Estimating Households’ Willingness-to-Pay for Improved Waste Treatment Service in Vietnam

Abstract

Waste pollution is becoming a major health issue in many developing nations. Waste-reduction options have been investigated and proposed, but environmental culture-based initiatives have not. This study explores and advances Vietnamese families’ environmental culture related to waste management, using the Culture Tower framework and a contingent valuation method coupled with a Bayesian model (CVBM). Specifically, descriptive statistics measure environmental literacy, while CVBM determines household willingness-to-pay (WTP) and estimates WTP for waste treatment services (WTP4WTS). Based on our survey of 487 households across 11 communes and wards in Hai Phong City, local waste pollution has decreased over time, although the respondents remain concerned. Over 13% of households were dissatisfied with waste treatment services (WTSs), while approximately 50% were neutral. Most respondents (79.26%) were willing to pay for improved WTSs, with an average WTP of 60,200 VND (US$2.32) per household per month. Behavioral and perceptual factors, such as the desire for improved waste services, current perceived waste pollution, and the perception that pollution has worsened, were found to significantly influence this willingness. Our study makes three major contributions. First, it develops a novel CVBM framework that links environmental culture and an economic valuation method, strengthening green economy micro-behavioral research. Second, it advances the circular economy literature by highlighting household engagement and willingness-to-pay as key drivers of sustainable waste financing and resource-loop closure. Third, it provides empirical evidence to inform and refine Vietnam’s revised Law on Environmental Protection (2020), particularly in implementing the “polluter pays” principle, promoting waste classification at the source, and designing socially acceptable environmental financing mechanisms.

1. Introduction

“…What is the issue? First and foremost, garbage. The pond is filled with plastic bottles, nylon bags, and more. Fish are dying, and even the living ones are hard to catch. Countless times, Kingfisher dives headfirst into a Coca-Cola bottle. On one occasion, he was tricked by a fish that made him struggle for ages, only to discover he had wasted his efforts catching an old plastic toothbrush that someone had discarded in the pond…”.

In “C’est génial!”; Wild Wise Weird [1]

Household waste is one of the fastest-growing environmental challenges of our time, especially in developing and transitional economies. As countries transition from low-income to middle- and high-income status, their waste generation and management patterns evolve alongside economic development. Rising prosperity, rapid urbanization, and population growth drive sharp increases in per capita waste generation, while space for waste treatment and disposal becomes increasingly scarce. Global waste could increase by 70% by 2050, threatening environmental quality, public health, and social well-being [2,3,4].

While this global trend poses challenges for all nations, it is particularly pressing in transitional contexts where economic growth outpaces institutional and infrastructural capacity. Vietnam illustrates this contrast between rapid economic growth and mounting environmental pressure. Since the Doi Moi reforms, sustained GDP expansion, urbanization, and rising household incomes have significantly transformed consumption patterns and waste generation. Vietnam now produces approximately 65,000–70,000 tons of solid waste per day, with landfilling still the dominant treatment method [5]. Vietnam’s GDP has maintained a high growth trajectory, reaching approximately 7.09% in 2024 and a per capita income of about USD 4700, reflecting strong macroeconomic expansion [6]. However, this rapid economic growth has not been matched by proportional investment in waste treatment infrastructure. For instance, landfilling continues to account for the majority of waste treatment, while advanced solutions such as waste-to-energy incineration remain limited in number and capacity. In addition, evidence suggests that up to 90% of provinces do not meet the regulated standards for landfill land-use efficiency, indicating systemic constraints in infrastructure planning and utilization [7]. This imbalance between rising waste generation driven by economic growth and the relatively slow expansion of treatment infrastructure highlights a critical structural gap in Vietnam’s waste management system. In particular, waste treatment infrastructure including controlled sanitary landfills and waste-to-energy incineration facilities has not expanded at the same pace as economic growth, creating increasing pressure on existing systems.

Although waste collection coverage has improved in many urban areas, treatment capacity remains limited and uneven across regions. Available evidence indicates that waste management financing in Vietnam remains structurally imbalanced, with a large share of operational costs covered by public subsidies while household contributions remain relatively low. Recent estimates further suggest that around 70–90% of solid waste management costs in Vietnam are financed through government subsidies to state-owned companies while households pay only a small share [8]. This subsidy-dependent financing structure places considerable pressure on local public budgets and constrains the resources available for upgrading treatment, recycling, and environmentally sound disposal infrastructure. Consequently, while basic collection services are relatively well maintained, investment in advanced treatment technologies and system modernization remains limited. As a result, the long-term sustainability of waste management systems remains uncertain. Within this context, estimating households’ willingness-to-pay (WTP) for improved waste treatment services becomes a critical analytical tool for assessing financial sustainability. Specifically, WTP estimates provide empirical evidence on the extent to which user-based financing could contribute to cost recovery and reduce reliance on public subsidies. In addition, such evidence is essential for evaluating the feasibility of attracting private sector participation, as stable and predictable revenue streams are widely recognized as a key prerequisite for developing public–private partnerships in environmental infrastructure [9]. Despite government initiatives promoting waste segregation and circular economy approaches, public participation and financial contributions to waste services remain low [10].

Vietnam exemplifies the dual burden faced by transitional societies balancing economic growth and modernization with environmental sustainability. Weak institutional capacity, fragmented governance, and inconsistent policy enforcement continue to hinder effective waste management [11]. At the same time, environmental education and public awareness are still evolving. As traditional communal norms emphasizing harmony with nature intersect with modern, market-driven lifestyles, Vietnam’s environmental culture is being reshaped. This coexistence creates a hybrid cultural landscape in which households’ environmental behaviors such as waste sorting and WTP for improved services are influenced by competing value systems and shifting moral priorities.

Within this evolving context, households play a pivotal role in promoting environmental sustainability. They are both primary waste generators and key participants in reduction and recycling efforts. Their engagement through waste separation, reduced plastic use, or paying for treatment services is vital for building sustainable waste management systems [12]. However, such participation extends beyond financial calculation; it is deeply influenced by cultural, psychological, and contextual factors that shape how individuals perceive and respond to environmental challenges [13]. Empirical evidence further confirms that knowledge-based and behavioral dimensions jointly predict survival and sustainability outcomes across diverse socio-ecological contexts [14].

From a regulatory perspective, Vietnam is implementing the revised Law on Environmental Protection [15], which introduces key reforms such as mandatory waste classification at the source, extended producer responsibility (EPR), the “polluter pays” principle, and a stronger orientation toward circular economy development. However, significant gaps remain between regulatory design and practical implementation, particularly in household awareness, behavioral readiness, waste separation practices, and recycling participation. Addressing these gaps has become an urgent policy priority, as Vietnam seeks to transition from a landfill-dependent system toward a green and circular economic model.

To fully understand these dynamics, the concept of environmental culture provides a valuable interpretive lens. It captures the shared beliefs, values, and norms that shape how individuals and communities perceive and interact with the natural environment [16], thereby offering deeper insight into the moral and normative dimensions of environmental behavior. Its importance lies in revealing that environmental issues are not merely technical or economic, but fundamentally cultural and behavioral phenomena, where decisions about waste, consumption, and sustainability reflect internalized social values rather than external incentives alone [17]. In transitional contexts like Vietnam, environmental culture helps explain how evolving cultural orientations mediate environmental action, as traditional collectivist ethics of stewardship increasingly intersect, and sometimes conflict, with market-oriented values emphasizing convenience and consumption. These overlapping value systems illuminate why households may express similar intentions yet differ in WTP or participation. By situating household waste behaviors within this broader value-centered perspective, the study reveals how Vietnam’s modernization process is not only transforming its economy and institutions, but also reshaping the cultural foundations of environmental responsibility.

From a broader environmental economics perspective, understanding households’ willingness-to-pay for waste treatment services is essential for designing sustainable financing mechanisms, mobilizing private contributions, and reducing fiscal pressure on local governments. Empirical evidence on payment capacity and behavioral drivers can provide a practical foundation for refining regulatory instruments under the 2020 Law, closing policy gaps related to waste treatment, recycling systems, and circular economy incentives, and supporting Vietnam’s long-term green growth strategy. In particular, by revealing households’ willingness to financially support improved waste treatment and their behavioral engagement with waste-related practices, the study provides actionable insights for enhancing resource recovery, strengthening recycling participation, and reducing reliance on landfilling—key pillars in Vietnam’s transition toward a circular economy.

