Life cycle cost assessment and economic analysis of a decentralized wastewater treatment to achieve water sustainability within the framework of circular economy

OeconomiA copernicana Volume 14 Issue 1 March 2023 p-ISSN 2083-1277, e-ISSN 2353-1827 www.oeconomia.pl Copyright © Instytut Badań Gospodarczych / Institute of Economic Research (Poland) This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ORIGINAL ARTICLE Citation: López-Serrano, M. J., Lakho, F. H., Van Hulle, S. W. H., & Batlles-delaFuente, A. (2023). Life cycle cost assessment and economic analysis of a decentralized wastewater treatment to achieve water sustainability within the framework of circular economy. Oeconomia Copernicana, 14(1), 103–133. doi: 10.24136/oc.2023.003 Contact to corresponding author: María J. López-Serrano, m[email protected] Article history: Received: 17.11.2022; Accepted: 7.03.2023; Published online: 25.03.2023 María J. López-Serrano University of Almería, Spain orcid.org/0000-0001-6439-0819 Fida Hussain Lakho Ghent University Campus Kortrijk, Belgium orcid.org/0000-0001-8559-3981 Stijn W.H. Van Hulle Ghent University Campus Kortrijk, Belgium orcid.org/0000-0001-5773-7773 Ana Batlles-delaFuente University of Almería, Spain orcid.org/0000-0003-2108-0516 Life cycle cost assessment and economic analysis of a decentralized wastewater treatment to achieve water sustainability within the framework of circular economy JEL Classification: Q25; Q53; Q56 Keywords: wastewater; economic analysis; LCCA; Sustainable Development Goals; monetary evaluation Oeconomia Copernicana, 14(1), 103–134 104 Abstract Research background: The increasing water demand together with an unceasing production of wastewater worldwide has resulted in a situation where the scarcity and pollution of water resources are jeopardizing and depleting such a vital asset. Purpose of the article: In this context, Nature Based Solutions (NBS) such as Vertical Flow Constructed Wetlands (VFCWs) are key because of their capacity of channelling a waste into a resource. However, and notwithstanding their essential role, their financial benefits too often go unnoticed because of missing research that study them from an economic perspective and this article has covered this existing gap. The objective of this research is to analyse the economic consequences of using VFCW against its traditional alternative through a comprehensive economic assessment. Methods: After doing a Life Cycle Assessment (LCA), a combination of two approaches has been carried out. This research has developed a holistic approach where a Life Cycle Cost Assessment (LCCA) based on a Cost Benefit Analysis (CBA) along with an economic evaluation of cleaning environmental costs have been calculated for two different scenarios. For this monetary analysis, the environmental externalities derived from the use of cleaning the pollution caused by a public water supply and sewerage system and the VFCW have been quantified. Findings & value added: Results conclude that VFCW apart of being a cost-effective and profitable alternative for an investor, it has also valuable benefits for the society in general because of its meaningful and positive externalities and the high removal cost of the environmental pollutants of the traditional water supply and sewage system both contributing directly to the achievement of Sustainable Development Goals (SDGs). Furthermore, 4/5 environmental impacts derived from the use of traditional alternative pollute more than twice as much as the VFCW does. Lastly, the cleaning costs difference between both alternatives is 1,984,335€. Introduction The demand of the essential, valuable, unfairly-distributed and limited resource, freshwater, has been steadily increasing in the last decades and the situation is still expected to worsen further due to varying anthropic reasons, thus raising major concerns worldwide (Bunn, 2016; Tociu et al., 2019; Ashu & Lee., 2021; Baggio et al., 2021; Truchado et al., 2021). Climate change, which comprises global warming and more unpredictable and changing weather patterns, along with the world’s growing population, both forecasted to exacerbate in upcoming years, have derived into increased water scarcity and pollution which endangers the water supply and fair distribution of finite freshwater resources, putting strain on water and food security (Melián-Navarro & Ruiz-Canales, 2020; Al-agele et al., 2021; Wang et al., 2021; Arellano-Gonzalez et al., 2021; Weerasooriya et al., 2021; Maniam et al., 2022). The envisaged worsening of a current fateful Oeconomia Copernicana, 14(1), 103–134 105 situation where more than two billion people experience water stress and four billion suffer from severe water scarcity for at least a month every year, bring to light the urgency of looking for alternative and sustainable water resources (UNESCO, 2021; UNESCO, 2022). Within this context, treated wastewater has become into a reliable and cost-effective water alternative that guarantees water supply and that has been proved to be able to address many of the problems derived by water constraints all at once (Hristov et al., 2021). The use of reclaimed water is also of major importance in the pursuit of the 17 SDGs proposed by the United Nations (UN) in 2015, since it directly encompasses