How Can We Improve the Consumer Acceptance Level for Disposers Considering Regional Characteristics?

Abstract

The volume of food waste is increasing, and research has highlighted the issues related to its disposal methods. Disposers are emerging as a solution for food waste recycling; they are already used in various countries. Only a limited portion of solid waste discharge has been permitted depending on the infrastructure capacity. Although additional administrative costs are required to adapt the existing food waste disposal system to include disposers, research on consumers’ willingness to pay (WTP) for such changes is lacking. Therefore, this study analyzes consumer WTP to increase the capacity of infrastructure. In this study, contingent valuation methods are employed to evaluate WTP, and data are collected based on a one-and-one-half-bounded dichotomous choice model with 1155 residents. In addition, this study considers the relevant knowledge, satisfaction, and expectations of the service. The results show that the average WTP for additional sewage rates is KRW 6860 (USD 5.2). Covariate models show that knowledge of water quality and awareness of the extent of untreated sewage discharge during rainfall in CSOs significantly influence WTP. Additionally, satisfaction with sewage odor, expectations regarding sewerage fees, and concerns about preventing sewer backflow impact WTP. However, satisfaction with the disposer does not significantly affect WTP. Additionally, a regional analysis is conducted to determine the priority of regional infrastructure improvements. In Incheon and Seoul, where the number of complaints was higher than the average, WTP showed a positive influence. The findings of this study have practical implications for policymakers, as they can be used to determine regional policy priorities.

1. Introduction

Advancements in agriculture and technology have increased the amount of food in the world; however, food waste is also increasing. The UN Environment Programme [1] defines food waste as the inedible parts generated during food and food supply processes and estimates the amount of food waste in 2022 to be 1.05 billion tons. Food waste has been identified as a waste of resources and a major source of greenhouse gas (GHG) emissions [2]. Food waste generates carbon dioxide during crop production and transportation and emits GHGs during the methane-curing disposal process. GHG emissions from food waste account for 8–10% of the total global GHG emissions. The Environmental Protection Agency (EPA) [3] reported that the GHGs generated from food waste in the United States were equivalent to the annual carbon dioxide emissions in 42 coal-fired power plants. Changes in management practices are necessary to reduce GHG emissions and to utilize food waste as a resource by recycling, reusing, or converting it into energy [4].

Food waste is generally classified as municipal solid waste or processed at wastewater treatment plants through landfilling, composting, incineration, or energy recovery [5]. The methods used vary across cities and countries; however, landfilling and incineration are the most commonly utilized methods. For example, New York manages food waste through incineration and landfilling, Beijing employs composting, incineration, and landfilling, and Tokyo uses feed conversion, composting, incineration, and landfilling. In South Korea, food waste recycling systems have been established through feed conversion, fertilization, composting, and energy recovery.

South Korea implemented policies such as volume- and radio frequency identification-based waste fee systems to reduce food waste. These systems encourage residents to reduce waste and save costs [6]. However, these methods create various issues, including lengthy waste collection and transportation times, unpleasant odors, pest problems during storage, and inconveniences in high-rise and multi-unit houses. Additionally, large quantities of organic matter discharged along with contaminants or leachates can pose environmental issues. In landfills, high salt concentrations from food waste can release harmful substances at incineration facilities [7].

Consequently, the need for new food waste disposal methods is apparent. There are three main food waste disposal methods: food waste disposers (FWDs), which grind and discharge waste into a sewer, dry-grinding, and microbial units. In the United States, approximately 50% of households use disposers; they are also used in Canada (10%), Australia (12%), and New Zealand (30%), among other countries [5]. South Korea permitted the limited use of FWDs in 2012, with estimated cumulative sales reaching 170,511 units by 2020 [7].

However, FWDs are regulated differently based on the size and structure of each country’s sewer system. Local governments, which oversee the management of food waste and sewer infrastructure, assess the implementation of disposers. Food waste is entirely ground and discharged into the sewers in the United States. The decision to use disposers was made after considering potential impacts, such as combined sewer overflow (CSO) and changes in the effluent quality of wastewater treatment plants. In Japan, households are equipped with FWDs that completely grind food waste, which is pretreated at drainage facilities before being discharged into the public sewer system. Consequently, food waste disposal systems are installed and managed at the public housing unit level [7]. In South Korea, FWDs are used only when the weight of solids discharged from wastewater is less than 20% of the ground food waste, as stipulated by Article 10 of the Enforcement Rules of the Waste Control Act. This restriction uses criteria similar to those of certain treatment facilities, considering factors such as flooding due to backflow in CSOs, unpleasant sewer odors, and disruptions to normal operations. However, consumers misinterpret the solid weight limit and household use of illegally modified FWDs is increasing. Concerns about water pollution due to improper use prompted a 2024 bill to ban the use of FWDs. Therefore, improving related infrastructure is essential to properly utilize FWDs in South Korea.

