This week's short reads

[SteamyTea]

Don't be fooled by El Niño's end – net zero is more urgent than ever

The El Niño climate pattern has contributed to a year of record-breaking temperatures. We must bend the curve of carbon emissions before the next one arrives

 

29 May 2024

 

 

md zakirul mazed konok/Alamy

The past few years have seen a significant rise in inflation in many countries, driven by a range of factors from pandemic-fuelled shortages to the war in Ukraine. But even now, as inflation is falling, prices are still rising, albeit more slowly. This subtlety is often missed, intentionally or otherwise, by politicians seeking to claim victory over inflation.

Don’t worry, you haven’t accidentally started reading The Economist. The point is that we may soon see a similar effect in the global climate. As we report in “El Niño is ending after a year of driving extreme weather“, the El Niño climate pattern is about to come to an end. Just like the recent inflationary period, El Niño has seen graphs soar, with a nearly year-long streak of record-breaking temperatures.

The trouble is, just as prices continue to rise when inflation falls, the carbon dioxide we have pumped into the atmosphere will keep pushing up temperatures, even without the influence of El Niño. While coming years may be cooler, overall, the planet is still warming at an alarming rate.

Precisely how close we are to exceeding 1.5°C above pre-industrial temperatures, a key limit to avoid the worst consequences of climate change, is hard to assess. Traditionally, climate scientists look at this over decades, meaning we would only confirm a breach in retrospect.

There is some good news here at least, as a new analysis shows that we can simply count the number of years in which average global temperatures exceed 1.5°C (see “Three years of high temperatures will mean we have breached 1.5°C“). It found that just three years above 1.5°C is enough to confirm a breach. The bad news is that 2024 may be the first.

As we have said many time before, despair isn’t the answer. Unlike inflation, climate spikes are somewhat predictable. The next El Niño is likely to occur between two and seven years from now, so almost certainly within this decade. Before it comes, bringing yet more heat, the world should use this period to finally bend the curve on carbon emissions with a proper push for net zero by 2050. We will all benefit – and politicians might have something real to celebrate.

 

Zero-carbon cement process could slash emissions from construction

Cement production is a huge source of carbon emissions with no green alternative, but a new process that uses waste from demolished buildings could dramatically reduce its climate impact

By Madeleine Cuff

22 May 2024

 

 

 

Cement being produced in an electric arc furnace at the Materials Processing Institute, UK, for the first time

Materials Processing Institute

 

A new technique can produce cement using waste from demolished buildings, which researchers say could save billions of tonnes of carbon by 2050.

“We have definitely proved that cement can be recycled into cement,” says Julian Allwood at the University of Cambridge. “We are on course for making cement with zero emissions, which is amazing.”

 

Producing cement is highly polluting – responsible for 7.5 per cent of total greenhouse gas emissions – but until now there was no known way to produce it at scale without impacts on the climate.

Making cement requires “clinker”, which is made by heating a mix of raw materials, including limestone and clay, to 1450°C (2650°F). Both the heat requirements and the chemical reactions involved in making clinker result in carbon emissions, and clinker production accounts for 90 per cent of cement’s total carbon footprint.

Allwood and his colleagues have developed an alternative process to make clinker, which involves reusing cement paste from demolished buildings. This paste has an identical chemical composition to lime flux, a substance used to remove impurities from recycled steel.

As the steel melts, the flux made from old cement forms a slag that floats on the top of the recycled steel. Once ground into a powder, the slag is identical to clinker. It can then be used to make Portland cement, the most common form of cement.

If the recycled steel and cement are produced using an electric furnace, powered by renewable or nuclear energy, the process is almost entirely free of emissions. “The idea is really simple,” says Allwood.

Laboratory trials have proved the process works. It offers a “drop in” solution that could be used with conventional equipment, and a global switch to this process could save up to 3 gigatonnes of carbon dioxide a year, the team calculates.

The research team is now working on industrial trials via a spin-out company, Cambridge Electric Cement, with partners such as construction firms Balfour Beatty and Tarmac. “Within the next few weeks, we are starting a set of trials which will be producing batches of 30 tonnes per hour,” says Allwood.

Scaling up the new cement-making process depends in part on the growth of recycled steel-making, which currently accounts for about 40 per cent of global steel production. Allwood says production rates will at least double over the next 30 years, and most likely treble, as the industry decarbonises.

Yet some challenges lie ahead. The recycled cement process requires furnace temperatures of 1600 to 1750°C (2900 to 3200°F), slightly hotter than traditional cement production. This will increase power costs, says Leon Black at the University of Leeds, UK.

Other hurdles include establishing supply chains for waste cement, attracting the necessary capital investment and convincing a notoriously cautious industry to adopt a new process on a large scale.

“They have overcome one barrier in as much as they have made a material that has the same composition as Portland cement,” says Black. “The devil is in the details: the energy requirements, the logistics, the scaling up.”

 

Journal reference:

Nature DOI: 10.1038/s41586-024-07338-8