the aims of Goal 6 (clean water and sanitation for all) and favors the complete achievement of many other goals due to interconnections (Brennan et al., 2021; Di Vaio et al., 2021; Rodríguez de Sá Silva et al., 2022). The already proven key role of treated wastewater is particularly critical in developing countries where data shows devastating consequences from not having an adequate water supply or wastewater management, resulting in the population being seriously affected in terms of hygiene, health, the economy, and socially (Lutterbeck et al., 2017; Sánchez Pérez et al., 2020). This alternative source of water channels waste into a resource, thus collaborating with circular economy and enhancing sustainable development without jeopardizing the environment, and preventing the degradation of ecosystems (Lavrnić et al., 2017; Makropoulos et al., 2018; Pahl-Wostl, 2019; Ponce-Robles et al., 2020; Estelrich et al., 2021). Against this background, the objective of this research is to analyse the economic consequences of using NBS against its traditional alternative through a comprehensive economic assessment able to show not only the financial profitability of the investment but also the treatment costs saved by implementing its use. This objective is key in order to show law makers, stakeholders and researchers in a measurable way the importance of investing in NBS to reach water sustainability within the framework of circular economy. Furthermore, by reaching the objective proposed, the pivotal role that both treating wastewater properly and channelling waste into resource have in view of the SDGs will be unveiled in a quantifiable way. For this purpose, prior to this research, a LCA following ISO 14044 was carried out where environmental impacts were evaluated and quantified in the same scenario here considered. This paper consists of a quantitative analysis that not only considers traditional financial indicators widely extended in economic evaluations in Oeconomia Copernicana, 14(1), 103–134 106 water-related analysis through a LCCA to see the profitability of the investment but also carries out a monetary evaluation of the cleaning costs derived from the use of NBS against the traditional alternative. For developing these ambitious methodologies, a combination two different approaches, which make this groundbreaking research holistic, have been taken. On the one hand, traditional financial indicators widely extended in economic evaluations in water-related analysis have been calculated in a LCCA through CBA. The decision criteria used to assess CBA are Net Present Value (NPV), Benefit-Cost Ratio (BCR), Internal Rate of Return (IRR) and Discounted Payback Period (DPP). On the other hand, a monetary evaluation of the cleaning cost of environmental indicators derived from the use of both scenarios considered, the traditional and the constructed wetland (CW), have been carried out thus truly evaluating and quantifying the real costs of both alternatives. Literature review The increasing water demand together along with the climate change and the unceasing production of wastewater worldwide, has led to a scenario where water resources are depleting and has resulted in a situation where reusing wastewater is not only an adaptive action but also a feasible solution to achieving sustainable development (Hejduková & Kureková, 2020; Zagklis & Bampos, 2022). Against the current situation, the importance of channelling waste into a new resource as reclaimed water is of fundamental importance, since it fosters circular economy and sustainability goals. Furthermore, it is important to analyse the potential environmental impacts derived from these alternative treatment systems (Resende et al., 2019). The use of these green systems is steadily increasing and anticipated to grow in both developed and developing countries, because of the positive reduction they may enhance of energy demand, environmental pollution and economic costs (Nuamah et al., 2020). While traditionally wastewater treatment systems have been centralized, for various reasons, such as their great capacity to transport large volumes of water, benefits of scale and their highly predictable treatment performance, their high economic cost and energy and resources consumption are leaving room for decentralized systems (Hasik et al., 2016; Peñacoba-Antona et al., 2021; Khalkhali et al., 2021). Decentralized systems are Oeconomia Copernicana, 14(1), 103–134 107 typically standalone system used for smaller wastewater flows where the reuse happens on site (Licciardello et al., 2018; Van de Walle et al., 2022). Energy consumption plays a crucial role within the “water-energy” nexus with large countries like the US spending over 45% of total primary energy on “energy for water”, which includes every process where water needs energy and water supply systems representing up to 15% of total energy usages (Kyle et al., 2016 Vakilifard et al., 2018,). Another limitation of Centralized Water Recycling Systems (CWRS) is their incapacity to effectively and efficiently provide water resources to rural and low-income urban areas whether because of geographical dispersion or low water pressure and leaking pipes (Pickering et al., 2015; Laitinen et al., 2017; Wang et al., 2019). This