It is a remarkable fact that around 25% of the population of the UK live on what remains of a deep coal-mine. This at least explains why their closure was a such a traumatic event in recent British history. They did, after all, fuel the country for many decades with coal from some 23,000 pits. The mineworkers were the advance guard of the working class. Mrs Thatcher’s destruction of both their jobs and their trade union, aided enormously by the discovery of North Sea natural gas, left many of the UK’s northern towns devastated.

Life as a coal-miner was hardly luxurious. Between 1900 and 2000 over 100,000 miners died on the job. The work was dangerous not least because of the heat down below. The deeper you went, the hotter it became. Around 20° C was pretty normal, but if you went down below a kilometre, the temperature rose to over 40°C and could go much higher. This is true about many rock formations in the earth, about which more later, but it is a pleasure to discover that what remains of the UK coal industry is thinking about using this heat to lower the carbon output of those who live above it.

The idea is simplicity itself and at Seaham in County Durham, the UK Coal Authority and local authority are planning to create a garden village of 1,400 homes, with a school and shops, by pumping 100-odd litres of water per second down the old mine and up again, thereby creating a district heating system at an eventual saving of around 3,000 tonnes of CO2 output per year, compared with gas central heating. This, in itself, is hardly going to challenge global climate change and district heating has its issues. One thinks of all those Russian tower blocks, with the windows flung wide in winter. Nonetheless, given its relative simplicity and the number of mines near small towns in Britain, it is more than worth the money to find out how well it works.

This may be a simple, small idea, but it is a useful beginning to the idea of “hot rocks”. Down in Cornwall, they have been thinking about geothermal energy for at least two decades, if not longer. Certainly, in the 1980s, it was a source of amused condescension. Now however, in the context of UK carbon targets, it is seriously up and running. Led by Geothermal Engineering Ltd at United Down near Redruth, they have now drilled 5,275 metres down into a granite fault zone, which is at 180°C. Water run into this will eventually go through a heat exchanger, creating steam to run a turbine and thus – initially – a 25 MW power generator. The target is 100 MW of capacity by 2028.

There is, naturally, the usual PR stuff about there being enough heat down there to power every house in the UK for the next 100 years, but that is forgivable since virtually every new environmentally acceptable form of energy supply says the same thing. And we need that sense of optimism. In addition, the geothermal guys want to make sure the great British public fully understand that this has nothing, no absolutely nothing, to do with “fracking” for oil, because they understand the seismic much better. Given the tonnes of ordure that fell on the heads of UK onshore crude “frackers” in the recent past, this is hardly a surprise. But it would be nice if, just occasionally, such people acknowledged their technical debts regarding deep directional drilling to the oil and gas industry.

That said, there is little doubt that geothermal energy is a seriously under-utilised resource. The US currently gets around 0.4% of its energy from this source, much of it in California and Nevada, amounting to 16 billion kWh. Indonesia follows with 14 billion and Kenya with 5 billion, the total amounting to around 88 billion. The Philippines draws about 17% of its power from geothermal and could produce a great deal more. One of the attractions is that apart from the occasional burst of steam, the well-managed plants are semi-invisible and do not make much noise.

Given that at least a billion people live in “the Ring of Fire”, or the area entirely around the Pacific Ocean that is notorious for volcanic activity, vast amounts of carbon-free electricity should be some compensation at least, for the inconvenience of having volcanoes around seemingly going off at random. In fact, according to rather estimated figures, more people have been killed digging up British coal than killed by volcanoes worldwide since 1900, a figure put at around 77,000. In addition, of course, volcanoes provide the areas around them with an abundance of excellent hot water spas and in some cases significant tourist revenues from those fascinated or foolish enough to climb up them. This is not to underestimate the dangers concerned, merely to point out that they are an indication of an abundance of energy under the earth that is severely under-utilised.

Nor is the technology concerned at the cutting edge of modern, scientific endeavour being developed at enormous cost like fusion. Way back in 1892, the inhabitants of Boise, Idaho realised that they could heat 200 of their homes in winter by piping water through the local ground, a project that has expanded to around 5 million houses now. They invented the geothermal heat pump.

Equally, creating electricity from hot rocks is hardly new either. The Italian businessman Prince Piero Conti of Trevignano used hot water from below to power five light bulbs amounting to 10 kW, situated at Larderello in Tuscany, in 1904. He then proceeded to expand the idea to a 250 kW plant in 1913. This has now expanded to 34 plants with a total capacity of 800 MW run by Enel Green Power and provides almost 2% of Italy’s electricity. Quite why nobody else copied the idea until 1958 in New Zealand remains a mystery.

Another unexpected turn-up of events comes from Climeworks, which built a carbon dioxide removal plant in Switzerland in 2017, with the avowed intention of selling its pure gas to the makers of fizzy drinks, like Coca Cola. The original plant provided the makers of carbonated drinks with around 900 tonnes of the clean gas a year and rapidly found a market. What it also found was a partner in Iceland, Carbfix, whose intention was to bury the stuff in the ground and make sure it never came up again.

One those odd things that people know, but rarely think about unless they drink too many glasses and suffer reflux, is that carbonated drinks are mildly acidic. But in a piece of lateral thinking that amounts to near genius, Carbfix CEO Edda Arrondottir and her team figured out that if you pumped carbonated water into a suitably fractured rock, like basalt, its acidity might link it with magnesium, calcium and iron and in effect make it part of the rock itself. Naturally, being geologists or those who think in eons, rather than months, they figured that it might take rather a long time, but was worth a shot. To their surprise 90% of the carbon dioxide was absorbed into the rock within two years and a joint venture was born.

