Why we should be using coal fines

Photo by Tom Fisk from Pexels
Photo: Pexels
Decarbonisation of the energy and industrial sectors is essential to meeting the Paris Agreement targets of keeping the global mean temperature below 2°C and aiming to limit it to 1.5°C above pre-industrial levels.

However, it is expected that coal will remain an important fuel in power generation until the 2030s at least, especially in countries whose energy sectors heavily rely on coal-fired power plants, such as China, India, and Poland. Carbon capture and storage is essential for coal-fired power generation to achieve the net-zero targets.

There are opportunities to reclaim and remediate ~20,000 km2 of land globally that is currently occupied by coal mining operations

However, many are unaware that coal will have a role to play in enabling our transition to a net-zero economy. Namely, the production of iron and steel relies heavily on the supply of metallurgical coal. For example, an onshore 2 MW wind turbine requires 240 t of steel. Currently, approximately 70% of steel is produced via the integrated steelmaking route, which requires approximately 187 tonnes of metallurgical coal to produce the steel for such a turbine. This figure falls to 36 t of met coal when the steel is produced in the electric arc furnace. (See Coking coal – the strategic raw material, CCC/306 by Baruya 2020 for more details.) Therefore, despite our activities to reduce reliance on fossil fuels, we may still require coal to support our construction, steel making and cement industries.

This continuing reliance on coal comes with environmental challenges. For example, the development of new coal mines will add to the already substantial methane emissions of 40 Mt/y from existing coal mines. Each tonne of coal extracted from a new coal mine results in 4 kg of CH4 emitted into the atmosphere. With the global warming potential (GWP) being 28-36 times that of CO2 over 100 years, methane emissions are a major contributor to global warming. This is an important reason why further coal supplies for industrial processes need to be re-invented and alternative coal sources need to be explored.

Decades of coal exploration, mining and processing have resulted in significant volumes of coal tailings and waste. It has been estimated that the waste produced during coal production corresponds to up to 40% of the total amount of material extracted and that the amount of coal fines and tailings produced reached approximately 30 billion tonnes (bt) in the  top 10 coal producing countries in 2014; these countries generate approximately 1 bt/y of coal waste. Recovery and reuse of this by-product can supply a significant fraction of the industrial coal demand and open a more economic route to land remediation and restoration.

Force Crag Mine - Water remediation ponds
© Ashley Dace

Recovery of the waste coal from existing coal impoundments is one way to avoid the need for opening new coal mines, with the added benefit of reducing the GWP per unit amount of energy supplied from coal. There are many organisations developing processes to reclaim and reuse waste coal and coal fines. For example, Changeover Technologies has developed a waste coal processing technology that can produce a pelletised coal from the material found in the coal waste impoundments. They estimate that their cradle-to-gate GWP for the production of the waste coal pellets is less than a quarter of that of that of conventional coal mine operations in the USA (2.73 kgCO2,eq/GJ compared with 12.76 kgCO2,eq/GJ). If the waste coal pellets are used in metallurgical processes, the specific CO2 emissions of steel production can also be lowered. Changeover Technologies estimate that replacing just 1% of the coal used globally in power, cement and steel industries with waste coal pellets, would reduce CO2 emissions by 35.5 Mt/y. Up to 3,650 km2 of land could also be reclaimed.

Thus the reuse of waste coal fines appears to be a promising route to reduce emissions from various coal-using sectors and to give a value to clearing up coal waste. The IEACCC is starting a study on fine coal treatment later this year and published a report in 2018 on The use of coal-derived wastes as a source of energy, CCC/288 by Dr Stephen Mills.

Dr Dawid P. Hanak is Senior Lecturer in Energy and Process Engineering at Cranfield University

E: ; LinkedIn: @DawidHanak

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