Waste to energy for a low emissions future

Embracing waste to energy in Australia offers a complementary way of diverting waste from landfill and reducing the nation’s emissions, explains Hitachi Zosen INOVA Australia.

After two weeks of negotiations, 196 representatives from nations around the world reached an agreement to cut their carbon emissions and limit global warming to 1.5 degrees Celsius by 2020.

On 12 December 2015, the nations adopted the consensus at the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change in Paris.

Historically known as the “Paris Agreement”, it would not become binding until 55 nations ratified the agreement. Some elements of the agreement were legally binding, including submitting an emissions reduction target and a regular review of it. The specific target set by each nation was voluntary and the entire agreement was conditional on 55 countries out of the 174 that signed it to ratify it, as the countries needed to cover more than 55 per cent of global emissions.

Australia ratified the agreement in November 2016, after more than 100 countries had done so, setting its own targets to reduce emissions to 26-28 per cent on 2005 levels by 2030. According to a fact sheet by the Federal Government, the nation is meeting its 2020 target through direct action policies that reduce emissions, increase energy productivity and improve the health of soils and the environment.

Hitachi Zosen Inova Australia (HZIA), a leader in waste to energy (WtE) solutions, sees renewable energy as a necessity in order to meet Australia’s global targets. The company estimates that to meet these targets, emissions of greenhouse gas will have to be completely halved between 2045 and 2060 and the production of carbon dioxide emissions re-introduced to levels that can be absorbed by photosynthesis. It asserts that a faster implementation should be considered due to the quicker than estimated rising of the average global temperatures – also experienced in Australia.

HZIA believes the process of meeting Australia’s targets will entail stopping the burning of fossil fuels entirely from 2040 and switching completely to renewable energy. According to an Australian Government fact sheet Emissions from landfill facilities, the waste sector produces around 15 million tonnes of carbon pollution every year, equivalent to three per cent of Australia’s emissions. It says without action to reduce emissions, a tonne of standard municipal solid waste will continue to release about 1.2 tonnes of carbon pollution in landfill.

Marc Stammbach, HZIA Managing Director, sees WtE as one solution to helping Australia meet its 2030 targets. Waste management in Europe sees biomass and recyclables collected separately, with residual waste processed in WtE plants. Marc believes this reduces or eradicates the need for landfill, cuts greenhouse gases and protects the human habitat from contamination and pollution.

Marc explains the French describe landfills as “stockage des déchets” which translates to “storages of waste”. This recognises that landfills for untreated waste aren’t a treatment method and hence not sustainable. He says due to the ongoing increase of landfill gas and leachate emissions over decades and centuries, the only question for future generations will be how to pay for the costly clean-up of landfills.

Grate combustion, flue gas treatment and material recovery technologies are just a few ways waste can be converted to energy and fed back into the grid to be used as base load power. Marc estimates a modern WtE plant can deliver enough district heating from a tonne of waste to replace about 240 kilograms of oil, generating 800 kilowatt hours of electricity – enough to help power an average household with a total annual consumption of about 3500 kilowatt hours for the year.

THE WASTE TO ENERGY MOVEMENT

Unfortunately, Australia is still some ways off from achieving a critical mass in WtE, Marc believes, with only a few proposals that use thermal treatment moving through approvals. While other forms of anaerobic digestion and refuse-derived-fuel are gaining increasing prominence in Australia, Marc sees thermal treatment as one required way to reduce waste to landfill by converting residual waste into energy. However, the regulatory environment needs to improve in order to do so.

“We need to move away from arbitrary recycling targets for WtE, as is the case in NSW, to get waste out of landfill and that means nothing going untreated,” Marc says.

“Regardless of how prominent WtE becomes, the economics alone will drive composting of biowaste and recycling as a priority and what cannot be brought back into the economy will go to WtE.”

Marc says that issues of interstate waste transport should serve as a wake up call for regulators. A need exists to harmonise landfill levy regulation across the nation and to ban the landfilling of any untreated waste, he says, in order to encourage investment certainty in local waste management infrastructure. This would provide more avenues for composting, recycling and WtE as seen in countries such as Austria, Belgium, Denmark and Switzerland, which dispose less than two per cent by weight of municipal solid waste to landfill, according to Eurostat data published in 2016. Countries such as Germany, Austria, Belgium and Switzerland also recycled at least half of their municipal waste.

“Although WtE is regarded as a necessary compliment to compost and recycling and preferred to landfilling in most other countries, we only hear about composting and recycling in Australia,” Marc says.

“Many local stakeholders talk about WtE as if it’s a threat to compost and recycling. However, if you look overseas, it is complementary. Countries with the highest WtE rates have higher rates of composting and recycling.”

AUSTRALIAN PROGRESS

Thankfully, there are some projects getting off the ground, as last year HZIA was selected as the preferred tenderer for a 20-year waste service agreement by Eastern Metropolitan Regional Council (EMRC), which represents six member councils in Perth’s eastern region.

The contract with EMRC forms the cornerstone waste supply for the East Rockingham Resource Recovery Facility, which will convert about 300,000 tonnes of residual waste per year into baseload renewable energy, producing 28 megawatts of electricity at full capacity – enough to power 36,000 homes. The plant will divert 96 per cent of the EMRC’s residual household waste. HZIA’s facility is part of a consortium with Perth-based WtE business New Energy Corporation and investment firm Tribe Infrastructure Group.

HZIA’s moving grate combustion technology, which will be used in Perth, is currently used in more than 500 projects worldwide, with the project scheduled to commence construction in the third quarter of 2018.

HOW IT WORKS 

The process begins with a fully automatic crane that will transport the thoroughly mixed waste from a bunker on site into the feed hopper. After the waste is pushed onto the HZI grate via a ram feeder, it passes through a variety of combustion phases, including drying, ignition, combustion and burnout. Five individually controllable grate zones ensure all the waste is combusted, irrespective of its constantly varying composition.

The process steps can be controlled separately. Swift adjustment of airflows and grate motion in every zone at all times responds to process fluctuations. The inclination of the grate, the drop-off after the main combustion zone and the horizontal burnout zone aim to ensure excellent burnout of all waste fractions.

Combustion is further controlled by injecting air from underneath the grate taken from the bunker area, while secondary air and recirculated flue gas are injected at high velocity into the secondary combustion chamber. This ensures flue gases are burnt out, as the energy released during combustion is transferred to the water stream cycle in a downstream five-pass boiler. It also assures the lowest carbon monoxide and nitrogen oxide emissions and volatile organic compounds are produced. The energy released produces superheated steam, expanded in a turbine generator to produce electricity. Flue gases are cleaned to European standards and continuously monitored prior to being released.

BARRIERS TO ENTRY

While the EMRC project is promising for the state of WtE in Australia, there are still some projects slow to progress.

HZIA has declared its interest as the chosen technology supplier to Dial A Dump Industries’ proposed TNG Eastern Creek WtE project. The $700 million facility is still undergoing planning approvals and the proponent has applied for a processing capacity of around half a million tonnes of residuals per annum from sorted commercial and industrial and construction and demolition waste. The capacity was halved in late 2017 by the proponent in its latest clarifications submissions.

Marc says he will be concerned about the state of WtE in Australia if the facility doesn’t get through. If approved, he believes it will be a catalyst for further plants. He encourages regulators to look to plants overseas if they want to progress thermal treatment and WtE in Australia.

“The clear difference in Western Australia is the politicians there went overseas to look at other plants as a reference,” Marc says.

“I think the lead project for WtE will come from EMRC in WA. NSW is regarded as the premier state and everyone wonders what is going on if it’s got highest waste levy and nothing is happening.”