From the Pyramids of Giza, the Great Wall of China, and the Colosseum, to now, with the construction of the Burj Khalifa, concrete has historically been one of the most popular building materials due to its adaptability, durability, and dependability. However, as the most used man-made material in the world, concrete accounts for at least 7% of all global carbon dioxide (CO2) emissions. Despite this evidence, due to population growth and urbanization, demand for cement (the primary binder of concrete) is set to increase by over one-third before 2050: that is the equivalent of building another New York City every month for the next 40 years.
Nevertheless, with the increasing severity of climate change, forward-thinking businesses and governments must work together and search for alternative ways to minimise their global environmental impact according to international and national guidelines. The Paris Agreement, perhaps the most well-known international treaty on climate change, sets a legally binding framework adopted by 196 countries outlining goals to limit global warming below 2°C. To meet these objectives, 50 major corporations – including Microsoft, Google, and Amazon – have pledged to begin purchasing low-carbon versions of cement starting this year. From the public sector, California (the US’s second-largest cement producer after Texas) has committed to cut 40% of carbon emissions per ton of cement by 2035, while the UK government’s Future Homes Standard is pushing for all new buildings to have a 30% lower carbon footprint than their predecessors. Also in Great Britain, the Mineral Products Association ambitiously takes the sector’s goals one step further to go beyond net-zero and become net negative by removing more CO2 from the atmosphere than it emits yearly.
So, what causes excessive carbon emissions from cement production? And what technologies are leading the way to a more sustainable and net-negative carbon future?
The cement industry today
According to the Global Efficiency Intelligence report, about 60% of the cement industry’s total CO2 emissions are related to the chemical reaction that results from heating limestone at temperatures of 2500°F (1371°C). The other 40% of CO2 emissions are mainly generated from fuel combustion and electricity use, and while some specialists look for ways to capture the greenhouse gasses released from these processes, others search for ways to avoid producing them altogether.
Carbon capture, utilisation and storage
Carbon capture, utilisation and storage (CCUS) is one such approach that seeks to permanently sequester greenhouse gasses from industrial processes before they enter the atmosphere. It involves capturing, transporting and storing greenhouse gas emissions underground, and companies like Carbon Clean are revolutionising the current value chain by reducing the size and cost of required equipment to extract CO2 from large-scale industrial plants. This carbon dioxide can then be transported and injected deep underground, primarily in geological formations that can safely and permanently trap the CO2.
This underground storage has the potential to lock up to 90% of current CO2 emitted from fossil fuels (coal, oil, or gas), power stations, or chemical plants —the primary sources of anthropogenic carbon emissions. With reservoirs around the Gulf of Mexico large enough to hold up to 500 billion t of CO2 (the equivalent of 130 years of US industrial and power-generated emissions) this becomes a reliable and scalable solution for increasing emissions, but what alternatives exist to make the sequestration of CO2 safe and profitable above ground?
Carbon utilisation is a method that recycles captured carbon to produce new products or services. For example, companies like Carbon Upcycling Technologies are working to combine previously captured CO2 with waste ash and slag to transform them into reactive materials that can be used in cement and concrete production – while additionally storing CO2 permanently. Such emissions can be directly collected from coal-fired power plants and other industrial facilities, and infused into new cement and concrete additives with a lower carbon footprint.
Carbon Upcycling Technologies and other utilisation companies demonstrate the high value that can be extracted from CO2, turning liabilities into opportunities for many emitters. Examples of it include solutions in the fast-moving consumer goods (FMCG), plastics, coatings, adhesives, battery, and pharmaceutical industries.
Eliminating the carbon-intensive footprint of clinker substitutes
Clinker is the stony material that results from heating limestone and is the main component of cement, making it an indispensable part of the concrete manufacturing process. Unfortunately, most of the sector’s overall emissions are inevitably attributed to the chemical reactions that take place at a cement kiln and are needed for production at scale.
That being said, CEMEX has been investing heavily in clinker substitutes to alleviate availability problems and pave the way to a 30% reduction of fossil energy use and CO2 emissions in both cement and concrete production. The company’s solutions include, among others, Vertua, a geopolymer and clinker-free concrete with up to 70% less CO2 than standard mixes. It can provide additional benefits including increased durability and multiple aesthetic finishes, and be used for applications such as foundations, roads, and groundworks. In a mission to be carbon neutral, its ‘Zero’ counterpart goes the extra mile by offsetting the remaining carbon percentage (30%) through an accredited offset provider.