Previous studies on FWDs have focused on changes in sewer characteristics resulting from introducing FWDs [8,9]. Considering the growing interest in biogas, research has emerged on energy production from sewage sludge generated by the influx of food waste [10,11]. When using FWDs, food waste is discharged into sewers, which can increase the amount of sewage sludge, presenting a potential advantage. However, few studies have considered improvements to sewer treatment systems resulting from introducing FWDs, the costs associated with expanding new facilities, and consumer acceptance of these changes. Therefore, this study analyzes consumers’ willingness to pay (WTP) for improvements to FWD usage restrictions using the contingent valuation method (CVM). The analysis results justify the increased costs of wastewater treatment facilities because of the introduction of food waste disposal. Additionally, based on regional complaints, this study provides a priority framework for introducing FWDs that consider regional acceptance. It presents the value of implementing FWDs and proposes a direction for their introduction, considering regional acceptance.

2. Literature Review

2.1. Food Waste Management Methods

The most employed methods to manage food waste are landfilling, incineration, recycling, and energy recovery. Incineration is a relatively simple technology that effectively reduces the volume of food waste. Food waste has a high moisture content, making incineration inefficient and increasing its volume. Therefore, a drying process is employed before incineration to enhance efficiency [12]. Furthermore, heat generated during incineration is recovered and utilized as energy by heat exchangers or turbines [13].

The landfill has advantages in terms of cost and convenience, as well as disadvantages such as leachate, lack of available land, and greenhouse emissions. Leachates generated during the decomposition of organic matter contain heavy metals, organic compounds, and nutrients such as ammonia, posing a risk of environmental contamination [14]. Additionally, landfill sites generate gases such as methane and carbon dioxide, contributing significantly to greenhouse gas emissions while presenting an opportunity for energy conversion [15].

Composting is a method of recycling food waste into a reusable resource, reducing greenhouse gas emissions from landfills and improving soil quality. Food waste undergoes processes such as shredding, sorting, and dewatering to remove contaminants and moisture. The organic matter is then decomposed and stabilized, resulting in a final product used as compost [16]. However, composting is influenced by factors such as food waste’s composition and moisture content, generates odors, and is affected by the collection and sorting system [17].

In the feeding process, livestock serve a biofunctional role in converting food waste into resources [16]. This process includes fermentation, which utilizes microorganisms to enhance the nutritional quality of the food waste. Feeding is also a method of recycling food waste into another resource, but it has the disadvantage of high initial equipment costs and expenses associated with maintenance and repairs [17]. The dry feed produced through animal feed processing is mixed by blending it with commercial feed, while the wet feed is utilized as livestock feed on farms [18].

Biogas is a valuable renewable energy produced through the anaerobic digestion of biodegradable organic materials. Biogas generated from the anaerobic digestion of food waste contains 60% methane [17]. The biogas produced can be used for electricity generation through power generation, and the waste heat can also be utilized [18].

In the past, food waste in South Korea was mixed with general municipal waste and disposed of through landfilling or incineration. However, the direct landfilling of food waste containing high moisture content led to secondary environmental issues such as odors and leachate, which became a social problem. As a result, direct landfilling of food waste was banned in January 2005, and resource recovery policies through animal feed processing and composting were implemented. More recently, energy recovery through the biogasification of food waste has also been promoted. Food waste management in South Korea focuses on recycling, such as composting, feeding, and biogas production. In 2015, 90.4% of the food waste generated was recycled, 2.5% was landfilled, and 7.1% was incinerated. Among the recycled food waste, 41.6% was processed into animal feed, 32.0% into compost, and 16.8% through biogasification and other methods, including the production of manure [18]. In 2022, among the 2497.7 tons of food waste generated per day in Seoul, 56.8% was processed into feeding, 24.9% was composted, and 7.3% was treated using other methods [17,19].