last disadvantage is of great importance as more than 40% of the global population live in rural areas (Welivita et al., 2021; Balk et al., 2021). Although fully centralized systems have been widely used in the last decades, the latest recommendations based on research and cost-benefit analyses suggest transitioning away from these systems towards more adaptable and sustainable ones, thus leading to a shift from conventional centralized systems to either hybrid or fully decentralized ones (Dev et al., 2021; Castellar et al., 2022). Decentralized Wastewater Treatment Systems (DWTS) have been shown to be a sustainable, viable, flexible, reliable, and cost-effective alternative source of water, especially useful on a small scale (Gukelberger et al., 2019; Liu et al., 2021; Maryati et al., 2022). Furthermore, the use of DWRS, apart from enhancing environmental protection and resource recovery, may lead to environmental and local economic development (Jahne et al., 2020; Van de Walle et al., 2022; Estévez et al., 2022). One of the most extended and consolidated decentralized technologies are NBS such as CW, which, apart from strictly meeting chemical and physical standards for water reuse, require low energy, are cost-effective, easily operational and low maintenance (Corbella et al., 2017; Ricart et al., 2021; Cao et al., 2021). Since the construction of the first CW in 1974, the technology of these artificial engineered wetlands has been developing to make them desirable and efficient in the task of treating wastewater physically, chemically, and biologically which has expanded their use and implementation worldwide (Zhang et al., 2021). CWs are considered a green, nature based technology that involves wetland vegetation, soil substrates and microorganisms, and whereby metabolic processes take place resulting in the transformation and removal of pollutants from water (Gattringer et al., 2016; Resende et al., 2019). Furthermore, if planted, they can be aestheti- Oeconomia Copernicana, 14(1), 103–134 108 cally pleasing while promoting biodiversity, contributing to flood protection, and offering cooling effects (Dumax & Rozan, 2021). To strengthen the comparison with traditional wastewater plants, the fact that the greenhouse gas emissions (GHG) of a CW have proved to be 2714 times lower can be highlighted (Liu et al., 2019). Their high efficiency linked to important ecological benefits, make them green technology that promote a sustainable water supply (Cui et al., 2022). Fostering the construction of CWs thus improves the water supply from a sustainable point of view by meeting human needs without depleting existing water resources nor affecting in a negative way local economies and the environment in a negative way (Diao, 2021; Kataki et al., 2021). Despite having been used for more than 50 years and all of the research stating the benefits of CWs, although there has been an increase in their popularity, their effective implementation still remains a challenge (Wu et al., 2015; Deng et al., 2021; Vymazal et al., 2021; Yang et al., 2022). This failing, which partially impedes a successful full adoption, might be a result of a lack of agreement on many specifities in the wastewater industry, concretely because environmental impacts studied in LCAs are highly dependent on many factors, such as the location, population, or socioeconomic conditions, among others (Lourenço & Nunes, 2021). Despite the importance of reducing negative externalities and fostering ecosystem services, which deeply benefit the whole society with their positive externalities, all the intangible benefits of using VFCW too often go unnoticed because of missing economic evaluations and cost-analyses (Freeman et al., 2019). In a previous study of the current authors, a comparative LCA was conducted to assess the environmental impacts of a decentralized wastewater treatment system combining a VFCW and a membrane-based purification unit for treating black water for drinking purposes with their conventional alternative of sewage treatment and potable supply (Lakho et al., 2022). The outcomes of the study showed that the decentralized system had overall lower environmental impacts as compared to its conventional alternative. Against this background, there is an imperative need for research that shows economic data that verifies and supports not only the financial desirability of the investment but also the environmental benefits of using this alternative water supply against its traditional competitor from a tangible, comparable and monetary perspective. Furthermore, and in order to put an end to this problem, this study introduces a groundbreaking methodology where through holistic research, traditional finan- Oeconomia Copernicana, 14(1), 103–134 109 cial indicators have been calculated along with the economic value of environmental indicators that may endanger human health and the environment and jeopardize ecosystem services. In this way and based on a previous LCA carried out, data variability from one geographical area to another would be mostly eliminated due to environmental indicators having almost the same human and environmental consequences worldwide, and so results can be representative and easily extrapolated to other areas (Lakho et al., 2022). Research