title: Phytocapping and ecological rehabilitation of landfills: practices, barriers, and opportunities in Queensland, Australia
Creators: name: Chulliparambil, Vishal Rajendraprasad
Publisher: name: Griffith University
Year: 2024
Subjects: subject: landfill phytocapping
subject: ecological rehabilitation
subject: GIS analysis
subject: habitat creation

description: Landfilling remains the predominant global waste disposal method, and effective landfill rehabilitation is crucial for converting the environmental liabilities of closed landfills into opportunities for ecological, social, and community benefits. Given the pressing need for usable land reuse, particularly in urban areas, landfill capping is a key component of landfill closure, designed to isolate waste and facilitate future land use. Traditional barrier-style landfill caps, comprised of clay and geosynthetics, often face limitations in establishing vegetations, including restricted rooting depth due to their impermeable nature. Phytocapping, a novel Nature-Based Solution (NBS), addresses these limitations by utilising a ticker uncompacted soil layer along with soil-plant interactions to manage waste. In this method, the soil layer functions as a sponge while plants use transpiration and evaporation to minimise water infiltration, thereby opening possibilities for ecological rehabilitation and enhancing biodiversity. These possibilities however have been given little consideration as landfill after-use. This research aims to enhance the understanding of ecological rehabilitation of landfills using phytocapping in Queensland. Chapter 1 introduces the rationale for the research aim, two research objectives, problem statement and background to the research topic. Chapter 2 presents an overview of the current state of knowledge in the field of phytocapping and its application for landfill ecological rehabilitation. This chapter highlights the gaps in existing theory and practice, showing the significance of this study. Chapter 3 presents the methodology and methodological rationale. The research conducted uses a mixed-method approach, incorporating qualitative, quantitative, and spatial analyses through expert surveys, stakeholder interviews, and GIS studies. Chapter 4 presents the results from surveys and semi-structured interviews with 38 industry experts and stakeholders in Queensland. The survey results were statistically analysed to design the semistructured interviews, which were then coded and analysed using SWOT analysis to identify major qualitative themes. Findings indicate that 82% of survey respondents and 100% of interview mentions highlighting the significant ecological benefits of phytocapping as a primary driver for selecting this capping method. Experts reported increased ecological value of landfills postphytocapping. However, there were significant barriers to adoption, such as lack of information and regulatory challenges. Chapter 5 uses GIS and a multi-criteria approach to analyse the spatial characteristics of areas surrounding landfills in Queensland, focusing on their potential for ecological after-use. This study addresses a major knowledge gap identified in Chapter 4 by assisting decision-makers in adopting phytocapping for landfill rehabilitation. The research employs various environmental features to represent ecosystem services and connectivity, creating two novel scores (environmental and habitat) based on the total area and number of these features. The evaluation reveals high ecological rehabilitation value in South East Queensland and the Wet Tropics. This study demonstrates the significance of considering landfill after-use for ecological conservation, providing a methodology to guide decision-making and prioritise landfills for local governmental areas. Chapter 6 investigates opportunities and barriers for ecological rehabilitation after-use of landfills in Queensland, using surveys, semi-structured interviews, and GIS case studies. This study involved 28 surveys and 12 interviews with industry experts and stakeholders. Results indicate that ecological rehabilitation is the preferred landfill after-use due to its community benefits, such as green spaces and restored natural habitats. However, regulatory barriers and lack of incentives often prevent these outcomes. The study highlights opportunities in creating ecosystems, connectivity, and visual amenities but also points to legal ambiguities between the Environmental Protection Act and the Nature Conservation Act as significant obstacles. The findings underscore the lack of knowledge among industry experts and stakeholders about phytocapping and ecological rehabilitation and emphasise the value of a GIS-based approach for informed decision-making to achieve beneficial after-use outcomes. Chapter 7 discusses the major findings from the consolidated insights of landfill stakeholders and the quantification of the ecological rehabilitation potential of landfill sites and their immediate periphery in Queensland from a spatial perspective. This thesis advances the understanding of barriers to implementing phytocapping for ecological landfill rehabilitation, highlighting issues such as conflicting policies and misconceptions regarding costs and impacts. The research reveals that these barriers are common to many Nature-Based Solutions and that integrating them into regulatory frameworks could enhance environmental management outcomes. The study underscores the interconnectedness between phytocapping and ecological rehabilitation after-use, showing that improved guidelines, knowledge, and stakeholder decision-making can lead to better ecological outcomes and multi-beneficial community after-use. Further research, including ecological and public stakeholder surveys, is recommended to deepen understanding of phytocapping's ecological benefits. Future research could valuably expand this work to other Australian states. Ultimately, this work supports the broader adoption of phytocapping for landfill rehabilitation, contributing to ecological sustainability and Australia's Nature Positive Plans.