title: Modelling and optimization of waste-to-energy developments for Net Zero Energy Buildings (NZEBs)
Creators: name: Ahmed, Asam Mohamed Fiaez
Publisher: name: University of Glasgow
Year: 2024

description: The pressing issues of waste management and decarbonizing the building sector in the context of climate change and global warming necessitate innovative solutions. This study explores Net-Zero Energy Buildings (NZEBs) and waste-to-energy technologies as pivotal low or zero-carbon alternatives to conventional fossil fuel-based approaches in building construction and waste management. 

Waste-to-energy technologies emerge as crucial players in the development of NZEBs, simultaneously addressing the triple crisis of waste accumulation, climate change, and escalating energy demands. The chosen waste-to-energy technologies employ thermochemical and biochemical processes to convert diverse waste feedstocks available in Glasgow. These technologies operate under specific operational conditions tailored to the unique characteristics of the waste materials. The waste treatment methods under consideration in this study include gasification (thermochemical), pyrolysis (thermochemical), and anaerobic digestion (AD). Three distinct types of feedstocks- gardening waste, food waste, and wood waste are considered to assess the efficacy of these technologies across various wastes. 

Energy hails from green sources, particularly bioenergy, playing a critical role in combatting fossil fuel depletion and climate change. Despite its increasing share in the energy mix, gaps persist in understanding the technological configurations of bioenergy-supported NZEBs, optimal feedstock, technology selection, and the absence of relevant optimization models. 

Scotland, where waste and building energy are significant contributors to individual emissions, becomes the focal point. Glasgow, chosen for its sizable population guaranteeing consistent waste supply, aligns with the city's commitment to decarbonization, which will be evident in strategies such as Net Zero by 2045. This study aims to showcase how low-carbon energy production from waste aligns with the city’s energy plan and supports waste management strategies. These plans and strategies are thoroughly examined in Chapter 7 of this study. This critical assessment delves into the current state of Scotland's zero waste initiatives and evaluates the region's renewable energy policies and targets. The evaluation encompasses environmental impact, economic implications, and alignment with climate policies. 

The research question centres on the economic and environmental feasibility of waste-to-energy technologies supporting NZEBs and sustainable waste management schemes within Glasgow. A feasible project should demonstrate carbon savings compared to conventional methods in waste management and energy production, ensuring positive returns on economic investment without outweighing the environmental benefits. The study critically assesses waste-to-energy technology development, considering environmental impact, potential carbon savings, financial implications, cost benefits, and climate policy. 

The novelty of this study lies in establishing a procedure defining how waste-to-energy technologies can serve as a renewable energy source for the burgeoning NZEBs and contribute to sustainable waste management. Environmental impact analysis and economic assessment results contribute valuable datasets to existing research. Life Cycle Assessment (LCA), Cost-Benefit Analysis (CBA), MultiCriteria Analysis (MCA), and Multi-Objective Optimization (MOO) have been conducted to determine the feasibility of waste-to-energy projects to support NZEBs and sustainable waste management schemes. 

Designing various waste-to-energy scenarios based on biomass waste feedstock, the study employs thermochemical and biochemical technologies to convert different waste feedstocks, including gasification, pyrolysis, and AD. The ten designed scenarios allow for a comprehensive comparison of environmental and economic results, considering variations in waste feedstock type and technology, leading to differences in energy production rates, yields, and process carbon emissions. 

The environmental approach centres on the LCA method, evaluating environmental performance through carbon-saving potential using Global Warming Potential (GWP) as the impact indicator for waste-to-energy technologies. The study reveals that waste-to-energy technologies can reduce 65% of CO2-eq emissions per tonne of feedstock. During transport and collection, emissions amount to 10 kg CO2-eq per tonne of feedstock, with diverse technologies powering the plants resulting in a range of 10 to 25 kg CO2-eq per tonne of feedstock. 

The economic assessment utilizes CBA to determine whether carbon savings outweigh the expected costs of waste-to-energy technologies, providing a comprehensive comparison of the economic feasibility of different waste-to-energy technology scenarios. In Scenario 5, the total energy production demonstrated the capacity to meet the average annual energy needs of 12,117, 12,096, and 12,094 households in districts A, B, and C, respectively. Among the scenarios, Scenario 9 is the most suitable technology-feedstock combination for NZEBs in Glasgow, boasting the highest efficiency at 70%. 

The sensitivity analysis reveals a direct correlation between economic, technical, and environmental parameters with technological advancements and the optimal technology pairing. Enhancing these parameters can amplify benefits, ensuring sustainable and systematic waste management. Hence, sensitivity analysis plays a crucial role in identifying optimal solutions for waste management. 

It is concluded that waste-to-energy technologies are economically viable for energy production in Glasgow. The outcomes of multi-objective optimization point towards the feasibility of optimizing scenarios to minimize both total cost and GWP. Through various analyses conducted in this study, it is evident that waste-to-energy technologies can harness Glasgow's waste for energy production, diminish the environmental impact of waste management practices, and yield economic advantages for both the energy and building sectors. 

This research adds valuable datasets to academia and the energy industry, providing insights into environmental impacts and economic viability. The study's novelty lies in establishing a framework for waste-to-energy technologies supporting NZEBs and sustainable waste management schemes.