Pros and cons for air quality of waste-to-energy
Written by Plistina Almeida and Simon Welchman
Waste-to-Energy (WtE/W2E) or Energy-from-Waste (EfW) facilities have faced historical resistance. The potential of WtE as an alternative energy source is gaining momentum including the recent introduction of the Energy from Waste Policy in NSW.
W2E relies on a range of proven and emerging technologies that have the potential to displace fossil fuel power generation and reduce the volume of waste disposal at landfills.
A common concern linked to WtE facilities is their potential to generate toxic air pollutants. Fortunately, new technologies can control these toxic emissions allowing the combustion of waste for energy generation to be viable.
Is waste-to-energy better than landfill?
In terms of the waste management hierarchy, energy recovery from waste, such as WtE, is always preferable to disposal of waste in a landfill. However, in complex economies such as ours, there is a need for a range of options to efficiently and effectively deal with waste whilst capturing important resources for higher uses.
The impact of a landfill on air quality can be significant at the local scale, particularly if it is poorly situated or managed, or if it is subject to urban encroachment. At a global scale landfills generate greenhouse gases.
“As organic matter breaks down in landfill both biogenic carbon dioxide (CO2) and methane (CH4) are emitted. Methane is the most important of these gases from a greenhouse gases perspective because it has a high global warming potential (21–25 times that of CO2).” (Air – EIS information guideline, 2021)
Energy recovery from waste may also generate air pollutants and greenhouse gases. Consequently, it is important to assess individual proposals on their merits considering the potential for local and global effects.
EfW facilities have the potential to reduce GHG emissions associated with electricity production. GHG emissions displaced by EfW facilities include methane emissions associated with the landfilling of municipal waste and GHG emissions associated with reduced consumption of fossil fuels. The extent of these reductions is highly dependent on the composition of the waste and is directly linked to the proportion of waste that is of fossil fuel origin.
The Basics: how is waste converted to Energy?
Two main technologies are used to generate energy from waste:
Some of the most common biological processes involve anaerobic digestion or the use of fermentation to produce biogas or alcohol. We covered some of the main discussions related to Anaerobic Digestion plants here.
On the other hand, technologies involved in the thermal processing are:
- Combustion to produce heat
- Gasification to produce a combustible syngas
- Pyrolysis to produce syngas, oil or char.
Combustion is indeed the most commonly employed technique in WtE facilities. It is also the most straightforward of the treatment processes: direct combustion of waste is used to create heat, which can then be used directly or via the production of steam to generate electricity.
The other processes have intermediate stages where fuel or gas is created, which is then combusted to generate heat, electricity, or converted into transport fuels or synthetic natural gas or other products.
Both types of technologies involve emissions into the atmosphere.
For example, the raw materials used in anaerobic digestion are often odorous and the gases produced by anaerobic digestion may also be odorous. Consequently, it is important to manage raw materials and gases to avoid odorous emissions that may otherwise negatively impact neighbours.
In relation to thermal treatment, all traditional forms of combustion involve emissions to air. For gaseous fuels (e.g. biogas or syngas), the key emissions are oxides of nitrogen and products of incomplete combustion such as carbon monoxide and volatile organic compounds (VOCs). For combustion of solid wastes, additional air pollutants might include particulate matter, heavy metals and other compounds.
Is it possible to efficiently control the emissions to avoid toxicity to a neighbouring population?
The short answer is yes!
The long answer is that it requires some investment and a lot of planning.
To obtain approval, Governments expect proponents of waste-to-energy facilities to demonstrate that:
- Emission control technologies are proven, effective and robust for the waste input streams
- Best practice management and controls will be implemented
- Regulatory limits will be achieved
- Health risks will be minimised as far as is practical.
Besides that, some other best practices may be considered for achieving a clean WtE facility:
- Continuous emissions monitoring and publishing of data on a public website.
- Strict emission limits e.g. EU’s Industrial Emissions Directive.
- Ensuring that the facility is designed to be able to accommodate future material recovery including steel, e-waste, recyclables and other hazardous materials.
In summary: is Waste-to-Energy bad?
The premise of utilising waste to generate energy is great where it diverts waste from landfill. Ongoing monitoring and management are important to ensure that emissions are effectively controlled and community concerns are addressed.
How can we help you evaluate the best control options for your W2E facility?
Katestone has had extensive experience in the air quality impact assessment and management of odours associated with WtE facilities. Our team has assisted clients at every stage of the process including the feasibility and preliminary design phase through approvals to operations.
Our highly experienced air quality and odour impact assessments and odour management plans help clients implement state-of-the-art emission control strategies.
References
Qld.gov.au. 2021. Air – EIS information guideline. [online] Available at: <https://www.qld.gov.au/__data/assets/pdf_file/0009/140004/eis-tm-air-information-guide.pdf> [Accessed 5 August 2021].
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This article featured in the Katestone’s Clear Skies 2021 Winter edition. Click here to view other featured articles.