2.2. Current Status of Food Waste Disposers

In the Enforcement Decree of the Sewerage Act in South Korea, an FWD is defined as a kitchen grinder that pulverizes food residues and discharges them with wastewater. FWDs are used in various countries, including the United States, Japan, Canada, and Australia, with each regulating them differently. In the United States, approximately 50% of households use FWDs, and over 95% of U.S. cities permit disposers [20]. In Canada, although the installation of FWDs is not legally restricted, each city makes decisions based on the load of its wastewater treatment system. For example, Toronto prohibits FWDs through municipal ordinances in areas that use CSOs [21]. In the Netherlands, FWDs are prohibited under the Environmental Management Activities Decree to prevent sewer blockages and avoid an increased load on wastewater treatment facilities (see Environmental Management Activities Decree, Article 3.131, paragraph 3, Section 3.6.1). Germany, Switzerland, and Austria have banned FWD methods, whereas Italy, France, and Sweden have applied different regulations in different municipalities [22].

Because municipalities manage food waste and sewer systems, they evaluate the urban sewer infrastructure to decide whether to implement FWDs. In South Korea, food waste disposal is permitted in certain situations. Despite the legal stipulation that 80% or more of solid waste must be recovered or less than 20% can be discharged, many consumers are unaware of the recovery obligation [7]. In response to concerns about increased sewer loads and water quality deterioration, a bill has been proposed to ban the sale and use of FWDs.

Countries decide whether to allow FWDs because 100% of solid waste is transported to wastewater treatment facilities through the sewer system. Introducing FWDs is prohibited if sewer pipe sizes and structures are inadequate or if no appropriate processing facility exists. Evaluating wastewater treatment facilities is a priority in countries that allow FWDs to operate under restrictions or those considering their introduction. If infrastructure development is required, the value of the investment must be assessed.

2.3. Previous Research on Food Waste Disposers

Research on FWDs began in the 1930s when it was introduced in the United States [7]. Studies on disposers can be categorized into technical, environmental, and economic impacts. Technical impacts analyze the effects on wastewater transport, including increased concentration and pollution load from food waste influx. Environmental impacts are evaluated from various perspectives, such as changes in sludge characteristics, energy production from methane gas emissions, carbon footprint, and life cycle assessment (LCA). Economic impacts analyze the social cost–benefit aspects and life cycle costs.

Regarding technical impacts, the effects of introducing disposers on sewage treatment facilities include increased water usage, sewage concentration, pollutant load, and issues related to sewer blockages and transportation systems [8,9,23,24]. The Canadian Water and Wastewater Association estimated that disposers would increase water usage by 4.8 L/cap/day, equivalent to 2% of the average household water consumption [23]. In pilot projects conducted in Sweden, the United Kingdom, Seoul, and Gyeonggi Province, no issues with sewer blockage were reported [6].

From an environmental perspective, studies have examined the environmental impacts of disposer introduction, including reducing food waste, changes in sludge composition and methane gas production, and power generation using sludge [10,11,22]. According to Iacovidou et al. [22], using disposers to manage food waste in the UK could reduce the amount of food waste sent to landfills by 12%, 81%, or 94% by 2035 (compared to 2008 levels), depending on the scenario. Thomsen et al. [10] argued that introducing FWDs could increase the amount of phosphorus, thereby boosting biogas production. This suggested that if disposers were applied in Aarhus, Denmark, electricity production from the sludge would increase by 0.3%, while heat production would decrease by 2%. In addition, Zan et al. [11] observed methane production by injecting wastewater and wastewater containing food waste into two sealed reactors to simulate actual sewage treatment processes. Long-term monitoring and batch tests conducted on Days 69 and 124 showed that methane production improved by 60% in the reactor injected with wastewater containing food waste.

The economic impact of introducing disposers must be considered. Introducing disposers entails changes in the operational costs of sewage treatment facilities and transportation costs. Ju et al. [25] assessed the feasibility of introducing disposers using life cycle cost analysis, revealing that while disposers incur significant costs at the generation stage, they reduce administrative costs. Zan et al. [26] used different sewage discharge standards to infer the changes in sewage treatment facilities’ operational costs after the disposer introduction in Hong Kong. The increased transportation and processing costs due to increasing sludge generation were negligible at a 30% discharge level but significantly increased at a 50% discharge level. The Ministry of the Environment [6] determined the costs of handling the increased sludge from disposer introduction. If disposers are introduced in multifamily housing and 20% of solids are discharged, the cost of expanding treatment facilities was estimated to be between KRW 1.4 trillion (USD 1.05 billion) and KRW 2 trillion (USD 1.5 billion). The cost of sludge treatment was considered to be at least KRW 27.1 billion (USD 20.3 million) for multifamily housing and up to KRW 212.5 billion (USD 15.9 million) annually for the entire housing sector.

