Gasification: Are smaller distributed WtE systems the solution for municipal solid waste in urban Australia?
By David Cocks, MRA Consulting Group Victoria Manager
Given the slow progress towards establishing large scale Waste to Energy (WtE) incinerators in the Eastern states, the question must be asked: Will smaller scale WtE rise to the forefront as a viable and preferred alternative for metropolitan Australia?
At face value, small to medium scale (150,000-200,000tpa) WtE facilities present a more palatable proposition, without the risk of being encumbered with the ”big hungry beast” label often associated with large scale incinerator proposals.
Potentially, smaller facilities could be distributed across multiple industrial precincts in a metropolitan setting, simplifying the waste logistics task and providing communities with a localised solution and opportunities for more equitable sharing of waste management responsibilities.
|Gasification is a process which converts carbon based materials into a gas primarily comprising carbon monoxide, carbon dioxide and hydrogen (Syngas). The Syngas is then combusted to produce heat, or recovered and cleaned for use as a fuel. The process operates in a controlled air environment that means direct combustion of the feed materials does not occur. The limited air supply and high temperature of the gasifier causes the feed material to rapidly decompose into Syngas which is then used as fuel, like Natural Gas, to produce heat, power or chemicals. This is quite different from an incineration/combustion process which requires large amounts of air to directly burn the feed material as fuel. The Syngas produced in gasification can be directly converted to energy with less potential emissions and higher conversion efficiency when compared to combustion. Gasification has been widely used for generating electricity from fossil fuels and reliably used on a commercial scale around the world for more than 50 years in the refining, coal, fertiliser and chemical industries.|
This approach has recently gained a lot more attention as an alternative to larger scale incinerators. For example, two smaller scale WtE gasification facilities are currently proposed for Melbourne:
- Recovered Energy Australia (Laverton North), granted an EPA Works Approvals in January 2020; and
- Great Southern Waste Technologies Australia (Dandenong), EPA Works Approval pending.
The history of gasification of mixed waste is littered with examples of technical issues, financial problems (e.g. the spectacular failure Tees Valley RE in the UK), and/or a technology that historically has been sensitive to changes in composition of waste feedstocks.
What has not been commonly observed has been the rise of gasification of mixed waste, outside of Japan, across Asia and in particular China where remote and constrained communities with strong environmental objectives have catalysed steady investment in small scale and medium scale gasification plants. Typically, these gasifiers process MSW and immediately combust the Syngas to produce steam, rather than recover it to be cleaned for use as fuel. The steam produced is directed to industrial applications or used to produce electricity. Notable examples include:
- Shengsi Island MSW gasification plant (10,000tpa commissioned 2016) – a small fishing village on an island, with no options for landfill;
- Shanxi Hong Tong MSW gasification plant (36,000tpa commissioned 2012);
- The Beijing Jinyu cement plant MSW gasification facility (36,000tpa commissioned 2013), built as part of its corporate environmental improvement commitment. The gasifier produces steam to supplement the facility’s heat requirements.
The above example systems are modular allowing them to be deployed at a wide variety of scale. MSW gasification systems in Asia have been deployed at capacities from 5,000tpa to 400,000tpa. Due to the controllable nature of the gasification process and their high operating temperatures they are also used to process hazardous waste.
In addition to the above, there are examples of facilities which have operated for almost 15 years, e.g. the Shandong Jinan MSW Gasification Disposal Centre (circa. 66,000tpa). The contemporary regulatory environment for WtE facilities in China comprises air emission limits and test methodologies that are comparable to those adopted in Australia. The track record of operating on MSW combined with acceptable environmental performance strongly suggests that any local technical challenges can be overcome.
So, is it time to revisit our classical misconception that Waste to Energy facilities are “big hungry beasts” and seriously consider the benefits of a more distributed smaller scale solution? Balancing the concerns of the community in the urban settings suggest that smaller scale solutions, such as that promised by modular gasification systems, may tip the scales in favour of WtE becoming a viable and preferred alternative to landfill. MRA will continue to explore and keep the industry up to date with relevant and emerging trends in WtE across the globe.
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