition of the Welsh Assembly Government captures this clearly: “An aspirational end point where all waste that is produced is reused or recycled as a resource without the need for any landfill or energy recovery” (Cole et al. 2014). Although 100% source recovery is emphasised, real-world systems operate under material and economic constraints that necessitate residual management. Consequently, terms such as “zero waste to landfill”, “net zero emissions” and “zero waste city” are now commonly used to describe systems achieving high diversion rates and near-zero landfill dependence, rather than absolute zero outputs (Bakkaloglu et al. 2022; Permana et al. 2023; Usapein & Chavalparit 2013).

Practical municipal-scale examples support this interpretation. San Francisco (USA) reports diversion rates of around 80%, through mandatory recycling and composting although residual waste treatment remains necessary (Kaza et al. 2018). Similarly, Kamikatsu (Japan) increased recycling rates from 59% in 2008 to 81% (2020) through intensive source separation yet still incinerates residual fractions including high health risk items such as cigarette butts and sanitary products (19%) (Shenyoputro and Jones 2023). Likewise, Ljubljana (Slovenian) reports diversion rates of 78% mainly through recycling and composting but also relying on residual treatment through incineration and landfilling (Brglez et al. 2025). Studies for the city to Tshwane in South Africa focused on technological configuration to achieve zero waste to landfill in the long term (Snyman and Vorster 2011). These cases demonstrate that even advanced municipal systems achieve near-zero landfill rather than absolute zero waste.

In this study, the term “zero waste” is applied in an operational rather than literal sense through a proposed Zero Waste Disposal (ZeWaD) system. It appropriately describes a zero waste-to-landfill framework which has a primary objective to minimize waste disposal to landfills and uncontrolled environments such as open spaces and drainage channels which is particularly common in Ghana (GSS 2022). Although diversion of waste from incinerators is important in some countries, this is not the case in Ghana. There are only 244 small scale incinerators mainly for onsite medical waste treatment which is not a key component of municipal waste management (Ofori-Boateng et al. 2013; Zaman 2015). Consequently, the ZeWaD system in this study considers diversion from landfill a top priority while seeking to only direct residual end of life materials to the incinerator.

Institutional waste management can provide an effective pathway towards broader zero waste implementation within communities and cities due to their relatively closed operational boundaries. Studies on higher education institutions shows that zero waste measures can be implemented with comparatively lower logistical and financial complexity such as lower collection and transportation costs (Rodríguez-Guerreiro et al. 2024). For example, the Utrecht University, has developed an operational management sustainability plan with a goal to achieve zero waste to incineration or landfill by 2030 by optimizing separation and circularity (Utrecht University 2025). Similarly, University of Malaya also introduced a Zero Waste Campaign in 2011 which operates onsite reuse, composting and anaerobic digestion and external recycling. Diversion rates of 620 tonnes from the landfill have been achieved over six years with the aim of 60% diversion rate by 2040 and to provide research outputs within the field (Yusoff 2018). Ebrahimi & North 2017 highlights best practices from some United States universities including prioritizing investment into a robust source separation model (bins) and education/ publicity campaigns, publication of long term zero-waste campus targets with specific timelines, sustainable procurement policies, extensive stakeholder engagement and comprehensive monitoring and audits.

The Council for Scientific and Industrial Research (CSIR-IIR) CSIR-IIR is located at East Legon in Accra, Ghana’s capital city. Prior to the implementation of ZeWaD, both solid and liquid wastes were managed through municipal disposal systems. Unsorted solid waste was collected and transported directly to landfill sites, while blackwater was stored in septic holding tanks and periodically desludged by municipal collectors. Between 2010 and 2024, several studies into sustainable waste management technologies were undertaken, leading to onsite development and installation of multiple systems (Table 1). The ZeWaD pilot system presents an integrated operation of these technologies as a single waste management system comprising source segregation, three onsite treatment pathways (anaerobic digestion (AD), plastics recycling, and incineration) and supported by external treatment (recycling).