In summary, previous studies indicate that increasing treatment costs are inevitable, and measures such as subsidies and cost-sharing with users will be needed to cover the increased costs. A few studies have examined the economic feasibility of kitchen waste, including food waste. A WTP of USD 30.42 per year was invested in implementing domestic food waste diversion services in Queensland, Australia [8], and a WTP of USD 1.44 per month was evaluated for household kitchen waste separation services [27]. Liang et al. [28] estimated a WTP of USD 3.7 per month for food waste management and recycling in Macau. These studies indicate that residents are willing to pay for food waste management services. However, few studies have estimated the WTP compared with the treatment costs associated with disposers. Valuation studies on increasing disposer treatment infrastructure are lacking.

Therefore, this study analyzes consumers’ WTP for a 30% increase compared to the current level and calculates the administrative costs. Treatment costs from the introduction of disposers are expected to vary with the number of households and the status of sewage treatment facilities. In addition, to assess the technical and environmental impacts of introducing disposers, regional characteristics should be considered, including sewer pipelines and sewage treatment systems. Changes in sewage treatment facilities resulting from sewer maintenance projects and the neglect of regional sewage conditions limit the applicability of the findings of past pilot projects. Thus, this study also analyzes the impact of regional characteristics on the WTP and proposes a sequential introduction of disposers by region.

3. Materials and Methods

3.1. Contingent Valuation Method

The consumers’ WTP for goods comprises the amount paid (market price) and the excess over the price (consumer surplus). Thus, the WTP reflects consumers’ preferences for goods and represents its economic value. For non-market goods that do not have a market price, measuring economic value involves identifying individuals’ preferences. A reliable demand curve must be derived with absent or incomplete related markets, and consumer surplus and WTP must be measured. CVM is a non-market valuation technique that involves creating a hypothetical market for non-market goods. CVM has been widely applied to various water resource projects, including cultural and scientific facilities [29], river environmental improvements [30], water quality enhancements [31,32], and waste management [8,33,34,35].

CVM encompasses various models, including single-bound dichotomous choice (SBDC), double-bounded dichotomous choice (DBDC), and a one-and-one-half-bounded dichotomous choice (OOHBDC) models. The SBDC model has the lowest risk of bias but is less statistically efficient than other models [36]. The DBDC model offers significant improvements in the statistical efficiency over the SBDC model. However, this also introduces a higher potential for bias. Cooper et al. [37] proposed the OOHBDC model, which is an innovative approach that enhances the efficiency of the baseline model. It improves the efficiency of the traditional SBDC model while retaining much of the DBDC model’s effectiveness. It also significantly reduces the response biases associated with the DBDC model, thereby securing a substantial portion of the consistency advantages of the SBDC model. Therefore, the OOHBDC model is used in this study.

To implement the OOHBDC model, the key aspects of the WTP elicitation questions are as follows. First, respondents are provided with information indicating that a cost within the range from $A^L$ to $A^U$ will be incurred monthly for the non-market good. Respondents are then divided into two groups. The first group is asked whether they are willing to pay $A^L$. If they respond “Yes”, they are subsequently asked whether they are willing to pay $A^U$. If they respond “No”, the questioning process ends. The second group is asked whether they are willing to pay $A^U$. If they respond “Yes”, the questioning process ends without further questions. If they respond “No”, they are then asked whether they are willing to pay $A^L$.

In the OOHBDC model, the situation in which the ith respondent responds can be described using Equation (1). The log-likelihood function is formulated as shown in Equation (2):

$$\begin{gathered} A^L=\left\{\begin{array}{c}{I}_i^{YY}=1\left(The response of the i^{th} respondent is “Yes”-“Yes”\right)\\ I_i^{YN}=1\left(The response of the i^{th} respondent is “Yes”-“No”\right)\\ I_i^N=1(The response of the i^{th} respondent is “No”)\end{array}\right. \\ {A}^U=\left\{\begin{array}{c}{I}_i^Y=1(The response of the i^{th} respondent is “Yes”)\\ I_i^{NY}=1(The response of the i^{th} respondent is “No”-“Yes”)\\ I_i^{NN}=1(The response of the i^{th} respondent is “No”-“No”)\end{array}\right. \end{gathered}$$

(1)

$$ln(L)={\displaystyle \sum _{i=1}^N}\left\{\begin{array}{c}(I_i^{YY}+I_i^Y)ln[1-G_C(A_i^U\left)\right]+\left(I_i^{YN}+I_i^{NY}\right)ln\left[G_C\left(A_i^U\right)-G_C\left(A_i^L\right)\right]\\ +(I_i^N+I_i^{NN})ln\left[G_C\right(A_i^L\left)\right]\end{array}\right\}$$

(2)

where $G_C\left(A\right)={\left[1+exp\left(a-bA\right)\right]}^{-1}$.