Climeworks could take it out of the air and Carbfix could stick it permanently into the ground. The first plant is currently taking CO2 from Iceland’s Hellisheidi power plant at the rate of 12,000 tonnes per annum, with plans for expansion to 24,000 tonnes. Optimistic plans now included shipping CO2 from Europe’ industrial areas by sea, with the intention of losing 500,000 tonnes by 2026 and 3 million tonnes by 2031. As always with enthusiasts for a new technological fix, they expand it to the point of incredulity. As they point out since basalt is present in around 5% of the earth’s crust, the US alone could sink 7,500 billion tonnes of CO2, with Europe managing 4,000 billion. Add in the Russians as well and we could probably increase the percentage proportion of oxygen in the atmosphere with probably explosive results!

This joke aside and they do have a point, the technology does work and the idea of changing our waste gas into rock has obvious attractions. Yet it might seem odd that the plan is to ship CO2 from Europe to Iceland, when the technology could simply take the gas out of the Icelandic air into the ground and leave the wind to bring the CO2 back to Iceland without the benefit of ocean transport. The short answer is money. The whole exercise is heavily dependent on the idea of carbon credits and in this regard, it is a considerably more accurate way to create them than allegedly planting trees in obscure parts of the planet. Trees take a long time to grow, even if the plantations are not fraudulent in the first place. Carbfix can count their carbon tonne after tonne. At $50-odd a tonne in Europe, carbon taxes are too low to get this ball as really rolling as it should be.

The same applies to schemes to dump the carbon back where it came from in oil and gas fields. It remains astonishing that the UK has allowed the oil industry to retreat steadily from its vast acreage, leaving a huge undersea region of corroding pipelines and capped wells to effectively decompose. In fact, under the Petroleum Act of 1998, the oil companies were required to remove as much of their activities as they could, from the top sides on down, using the wonderful phrase “as low as reasonably practical” (ALARP). In fact, the emphasis was on the environment and Shell’s outline plan for the decommissioning of the Brent field – which still gives its name to the world price of oil – amounted to 437 pages of detailed description as to how to do it, with concerns particularly about fishing.

It never occurred to anybody that these pipes might be used for a different purpose. The fact that the oil industry has been pumping gas down oil wells for better oil production for decades was quietly forgotten. This is perhaps because anything to do with the oil industry is universally regarded by the environmental lobby as the work of the devil. However, the industry has been pumping natural gas down its wells for as long as it has been around. More importantly, it has been doing the same thing with CO2 as well in the last three decades alone.

Shell is one example. In its Wesson Field in West Texas, it has been injecting CO2 since 1983, with a significant increase in oil output from what was previously a dying field. They are not alone, particularly in the Permian basin in Texas. Given the cost of the CO2, a lot of this gas was collected from the methane wells that produced the carbon gas as well. Way back in early 2010 a red light seems to have gone on in the US Department of Energy, that noticed this and it occurred to them that if the oil industry was using natural CO2 to increase its oil production, then it could use its fields as a way to dispose of the gas from human heating as well. 

More detailed work by the Department revealed that in the past 40 years, Enhance Oil Recovery (EOR) had pumped over a billion tonnes of CO2 into oil wells and 99% of it had remained there and got increasingly mineralised. The trouble was that it was not anthropogenic CO2. On their reckoning, if the piping infrastructure were put in place, EOR could dispose of around 50-200 million tonnes of CO2 every year and increase their oil production by around 85-180 billion barrels a year. There was room for around 55 to 119 billion tonnes in existing fields. The truly interesting idea here is that the additional oil recovered would – at the right price – pay for the process.

Like the British, the Norwegians too have their North Sea structures, the most remarkable being the two Condeep concrete platforms, Gulfaks C and Troll A, which are the first and second heaviest structures ever moved over the surface of the earth at 1.5 million and 1.2 million tonnes with ballast respectively. It will be interesting to see how and indeed if, the Norwegian government decides that they are to be removed when the gas runs out. Troll is 472 metres high and made a mild seismic bump when it landed on the sea floor. Getting rid of it would require a truly gigantic amount of dynamite.

But now at least the Norwegians are thinking about the idea of carbon sequestration in their part of the North Sea. The Northern Lights project, in partnership with Shell, Equinor and Total, is signing up deals to permanently store 1.5 million tonnes of CO2 in 2024, rising to 5 million tonnes in 2026 at some 2,600 metres below the sea bed. Seen as a European-wide project, the project has already signed up a deal with the Dutch fertiliser and Ammonia manufacturer Yara Sluiskil for 800,000 tonnes a year and is in negotiation with a German cement manufacturer in Heidelberg for 400,000 tonnes. At a cost of some $1.7 billion, this is serious stuff.

Overall, the earth provides a huge potential resource in terms of carbon-free energy and a place to store carbon when it come from combustion. The subject is full of surprises, which should be better known. First, the earth is a source of warmth and electricity, which we tend to ignore. Secondly, we can turn our CO2 into rock, and put it where it can no longer affect the climate permanently. And finally, we have the technology to do these things, directly as a result of our hydrocarbon extraction abilities. The fact that we have not paid enough attention to this is perhaps due to our geopolitical obsession with oil, which has dominated our perception of what energy actually is.