The system boundary of ZeWaD involves waste generation, onsite treatment, production of new products and linkages to external value chains. Figure 1 shows how these individual systems operate in one integrated system to achieve a zero-waste outcome. Interaction between the inner system and external value chains involve importation of medical waste and exportation of recyclables. This is intended to improve the financial sustainability of the system through additional revenues and reduce disposal of waste to landfills.

Source segregation is the first stage. Preliminary waste characterization was conducted which led to the design of a four chambered bin (Figure 2). The bin is locally welded with scrap metal, metal mesh and aluminium foil with local materials and expertise. Different coloured plastic bags are used to make segregation easier for users. Also, aluminium foil is required at the edge of the input area to reduce rust and avoid injuries due to rusting metal edges. An extensive education and feedback system was put in place to enhance user compliance with source segregation and reduce post collection segregation.

The anaerobic digester (AD) is constructed onsite using an anaerobic baffled reactor design with the same design as shown in Quashie et al. (2019) (Figure 3). The organic fraction of source segregated waste and the blackwater from water closet toilets are co-digested to produce digestate and biogas. The liquid digestate is pumped into an overhead tank for irrigation of an onsite garden whiles the solid digestate is disinfected and used as manure. The biogas is used for energy in the laboratory.

Onsite plastic recycling is done with the use of the hot melt process. Specifically, the hot melt process has been applied to water sachet bags (Mohammed et al. 2024; Tagbor et al. 2022) and polystyrene food packaging (Antwi et al. 2022; Antwi et al. 2024). The preliminary study for this process successfully produced name plates, floor tiles, and educational learning materials from a combination of waste polystyrene and 20% v/w of lauric fatty acid (Figure 4). The final material showed good tensile strength, moderate heat resistance and a smooth surface (Antwi et al. 2022).

The onsite incinerator treats residual waste which mainly contains end-of life plastics and paper and medical waste from nearby health facilities. The De-Montfort type incinerator was constructed with local materials and expertise. The design integrates a front-loading mechanism and a 5 m high refractory brick chimney: leaving only the metal grate exposed to high temperatures between 500-800 °C (Akufo-Kumi et al. 2014; Oduro et al. 2016) (Figure 5). Periodic maintenance ensures combustion and emission control is functioning effectively. The bottom ash is used as a construction material in sand plastic composite material, however with caution (Zhang et al. 2020). Bottom ash from incinerated medical waste in Ghana may contain high heavy metal concentrations above WHO permissible levels for soil (Debrah and Dinis 2023). Ongoing studies aim to optimize the incineration process through heat recovery and alternative safe uses of the bottom ash (Adazabra et al. 2023). With increased optimization, incineration may contribute to resource recovery rather than a disposal pathway.

The total recorded capital cost was $13,584, which is relatively low for the annual waste throughput because internal expertise was used; thereby significantly cutting the labour costs. The AD and incinerator systems constitute the highest technological investment (Figure 7b). Labour, materials, and parts replacement formed the major cost components of O&M. Total benefits on the other hand amounted to $4,100.5 over the 12 months monitoring period, comprising $2,778.5 in revenues and $1,322 in avoided costs. Compared to the baseline, the system is projected to save $82,010 over 20 years, excluding revenue escalation. Figure 7 presents the detailed comparative analysis.

Among the three technologies, incineration provided the highest economic return, whereas AD accounted for the highest share of capital cost. However, AD remains environmentally significant because landfill methane impacts from raw organics can be reduced by more than 50% (Bakkaloglu et al. 2022). Future improvements in heat recovery could further improve incineration economics. For example, waste incineration in Ghana has been projected to generate 400 MW from 14,000 tonnes/day, although tariff structures currently reduce profitability, as with AD and plastic pyrolysis systems (Armoo et al. 2024a; Yakah et al. 2024). Additional valorization of bottom ash in agriculture, ceramics, and wastewater treatment presents further opportunities (Bansal et al. 2024). The locally designed biodigester offers a flexible and cost-effective solution for institutions and households, consistent with successful co-digestion systems in Ghana (Agyenim et al. 2020). By reducing the volume requiring transport, the system supports local businesses and small-scale aggregators while creating jobs in external value chains (Lane et al. 2023). Revenues remain essential for long-term financial sustainability (Zaman 2022).