methods Scenario All the calculations of this research have been done considering a VFCW coupled with a membrane-based potable water production system as the investment proposal. This scenario, which has already gone through an LCA, is operated at a restaurant in Belgium with a water flow of 4 m3.d−1, and it has been compared with its traditional alternative: a public water supply and sewerage system in the same geographical area of Belgium which is ±300m away from the restaurant (Lakho et al., 2022). The restaurant is open 5 days a week and can serve a maximum of 135 customers per day. The expected discharge rate is ¼ population equivalent per customer (1/4 × 150 = 37.5 L). If it is considered that is going to be working fifty-two weeks per year and a period of twenty years, this means that the initial investment figures have been calculated for a VFCW that is going to be capable of treating 20,800m3 of wastewater during its useful life. Figure 1 shows the different steps that water go through in both of the scenarios considered in this research, VFCW and conventional system. Life cycle cost analysis An LCCA was carried out in order to appraise the economic viability and efficiency of a CW used as an alternative to traditional sewerage system in a restaurant. LCCA is an analytical approach based on cost-benefit analysis (CBA) and its use to evaluate the profitability of an investment project is widely extended especially for alternative water supply systems like VFCW (Diaz-Elsayed et al., 2020; Cao et al., 2021). Through CBA, mone- Oeconomia Copernicana, 14(1), 103–134 110 tary value is assigned to each input and output that result from the project that is being evaluated. Nevertheless, and despite its key value in project evaluation, its use is rarely seen in methodologies related to wastewater reuse projects, leaving a research gap in this field of study (Declercq et al., 2020). The most common decision criteria used to assess cost-benefit analysis are NPV, BCR, IRR, DPP (Galvis et al., 2018; Omole et al., 2019; Freeman et al., 2019; Loarte-Flores et al., 2020; Pahunang et al., 2021; Sakcharoen et al., 2021; López-Serrano et al., 2021; Ghafourian et al., 2022). In the context of developing an LCCA this research is of great importance because a new factor related to the interest rate calculation has been introduced into the economic methodology. Although there is existing literature where traditional indicators have been calculated, in all of the papers previously published only a single fixed interest rate for the whole period has been considered, thus leaving behind the interest fluctuations that may happen in periods as long as 20 years (Abdulfatah et al., 2019; Otter et al., 2020). Furthermore, and in a context of uncertainty in the international financial markets where interest rates are changing almost daily, different rates within a yield curve for the next two decades are of special relevance to study the viability of a project. The Euro area yield curve that has been considered for this research takes into account both, the Euribor rates based on interbank loans of the Euro area and longer maturities of interest rates of the most relevant European bonds, particularly the German bond. Projections of the yield curve are from September 27th, 2022 and are based on Bloomberg analyses. Furthermore, and since cash inflows may be monetary benefits or savings, for all the financial indicators calculated in this research the gross income and revenues are based on savings resulting from the use of the alternative studied against that of the traditional option (Zadeh et al., 2013; Abdelhay & Abunaser, 2021). Before calculating the traditional indicators, and in order to complete a detailed LCCA, it is also crucial to develop an initial cost structure based on the start-up costs that are needed for the constructed wetland (Bassi et al., 2022; Bolinches et al., 2022). For this survey construction and operational costs have been evaluated based on primary data. Data collection has been done in the last quarter of 2022 by contacting local, national and international companies which provided internal data, local, national and international authorities which provided public reporting and data and stakeholders. Data from the different sources were crossed and validated before being used in this research. The initial investment has been calculated based Oeconomia Copernicana, 14(1), 103–134 111 on the materials needed for the construction of the wetland that have been provided by local supply companies, but double-checked with international companies in order to see that data, and therefore results, used for this research can be easily extrapolated to other areas where water scarcity is an issue. The following assumptions have been made: − The project lifetime has been set at 20 years as in previous VFCW assessments (Abdelhay & Abunaser, 2021; Lakho et al., 2022). − Discount rates are different each year and are based on the Euro area yield curve. − Costs derived from constructing and installing a VFCW system at a restaurant of medium level with local knowledge and resources were independently investigated and collected through a market survey. Economic indicators NPV To carry out an economic analysis that displays the