# Life Cycle Assessment of Substitutive Building Materials for Landfill Capping Systems in Vietnam
###### Abstract
The drainage layer forms an integral part of the leachate collection system, comprising of inert material with high permeability along with drain pipes to collect infiltrating water and prevent leachate. The drainage layer lies below the recultivation layer and above the mineral sealing layer [26]. The commonly used drainage layer materials are sand or gravel and geosynthets [27]. The recultivation layer usually lies above the drainage layer of the landfill, forming a top part of the landfill capping system acting as vegetation and lateral drainage layer [23]. To meet the basic requirements, a recultivation layer should consist of sandy/loamy materials supporting plant growth at least 1 m thickness and should have a hydraulic conductivity of at least 7.2 \(\times\) 10\({}^{-6}\) m/s [28]. The commonly used recultivation layer material is locally available topsoil [29]. The paper presents the result of the research project 033R212C (SAND! ), funded by Germany's Federal Ministry of Education and Research (BMBF), that is focusing on mitigating the scarcity of primary raw materials as building materials through the feasibility assessment of secondary raw materials. Among other building applications, the need for mineral resources in landfill construction was addressed in the framework of the assessment of potential substitutive materials. The landfill sealing layer is a compartment of the capping system with particular low permeability requirements. The availability of primary materials that meet the requirements, like clay, is usually limited, especially in the Vietnamese context. For that reason, an environmental assessment was performed using the Life Cycle Assessment (LCA) method to identify feasible options for substitutive building materials to construct the landfill, as well as the environmental benefits. LCA is a rapidly evolving tool used to determine the impacts of products or systems for relevant environmental and resource aspects. Vietnam is geographically located in Southeast Asia, along the Indochina peninsula, with a total area of 329,566 square kilometres. Due to the considerable north-south extension, the climate is divided into northern and southern climate zones. The north of Vietnam is characterised by a winter-dry subtropical climate. In the south of the country, the tropical climate prevails throughout the year and is also described as variable humidity [31]. The climate of Vietnam overall is tropical typhoon and monsoon, with abundant rainfall and humidity up to 80-90%. The northern part of the country receives annual precipitation of about 1700 mm, while the southern region receives 2000 mm on average [32]. Vietnam's population was estimated to be 96.4 million people in 2019, including an urban population of 32.8 million people [33]. The Vietnamese population is expected to increase by  
Figure 1: Different layers involved in landfill capping—Landfill Class I Germany (Adapted source: [30]). 100 million by 2025 [34]. According to the Vietnam Urban Development Vision of 2020-2025, the urban population is expected to grow from 45% by 2020 to 50% by 2025 [35]. Since the 1986 \"Doi Moi\" reform, Vietnam has undergone rapid development and urban growth. Owing to the increasing population and urbanisation, the municipal solid waste (MSW) volume is increasing. The MSW generation rate is estimated to rise yearly by 10-16%, with sources including households, restaurants, markets, municipal activities, and businesses [36; 37]. Vietnam generates more than 27.8 mil tons/year of waste from various sources such as municipal, agricultural, and industrial waste [38]. According to [39], in municipal areas, the ratio of solid waste disposed of in landfills was approximately 34%, recycled waste accounts for approximately 42%, and the remaining other disposal processes comprise about 24%. On average, Vietnam's waste generation was 0.7 kg/cap/day in urban areas and 0.4 kg/cap/day in rural areas [40]. According to [41], about 63% of collected waste ends up in landfills and 22% goes to various treatment facilities.