Most studies on household willingness-to-pay (WTP) for waste treatment services focus on economic or demographic factors [18,19,20], whereas cultural and psychological dimensions are often overlooked, leaving the underlying reasons why some households actively engage while others remain disengaged, insufficiently understood. A few studies employed value-centered frameworks, such as the mindsponge mechanism [21], to explain how individuals absorb and internalize environmental values through cultural and cognitive filtering. Building on this perspective, the Culture Tower framework highlights how environmental awareness, behavioral engagement, and financial contribution emerge from layered cultural structures and shared social norms [22]. Notably, recent applications of the CBMM approach, combining Culture Tower with the Bayesian mindsponge framework (BMF), have demonstrated its analytical power in uncovering knowledge–behavior–survival linkages in diverse empirical contexts [23], lending further support for its extension to environmental valuation settings.

This study, therefore, employs the contingent valuation method [24] coupled with the Bayesian mindsponge framework [25] to investigate how environmental culture and household environmental perceptions influence willingness-to-pay for improved waste treatment services in Vietnam as a transitional country. By integrating cultural, perceptual, and economic dimensions, it provides insights into the drivers of pro-environmental behavior and offers practical guidance for designing policies that strengthen household engagement and financial participation in Vietnam’s waste management systems.

2. Literature Review

Household participation has become a cornerstone of effective solid waste management, particularly in decentralized and community-based systems. However, participation remains uneven across socio-economic groups and localities, shaped not only by socio-economic factors and institutional trust [26,27,28] but also rooted in environmental culture, which informs how households perceive responsibilities, evaluate environmental initiatives, and decide whether to contribute financially or behaviorally to sustainable waste management [29,30].

Environmental culture refers to the collective values, beliefs, norms, and practices through which communities interpret and interact with the natural environment. It shapes how individuals perceive environmental risks, civic obligations, and social expectations surrounding ecological behavior. These cultural dimensions influence households’ environmental perceptions and their willingness-to-pay (WTP) for environmental services, as individuals who internalize pro-environmental values are more likely to perceive environmental contributions as legitimate collective responsibilities rather than individual burdens [31,32]. In this sense, environmental participation can be understood not only as an economic decision but also as a culturally embedded process shaped by shared norms and values.

WTP for improved waste management services remains a critical indicator of financial and moral commitment. The theory of planned behavior (TPB) [33] and value-belief-norm (VBN) model [34] explain how attitudes, norms, perceived control, and moral obligations shape WTP. When households perceive waste fees as fair and controllable, they are more likely to contribute. Protection motivation theory (PMT) [35] suggests that WTP arises from threat appraisal (perceived risk severity) and coping appraisal (confidence in collective efficacy).

Empirical evidence from developing countries supports these theoretical predictions. For example, Afroz and Masud (2011) [36] found that in Kuala Lumpur, education, income, and concern significantly influenced WTP, with households willing to pay MYR 22 (USD 6.89) monthly. Research in Dhaka revealed that trust in service providers, moral norms, and perceived difficulties were critical WTP determinants, with mean values of 13 Taka (USD 0.18) monthly [37]. These findings highlight that WTP reflects a combination of economic capacity, environmental perceptions, and institutional trust rather than purely financial considerations.

Traditional models highlight income, education, and gender as primary predictors, yet growing evidence emphasizes non-economic factors such as environmental perception, service satisfaction, and institutional trust [38,39]. Financial capacity alone does not guarantee pro-environmental behavior unless environmental responsibility is internalized [40,41]. Households’ perceptions of waste significantly influence WTP. Viewing waste accumulation as a threat or perceiving deteriorating service quality increases willingness to contribute [42,43,44,45]. Behavioral engagement such as waste separation or experiencing sensory cues (odors, visible overflow) signals internalized pro-environmental norms and strengthens WTP [46,47].

Institutional trust and service satisfaction also play a crucial role in shaping environmental participation. Confidence in transparency, consistent service, and effective communication enhances perceived payment efficacy, whereas limited transparency or weak feedback loops reduce motivation to pay [48,49,50]. Evidence from Malaysia similarly shows that households receiving reliable door-to-door waste collection services demonstrate higher willingness-to-pay for service improvements [37].

Community dynamics also influence environmental participation through collective action mechanisms. Social dilemmas in waste separation behavior have been examined through trust and reciprocity. For instance, Nguyen et al. (2015) [51] demonstrated in Hanoi that trust in government and service providers was the strongest predictor of waste separation intentions, followed by personal moral norms and perceived difficulties, with 72% of households willing to commit financially. The study also showed that households were more willing to participate when they believed that others would do the same, highlighting the importance of community-based management approaches in overcoming collective action problems.

These dynamics are particularly relevant in Vietnam, where environmental culture continues to evolve during socio-economic transition. In rural and peri-urban areas, environmental culture remains emergent. While the New Rural Development movement has promoted civic order and hygiene, a coherent environmental culture rooted in shared ecological awareness has yet to fully develop. Traditional values of community harmony and resource thrift coexist with rising consumerism, leading to cognitive dissonance between environmental concern and daily practices [49,50]. Weak environmental culture often results in low participation and free-riding despite the moral awareness of pollution [52,53,54].

Since Doi Moi reform, rapid industrialization and urbanization have intensified waste challenges. Vietnam generates about 69,400 tons of solid waste daily, with 37,250 tons from urban areas and 32,150 tons from rural areas [55]. While urban collection coverage exceeds 97%, rural treatment remains around 80%, revealing service quality and cost recovery disparities [55]. The 2020 Law on Environmental Protection mandates household waste separation and user fees, yet WTP varies greatly.

Empirical studies in Vietnam reveal substantial WTP variation reflecting socio-economic conditions, regional context, and service quality perceptions. In urban areas such as Bien Hoa and My Tho, average monthly WTP was estimated at VND 14,450 and VND 13,000 [56], while other studies indicate WTP ranging from VND 111,000 to VND 155,000 per month [48]. In contrast, studies in rural and mountainous areas estimate WTP based on the amount of waste generated rather than a fixed monthly household fee, reflecting different waste charging schemes. For example, WTP was estimated at 673 VND/kg to 779 VND/kg [48,57]. These differences indicate that WTP estimates are closely related to local pricing mechanisms and service arrangements. In addition, perceptions of fairness, transparency, and visible improvements further influence WTP, with higher contributions when residents recognize environmental benefits and trust local authorities [49,50].

Despite the growing body of research on WTP determinants, many existing models treat WTP as purely economic behavior, overlooking the role of environmental culture and cognitive filtering processes in shaping financial participation. Most studies examine determinants such as income, perceptions, and institutional trust separately rather than as components of a broader socio-cultural system influencing environmental decision-making.

Recent conceptual approaches increasingly emphasize the role of cultural and cognitive systems in shaping environmental behavior. The mindsponge [21] conceptualizes individuals as information filters who absorb environmental values based on trust and perceived benefits. Building on this perspective, the Culture Tower [22] emphasizes that cognitive mechanisms operate within shared cultural structures—social norms, moral codes and collective expectations—shaping how people interpret environmental information. Compared with conventional behavioral models, the Culture Tower framework offers an integrative perspective that connects environmental awareness, behavioral engagement, and financial contribution within a unified cultural system. By conceptualizing environmental culture as a multi-layered structure consisting of awareness, action, contribution, and innovation, the framework provides a useful lens for examining how environmental perceptions evolve into consistent pro-environmental behaviors and financial participation [23,40]. Yet, despite its conceptual relevance, the application of this framework to empirical studies of household willingness-to-pay remains limited, particularly in transitional economies.

This study addresses that gap by integrating environmental culture, perceptions, and behavioral engagement into a unified framework grounded in the mindsponge mechanism. By doing so, it extends WTP research beyond income-based determinants to reveal how cultural internalization of environmental values translates into monetary support for sustainability initiatives.

3. Culture Tower-Based Framework of Environmental Culture Associated with Waste Management

In this study, the Culture Tower framework [22] was adopted to explore the multidimensional interaction between people and waste management systems. The framework emphasizes the role of environmental culture in shaping awareness, behavior, and contribution toward improving local waste management services (Figure 1).

Figure 1. Conceptual framework of waste management, adapted from [22,23].

In this framework, Block K refers to an individual’s knowledge, perceptions, interests, and attitudes toward waste generation and management. This stage reflects the initial level of environmental engagement, where perceptions of waste-related problems such as pollution, improper disposal, and recycling are formed. Heightened awareness and concern about these issues are often associated with greater participation in environmentally responsible actions such as sorting waste at the source, reducing household waste, or contributing financially to the improvement of waste services.

Block A stands for action (“Hanh dong” in Vietnamese), highlighting the transformation of environmental knowledge and awareness into concrete behavioral practices. While knowledge is essential, it is not sufficient to achieve behavioral change. Actions such as consistent waste separation, participation in community clean-up activities, and cooperation with local waste collection systems reflect higher levels of civic engagement. In this study, action (Hanh dong) reflects the habitual and skill-based practices through which individuals contribute to improving waste management performance in their communities.

