Environmental and economic assessment of municipal solid waste management scenarios in NSW, Australia
The significant amount of solid waste generation has become one of the most important challenges worldwide to achieve environmental sustainability. Australia is facing serious issues in waste management. Waste generation per capita in Australia is one of the highest in the world. The recycling rate in Australia compared to the other countries is at a high level. In contrast, the contribution of Waste to Energy (WtE) technologies in waste management are minor. Therefore, Australian waste management largely relies on landfilling. Disposal of waste has the lowest priority in the waste hierarchy and is not sustainable. In order to establish sustainable waste management, decision-makers require the results of environmental and economic assessment of alternative waste treatment technologies. The evaluation of environmental and economic aspects of waste treatment technologies could provide essential outcomes to compare WtE technologies and define sustainable waste management scenarios. The potential of waste treatment technologies for resource recovery should also be determined as a requirement for conducting environmental and economic assessments. This thesis examines alternative waste management scenarios to find sustainable waste management for Australia's future.
The primary objective of the thesis was to investigate electricity generation and greenhouse gas (GHG) emission potentials from major streams of solid wastes in New South Wales (NSW). The evaluation was conducted on four waste management scenarios, employing WtE technologies for three different waste classes (classified into combustible, non-combustible and food organic waste) in each stream of residual waste (municipal solid waste (MSW), commercial & industrial waste and construction & demolition waste). The results showed that the scenario which includes incineration of combustible waste and anaerobic digestion (AD) of food waste could generate the highest amount of electricity with the lowest GHG emissions. Implementation of this scenario can lead to generation of about 4165 GWh electricity, reduction of approximately 1.7 million tonnes of GHG emissions and diversion of about 3 million tonnes of residual waste from NSW landfills annually.
The second objective was to analyse the environmental impacts of alternative residual MSW management scenarios. The environmental burdens of six different scenarios in midpoint and endpoint impact categories of ReCiPe method were assessed. The Ecoinvent database was employed for this study. The results revealed the scenario with gasification for treatment of combustible waste and recycling for plastic waste had the lowest level of environmental burdens in global warming, freshwater and marine ecotoxicity and human non-carcinogenic toxicity. The sensitivity analysis for energy conversion rate and plastic recycling rate showed that variation in energy conversion rate could change the order of scenarios. In the next research, real-world data published by national pollutant inventories was employed to investigate the environmental impacts of electricity generation from WtE technologies. The results showed that the most significant damage to human health and ecosystems was related to incineration, followed by bagasse. The global warming impact category was found as the primary contributor. In contrast, incineration had lower global warming impacts for treating one tonne of residual waste than landfilling. The sensitivity analysis for the power grid GHG emissions revealed that growth in the share of renewable energy in the power grid will change the preference of WtE technologies.
The economic aspect of five waste management scenarios, including economic cost and benefits from gate fees, governmental taxation and incentive, recovery of electricity and material, was further investigated. The study also investigated the sustainability of scenarios considering economic cost, environmental damage to human health and environmental damage to ecosystems. The scenario employing incineration for combustible and plastic waste and AD for food waste showed the lowest economic cost of about m$ 238, while the landfilling of all types of wastes in the baseline scenario showed the highest economic cost at approximately m$ 476. The results of the sustainability assessment confirmed the priority of scenarios based on economic cost. Considering the current conditions in NSW, implementing AD for residual food waste and incineration for residual combustible waste and residual plastic wastes were suggested as the most sustainable management. The results revealed the potential of each WtE technology for integrating into the residual MSW management.