The mean WTP derived from the analyzed results $\alpha$ and $\beta$ is given by Equation (3).

$$mean WTP=\left({\displaystyle \frac{1}{\beta }}\right)\mathrm{l}\mathrm{n}(1+\exp \left(\alpha \right))$$

(3)

3.2. Data

This survey was conducted by Gallup Korea, a specialized survey company, in 2020 as a preference study for sustainable water resource (sewage) services. Based on the guidelines of Arrow et al. [38], the sample size was determined and the survey process were carried out. It included 1155 participants, and a stratified sampling method considering gender, age, and region was used to ensure the representativeness of the sample.

Table 1. Demographic characteristics of respondents.

Category		Respondents	Percentage (%)
Total		1155	100
Gender	Male(0)	609	52.7
	Female(1)	546	47.3
Age	20–29	218	18.9
	30–39	259	22.4
	40–49	268	23.2
	50–59	253	21.9
	60–69	157	13.6
Average monthly income per household (KRW 10,000)	<199	98	8.5
	200–299	177	15.3
	300–399	175	15.2
	400–499	196	17.0
	500–699	273	23.6
	>700	236	20.4

presents the basic statistics of the samples used in this study.

The questionnaire provided definitions, advantages, and disadvantages of disposers, and the current usage status, to enhance respondent understanding. The CVM scenario specified that food waste would increase from the current level of less than 20% to less than 50%, representing a 30% improvement, and that individuals would bear the installation cost of the disposer. With increased convenience, sewage treatment costs rose, prompting the proposal of sewerage fees to cover these costs. Simultaneously, the average monthly sewerage fee for a household and the additional monthly sewage treatment costs incurred by disposer introduction were presented, allowing the respondents to consider a realistic situation.

This survey was designed based on an OOHBDC model, with $A^L$ and $A^U$ presented differently depending on the group. Based on the pilot survey results, seven proposed amounts were established, ranging from a minimum of KRW 1000 to a maximum of KRW 10,000. The sample was randomly assigned to seven groups. The detailed response results are presented in

Table 2. CVM respondent distribution.

Bid Amount		Lower Bid Suggested First				Higher Bid Suggested First
		Yes–Yes	Yes–No	No–Yes	No–No	Yes	No–Yes	No–No–Yes	No–No–No
1000	2000	52	12	3	17	50	2	1	28
1500	2500	41	6	2	31	51	5	2	24
2000	4000	33	19	3	30	39	5	3	33
3000	5000	36	13	6	37	46	5	5	18
4000	6000	39	16	6	24	40	6	8	26
5000	8000	33	8	10	43	34	6	2	30
6500	10,000	25	23	14	30	37	7	5	25
Totals		259	97	44	212	297	36	26	184
		(22.4%)	(8.4%)	(3.8%)	(18.4%)	(25.7%)	(3.1%)	(2.3%)	(15.9%)

.

Demographic, prior knowledge, satisfaction, and expectations variables were selected for analysis. Among the demographic variables, “Gender” was defined as 0 for males and 1 for females, while “Age_50” was defined as 1 for respondents in their 50s and 0 for those not in that age group. For “Income”, household income was designated as a continuous variable ranging from 1 to 10. Additionally, data on the number of complaints by region from the 2022 sewerage statistics provided by the Sewerage Information System were used to examine regional acceptance. All other variables were answered on a 5-point scale. Questions about prior knowledge were structured with 1 for “not at all knowledgeable” and 5 for “very knowledgeable”. Questions about satisfaction were structured as “very dissatisfied” as 1 and “very satisfied” as 5. Questions about expected levels were structured on a 5-point scale, with “current level” as 1 and “more than 41% reduction from the current level” as 5. For “know_hasudo_unnecessary” and “know_hasudo_untreatment”, responses were set to 1 for “very knowledgeable” and 0 for all other responses. For “know_water_safey” and “know_water_service”, responses were set to 0 for “not knowledgeable at all” and 1 for all other responses, which were used in the analysis. For “satisfy_hasudo_odor”, responses were set to 0 for “not used”, “very dissatisfied”, and “somewhat dissatisfied”, and to 1 for “neutral”, “somewhat satisfied”, and “very satisfied”. For “expect_hasudo_cost” and “expect_hasudo_old_improvement”, responses were set to 0 for “current level” and 1 for all other responses, and these were used in the analysis. For “Region”, the national average number of complaints was calculated by using data from Ministry of Environment [39]. Regions with more complaints than the average were coded as 1; otherwise, they were coded as 0.

