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Carbon capture and storage can clean up coal power. Coal image from www.shutterstock.com

As the world moves to combat climate change, it’s increasingly doubtful that coal will continue to be a viable energy source, because of its high greenhouse gas emissions. But coal played a vital role in the Industrial Revolution and continues to fuel some of the world’s largest economies. This series looks at coal’s past, present and uncertain future.

Coal is the greatest contributor to climate change of all our energy sources. This means that if the world acts to limit global warming to well below 2℃, coal will likely be constrained – unless its greenhouse gas emissions can be removed.

One of the great hopes of the industry is carbon capture and storage (CCS), a way to burn coal, remove the carbon dioxide (CO₂) emissions and store it safely away from the atmosphere. While there have been several breakthroughs, the technology remains expensive.

Advances in energy technologies mean that adding CCS doesn’t just need to work; it needs to work at a lower cost than its growing legion of competitors. And while the alternatives are good news for avoiding dangerous climate change, it’s a substantial challenge for the coal industry.

Capturing carbon

The current range of CCS technologies can be grouped into “pre-combustion” and “post-combustion” methods.

Pre-combustion methods typically react the carbon in the fuel with high-pressure steam to make hydrogen CO₂. The CO₂ is then separated (captured) from the hydrogen before the hydrogen is burned in the power station to make energy, with the only emissions being water vapour.

Post-combustion technologies try to capture the carbon after it has been burned and becomes CO₂. If the fuel is burned in air, then the CO₂ needs to be separated from the exhaust gas stream which, like air, is mostly composed of nitrogen gas. This is usually done by passing the gas stream through a liquid that dissolves the CO₂ but not the nitrogen.

Another technique, called “oxyfuelling”, separates oxygen out of the air and then uses it to burn the fuel in an atmosphere of oxygen and recycled CO₂. The exhaust gas stream from this process is close enough to pure CO₂ that it can be sent directly to the storage process.

Several options have been explored for storing the carbon. These include the deep ocean, depleted oil and gas wells, deep saline aquifers, as manufactured mineralised carbonate rock, or as naturally mineralised carbonate by injection into basalt reservoirs.

Regardless of the technique, the outcomes for coal combustion are similar. The amount of emissions is reduced by 80-100%, while the cost of coal-fired electricity generation increases by at least the same amount.

These costs come from building the capture plant, CO₂ transport pipelines and the sequestration plant. More than double the amount of coal must be burned to make up for the energy cost of the CCS process itself.

When CCS was first considered as an emissions solution, competition from renewables, such as solar and wind, was weak. Costs were high and production volumes were negligible.

How cheap?

In the 1990s, many believed that renewables (other than existing hydro, geothermal and biomass for heating) might never be able to replace coal cheaply. The future of energy was going to be a centralised grid, rather than the distributed power models being discussed today, and there were only two widely backed horses in the technology race: CCS and nuclear.

But the early part of this century has seen an energy revolution in both renewables and fossil fuels. Among renewables, solar and wind have both taken enormous strides in reducing production costs and building manufacturing scale.

For fossil fuels, the expansion in gas pipeline infrastructure, the development of liquefied natural gas (LNG) shipping and the growth of both conventional and unconventional gas production have encouraged fuel switching from coal in European and US markets in particular.

Trying to compare the costs of different types of electricity can be tricky. Power stations require capital to build and have heavy financing, operational and decommissioning costs. Nuclear and fossil fuel power stations also have to buy fuel.

Analysts use the term “levelised cost of electricity (LCOE)” to aggregate and describe this combination of factors for different methods of electricity generation.

A significant challenge for coal and CCS is that the LCOE for wind and solar at a comparable scale is already competitive with coal generation in many places. This is because the cost of manufacturing has fallen as production has increased.

While this seems not to bode well for coal and CCS, there’s a caveat: a coal with CCS power station makes power when the sun doesn’t shine and the wind doesn’t blow.

It’s easier for wind and solar to compete when traditional fossil fuel power stations are there to back them up, but not so easy when renewables become dominant generators and the cost of storage needs to be taken into account to ensure a consistent supply.

A game changer?

That was until batteries came along and offered the ability to store renewable energy for when the sun doesn’t shine. There is considerable hype around the entry of the Tesla Powerwall into the home electricity market.

