Sustainable Electricity Generation Via Cofiring
By Associate Professor Dr Adlansyah Abd Rahman
October 29, 2024 - AS Malaysia transitions towards Net-Zero greenhouse gas emission status by the year 2050, efforts are on the way to ensure the main source of electricity generation is 'green'.
Currently, the nation is still firing fossil fuels in thermal power plants for a secure and relatively affordable supply of electricity.
This reliance on thermal power plants is likely to continue into the future as it is the only viable option for providing stable grid network power for sustainable economic growth and being socially equitable.
Cofiring: A Pathway to Greener Thermal Power
There are means of making thermal power plant operations environmentally friendly and eventually assisting in mitigating climate change.
The first stage is gradually switching the fossil fuel with bio-derived fuel, such as biomass that absorbs carbon dioxide (CO2) during its growth. This then can be followed by the full conversion of these power plants to run purely on biomass. Ultimately, carbon capture, utilization and storage (CCUS) when integrated with these thermal power plants, will make them the only energy source capable of being carbon-negative.
The first stage, commonly known as cofiring, is defined as the combustion of two or more different fuels in a single furnace although, previously the term has been specifically used for describing the partial substitution of coal with biomass fuel in a utility-scale boiler.
The most common type is direct cofiring where solid biofuel is injected into the coal combustion region of the boiler. This has proven to be a cost-effective method of incorporating biomass into a large-scale centralized power grid network.
Global Practices on Cofiring
Notable examples of cofiring are Fiddler's Ferry Power Station and Drax Power Station being the pioneers in the UK, burning a range of biomass fuel sourced both locally and imported from abroad.
The Drax Power Station has completed the full conversion of all operating boiler units to biomass-only firing and recently has been selected as the main research station for bioenergy with carbon capture and storage (BECCS) to provide carbon-negative power in the future.
Lynemouth Power Station is the latest in the UK to have been converted to full biomass firing in 2019 from cofiring with coal.
In the Netherlands, Amer 9 Power Plant and Eemshaven Power Plant are cofiring mainly wood pellets at 50 per cent and 15 per cent substitution rates respectively.
Both power plants have plans to increase biomass fuel firing by the middle of the decade.
Denmark's Amager Power Station operates a cofired coal with biomass boiler unit and fully converted to biomass boiler units for electricity generation and district heating steam production.
Avedøre Power Station and Studstrup Power Station in Denmark have been converted for full biomass firing with the option for firing coal when needed. Rodenhuize Power Station is a large-scale 1300 MW multi-fuel power station located in Belgium capable of firing coal, gas and biomass for combined heat and power generation.
In Asia, Japan leads the cofiring effort with commercial operations developed in the late 2000s as a way of keeping connected essential thermal power plants for a stable and secure grid network amidst growing other intermittent renewable sources.
Shin Onoda Power Plant fires wood pellets and wood chips in its two 500 MW supercritical units starting in 2007. In 2008, Hofu Biomass-Coal Mixed Firing Power Plant was a then newly installed 112 MW thermal power plant cofiring wood pellets and palm kernel shells with coal.
Newer thermal power plants such as Hitachinaka Power Station and Taketoyo Power Station are specifically designed for cofiring various types of biomass fuel and coal as Japan's energy demand continues to grow.
Research and development here is also looking at cofiring hydrogen in the forms of ammonia and methylcyclohexane as complementary efforts in reducing greenhouse gas emissions of thermal power plants.
India is another country seeing rapid growth in energy demand and the country relies heavily on thermal power plants for stable and equitable power supply.
It launched the National Mission on the use of Biomass in Thermal Power Plants in 2021, which mandated a minimum of 5 per cent cofiring of biomass pellets at all thermal power plants.
The main source of biomass is targeted from local farming waste as India also aspires to be a major biomass pellet exporter.
Within Asean, Thailand and Indonesia share a similar outlook of utilizing locally produced biomass from agricultural residues for cofiring at thermal power plants.
Both nations have limited experience in several boiler units such as at the Suralaya Power Station and Mae Moh Power Station.
Malaysia's Cofiring Initiatives
Malaysia's venture into commercial-scale cofiring was at Malakoff's 2100 MW Tanjung Bin Power Plant as a flagship project of the National Energy Transition Roadmap (NETR).
A trial burn at a substitution level of 0.5 per cent empty fruit bunch (EFB) pellets from palm residue was successfully conducted in 2022.
This was followed by increasing the biomass to 2 per cent of washed EFB and wood pellets in 2024, making it the largest installed bioenergy capacity for the nation as of today.
Malakoff plans to increase this further to 3-5 per cent in 2025 and ultimately reach a target capacity of at least 15 per cent in 2027.
It is intended that the flagship initiative would create the demand center to entice mass production of biomass pellets from commodity crop residues in Malaysia.
This effort has also identified several opportunities for expanding cofiring to other thermal power plants in the country.
Cofiring biomass in thermal power plants has proven in many locations as the most effective way of increasing renewable energy capacity to accelerate towards Net-Zero status.
Cofiring also ensures the stability of the existing grid network and the security of supply as it poses less risk of implementation when compared to other intermittent renewable energy sources.
Utilizing residues from crops as co-firing fuel also reduces agricultural greenhouse gas emissions whilst at the same time developing a new green energy support industry.
Moving forward, Malaysia can provide further green energy in the generation mix especially when demand is expected to increase with the recent introduction of the Corporate Renewable Energy Supply Scheme (CRESS) and Renewable Energy Certificates (RECs) through the Malaysian Green Attribute Trading System (mGATS).
The writer is from the School of Engineering and Physical Sciences, Heriot-Watt University Malaysia