Block U refers to utility, capturing the extent to which individuals benefit from effective waste management. When waste is properly managed, residents enjoy cleaner, safer, and healthier living environments. These benefits create positive reinforcement for continued engagement in pro-environmental behavior. In contrast, negative utilization, such as littering or illegal dumping, undermines community well-being and collective environmental responsibility. Therefore, perceived utility acts as a determinant that can either encourage or hinder waste management participation depending on the level of satisfaction and perceived community benefits.

The highest level of engagement is Block C, which represents contribution. At this stage, individuals move beyond compliance and participation to actively contribute their financial or voluntary resources to community waste management initiatives. Such contributions may include a willingness to pay higher waste collection fees, donate to environmental improvement funds, or participate in co-management programs for local waste infrastructure. Traditionally, municipal waste management has been viewed as a public service financed exclusively by local authorities. However, households’ readiness to contribute indicates a shift toward shared environmental responsibility and collaborative governance. This evolution reflects a mature stage of environmental culture in which collective actions may help alleviate local fiscal constraints and enhance the long-term sustainability of waste management systems.

In summary, the Culture Tower comprises four interrelated dimensions of environmental engagement: knowledge, action (Hanh dong), utility, and contribution. Knowledge influences action, action affects perceived utility, and utility, in turn, stimulates or constrains contribution. Positive experiences with waste management outcomes reinforce environmental awareness and encourage higher levels of community participation. The adapted KAUC framework provides the conceptual foundation for this study and guides the empirical analysis presented in the following sections.

4. Methods

4.1. Contingent Valuation-Bayesian Model (CVBM) Method

This study introduces the CVBM approach, integrating the contingent valuation method (CVM) [24] with the Bayesian mindsponge framework (BMF) [25] grounded in Culture Tower theory (Figure 1). The Culture Tower depicts participation in environmental initiatives as evolving from awareness to contribution behavior through Bayesian information-processing mechanisms. BMF conceptualizes individuals as “information sponges” filtering information based on cognitive comfort zones and core cultural values [58], enabling the analysis of cognitive-behavioral factors influencing payment decisions that are often overlooked in traditional econometric models.

CVM is widely employed to estimate willingness-to-pay (WTP) for non-market environmental goods through hypothetical scenarios [59]. In this study, CVM provides the empirical basis for eliciting both the decision to pay and the monetary amount households are willing to contribute, thereby generating the key dependent variables for analysis. Integrating CVM with BMF offers an advanced pathway that quantifies WTP while elucidating cognitive–behavioral–utility mechanisms underlying decisions. Specifically, CVM captures the observable outcomes of willingness-to-pay, whereas BMF helps explain the underlying decision-making process by modeling how individuals cognitively filter environmental information before accepting or rejecting payment. This approach enhances both reliability and interpretative depth, providing quantitative evidence and socio-psychological explanations for sustainable waste management policymaking. The integration is operationalized through a two-stage analytical structure: the BMF-based Bayesian model first examines the probability of participation (whether households are willing to pay), while the CVM-based interval regression subsequently estimates the magnitude of WTP (how much they are willing to pay). By incorporating BMF, CVBM explores the “black box” of decision-making, identifying roles of cognitive comfort zones and cultural values in accepting payment scenarios, thus enabling policymakers to understand barriers and levers for transforming WTP into actual contribution behavior.

The CVBM framework (Figure 2) comprises three interconnected components: inputs (A), processes (B), and outputs (C). Input data are collected through contingent valuation (CV)–based questionnaires, incorporating both open-ended and payment card formats to elicit households’ willingness-to-pay (WTP) alongside relevant socioeconomic and environmental perception variables. The analytical process builds on this dataset by selecting variables that reflect the layered structure of the Culture Tower framework (knowledge, action, utility, and contribution), capturing the progression from environmental awareness to behavioral engagement and financial participation. Within this structure, the Bayesian mindsponge approach is employed to examine how individuals cognitively process environmental information and translate it into WTP decisions. At the same time, the CV-based payment card method enables the estimation of WTP amounts while accounting for variability and uncertainty in the respondents’ stated preferences. The resulting outputs integrate these behavioral and empirical components to generate methodological, theoretical, and policy-relevant insights, ultimately contributing to a more comprehensive understanding of how environmental culture can be mobilized to support sustainable waste management and broader environmental sustainability goals.

Figure 2. CVBM framework for waste management, adapted from [60]. Note: Empirical Model* and Empirical Model** correspond to the Bayesian and interval regression models estimated in the first and second stages of the CVBM approach, respectively.

The payment card approach was adopted to operationalize WTP quantification, enabling intuitive visualization of contribution levels while mitigating strategic and starting-point biases [61]. It was selected for visual clarity, respondent friendliness, and superior bias reduction versus dichotomous choice or open-ended formats [24]. Respondents indicating willingness to contribute were presented a payment card to indicate maximum donation amounts. The card construction involved: (1) deriving initial monetary ranges from pilot interviews reflecting realistic capacities; (2) arranging values in a structured bid sequence covering the full range of feasible payment levels, presented in descending order; (3) having respondents select their highest WTP, revealing individual valuation [62,63]. Within CVBM, payment card data are utilized to estimate contribution probability and jointly analyze cognitive, behavioral, and utility determinants shaping household decisions.

4.2. Study Area

The study was conducted in the former Hai Duong Province, now part of Hai Phong City, a key economic area in Vietnam’s Red River Delta (Figure 3). Characterized by rapid industrialization and growing population, Hai Phong faces escalating environmental challenges. Its strategic location and industrial base make it a major economic gateway where industrial, service, and residential activities converge, exerting considerable pressure on waste management systems.

Figure 3. Map of the study area.

Over the past decade, intensifying pressures in household waste management have emerged. Accelerated urbanization and rising consumption have surged waste generation, exceeding existing collection and treatment capacity, which remains fragmented and technologically limited. Substantial household waste continues to be disposed of through traditional landfilling, with many sites operating near or beyond capacity, causing environmental pollution and adverse community impacts [64,65]. Residents report unpleasant odors, groundwater contamination, and a lack of effective mechanisms for waste collection, segregation, and recycling.

Although the provincial government has introduced policies and community-based models encouraging waste segregation and collection initiatives, implementation remains inconsistent. Weak institutional coordination, incomplete technical guidelines, and limited financial incentives hinder enforcement and participation [66]. Despite public awareness campaigns, household engagement in waste sorting and recycling remains relatively low, especially in peri-urban and rural areas with uneven infrastructure.

Hai Phong represents a microcosm of Vietnam’s urban waste management challenges, where the pace of urbanization outstrips policy effectiveness and infrastructural capacity. The province provides a representative case to analyze public behavior and perceptions toward waste issues while exploring household WTP for environmental improvements. The field survey was conducted over two months (July–August 2025), employing random sampling with 487 households across 11 communes and wards, ensuring diverse socio-economic and spatial representation.

4.3. Data Collection

The survey process involved four stages. First, an extensive literature review identified factors influencing public awareness, behavior, and WTP for waste management, informing the first questionnaire draft. Subsequently, an expert focus group (with more than 10 years of experience in environmental economics and CVM) assessed the clarity, relevance, logical consistency, and alignment with valuation practice. Focus group discussions explored the participants’ understanding and experience with waste management issues, providing insights into public interpretation of survey items. Feedback refined the questionnaire, ensuring contextual appropriateness, validity, reliability, and structured design aligned with study objectives.

Data collection proceeded in two phases. For phase 1 (Pre-survey), the team visited local authorities to introduce objectives, align plans, and conduct pilot surveys with representative households, assessing questionnaire quality and identifying unclear items. Based on feedback, the questionnaire was finalized with 58 questions across four parts: (A) Public awareness of waste management; (B) Improvement measures and solutions; (C) Demographic information; (D) Participation levels and WTP for sustainable solutions. For phase 2 (Main survey), data were collected via face-to-face interviews and online surveys. Trained collectors conducted interviews based on sample lists from local authorities. Online questionnaires were distributed through Google Forms. Focus group members provided methodological oversight during the main survey. To facilitate coordination, survey-specific Zalo groups were established with five key members (research team, collectors, local officials), enabling daily progress checks, real-time communication, and immediate support. Daily online meetings reviewed progress, exchanged experiences, and addressed issues, maintaining timeline consistency and data reliability.

Sampling focused on households willing to participate and providing complete responses. Respondents aged 21–60 years represented households, selected for their adequate social awareness, comprehensive understanding of household activities and expenditures, and information technology proficiency advantageous for online surveys. These characteristics enhanced accuracy, reliability, and validity while minimizing response bias.