But that is only one of numerous home battery solutions from the likes of Samsung, LG, Bosch, Panasonic, Enphase and others. All are designed to store excess solar power for use at night.

The emerging breakthrough of these products is the price, which is bringing batteries into the realm of competition with centralised electricity generation.

While a battery won’t take your family entirely off-grid at first, such batteries mean most suburban households can become largely energy-independent. They need only top up from the grid now and then when a run of cloudy days comes along during the shorter days of winter.

In the longer term, there’s a clear pathway for most homes to disconnect completely from the grid, should battery prices continue to fall.

Why are batteries a threat?

The reason that batteries can compete with centralised generation is because the cost of transmission and distribution from a coal-fired power station to your home is considerable.

These costs are not normally considered in the LCOE calculations, because it is assumed that all power generators have access to the same, centralised electricity grid.

But a battery in your home means that these costs are largely avoided. That makes home energy generation and storage much more competitive with traditional power generation in the longer term.

For developing nations without a strong centralised grid it also means that energy systems can be built incrementally, without large investments in infrastructure.

This is an ill wind for the competitive future of CCS, which depends on the centralised generation model and a lack of low-cost competitors to stay viable.

That doesn’t mean the coal industry should give up on CCS. Having a range of options for a low-emission future is a good thing. Affordable energy is at the heart of our modern civilisation and standards of living.

CCS may also lay the foundations for Bioenergy with Carbon Capture and Storage (BECCS), one of the few (albeit expensive) technologies with the potential to recoup significant amounts of CO₂ from the atmosphere. But this points to a renewable biomass future, not a coal future.

The odds that CCS will keep coal alive as an industry into the future are getting longer each year.

What we are seeing is the start of the great transition from fossil fuel mining to manufacturing as the basis for our energy systems. It’s not dominant yet, but you would be starting to get very nervous if you were betting against it.

Gary Ellem has received funding in the past from state and federal governments for research into renewable energy technologies, cleantech industry development and social licence in the Australian unconventional gas sector. He has previously consulted to the solar, bioenergy and mining sectors.

Certainly larger and more frequent storms are one of the consequences that the climate models and climate scientists predict from global warming. But you cannot attribute any particular storm to global warming, so let’s be quite clear about that. – Prime Minister Malcolm Turnbull, speaking to reporters in Tasmania on June 9, 2016.

In the aftermath of the deadly East Coast Low that swamped eastern Australia, dumping massive amounts of rain in early June, the prime minister toured flood-affected Launceston and announced emergency relief funding.

Turnbull told reporters that larger and more frequent storms were forecast by climate scientists but cautioned that no individual storm could be attributed to global warming.

Is he right?

Checking the source

The Conversation asked the prime minister’s office for sources to support his statement but did not hear back before publication deadline. Nevertheless, we can test his statement against recent published and peer-reviewed research on this question.

The science shows that, just like real estate, climate change is all about location. Different parts of Australia will be affected in different ways by climate change.

And global warming will have different effects on different types of weather systems.

Let’s break Turnbull’s statement into two parts: is it true that we can expect larger and more frequent storms as a consequence of global warming? And is it possible to attribute a specific storm to global warming?

Can we expect larger and more frequent storms as a result of global warming?

Yes – but not for all regions or types of storms.

There are many types of storms that affect different parts of Australia, among them East Coast Lows, mid-latitude cyclones (a category that includes cyclones that happen in the latitudes between Australia and Antarctica), tropical cyclones, and associated extreme rainfall events. Each will be affected in a different way by climate change, and the effect will vary by region and by season.

On East Coast Lows: Acacia Pepler, who is studying extreme rainfall and East Coast Lows in relation to climate change, recently wrote in The Conversation that her research showed that:

… East Coast Lows are expected to become less frequent during the cool months May-October, which is when they currently happen most often. But there is no clear picture of what will happen during the warm season. Some models even suggest East Coast Lows may become more frequent in the warmer months. And increases are most likely for lows right next to the east coast – just the ones that have the biggest impacts where people live.

For all low-pressure systems near the coast, “most of the models we looked at had no significant change projected in the intensity of the most severe East Coast Low each year,” Pepler wrote.

On mid-latitude cyclones: Another study predicted that the overall wind hazard from mid-latitude cyclones in Australia will decrease – except in winter over Tasmania.

