Cement and the road to net zero

TL;DR

• Cement plays a key role in infrastructure, but it’s also the world’s highest industrial emitter of CO2, responsible for 8% of all global emissions.  

• The process of splitting carbon dioxide from limestone to form carbon oxide is responsible for 60% of these emissions and is based on legacy processes that pre-date electricity.   

• There are currently no cost-effective alternatives to cement and emissions have increased in recent years as developing countries continue to build out their infrastructure.  

• Several start-ups are finding ways to bring electrification into the process and replace certain components with cleaner alternatives, including using calcium silicate rocks and making supplementary cementitious materials (SCMs) from widely available silicate-based raw materials.  

• The University of Cambridge has also created the world’s first-ever zero-emissions cement, hailed as a potential “turning point” for climate change.  

• Even so, these alternative options are still more costly and not being produced at a large enough capacity (350 Mt) to achieve net-zero by 2050.  

• A collaborative approach that involves international commitments to fund and buy clean cement, encourages private and philanthropic investment, and sharing of technologies is required if the cement industry has any hope of becoming greener in the coming decades.

The detail

Concrete – a mix of cement and water – is the second-most consumed material on the planet.  

Its use dates back to Roman times. Today, it forms the backbone of infrastructure, playing a crucial role in the construction of buildings, roads, dams and bridges. The ubiquitous nature of the cement has led to the global market becoming worth nearly $900 billion and more than four billion tonnes of cement are produced each year. 

As the world’s population expands and the trend towards urbanisation extends further into the developing world, demand for cement is only set to increase. By 2060, it’s estimated that the number of buildings on Earth will double. Globally, cement production is expected to grow from 48% from 4.2bn to 6.2bn tonnes by 2050. This expansion is predominantly being driven by the developing world, as well as international superpowers looking to increase their infrastructure – China, for example, used more concrete between 2011 and 2013 than the US did in the entire 20^th century. 

Cement vs. the climate  

Unfortunately, cement is also the world’s largest industrial emitter of CO2. It currently accounts for around 8% of global emissions and if the cement industry were a country, it would be the third-largest emitted of carbon dioxide in the world, after the US and China. Cement is made by heating calcium carbonate to nearly 1,500 degrees Celsius using a process that pre-dates electricity. This releases a relatively conservative amount of carbon dioxide, but the sheer quantity of cement produced makes it a huge emitter.  

The heating process is currently responsible for 60% of cement emissions as carbon dioxide is released from limestone to form calcium oxide. The remaining 40% is generated from the energy or heat that powers the mining and processing of the limestone itself. Proposed alternatives to cement, such as clay bricks, have failed to provide a viable solution, not least because they release a higher rate of emissions per unit, cost more and have limited functionality.  

Decarbonising cement: An unachievable goal?  

It’s fair to say that the current outlook is bleak. According to the latest report by the International Energy Agency (IEA), cement is not on track to meet net-zero by 2050.  

In fact, the report confirms that total CO2 emissions generated by the cement industry have increased since 2015. The emissions intensity of cement production has also risen by almost 10% in the last nine years, largely due to the increase in the clinker-to-cement ratio in China. To get back on track by 2030, total carbon emissions must fall by around 20% and 8% of all cement production needs to be near-zero.  

That being said, there are some bright spots on the horizon. A report by Breakthrough Energy – the organisation founded by Bill Gates – has highlighted the work of several start-ups which have found innovative ways to cut down the emissions associated with the current methods of cement production. These companies look at finding ways to introduce electrification into the process and cut down cement’s energy footprint as well as integrating cleaner components as part of cement production. 

Much of the cement used today is known as Portland Cement. This is made from a mixture of limestone, clay, and other minerals, which are then burned in a kiln following a recipe originally developed in the 19^th Century. Brimstone is a start-up challenging this original recipe by making Portland Cement from calcium silicate rocks instead of limestone. The benefit of these rocks is that they can fit almost seamlessly into the existing cement supply chain (requiring just one extra step) and have no embedded carbon dioxide.  