Following [24,61], respondents were first asked whether they would be willing to pay higher monthly fees for service upgrades. Those answering “yes” were then presented with a payment card containing 17 predetermined bid values, ranging from 0 to >1000,000 VND per household per month. The design of the bid range was grounded in multiple sources to ensure both empirical validity and contextual relevance. Specifically, the range was informed by (i) previous WTP studies employing payment card formats in environmental valuation [48,56], (ii) prevailing service fee levels stipulated under current government regulations [67,68], and (iii) a pilot survey conducted to verify the appropriateness, clarity, and realism of the proposed payment levels. Insights from the pilot survey indicated that respondents tended to concentrate their willingness-to-pay estimates within lower monetary ranges, which guided the refinement of the lower-bound intervals, while the upper range was maintained to capture potential high-value responses and avoid bias. Accordingly, bid values were arranged in a descending order: >1000, 1000, 900, 800, 700, 600, 500, 400, 300, 200, 160, 120, 100, 80, 40, 20, and 0 thousand VND (Box S1). This non-uniform distribution allows for finer granularity at lower payment levels where responses are more likely to cluster while still preserving sufficient coverage of higher valuation levels. Respondents selected their maximum willingness-to-pay from the card, thereby revealing their valuation ceiling. Presenting bids in descending order allowed the respondents to consider upper-bound possibilities before moving to more realistic contribution levels, thereby reducing anchoring at very low initial values and mitigating starting point bias while providing more information than open-ended formats [24].

4.4. Models

CVBM examines household interactions with waste management through four hierarchical dimensions: Knowledge (K) captures awareness of waste conditions and desire for improvements; Action (A/H) reflects waste sorting behaviors; Utility (U) measures satisfaction with collection services; Contribution (C) examines financial willingness through decisions and amounts. From the mindsponge perspective, contribution decisions arise from internal filtering processes mediated by cognitive perceptions and norms. Environmental signals such as perceived pollution, odor, and service quality are cognitively processed and evaluated against perceived costs and benefits, thereby shaping both the acceptance of payment and the level of contribution. Beyond socioeconomic factors (gender, age, income, education, household head), environmental perceptions and waste behaviors critically shape WTP.

Analysis proceeds through two stages using consistent explanatory variables reflecting households’ knowledge, actions, utility perceptions, and socioeconomic characteristics. Stage one employs Bayesian logit regression examining WTP decisions. This stage models the probability that a household is willing to contribute, capturing the participation decision as a binary outcome shaped by the cognitive evaluation of environmental conditions and perceived benefits. Stage two applies interval regression estimating WTP amounts, appropriate for payment card data where responses fall within predefined intervals. Both stages use a consistent set of explanatory variables; this stage quantifies the magnitude of contribution conditional on the stated payment range, thereby translating behavioral willingness into monetary terms. Together, the two methods are jointly implemented to capture complementary dimensions of WTP: the Bayesian model identifies the likelihood of participation, while the interval regression estimates the level of contribution. This integrated structure ensures that both decision and intensity are consistently explained within a unified empirical framework, avoiding fragmentation between behavioral acceptance and monetary valuation (Figure 4).

Figure 4. The two stages of the CVBM model.

4.4.1. Bayesian Regression Model

The following model examines determinants of households’ WTP decision for improved waste treatment:

$${\mathrm{WTP}}_{\mathrm{i}} ~ \mathrm{normal} (\log ({\displaystyle \frac{{\mathsf{\mu }}_{\mathrm{i}}}{(1-{\mathsf{\mu }}_{\mathrm{i}})}}),\mathrm{\sigma })$$

(1)

Equation (1) specifies the likelihood function of households’ WTP decision within a Bayesian framework, where WTP_i is a binary variable indicating whether household i is willing to pay and μ_i represents household I’s WTP probability.

$$\begin{gathered} \log \left({\displaystyle \frac{{\mathsf{\mu }}_{\mathrm{i}}}{(1-{\mathsf{\mu }}_{\mathrm{i}})}}\right) = {\mathrm{\beta }}_0 + {\mathrm{\beta }}_1*{\mathrm{Gender}}_{\mathrm{i}} + {\mathrm{\beta }}_2*{\mathrm{Education}}_{\mathrm{i}} + {\mathrm{\beta }}_3*{\mathrm{Age}}_{\mathrm{i}} + {\mathrm{\beta }}_4*{\mathrm{HouseholdHead}}_{\mathrm{i}} + \\ {\mathrm{\beta }}_5*{\mathrm{Income}}_{\mathrm{i}} + {\mathrm{\beta }}_6*{\mathrm{OdorDetected}}_{\mathrm{i}} + {\mathrm{\beta }}_7*{\mathrm{WastePollution}}_{\mathrm{i}} + {\mathrm{\beta }}_8*{\mathrm{PollutionVsPast}}_{\mathrm{i}} + \\ {\mathrm{\beta }}_9*{\mathrm{ImproveWasteService}}_{\mathrm{i}} + {\mathrm{\beta }}_{10}*{\mathrm{WasteSorting}}_{\mathrm{i}} + {\mathrm{\beta }}_{11}*{\mathrm{ServiceSatisfaction}}_{\mathrm{i}} \\ \mathrm{\beta } ~\mathrm{normal}(\mathrm{M},\mathrm{S}) \end{gathered}$$

(2)

Equation (2) defines the linear predictor linking household characteristics to the log-odds of willingness-to-pay, capturing how socio-economic and environmental factors influence households’ decisions. The model includes 13 parameters: intercept β₀, coefficients β₁–β₁₁, and standard deviation σ. Coefficients follow normal distributions centered on mean M with standard deviation S.

BMF analytics was applied for several reasons. First, combining logical reasoning strengths of granular interaction thinking theory [69] with Bayesian inference power offers strong theoretical compatibility. Second, Bayesian inference treats all parameters probabilistically, facilitating parsimonious yet robust predictive models. Moreover, incorporating the Markov chain Monte Carlo (MCMC) technique, Bayesian analysis handles complex model structures. Third, rather than binary p-value thresholds, Bayesian inference provides credible intervals for nuanced interpretations. Detailed Bayesian model specification appears in R code commands S1.

Markov chain convergence was assessed using statistical indicators and visual diagnostics. Key metrics: effective sample size (n_eff) and Gelman–Rubin shrink factor (Rhat). n_eff reflects effectively independent samples not autocorrelated during simulation; Rhat measures estimate consistency across chains. n_eff > 1000 indicates sufficient effective sampling for reliable inference. Rhat close to 1 indicates convergence; Rhat > 1.1 signals non-convergence and mixing issues. Visual examination through trace plots, Gelman–Rubin–Brooks plots, and autocorrelation plots provided further validation.

4.4.2. Interval Regression Model

The following model examined the determinants of households’ WTP decision for improved waste treatment:

To estimate households’ WTP for improved waste treatment, we employed interval regression—an extension of censored regression techniques suitable when exact dependent variable values are unobserved but known to lie within intervals. This method fits contingent valuation data from payment cards presenting monetary value ranges. Building upon the Bayesian specification in Equations (1) and (2), this model incorporates additional socio-demographic factors (Gender, Education, Age, Household head, Income) alongside environmental perception variables reflecting households’ awareness and assessment of local waste conditions (OdorDetected, WastePollution, PollutionVsPast, ImproveWasteService, WasteSorting, ServiceSatisfaction). This extended specification provides a holistic understanding of how economic, social, and perceptual dimensions shape WTP magnitude, offering deeper insights into household environmental-economic behavior.