4. Results and Discussion

4.1. Results of the CVM Analysis

Empirical models are divided into three main types. Model 1 is the base model used to analyze WTP. Model 2 examines the impact of consumers’ prior knowledge on their WTP. Model 3 assesses the impact of satisfaction and expected service levels on WTP. The results of this study are summarized in

Table 3. Estimation results of the CVM model.

Variables	Model 1	Model 2	Model 3
	Coefficient	Coefficient	Coefficient
Constant	0.0971 ***	0.5501	0.8410 ***
bid	−0.00019 ***	−0.00019 ***	−0.00019 ***
Gender		−0.1673	−0.2130 *
Age_50s		−0.2887 **	−0.2911 **
Income		0.0625 **	0.0468 *
Know_water_quality		0.1378 *
Know_hasudo_old_improve		−0.0379
Know_hasudo_unnecessary		−0.0087
Know_hasudo_untreatment		0.5844 *
Know_water_safety		−0.1414
Know_water_service		−0.0997
Know_hasudo_cost		0.0912
Know_sudo_cost		−0.0144
Satisfy_hasudo_disposer			0.0739
Satisfy_hasudo_odor			−0.4513 **
Expect_hasudo_cost			−0.5091 ***
Expect_hasudo_flood			0.1308 **
Expect_hasudo_old_improvement			0.0340
Region_cost			0.0605
Region_complain_avg			0.3427 **
Region_complain_odor			−0.1067
Region_complain_cost			0.1737
Number of samples	1155	1155	1155
Mean WTP (95% confidence level)	6860.186 (6879.629–6840.743)
Log-likelihood	−1115.89	−1105.27	−1097.02

Note: Significance level *** 0.01, ** 0.05, * 0.1.

. In Model 1, all variables are statistically significant, and the average WTP is approximately KRW 6860 (USD 5.23) per monthly household. In Models 2 and 3, gender, age, and income were considered as control variables. The analysis revealed that age and gender affect WTP. Respondents in their 50s exhibited significantly lower WTP than other age groups at the 5% level. Conversely, income positively correlated with WTP, indicating that higher income levels are associated with higher WTP.

Model 2 assesses the impact of respondents’ prior knowledge of the services presented on their WTP. The level of knowledge about water quality, such as water pressure, taste, color, and odor, is found to have a positive and significant effect on the WTP at the 10% level. Similarly, del Saz-Salazar et al. [40] found that water quality positively affects WTP, highlighting the importance of water characteristics that people can directly experience. Additionally, awareness about the extent of untreated sewage discharge during rainfall in CSO positively affects WTP at the 10% level. These results show that a higher level of knowledge about water quality and untreated discharge from CSO is associated with a higher WTP. Knowledge about sewer services, such as improvements in aging treatment facilities and pipelines, the level of unnecessary water inflow into pipes, and the safe operation of water resource facilities, have no impact on WTP. Furthermore, knowledge about water services related to the water used, such as tap water, and recognition of water and sewer costs have no influence on WTP. It is assumed that the issues presented in our survey regarding the introduction of disposers do not include aspects related to water service.

Model 3 examines the effects of respondents’ satisfaction, expectations, and regional complaint rates on WTP. Satisfaction with sewer services, specifically odor-reduction services, negatively affects WTP at the % level. This indicates that individuals satisfied with the current odor-reduction service have a lower WTP. As the survey highlights odor issues related to the installation and use of disposers, people currently satisfied with this service can be assumed to have a lower WTP. Regarding satisfaction with disposers, both the usage of disposers and the level of satisfaction based on their use were surveyed. Based on the response rate, 89.3% of the 1155 respondents used disposers. Among them, 17.3% were dissatisfied, 43.1% were neutral, and 39.6% were satisfied with the disposer. However, satisfaction with disposers as part of sewer services reveals no significant impact on the WTP.