Ecocem is another company that is hoping to pioneer new concrete formulations to help reduce emissions and combat climate change. Its mixes use finely ground binders and fillers to produce concrete with only 4% ordinary Portland Cement – and it’s proved so successful that it’s already been used in construction projects for the Paris 2024 Olympic Games. 

Innovators are looking to make improvements at every stage of the cement production process. Terra CO2 is a company that is actively looking to reduce the amount of clinker (the stony pieces left behind when coal is burned) by making supplementary cementitious materials (SCMs) from the widely available silicate-based raw materials found near existing aggregate mines.  

An academic approach 

Academics have also been working hard to find low emission solutions to the concrete problem.  

For example, a team from the University of Cambridge announced in May 2024 that it may have created the world’s first-ever zero-emissions cement. Its approach substitutes a key ingredient in the steel manufacturing process with old cement taken from demolished buildings. Instead of producing waste, the result is recycled cement, ready to be used in concrete production.  

This new method bypasses the emissions-heavy process of superheating limestone in kilns and produces zero-emissions, with the electricity used to heat the furnaces coming from renewable sources. This development has generated excitement among climate change activists and academics alike. As one member of the research team, Professor Allwood, said: “This could be a turning point in the journey to a safe future climate.”  

There are also ways that engineers and architects can satisfy the demand for more buildings without increasing the use of concrete. It is believed that using automated design tools can help these experts to explore different structural options that take material efficiency into consideration. In fact, this approach has already reduced the amount of concrete needed in the construction of New York’s Freedom Tower by 40%.  

Collaboration is key 

However, despite these positive breakthroughs, there are still several hurdles to overcome.  

The aforementioned IEA report found that the cost of producing near-zero emission cement is likely to remain significantly higher than conventional cement for the time-being – currently, low-emission cement comes at a 75% premium versus conventional cement.  

Capacity also needs to improve. The projects already announced to be introduced by 2030 will put zero-emission cement production at 22 Mt, plus another 2 Mt near-zero emission capable. The project pipeline is expanding, but the projected capacity remains a long way from the approximately 350 Mt required to achieve net-zero.  

Collaboration is essential to harnessing the potential of these innovative new processes and ramping up capacity. Global co-ordination that unites both public and private sectors could help to expediate the behavioural changes required to increase the uptake of innovative alternatives to traditional cement production.   

Organisations like the IEA suggest that countries should implement a carrot and stick strategy to enact change – adopting guidelines around the efficient use and reuse of building materials while also making high-quality, multi-year purchase commitments to create a new market for near-zero emission cement. The timeline for these policy changes and new regulations, the IEA says, should be globally agreed to ensure developing countries aren’t left out of the conversation.  

When it comes to developing countries, public opinion must shift in favour of near-zero options, and the pace of learning accelerated so that those nations looking to build out their infrastructure can benefit from all the financial and technical assistance available worldwide.  

This macro strategy must also be supported by investment – IFIs, national development banks, philanthropic organisations, private financial institutions, industry coalitions, and individual companies must all be inspired to get involved. The funds raised can go towards supporting the delivery of pilot and demonstration scale projects for deep decarbonisation technologies and helping to match requests from developing countries with private sector investment.  

In other words, there is no easy fix. Cement is a legacy industry generating solid profits and facilitating essential construction projects worldwide. As it stands, there is no cost-effective solution that can seamlessly replace the well-trodden production process, despite the ongoing efforts of companies, philanthropists and educational institutions.  

Yet action must be taken – and quickly – if the emissions generated by cement are to reach net-zero, or even simply stop increasing year-on-year. A combined effort encompassing global commitment; support from governments, private investors, and philanthropists; and incentives for construction companies to seek near-zero cement options is vital.  

Change is possible, but only if individual efforts and innovations are underpinned by international cooperation and collaboration.   

 — Lew 👋

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