Formally, consider a series of bid levels 0 = p₀ < p₁ < p₂ < … < p_n on the payment card (with p_n potentially approaching infinity). Let WTP_i^T be respondent i’s reported WTP and WTP_i^T be their true valuation. Then,

$$\begin{gathered} {\mathrm{p}}_1 \le {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} \le {\mathrm{p}}_2 \mathrm{if} {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} = {\mathrm{p}}_1 \\ {\mathrm{p}}_2 \le {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} \le {\mathrm{p}}_3 \mathrm{if} {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} = {\mathrm{p}}_2 \\ \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \\ {\mathrm{p}}_{\mathrm{n}} \le {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} \le {\mathrm{p}}_{\mathrm{n}+1} \mathrm{if} {{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} = {\mathrm{p}}_{\mathrm{n}} \end{gathered}$$

We specify the estimation equation as follows:

$$\log \left({{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}}\right) = {\mathrm{\beta }}^{\prime }{\mathrm{x}}_{\mathrm{i}} + {\mathrm{\epsilon }}_{\mathrm{i}}$$

(3)

It is noted that the error term εi follows N (0, σ²), xi and β are the variable and coefficient vectors, respectively. Respondent i’s response falls in [li, ui], where li = pk and u_i = p_k+1 for k in {1, 2, …, n − 1}. The probability of i’s true WTP being in [li, ui] follows the below equation:

$$\mathrm{Pr} ({{\mathrm{W}\mathrm{T}\mathrm{P}}_{\mathrm{i}}}^{\mathrm{T}} \mathrm{in} [{\mathrm{l}}_{\mathrm{i}},{\mathrm{u}}_{\mathrm{i}}] = \mathrm{Pr} (\log {\mathrm{l}}_{\mathrm{i}} - {\mathrm{\beta }}^{\prime }{\mathrm{x}}_{\mathrm{i}} \le {\mathrm{\epsilon }}_{\mathrm{i}} \le \log {\mathrm{u}}_{\mathrm{i}} - {\mathrm{\beta }}^{\prime }{\mathrm{x}}_{\mathrm{i}})$$

(4)

We obtained the mean of WTP by the following equation:

E (WTP) = exp (β’x_i) * exp (σ²/2)

(5)

From Equation (3), the expected value of WTP is derived as shown in Equation (5), providing an interpretable measure of households’ average willingness-to-pay.

To assess the reliability and robustness of the interval regression estimates, model diagnostics were based on the overall log-likelihood (LL) value and the corresponding model p-value. The log-likelihood indicates the model’s goodness of fit, with higher LL values (less negative) suggesting better model fit to the data. The p-value was used to evaluate the joint statistical significance of the estimated relationships, with p < 0.05 typically indicating that the model’s predictors collectively have a statistically significant effect on WTP. Together, these indicators offer a concise assessment of the adequacy of the interval regression model in explaining variation in willingness-to-pay amounts.

The detailed information of variables used in the CVBM model are presented in Table 1.

Table 1. Variable description.

Variables	Type	Meaning	Category	Code/Interval	Proportion
Dependent variables
WTP1	Binary	Whether the respondent is willing to pay (WTP) for improving the quality of local waste management services	No	0	20.74%
			Yes	1	79.26%
WTP2	Continuous	Maximum amount the respondent is willing to pay for improving household waste collection and treatment services (thousand VND/month)	Payment interval	0–20	27.93%
				20–40	31.21%
				40–80	14.78%
				80–100	8.62%
				100–120	10.06%
				120–160	2.26%
				160–200	1.23%
				200–300	3.08%
				500–600	0.82%
Independent variables
Gender	Binary	Gender of the respondent	Male	0	18.89%
			Female	1	81.11%
Education	Ordinal	Highest level of education attained by the respondent	Lower secondary or below	1	20.74%
			Upper secondary	2	20.33%
			Technical/College	3	10.68%
			University	4	44.76%
			Master’s degree	5	3.29%
			Doctorate	6	0.21%
Age	Ordinal	Age of the respondent	21–30	1	5.54%
			31–40	2	34.70%
			41–50	3	29.36%
			51–60	4	18.69%
			Over 60	5	11.70%
HouseholdHead	Binary	Whether the respondent is the head of the household	No	0	35.73%
			Yes	1	64.27%
Income	Continuous	Natural logarithm of total monthly household income (million VND/month)	-	-	-
OdorDetected (OD)	Binary	Whether the household perceives unpleasant odors from nearby waste collection or storage sites	No	0	81.93%
			Yes	1	18.07%
WastePollution (WP)	Binary	Whether the respondent perceives household waste pollution as a problem in the locality	No	0	56.06%
			Yes	1	43.94%
PollutionVsPast (PVP)	Ordinal	Perceived change in waste pollution compared with previous years	Worse than before	1	8.71%
			No change	2	25.59%
			Improved	3	65.70%
ImproveWasteService (IWS)	Binary	Whether the respondent expresses a desire to improve local waste collection, transportation, and treatment services	No	0	7.19%
			Yes	1	92.81%
WasteSorting (WS)	Binary	Whether the household practices waste separation at the source prior to disposal	No	0	34.70%
			Yes	1	65.30%
ServiceSatisfaction (SS)	Ordinal	Level of satisfaction with the current local waste collection services	Very dissatisfied	1	3.90%
			Dissatisfied	2	9.86%
			Neutral	3	50.92%
			Satisfied	4	31.62%
			Very satisfied	5	3.70%

5. Results

5.1. Households’ Perceptions of Waste Pollution and Waste Treatment Services

When asked about the current state of household waste pollution, more than half of the respondents (56.1%) acknowledged that waste pollution remains a visible issue in their locality, while 43.9% perceived it as not particularly serious (Figure 5a). This indicates that environmental concerns related to waste are still widespread within the community. In terms of environmental quality, the majority of respondents (65.7%) reported that local waste pollution had improved compared with previous years, whereas 25.6% observed no noticeable change and only 8.7% perceived deterioration (Figure 5b). Taken together, these findings suggest that although improvements are recognized, waste pollution remains a noticeable concern in everyday life.

Figure 5. Household perceptions of waste treatment services: (a) Waste pollution perceived around the household area. (b) Perceived change in pollution compared to the past. (c) Perceived reasonableness of the current waste services fee. (d) Distribution of households’ service quality rating (1–10 scale).

Against this backdrop, perceptions of waste treatment services appear relatively positive. As shown in Figure 5d, the mean rating of service quality stands at 6.92 on a 10-point scale, indicating a generally satisfactory level of performance. Similarly, the majority of respondents (47.4%) regarded the current service fees as “neutral” and 43.7% considered them “reasonable”, with only a small fraction viewing them as “unreasonable” or “very unreasonable” (Figure 5c). This pattern implies that most households perceive the existing service cost as fair relative to the quality delivered. Taken together, this pattern suggests that households tend to evaluate service provision favorably, even as environmental concerns persist.

To further contextualize these perceptions, the perceived causes of local waste pollution exhibit a multi-dimensional structure, reflecting the interplay of several interrelated drivers (Table 2). Behavioral factors, particularly limited public awareness (76.0%), stand out as the most prominent contributors, underscoring the central role of individual and community practices in shaping waste generation and disposal patterns. At the same time, socio-economic dynamics are evident in the substantial shares attributed to the expansion of production and daily activities (62.6%) and rising living demands (56.7%), both of which signal increasing consumption intensity and the associated pressure on waste management systems. In parallel, sector-specific sources, including household waste (55.6%) and industrial waste (45.6%), further highlight the combined contribution of residential and production activities to overall pollution levels. Underlying structural and demographic constraints compound these drivers. Population growth (45.0%) and weaknesses in infrastructure and waste management systems (42.5%) suggest that existing capacities may not be sufficient to manage the growing volume and complexity of waste effectively.

Table 2. The causes leading to an increase in waste pollution in the locality.

Reasons	N	Percentages
Population growth	219	45.0
Rising living demands	276	56.7
Expansion of production and daily activities increases waste generation	305	62.6
Limited public awareness	370	76.0
Industrial waste contributes to rising pollution levels	222	45.6
Household waste contributes to rising pollution levels	271	55.6
Weak infrastructure and waste management systems	207	42.5
Others	6	1.2

Note: Respondents can choose multiple causes.

5.2. Determinants of Households’ Willingness-to-Pay for Improved Waste Treatment Services (WTP4WTS)

5.2.1. Determinants of WTP4WTS Using Bayesian Models

Table 3 provides a detailed analysis of the determinants of households’ willingness-to-pay (WTP) for improved local waste treatment services. In Bayesian estimation, it is essential to verify the convergence of Markov chains to ensure the reliability of simulated posterior draws. The convergence of the Markov chains was evaluated using two standard diagnostics: the effective sample size (n_eff) and the Gelman shrink factor (Rhat). All estimated parameters satisfied the convergence criteria, with n_eff values well above the minimum threshold (the lowest value is 6969, far exceeding the threshold of 1000) and Rhat equal to 1 for every coefficient. These results confirm that the Markov chains mixed well and reached a stable equilibrium, satisfying the Markov chain central limit theorem. The trace plots further corroborate this stability, displaying rapid oscillations around constant means without visible drift, indicating that the posterior simulations are robust and reliable for interpretation (Figure 6). Further information on the estimated results of the Bayesian model is presented in Figures S1–S6.

Table 3. Results of Bayesian model of households’ WTP participation.