In expected service levels, impacts on the WTP are observed for sewerage charges and sewer backup prevention. Specifically, the respondents who indicated that the level of backup-prevention services should be improved showed a statistically positive effect on their WTP at the 5% level. For sewerage fees, respondents expecting a reduction exhibited a statistically significant negative effect on their WTP at the 1% level. The survey indicates that additional sewerage charges are necessary to improve sewer facilities, which may negatively impact WTP, as respondents likely perceive water supply as a government responsibility [38]. Therefore, respondents who prefer decreasing sewerage fees have a lower WTP. The expectation for improvements in the aging of sewerage treatment facilities and pipelines did not impact WTP.

Using regional sewerage-related complaint data from the 2022 sewerage statistics, the analysis shows that regions with higher-than-average complaint frequencies have a statistically significant positive impact on the WTP at the 5% level. No significant relationship exists between the incidence of odor-related complaints and WTP, unlike the significant negative relationship between satisfaction with sewerage odor-reduction services and WTP. Additionally, complaints about sewerage unit cost (KRW/ton) and sewerage fees are nonsignificant. Therefore, respondents in regions with a higher-than-average number of sewerage complaints generally exhibit a higher WTP, regardless of complaint type or sewerage unit cost.

4.2. Economic Evaluation and Implementation Strategies for Disposers

In Model 1, the average monthly WTP per household is approximately KRW 6860 (USD 5.23). According to the 2022 Population Census of Statistics Korea (kostat.go.kr), there are 21.7 million households in Korea. Assuming that all households are willing to bear an additional cost of KRW 6860 (USD 5.23) to introduce disposers, the potential additional revenue from water bills is approximately KRW 1.5 trillion (USD 1.06 billion), that is, 1.3% of the 2020 national sewage budget of approximately KRW 11.68 trillion (USD 8.90 billion). Furthermore, according to the Ministry of the Environment [6], the cost of facility expansion due to the additional generation of sewage sludge was estimated at KRW 1.4 trillion (USD 1.05 billion) if 20% of solid waste is discharged from multifamily housing and KRW 2 trillion (USD 1.5 billion) if the total amount of solid waste is discharged from multifamily housing. Considering this, approximately 10% and 7% of the expansion costs could be covered under each scenario. The estimated treatment costs for the additional sludge range from a minimum of KRW 27.1 billion (USD 20.3 million) per year (in the case of multifamily housing) to a maximum of KRW 212.5 billion (USD 15.9 million) per year (for all housing types). Additional support from the government or local municipalities is likely to be required to compensate for these costs.

According to Model 2, respondents’ knowledge of water services, including water pressure, tap water taste, and quality (color and odor), and their knowledge of untreated sewage discharge during rainfall in CSOs, positively influence their WTP. Regarding water quality, the public water supply can be considered unrelated to the introduction of disposers. However, because this factor significantly influences respondents’ WTP, sufficient information should be provided to clarify that water quality and the introduction of disposers are not directly related. Untreated sewage discharge from CSOs is often highlighted as a potential issue associated with disposer introduction. Depending on the condition of sewer systems, local governments consider this criterion to determine whether they will restrict introduction based on their specific circumstances. Therefore, a system that can prevent CSOs must be established before introducing disposer introductions. In addition, promoting the existence and effectiveness of such systems is essential to ensure public confidence and support for their implementation.

According to Model 3, respondents’ expected value of sewer fees and satisfaction with odor-prevention services have a negative effect on their WTP. In contrast, the expected level of sewer backflow prevention has a positive effect. Therefore, to enhance WTP for the introduction of disposers, odor-prevention services and sewer backflow-prevention levels must be maintained at their current levels or further improved.

Figure 1 illustrates the regional analysis of sewer-related complaint data from Model 3. Among the surveyed regions, Seoul recorded the highest number of complaints, followed by Incheon, Busan, and Daegu. Among the surveyed regions, Seoul recorded the highest number of complaints, followed by Incheon, Busan, Daegu, Ulsan, Daejeon, Gwangju, and Sejong. Among them, only Seoul and Incheon had complaint numbers exceeding the national average. In areas where complaints exceeded the national average, respondents’ WTP was positively affected, indicating that the expectation of resolving current issues related to sewer systems through disposers likely influenced the consumer WTP.

Considering the sewer budget and number of households by region for 2020, the additional sewer budget that could be secured and its ratio to the total sewer budget is shown in

Table 4. Sewer budget by region and additional budget secured from disposer introduction.