The financial assessment was conducted using the MFA and the financial parameters indicated in the methodology section. Table 3 shows the values for all parameters analysed. As compared to the capital cost, the NPV is positive, the IRR is far above the discount rate of 10% and the PBP is 5 years as compared to a project lifespan of 20 years. This shows a strong feasibility for replication. It must be noted that both revenues and costs were escalated at the 20-year historical average inflation rate of 15.12% which is higher than reported values from other countries. However, NPV results are positive with a short PBP.

The financial feasibility of the ZeWaD concept compares favorably with similar decentralized and hybrid systems reported in both African and global contexts. The internal rate of return (IRR) of 35.7% and discounted payback period of 4.68 years obtained in this study are stronger than the 16% IRR and 15.2-year payback period reported for a large-scale waste-to-energy plant at the Oti landfill in Kumasi, Ghana (Asante et al. 2023). The shorter payback in the present work is likely due to the modular integration of multiple resource recovery pathways—including composting, recycling, and ash valorization—which distribute revenue risks across several product streams rather than relying solely on electricity sales. Similarly, the strong feasibility aligns with the findings of Amponsem et al. (2023), who demonstrated that decentralized biogas-to-electricity recovery from municipal organic waste in Ghana is technically and economically viable. Compared with large thermochemical systems such as the hybrid anaerobic digestion–gasification configuration reported in South Africa by Mabalane et al. (2021), ZeWaD benefits from lower capital intensity and phased deployment, making it particularly suitable for institutional and district-scale applications. These comparisons suggest that ZeWaD’s hybrid circular design improves financial resilience by combining material recovery, biological treatment, and future energy recovery potential within a single modular system.

Beyond the positive financial indicators, the feasibility of ZeWaD should also be interpreted within the global circular economy transition, where decentralized waste valorization systems are increasingly recognized as financially resilient alternatives to centralized disposal systems. The strong IRR of 35.7% and short payback period of 4.68 years compare favorably with similar zero-waste and circular resource recovery systems reported in higher education institutions and industrial pilots globally (Monte et al. 2009; Trushna et al. 2024 and Vea et al. 2018). This suggests that the ZeWaD model does not only perform well within the Ghanaian institutional context, but also aligns with international evidence that modular circular systems can achieve economic returns when supported by effective segregation and downstream value chains.

A sensitivity assessment is carried out to compare the impact of NPV, IRR and PBP on four parameters: capital cost, O&M costs, Total benefits and Escalation rates (Figures 8 & 9). The increase in the Capital and O&M costs has a negative effect on the NPV, IRR and PBP whiles the Total benefits and escalation rate have a positive effect. Figure 8 shows relatively limited sensitivity to capital and O&M cost escalation. This may be due to the simple modular configuration which was developed over a four-year period and the extensive use of internal expertise. Compared to the financing models for commercial systems, items such as taxes, debt interest rates, high labour costs are not included in the capital and O&M costs. This explains the wide sensitivity ranges which assumes a comparatively high capital and O&M when installed under different scenarios requiring the excluded parameter. It may also give an indication of the low and high investment scenarios (Hadidi and Omer 2017). This confirms the deduction by Rodríguez-Guerreiro et al, 2024 that zero waste systems can be implemented at lower cost at higher education institutions (HEI). Although CSIR-IIR is not a HEI, its research activities and operations are similar to it.

The sensitivity of the total benefits and its escalation rate in Figure 9 shows that total benefits exert the strongest positive influence on financial performance. Increases in revenues and avoided disposal costs substantially improve NPV and IRR while shortening the payback period. This indicates that the long-term economic sustainability of ZeWaD depends strongly on stable and diversified value chains for recyclables, and possible waste treatment services for external institutions. In global circular economy systems, economic viability is highly dependent on stable demand for compost, recyclable materials, and residual treatment (Makan et al. 2025). The strong sensitivity to benefits highlights the policy direction in to improve economic feasibility for institutional waste management systems— particularly focusing on the recycling industry, construction material users, and compost market.