Parameters	Mean	SD	n_eff	Rhat
a_WTP	−4.93	1.83	6969	1
b_OdorDetected_WTP	0.27	0.52	14,307	1
b_WastePollution_WTP	0.88	0.42	13,145	1
b_PollutionVsPast_WTP	0.62	0.28	13,070	1
b_ImproveWasteService_WTP	1.26	0.74	14,384	1
b_WasteSorting_WTP	1.03	0.38	13,194	1
b_ServiceSatisfaction_WTP	0.02	0.23	12,527	1
b_Income_WTP	0.64	0.31	12,291	1
b_Age_WTP	0.14	0.19	11,006	1
b_Gender_WTP	0.78	0.46	12,871	1
b_HouseholdHead_WTP	0.2	0.4	15,643	1
b_Education_WTP	0.02	0.16	12,552	1

Figure 6. The MCMC chains for the Bayesian model of households’ WTP participation.

5.2.2. Determination of WTP4WTS Using Contingent Valuation and Interval Regression Model

Table 4 reports the estimation results from five separate models, where FM represents the full model containing all variables identified as relevant in the Bayesian model, while RM1–RM4 are restricted models in which different subsets of statistically insignificant variables are excluded. Notably, all five models yielded p-values of 0.000, well below the 0.01 threshold, indicating strong statistical significance at the 99% confidence level and confirming the robustness and adequacy of the model specifications. The log-likelihood values were further used to assess model fit, with higher values indicating better performance. Accordingly, the full model (FM) exhibited the highest log-likelihood (−622.6) and was therefore selected as the primary basis for subsequent reporting and interpretation.

Table 4. Results of interval regression model of WTP4WTS.

Models	Full Model	Restricted Models
Variables	FM	RM1	RM2	RM3	RM4
OdorDetected (OD)	0.267 **	0.262 **	0.258 **	0.252 **	0.247 **
	(0.121)	(0.121)	(0.121)	(0.121)	(0.121)
WastePollution (WP)	0.195 *	0.201 *	0.201 *	0.205 *	0.197 *
	(0.107)	(0.107)	(0.107)	(0.107)	(0.107)
PollutionVsPast (PVP)	0.142 *	0.137 *	0.138 *	0.139 *	0.135 *
	(0.0774)	(0.0770)	(0.0770)	(0.0771)	(0.0775)
ImproveWasteService (IWS)	0.585 **	0.582 **	0.578 **	0.588 **	0.582 **
	(0.249)	(0.249)	(0.248)	(0.249)	(0.250)
WasteSorting (WS)	0.359 ***	0.355 ***	0.352 ***	0.342 ***	0.346 ***
	(0.104)	(0.104)	(0.103)	(0.103)	(0.103)
ServiceSatisfaction (SS)	−0.164 **	−0.163 **	−0.161 **	−0.158 **	−0.164 **
	(0.0641)	(0.0641)	(0.0640)	(0.0640)	(0.0642)
Income	0.251 ***	0.253 ***	0.253 ***	0.252 ***	0.258 ***
	(0.0819)	(0.0818)	(0.0818)	(0.0819)	(0.0822)
Age	−0.00458	−0.00584	−0.00638	−0.00689
	(0.00511)	(0.00462)	(0.00450)	(0.00447)
Gender	0.0886	0.0952	0.106
	(0.123)	(0.123)	(0.121)
HouseholdHead	−0.0628	−0.0548
	(0.108)	(0.107)
Education	0.0249
	(0.0430)
Constant	2.299 ***	2.427 ***	2.405 ***	2.502 ***	2.209 ***
	(0.532)	(0.483)	(0.482)	(0.469)	(0.432)
Sigma	0.845	0.845	0.845	0.847	0.851
Log-likelihood	−622.6	−622.8	−622.9	−623.3	−624.5
Prob > chi2	0.000	0.000	0.000	0.000	0.000
Observations	487	487	487	487	487
Estimated E[WTP]
In thousand VND	60.161	60.173	60.169	60.193	60.265
In U.S. dollar	2.31	2.31	2.31	2.32	2.32

Note: *** p-value < 0.01, ** p-value < 0.05, * p-value < 0.1, t statistics in parentheses. Values in USD are based on an assumed rate of 1 USD = 26,000 VND.

As presented in Table 4, the estimation results identified seven statistically significant variables influencing households’ willingness-to-pay (WTP) for improved waste treatment services. Income and WasteSorting were significant at the 1% level; ImproveWasteService, OdorDetected, and ServiceSatisfaction were significant at the 5% level; while WastePollution and PollutionVsPast were significant at the 10% level. First, regarding environmental perception, the three variables OdorDetected (0.267), WastePollution (0.195), and PollutionVsPast (0.142) all displayed positive coefficients. This indicates that households perceiving higher levels of pollution, noticing unpleasant odors from waste collection points, or recognizing improvements in local environmental conditions tend to exhibit higher WTP. In other words, perceived environmental discomfort, heightened awareness of environmental risks, and the desire to sustain improvements in environmental quality collectively motivate households to contribute more toward waste treatment enhancement. Next, in terms of practical environmental behavior, the variable WasteSorting (0.359) showed a positive and statistically significant relationship with WTP. Households that actively sort their waste at source demonstrate a higher likelihood of contributing financially, reflecting a stronger sense of environmental responsibility and a greater willingness to support more effective waste management services. Regarding service needs and expectations, the variable ImproveWasteService (0.585) exerted a substantial positive effect, indicating that households perceiving greater needs for service improvement are more willing to pay. This highlights the motivational role of perceived service inadequacy in driving higher financial contribution. Conversely, ServiceSatisfaction (–0.164) had a negative coefficient. This suggests that as households’ satisfaction with the current waste collection and treatment services increases (e.g., from “neutral” to “satisfied”), their WTP declines. This implies that households already content with existing services perceive less necessity for further improvement and therefore express lower willingness to contribute. Finally, the positive coefficient for Income (0.251) indicates that households with higher income levels tend to have higher WTP, consistent with the expected influence of financial capacity on environmental payment decisions. The estimated WTP was VND 60,161 (US$2.32), indicating that, on average, surveyed households were willing to contribute approximately VND 60,161 to improve the quality of local waste treatment services. Taken together, these findings underscore that households’ economic capacity, responsible behavior, and environmental perceptions play pivotal roles in shaping their willingness-to-pay for improved waste treatment services, while satisfaction with current service quality tends to diminish the perceived necessity for additional financial contributions. Further information on the estimated results of the interval regression model is presented in Tables S1–S5.

6. Discussion

In this section, we present in-depth discussions of the key results regarding environmental awareness, waste-sorting behaviors, and contribution commitment presented in previous sections to advance our understanding of environmental culture associated with waste management in the study area.

Firstly, descriptive data show that households are increasingly aware of environmental improvements and view existing waste-collection costs as fair. Moderate to high environmental awareness and favorable perceptions suggest that recent Vietnamese initiatives are achieving success in raising service visibility and citizen recognition. However, many households observed persistent waste pollution and perceived room for improvement. Notably, the coexistence of perceived environmental improvement and the continued visibility of waste pollution indicates that recent progress is recognized but remains insufficient from the public’s perspective. This pattern suggests that households acknowledge ongoing efforts in waste management while simultaneously expressing expectations for more substantial and effective interventions. Importantly, the relatively positive evaluation of waste management services, despite the continued visibility of pollution, suggests that household satisfaction is likely anchored in the performance of upstream service components, particularly the frequency and reliability of waste collection. Regular and timely collection may create a sense of service effectiveness at the point of use, even when broader environmental outcomes remain suboptimal. In contrast, the persistence of visible pollution points to structural constraints in downstream stages, including limited treatment capacity, outdated technologies, and inefficiencies in final disposal processes. This divergence indicates that while collection systems may have improved, the overall effectiveness of waste management remains constrained by weaknesses in end-of-pipe treatment and environmental control. This growing critical awareness reflects an evolving environmental culture where citizens are becoming informed stakeholders rather than passive service recipients, signaling a broader societal shift toward a greener transition. From a broader green and circular economy perspective, this shift in awareness represents an essential precondition for transitioning from a linear “collect–dispose” system toward a resource-efficient and recycling-oriented model. In transitional economies like Vietnam, behavioral readiness at the household level is often an important constraint on circular economy implementation. Thus, strengthening environmental culture is not merely complementary to infrastructure development but may constitute a structural pillar of sustainable transformation.