Region	Sewer Budget (KRW 100 Million)	Number of Households	Additional Budget Secured from WTP (KRW 100 Million)	Ratio (Additional/Sewer Budget)
Seoul	12,042.8	4,417,954	303.07	2.52
Busan	5913.3	1,530,431	104.99	1.78
Daegu	6501.8	1,056,627	72.48	1.11
Incheon	2359.6	1,267,956	86.98	3.69
Gwangju	2047.2	633,582	43.46	2.12
Daejeon	2032.4	652,783	44.78	2.20
Ulsan	2368.2	476,893	32.71	1.38
Sejong	558.7	144,275	9.90	1.77

. In Seoul and Incheon, where the number of sewer-related complaints exceeds the national average, the WTP is higher than the base value of KRW 6860, reflecting the positive influence of sewer-related complaints on WTP. Additionally, considering the number of households, the additional sewer budget that could be secured represents the highest ratio to the total budget. Therefore, prioritizing the introduction of disposers in these two regions could help ensure financial stability. In particular, it is suggested that this should be introduced first in Incheon, where the ratio of the additional budget to the sewer budget is the highest. Introducing it in a single city first can establish a valuable precedent for nationwide expansion by ensuring economic stability and addressing various issues that arise during the implementation process.

5. Conclusions

Food waste generation is a significant issue and is expected to increase with the global population. Countries are shifting their policies and management approaches to mitigate adverse environmental and economic impacts. In South Korea, discussions on introducing disposers to address the increasing food waste and improving existing methods are ongoing. While using disposers offers benefits, such as increased user convenience and energy production, the current state of public sewer systems and the potential need for new facilities must be considered. Therefore, thorough economic considerations are necessary. This study was conducted to provide an economic value for introducing disposers through the CVM. This study estimated the respondents’ WTP for the improvement of legal limitation from the current level of less than 20% to less than 50%, with a targeted 30% enhancement, assuming that individuals bear the installation costs of disposers.

The key findings of this study are as follows. First, the average monthly WTP per household is KRW 6860, representing 34.7% of the average monthly sewer fee for a four-person household. Second, in Model 2, the analysis reveals that the level of awareness regarding water quality aspects—such as water pressure, taste, color, and odor—and untreated sewage discharge during rainfall in CSOs influence WTP. Third, in Model 3, the factors influencing WTP included satisfaction with odor-reduction services in sewer systems, the expected value of sewer fees, and the expected level of sewer backflow prevention.

The suggestions for introducing disposers based on this study’s results are as follows. First, considering the WTP derived through CVM and the total number of households in South Korea, the additional sewer fee for introducing disposers could cover only 1.3% of the sewer budget. Therefore, appropriate support is necessary to address the costs of sewer sludge treatment and repairs resulting from introducing disposers. Second, water quality and CSO services should be promoted to increase respondents’ WTP. The results indicate that the current sewer fee levels and odor-prevention services should be maintained or improved. Third, considering the regional distribution of complaints, Seoul and Incheon have higher WTP than other regions. Combined with the number of households, those cities are the regions where the greatest additional budget could be secured relative to the sewer budget. Therefore, to ensure financial stability, disposers should be introduced first in Seoul and Incheon.

The limitations of this study are as follows. First, residence type was not considered. Individuals living outside apartments incur higher inconvenience costs related to waste separation than apartment residents. Therefore, incorporating the residence type into the analysis could provide more realistic grounds for policy decisions. Second, owing to differences in public sewer conditions and sewage treatment facilities among regions, integrating these factors into policy decision-making has limitations. Therefore, each region’s public sewer systems and sewage treatment facilities must be considered before introducing disposers. Third, this study analyzed WTP using a survey suggesting a 50% reduction in disposer usage restrictions. However, the cost estimates provided by the Ministry of the Environment (2020), which include scenarios allowing 20% and 100% discharge, differ from the survey’s assumptions. To compare economic costs accurately, deriving economic cost estimates for identical scenarios would be necessary.

The future research directions derived from this study include the following. First, it can be used to assess the economic feasibility of policy decision-making. The introduction of disposers is expected to yield advantages such as reduced transportation costs for food waste disposal and labor expenses, more efficient food waste collection, and energy production from food waste. Comparing these advantages with the infrastructure costs required for disposer implementation will aid in policy decision-making. Second, it can serve as a reference for budget allocation in policy-making. The results of Model 2 are utilized to identify residents’ concerns regarding disposer introduction, enabling the development of policies to mitigate these issues. Additionally, the results of Model 3 provide insights into the information and measures needed to reduce public resistance and increase WTP. This, in turn, can facilitate efficient budget allocation.