On tropical cyclones: Northern Australia is expected to get fewer cyclones in future – but their maximum wind speeds are expected to become stronger.

On rainfall: Scientists tend to be quite confident that climate change will be accompanied by an increase in extreme rainfall for most storms in future. One of the main reasons for this is that increased temperatures will cause increased evaporation. While the total amount of water held in the atmosphere will also increase slightly in future, the total amount of rain has to go up too.

Is it true you can’t attribute any particular storm to global warming?

Turnbull is correct. We cannot say for sure that a particular flooding rainfall event was solely “caused” by climate change, any more than we can say for certain that a particular car accident was solely caused by speeding (even if excessive speed was a likely or even major contributing factor).

Evidence for the effects of global warming on extreme rainfall events that have already occurred is currently equivocal for most regions.

According to a collection of studies published in 2015:

A number of this year’s studies indicate that human-caused climate change greatly increased the likelihood and intensity for extreme heat waves in 2014 over various regions. For other types of extreme events, such as droughts, heavy rains, and winter storms, a climate change influence was found in some instances and not in others.

One recent study in that report found:

evidence for a human-induced increase in extreme winter rainfall in the United Kingdom.

Verdict

Malcolm Turnbull was essentially correct on both points.

It’s true that scientists predict more frequent and intense storms for some parts of Australia as the climate changes. The evidence appears to be strong that extreme rainfall will increase. Some increases in extreme wind speeds are possible – but not in all regions or all seasons.

Turnbull was right to say you cannot attribute any particular storm to global warming. –Kevin Walsh

Review

This is a good FactCheck that summarises the broad conclusions from a range of studies examining the nature of current and likely future storms across Australia.

As the author points out, Australian storms range from tropical cyclones in the northern tropical regions to temperate east coast lows and mid-latitude cyclones.

The consensus regarding tropical cyclones is that they will generally decrease in frequency in the Australian region. In northeast Australia, they are forecast to experience the most dramatic decrease in frequency of any ocean basin globally. Some northern hemisphere ocean basins will see an increase in their frequency.

The intensity of these types of storms is expected to increase. This will not only involve higher wind speeds but also higher storm surges and floods. That will mean greater coastal impacts and damage to coastal developments and infrastructure.

So the prime minister’s statement about more frequent storms resulting from climate change does not apply to tropical cyclones – however, he was right to say that larger and more frequent storms are one of the predicted consequences of climate change. This consequence is predicted to apply to other storm categories, but not tropical cyclones.

And yes, climate scientists are hesitant to attribute the occurrence of any single storm to global warming. – Jonathan Nott

Have you ever seen a “fact” worth checking? The Conversation’s FactCheck asks academic experts to test claims and see how true they are. We then ask a second academic to review an anonymous copy of the article. You can request a check at checkit@theconversation.edu.au. Please include the statement you would like us to check, the date it was made, and a link if possible.

Kevin Walsh receives funding from the ARC, Australian government grants and various overseas organisations.

Jonathan Nott receives funding from the ARC.

I, too, used to walk up Piggies Lonnen (Letters, 13 June) with my sisters on our way from Lemington to Walbottle, to see my Grandpa, Johnny McSwine. We were allowed to help feed his pigs and clean out their pigsties. Though the lonnen was near the “piggery”, it had nothing to do with Grandpa’s pigs, who never left their sties. On a memorable visit he took us to see the sow and her piglets cosseted under a heat lamp in the biggest of the three sties. The pigs were fed on scraps and meal which was weighed out in the “flower house”, – so called because that was where mounds of freshly cut blue scabious would be bunched and boxed ready for market. Around the tea table at his house, I would hear about the Bull family who lived in the village, but I don’t think had bulls. My grandfather died in 1963 but his name, or his father’s, lives on – “Johnny’s Bank” is the road that ran past the market garden up to Walbottle Stores. The market garden continued until my Uncle Fred retired.
Judith McSwaine
Newcastle upon Tyne

• The street names of south-west Scotland are evidence of a culture shared with north-east England, at least in their alleyways. For example, Jenny’s Loaning in Castle Douglas clearly matches the lonnens of Northumberland, while Friars Vennel in Dumfries would fit in well in Durham.
Steven Edgar
Bristol

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