Our findings highlight the multidimensional nature of households’ willingness-to-pay, revealing that economic capability and environmental culture jointly shape contribution behaviors. Income, waste-sorting behavior, desire for improved services, and odor detection all contribute to higher WTP, indicating that households with greater economic capacity, stronger pro-environmental behaviors, and heightened awareness are more inclined to financially support improvements. Rather than operating independently, these factors appear to interact through a cumulative process in which environmental awareness, everyday practices, and perceived benefits are progressively reinforced, ultimately shaping contribution decisions through the Culture Tower’s layered dynamics of engagement. Earlier Vietnamese evidence similarly highlights the role of income, education, and environmentally responsible behaviors in shaping WTP [48,56,70], suggesting that households recognize waste as a potential resource and are culturally primed to support treatment initiatives. In particular, direct sensory experiences such as odor exposure play a critical role in shaping this process. Persistent unpleasant odors serve as salient signals of environmental degradation that are difficult to ignore. When interpreted through mindsponge, these negative inputs heighten the perceived costs of environmental inaction, making the financial burden of waste fees comparatively more acceptable. In effect, the discomfort associated with pollution begins to outweigh the cost of contribution, thereby lowering resistance to payment. At the same time, households already engaged in practices such as waste sorting or expressing a desire for improved services appear more receptive to supporting system upgrades. These behaviors reflect not only prior awareness but also a degree of internalization, whereby environmental considerations are incorporated into routine decision-making.

These patterns align with international evidence showing that moral norms and trust constitute critical non-economic determinants. In Hanoi’s pilot programs, trust emerged as the strongest predictor of waste separation intentions [51]. Our findings extend this by demonstrating that desire for service improvement and current satisfaction jointly shape financial contribution behaviors, suggesting that building institutional trust and delivering visible improvements are mutually reinforcing strategies. In this context, trust is not merely attitudinal but closely linked to how households perceive the use of financial contributions: willingness-to-pay is more likely to be sustained when residents believe that additional fees are transparently managed and effectively translated into tangible improvements, whereas uncertainty about fund allocation may weaken this linkage. Environmental perception variables highlight the cognitive dimension of environmental culture. Households recognizing deterioration in local conditions tend to exhibit higher WTP, reflecting the internalization of environmental responsibility at the community level [48,50]. This aligns with the Culture Tower, where awareness and knowledge gradually translate into participation and contribution. Conversely, the negative association between ServiceSatisfaction and WTP reveals a counterintuitive dynamic, consistent with a “satisfaction paradox”. This satisfaction paradox has also been observed in prior studies, where higher service satisfaction does not necessarily translate into stronger willingness to contribute [71,72], and may even reduce motivation for further engagement unless linked to active participation [73]. While higher satisfaction is typically expected to enhance willingness to financially support services, our results suggest the opposite effect. This paradox may arise because satisfied households perceive current service performance, particularly in terms of collection frequency and reliability, as adequate, thereby reducing the perceived necessity for additional improvements. In this sense, satisfaction may reinforce a status quo bias, dampening the urgency to contribute further resources. Moreover, in the context of Vietnam, where waste management is traditionally viewed as a public service responsibility, higher satisfaction may also strengthen the expectation that service provision should remain state-funded. As a result, even when environmental outcomes remain imperfect, households may be reluctant to increase their financial contributions if they perceive that the existing system is functioning acceptably. This finding underscores an important distinction between trust and willingness-to-pay: while trust and satisfaction can enhance the acceptance of services, they do not necessarily translate into greater financial commitment. Taken together, these results suggest that policy strategies should carefully balance maintaining user satisfaction with fostering a continued sense of environmental urgency. Without visible signals of ongoing environmental challenges or clear communication about the need for system upgrades, high satisfaction may inadvertently reduce public support for necessary investments in waste management improvements.

The estimated mean WTP of approximately VND 60,200 (US$2.32) per household per month indicates moderate yet meaningful willingness to invest in improved waste services. Relative to the average monthly household income in our sample (US$547.86), this amount corresponds to roughly 0.4% of household income, suggesting that such contributions are noticeable but still within an affordable range for most households. Comparative Vietnamese evidence shows that WTP varies widely across regions, reflecting differences in income, service quality, and environmental awareness [48,56]. This variation underscores the importance of both economic capacity and prior exposure to organized waste management systems in shaping household valuation of environmental services. Notably, the estimated WTP exceeds the current waste collection fees applied in many localities, which remain modest under existing government regulations. This gap indicates that households may be willing to contribute beyond the mandated fee levels when improvements in service quality are perceived as credible and beneficial. Rather than reflecting overestimation, this difference points to a latent capacity for increased cost recovery that has not yet been fully leveraged in current policy frameworks. However, this gap should not be interpreted as uniform affordability across households. For lower-income groups in particular, even modest increases may represent a disproportionate burden, despite a generally positive willingness to support environmental improvements. This highlights the distinction between expressed willingness and actual financial capacity, suggesting that any potential fee adjustment should be approached cautiously and, where relevant, accompanied by equity-sensitive considerations. At the same time, expressing WTP as a share of household income helps situate this result within Vietnam’s broader development context. A contribution of around 0.4% of income reflects a transitional pattern: environmental services are no longer viewed as negligible expenses, yet they have not reached the level of prioritization observed in higher-income settings. This positioning is consistent with Vietnam’s status as a lower-middle-income economy, where rising living standards are accompanied by gradually strengthening environmental preferences. Calibrating service fees to reflect demonstrated payment capacity—while ensuring transparency and service quality—could help close financing gaps in recycling systems, composting facilities, and waste-to-energy investments central to circular economy development. Importantly, the alignment between households’ stated willingness-to-pay and the policy space for fee adjustment suggests potential for more cooperative governance arrangements, in which both public authorities and citizens share responsibility for improving environmental outcomes.

Building on this domestic perspective, international benchmarking provides additional context. In Malaysia, the mean WTP represented 1.7% of household income [36] while in Bangladesh it represented 0.12% of income [37]. At approximately 0.4%, the Vietnamese estimate falls between these values, and is closer to the lower bound of the range. This intermediate position suggests that Vietnam’s environmental valuation is more aligned with emerging middle-income contexts than with low-income settings while still reflecting budget constraints typical of economies in transition. Vietnam’s estimated WTP falls within this regional spectrum, suggesting moderate financial capacity coupled with emerging environmental consciousness characteristic of transitional economies. Within Vietnam’s broader transformation, these findings reflect a society where modernization, environmental awareness, and institutional reform increasingly intersect. The willingness of households to support higher service levels beyond the current fee structures signals a growing convergence between public policy goals and citizen preferences, reinforcing the feasibility of co-financed and participatory approaches to environmental management. Household participation embodies the country’s Four Transformation Pillars including technological innovation, international integration, institutional modernization, and social mobilization.

From a policy perspective, results point to clear opportunities for institutional and fiscal innovation. Local governments may have some scope to consider revising service fees or introducing targeted environmental charges, provided that such measures accompany visible service improvements and transparent fund management. Participatory mechanisms such as public feedback systems, co-design of local waste plans, and transparent reporting can sustain trust and accountability. These mechanisms also address potential stagnation from perceived satisfaction by drawing attention to improvements that might otherwise go unnoticed. At the same time, the identified “satisfaction paradox” suggests that high levels of service satisfaction, while desirable, may unintentionally reduce households’ willingness to support additional financial contributions. When basic service functions, particularly waste collection, are perceived as effective, households may assume that the current arrangements are sufficient and adequately financed, thereby lowering the perceived necessity for further investment. This highlights an important policy challenge: sustaining public support for system upgrading in contexts where baseline service delivery has already met the user expectations. Policy effectiveness depends on aligning financial instruments with behavioral reinforcement, linking fee adjustments to community engagement, waste-separation initiatives, and environmental education. In this regard, a critical policy priority is to clearly differentiate between basic collection services and more advanced waste treatment systems associated with circular economy transitions. While households tend to evaluate service quality based on collection performance, downstream processes such as recycling, composting, and waste-to-energy conversion require significantly higher investment and generate benefits that are less immediately visible. Without explicit communication of this distinction, households may underestimate the need for additional financial contributions. Crucially, these findings offer evidence-based inputs for refining the implementation of the 2020 Law on Environmental Protection [15]. While the Law mandates waste classification at the source and extended producer responsibility (EPR), effective enforcement depends on household compliance and financial participation. Our results suggest that regulatory instruments may benefit from being complemented by behavioral and communication strategies that strengthen perceived service benefits, institutional trust, and environmental literacy. Accordingly, policy design should not only focus on improving service performance but also on enhancing the public understanding of the full waste management value chain. Communication strategies, environmental education programs, and transparent disclosure of cost structures could help align household perceptions with the actual requirements of circular economy systems. Framing additional fees as investments in environmental upgrading and long-term sustainability rather than as responses to service deficiencies may further support public acceptance and participation. In this sense, environmental culture functions as a bridge between formal regulation and practical implementation.