Accordingly, buyers can feel confident in their actions toward the 2050 ‘net-zero’ CO2 goal when they receive their post-purchase certification that meets the requirements of The Carbon Neutral Protocol. Vertua’s clinker-free cement alternative is comparable to taking 105 cars off the road or planting 21 new trees, representing a 1.3 t decrease in CO2 emissions. This low-carbon cement has already been applied in landmark projects worldwide, such as the skyscraper La Marseillaise in France, the Querétaro-Irapuato highway in Mexico, the new stadium at San Diego State University in California and the Pereira shopping centre in Colombia.
Other clinker substitutes include different hydraulic materials and pozzolans, supplementary cementitious materials (SCMs) that can be both naturally occurring or derived from industrial by-product materials and present benefits related to cost and environmental impact. In a mission to achieve carbon neutrality by 2050, many solutions also aim at giving a second life to waste streams so that manufacturers can make new and sustainable products out of them.
Creating a circular economy
The circular economy model implies much more than recycling final products back into the production process; it also repurposes the waste created throughout the different production stages. With increased attention on sustainability, stakeholders are increasingly reviewing the entire material life cycle, from how a plan is designed to how demolition waste is handled. This is known as green construction.
The United Nations recognises that concrete can absorb up to 50% of the CO2 emissions it exudes during its built form, making it the most sustainable and resilient building material worldwide. Part of the CO2 emitted during cement production is re-absorbed when the limestone found in the concrete reacts with CO2 in the atmosphere, making carbon carbonate and trapping the carbon dioxide (almost) forever.
Nonetheless, the world is still emitting more CO2 than ever before. In 2021, carbon dioxide levels jumped above 2.58 ppm, the 5th-highest (tied) annual increase in the National Oceanic and Atmospheric Administration’s (NOAA) 63-year record. Consequently, leading cement producers are accelerating their adoption of (among others) clean energy to power the high amounts of electricity that clinker and cement production operations require.
On that note, Swiss start-up " erikkobayashisolomon="" href"https:="" sites="" we-have-an-energy-storage-problem="" www.forbes.com=""> Energy Vault has developed a transformative, long-duration energy storage solution to deliver reliable and sustainable electricity. To do so, the company uses locally sourced soil and waste material ‘composite blocks’, which are lifted and lowered on demand to store and release electricity via a potential and kinetic energy solution.If we look at the end of a carbon-intensive material’s life cycle, generally glass waste is the most difficult to recycle in a cost-effective manner. Accordingly, UK Research and Innovation (UKRI) awarded £2.3 million to Carbon Upcycling in an effort to create the world’s first commercial-scale cement additive plant that combines CO2 sequestration and recycled waste glass. The pilot programme, looping 50 tpd of glass that would otherwise be landfilled, will seize over 15 000 t of carbon emissions on a lifecycle basis through cement reduction.
The aforementioned glass waste recycling project is a significant step towards a circular economy and will help to double the cement industry’s replacement efforts by 2030. By creating a valuable product from one of the most challenging waste streams combined with cement flue gas in its process, Carbon Upcycling will provide the UK market with a low-cost and low-carbon alternative to currently imported cementitious materials.
Players within the industry value chain should consider at least three main themes in their decarbonisation strategies and portfolios: redesign, reduce, and repurpose. A truly circular carbon economy vision includes maintaining the value of products and resources for as long as possible, and in each stage of return to the product cycle looking for ways to maintain the material’s durability while minimising the release of carbon and waste into the atmosphere. Additionally, in cases where carbon is released, as is inevitable, the sector should jointly outline strategies and develop projects to meet common goals and reach net zero as an industry.
With government and industry goals of becoming carbon neutral or even net negative by 2050, there is no other option than to start making giant leaps today towards a greener and more sustainable future.
About the author
Alfredo is a trained Architect, BIM enthusiast, and college professor who scouts for breakthrough technologies and solutions in the decarbonisation space for the construction industry. As a Venture Capital Advisor, he oversees investment activities and strategic partnerships at CEMEX Ventures, putting a special focus on startups that effectively tackle the carbon footprint challenge of the built sector.
Read the article online at: https://www.worldcement.com/europe-cis/09032023/delving-deeper-into-decarbonisation/
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