financial viability of using a VFCW, the NPV was adopted. The NPV is the difference between cash inflows and outflows during a certain period by taking into consideration a discount rate. Its result may be positive or negative, and while a positive magnitude reflects net profit and therefore the desirability of the project, a negative figure shows the lack of economic profitability. This means that the higher the NPV, the greater its profitability. The NPV has been calculated according to the following equation: NPV =       ()    (1) where: d Discount rate (%) R Revenues or Savings (EUR) C Costs (EUR) n Number of years (from 0 to n) Oeconomia Copernicana, 14(1), 103–134 118 sewerage system compared to the VFCW) the treatment cost for the traditional alternative that are displayed in Table 5 are always more expensive than those for the VFCW. Conclusions The scope of this research is of great importance if the value of water worldwide is taken into account. VFCWs have been verified in this study as a viable alternative that may enhance water supply in those areas where the traditional systems are either inexistent or unprofitable. Furthermore, all the traditional financial indicators used here to analyze the viability of the investment have stated the desirability of the project from an economic point of view and, moreover, the evaluation of the treatment costs of VFCW against the traditional alternative bolster the importance of fostering the construction of VFCW to help both the environment and the society. In this context, VFCWs are especially useful in rural areas that are not connected to public sewerage systems because of long distances or a small population. For these reasons, VFCWs may also help with combating rural exodus since the construction of traditional water supply and sewerage systems is often far too expensive and unprofitable for the low number of people who would benefit from their construction. In these situations, building VFCWs would benefit all the stakeholders; the government by saving money if compared with the traditional alternative, citizens by having a way of treating wastewater is an environmentally friendly manner, and all the society as a whole by developing sustainable communities and promoting rural development that are also a fundamental part of SDGs. Last, but not least, results derived from this research justify the construction of VFCWs to treat wastewater as being cost-effective for all, the investor, the environment, and society in general. The use of VFCWs for treating wastewater also makes an indirect contribution to the economy since as well as enhancing economic development through standalone businesses like restaurants, it also promotes the protection of water bodies, their availability, and regeneration. This in turn enhances its use in other contexts and economic sectors where water resources are of vital importance, and its implementation would uplift the achievement of SDGs due to the critical role water supply has directly and indirectly on their fulfilment. Oeconomia Copernicana, 14(1), 103–134 119 Some limitations of this research might be linked to the availability of supplies needed for the construction of the VFCW that can be hard to find in some geographical regions, especially in underdeveloped countries where rural areas are of great importance and water supply a key issue affecting millions of people. On the other hand, the “yuck factor” also deserves special attention, since it may slow down or even stop the reuse of treated wastewater based on wrong extended beliefs and perceptions that consider this alternative water resource as negative or even harmful. Another limitation that might limit the scope of this research is linked with the relatively high initial investment. This, together with the current high interest rate scenario may be potential barriers for the successful implementation of VFCWs. In this sense, public authorities could really foster their adoption through public grants or loans thus reducing or minimizing the initial economic effort. Furthermore, public, and international institutions could enhance the construction of VFCW by subsidizing part of the initial investment or through tax incentives for those people investing in this green technology that foster sustainable development within the framework of circular economy. Finally, another limitation of this research may be connected with the traditional financial indicators used in the methodology as qualitative variables and risk factors are not assessed. Against this background, and in order to solve the problem of the potential disadvantage that the unavailability of supplies may cause, future research should focus on looking for easy-to-supply alternatives and materials with which to construct the VFCW itself and the Membrane-based potable water production system. Apart from that, and since this research is based on a previous LCA, where an analysis of a mobile CW to treat grey water at music festivals against the traditional bottled water was also carried out, future research could include its LCCA and the monetary evaluation of its treatment costs. Oeconomia Copernicana, 14(1), 103–134 120 References Abdelhay, A., & Abunaser, S. G. (2021). 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