Lessons from pilot programs in transitional contexts highlight critical success factors. In Rasht, Iran, despite initial success, programs proved unsustainable after pilot funding ceased due to inadequate resources and public participation [74]. Similarly, Hanoi’s JICA-supported 3R program achieved high awareness but failed large-scale replication, with continued participation depending critically on trust consolidation [51]. These experiences indicate that beyond initial infrastructure investments, sustaining behavioral change requires continuous trust-building, visible service improvements, and community ownership mechanisms.

Strategically, scaling up waste management infrastructure at the commune level offers both technical and social advantages. Vietnam’s plan to expand waste treatment plants should integrate household contributions into spatially optimized investment models. A decentralized model serving 5000–20,000 residents per commune, with facilities processing 8–20 tons of waste per day and investment costs of 1–6 billion VND per commune, appears most feasible. Multi-commune clusters can achieve economies of scale while maintaining local accountability. Linking these costs with observed willingness-to-pay suggests that capital recovery could potentially be achieved within a relatively short horizon under certain assumptions. Under plausible population assumptions, a 1 billion VND investment could be recouped in approximately 3–13 months, while a 6 billion VND system would require roughly 1.3–6.5 years. Although illustrative, this range suggests that household contributions may help support infrastructure financing, easing fiscal pressure on local governments. In turn, such recovery potential may allow for more strategic allocation of public resources, including reinvestment in system expansion, technology upgrading, and higher-value circular economy processes. A joint investment framework combining state funds, community payments, and potentially private partnerships can operationalize co-production principles central to Vietnam’s rural governance.

Methodologically, this study contributes a novel CVBM method that is a special extension of existing BMM [75] and CBMM [23] methods by empirically operationalizing environmental culture into quantifiable indicators, linking perceptions, behaviors, and financial contributions. By integrating measures of household awareness, waste-sorting practices, and willingness-to-pay, the approach enriches traditional WTP analysis, embedding behavioral economics within a culturally relevant framework. The study’s conceptual foundation draws upon the mindsponge mechanism [21] and Culture Tower [22], both modeling human cognition as dynamic information-filtering shaped by contextual trust and cultural resonance. Within mindsponge logic, households selectively absorb or reject environmental information based on perceived core value, gradually internalizing these inputs into belief systems that shape whether pro-environmental attitudes translate into tangible action. The Culture Tower serves as an analytical scaffold linking perception, behavior, and financial engagement, where environmental knowledge informs action, effective action generates perceived utility, and positive utility reinforces contribution—the highest stage of environmental culture maturity.

Beyond methodological contributions, this study underscores the strategic role of environmental culture-based willingness-to-pay in Vietnam’s evolving waste governance. In the context of administrative consolidation and transition toward a two-tier local government system, post-merger communes benefit from economies of scale enabling centralized or clustered waste treatment facilities. Household willingness-to-pay functions not merely as revenue but as a mechanism for social mobilization, supporting co-production where local authorities and citizens jointly invest in infrastructure and service improvement. This becomes particularly salient amid intensifying environmental stress, where air pollution increasingly overlaps with severe solid-waste pollution. The observed associations between perceived pollution, odor detection, and higher willingness-to-pay indicate that households internalize environmental degradation as tangible cost and are more inclined to contribute when credible institutional channels exist. Taken together, these patterns point to a broader insight: in economies undergoing transition, environmental awareness, social norms, and everyday experiences of pollution do not remain confined to the realm of attitudes but can be translated into concrete financial commitments. What emerges is a form of environmental and cultural capital that, while often overlooked, carries real economic value. When effectively mobilized, this latent capacity may help alleviate pressure on public budgets and, in decentralized settings, could act as a complementary though partial support to state financing for environmental infrastructure. Focusing on rural and peri-urban communities in the Red River Delta—Vietnam’s most densely populated region and among those most severely affected by waste accumulation—further elevates this topic’s importance, as effective mobilization can generate disproportionate gains in environmental quality and public health. Finally, the finding that estimated willingness-to-pay exceeds the current environmental service fees suggests that existing financing mechanisms under the 2020 Law on Environmental Protection may warrant careful reassessment, taking into account household capacity, rising environmental awareness, and evolving service expectations.

Our study has some limitations that should be acknowledged. First, the empirical analysis was confined to Hai Phong—a rapidly urbanizing coastal city with relatively advanced economic conditions, governance capacity, and waste management infrastructure. While this provides a relevant context for examining urban environmental behavior, it reflects a specific institutional and developmental configuration that may not represent other provinces and cities in Vietnam, particularly those with lower development levels or weaker service provision. Accordingly, the findings are context-bound and should be generalized with caution. Second, the study employed the contingent valuation method (CVM) to elicit households’ willingness-to-pay (WTP), which entails well-known methodological constraints. As a stated-preference approach, CVM is susceptible to hypothetical bias, where stated intentions may diverge from actual behavior. Strategic bias, social desirability effects, and anchoring or information biases may also influence responses. Thus, the estimated WTP should be interpreted as a conditional valuation under hypothetical scenarios rather than a precise proxy for real-world behavior. Third, although the sample size was sufficient for statistical estimation, it may not have fully captured the heterogeneity of urban households across socio-economic and spatial contexts. The framework also emphasizes the knowledge–contribution linkage, while other dimensions of environmental culture, particularly action and utility, remain underexplored. Future research should broaden the scope to major metropolitan areas such as Hanoi and Ho Chi Minh City to enable cross-city comparisons and improve generalizability within Vietnam’s urban system. Applying alternative valuation approaches such as open-ended formats, discrete choice experiments, or hybrid methods would help triangulate and strengthen WTP estimates. Incorporating longitudinal data and additional variables, including institutional trust, social norms, and behavioral consistency over time, would further support a more dynamic understanding of environmental behavior. Despite these limitations, the study provides robust evidence that strengthening environmental culture through awareness, participation, and perceived environmental improvements constitutes a critical pathway for advancing sustainable waste management governance and supporting Vietnam’s fourfold transformation agenda.

7. Conclusions

This study advances our understanding of environmental culture-based approaches to addressing waste pollution in Vietnam. Employing the Culture Tower-based contingent valuation and Bayesian model (CVBM) approach, we identified key determinants of households’ willingness-to-pay (WTP) for improved waste treatment services (WTSs). We operationalized environmental culture through measurable indicators linking awareness, behavior, and financial participation, offering practical insights for improving governance and mobilizing community resources. Rather than acting independently, the determinants of WTP can be understood along three interrelated pillars: economic capacity, environmental awareness and experience, and behavioral engagement. Environmental culture, manifested through awareness, waste-sorting practices, and perceived service improvement, significantly influences WTP. Average WTP of VND 60,200 (US$2.32) per household per month indicates meaningful co-financing capacity, exceeding the current fees and suggesting fiscal space for policy innovation. This level can be considered moderate to relatively high within the Vietnamese context and falls within the mid-range observed across developing countries. The first pillar, economic capacity, is reflected in income, which enables households to translate pro-environmental intentions into actual financial contributions. The second pillar, environmental awareness and lived experience, is captured by perceived pollution, odor detection, and the belief that environmental conditions have deteriorated, all of which heighten the perceived cost of inaction and strengthen willingness to contribute. The third pillar, behavioral engagement, is expressed through practices such as waste sorting and the desire for improved services, indicating deeper internalization of environmental responsibility. In contrast, service satisfaction moderates this process by reducing perceived urgency, highlighting a potential “satisfaction paradox” in contribution behavior. Strong public support suggests pressing need to enhance living environment quality and opportunities for public–private partnerships addressing waste pollution. Findings support policymakers in designing effective financing mechanisms for Vietnam and developing countries. Targeted environmental communication and education are crucial for improving contributions and fostering environmental culture for sustainability. Beyond immediate financing implications, the findings contribute to Vietnam’s broader green growth and circular economy transition by demonstrating that household-level environmental culture constitutes a foundational driver of resource recovery, waste reduction, and recycling participation. Strengthening willingness-to-pay and waste-sorting behavior can accelerate the shift from landfill dependence toward integrated systems emphasizing reuse, recycling, composting, and waste-to-energy solutions. In the context of rapid urbanization and mounting pressure from municipal solid waste, this evidence supports strategic recalibration of urban waste management policies toward decentralized treatment models, co-financing mechanisms, and stronger community engagement. By aligning behavioral incentives with regulatory reforms under the 2020 Law on Environmental Protection, the study provides an evidence-based pathway for advancing urban waste governance, promoting circular economy practices, and consolidating Vietnam’s transition toward a resilient and environmentally sustainable green economy. Future research may further refine the measurement of these pillars, particularly by improving the operationalization of environmental culture and testing the robustness of CVBM estimates across different contexts and data settings.