ELECTRICITY

2020 was a significant year for the UK energy sector, marking the first annual period when renewable technologies generated more electricity than fossil fuels.

In Britain, the burning of coal and gas to produce electricity continues to fall.

In 2020, the UK closed its last three deep coal mines, and there are plans to phase out the final two coal-fired power stations by 2025.

Currently, coal is used to generate just 0.1% of Britain's electricity.

Globally speaking, the consumption of fossil fuels remains one of the biggest threats to our environment.

Firstly, fossil fuels are limited resources: it is estimated that the Earth only has enough coal to last for the next 132 years.

Secondly, fossil fuels pollute our atmosphere as they are burned. Perhaps the most familiar pollutant released by fossil fuels is carbon dioxide, a greenhouse gas and a leading cause of climate change. However, there are many other pollutants released by the burning of coal, like the solid Coal Combustion Products photographed by J Henry Fair.

COAL

Coal is a sedimentary rock that is high in carbon.

It occurs underground in 'coal seams', the largest of which can be found in the United States, Russia, China, Australia, and India.

The oldest coal seams originated from plants and algae that lived up to 400 million years ago.

These plants and algae lived in water-logged areas, meaning that they decomposed very slowly after they died, and were turned into peat.

Over long stretches of time, this peat would have been gradually buried under layers of sediment and exposed to very high temperatures and pressures.

Under the right conditions, the peat would carbonise and eventually turn into coal.

The high carbon content of coal means that it stores a lot of energy. In order to release this energy, coal must be combusted (burnt).

In traditional coal-fired power stations, the heat given off by burning coal is used to turn water into steam. This steam can propel turbines which are attached to generators, producing electricity.

The hazardous nature of fly ash presents problems for its disposal.

In some cases, fly ash is repurposed to make concrete and cement. However, only 25-30% of the world's total fly ash ends up getting recycled, with the remainder being sent to landfill. These landfill sites take up large areas of land and can leach toxins into the environment.

Using waste to combat waste?

Are there any other ways of reusing fly ash? In some cases, fly ash can be repurposed as soil fertiliser. However, fly ash is not always suitable for use in agriculture: studies have shown that crops fertilised with fly ash can accumulate arsenic and other heavy metals.

Another possible use of fly ash is in the treatment of wastewater from industrial processes.

Fly ash particles have properties that allow them to adsorb toxins from wastewater, and the high pH of fly ash means that it can also neutralise liquid waste.

This means that the waste from burning coal could potentially be used to process the waste from other industrial processes, allowing wastewater to be released safely into the environment.