CCUS only pathway to achieving net-zero emissions in the global cement industry

Mar 06 2020


With cement demand predicted to rise, carbon capture is an essential technology that can achieve the goal of net zero emissions. By Ian Riley and Manon Burbidge, World Cement Association.

It is widely recognised that the cement industry is one of the key contributors to global CO2 emissions, due to the scale of global cement production, as well as carbon dioxide emissions being inherent to the production process.

Scope 1 emissions, defined by the Greenhouse Gas Protocol as direct emissions created by an organisation’s activities, make up about 90% of the industry’s CO2 output. This is mainly due to the fuel used to heat the cement kilns, and the limestone feedstock, calcium carbonate, which breaks down to form carbon monoxide and carbon dioxide.

To combat the scale of the industry’s emissions, several steps have been taken over the past 30 years. New technologies have improved average energy efficiency in plants by about 30%, and there has been an increase in alternative fuels, such as municipal wastes, replacing fossil fuels. The adoption of blended cements has also helped reduced average clinker use per ton of cement and hence the emissions produced from the breakdown of limestone.

Despite this progress, analyses by both cement and non-industry experts have concluded that there is no path to net-zero emissions that does not include carbon capture, usage and storage (CCUS).

Although there are alternatives to concrete for some applications, the material will continue to be necessary for the construction of core infrastructure, such as metro networks, dams and bridges, for the foreseeable future. Indeed, ongoing global urbanisation will mean that cement demand is likely to continue to grow until at least 2050.

CO2 storage vessels, and a lorry being loaded with liquid CO2 for transport to the usage endpoint at the Conch Wuhu CCUS facility in China. The Baimashan Cement Factory in Wuhu uses amine technology to capture CO2 from its cement kiln

 

 

Where We Are Today

To date, the development of CCUS has not received the large-scale investment required to generate rapid progress. While carbon capture is a proven technology, it is still expensive to use and unlikely to progress without strong policies and regulatory incentives. In addition, carbon storage is both high-cost and geographically limited, whilst most carbon usage applications are still in the early stages of development.

There are, however, a handful of current technologies and pilots in the CCUS sphere that show particular promise for use in the cement industry.

Carbon Capture

There are two widely used processes to capture CO2. The first is post-combustion capture which uses CO2 absorption reactors, whereby exhaust gases are mixed with a solution that absorbs and removes the carbon dioxide.

The second is pre-combustion gasification, where CO2 is removed using gasification processes. Feedstock is partially oxidised in steam and oxygen at high temperatures and pressures to form synthesis gas (a mixture of hydrogen, carbon monoxide, carbon dioxide and others). This is usually done using a fluidised bed, which suspends the fuel while flue gas and steam are introduced at the base of the reactor.

Conch Wuhu, one of Conch China’s cement plants, piloted a carbon capture project in 2018 to demonstrate that post-combustion capture technology can be used in a cement plant, with its relatively low concentration of CO2 in the flue gas.

This captured 50,000 tons of CO2 over the timescale of the pilot, or 0.5% of the plant’s total emissions. The captured gas was sold to carbonated drinks manufacturers and for use in agricultural greenhouses. Although technologically this project was a success, low demand made it difficult to sell even the small proportion of CO2 captured, which has limited future scale-up possibilities.

A different approach to carbon capture is being pioneered at the LEILAC Project in Lixhe, Belgium, using technology engineered by Calix Global. The aim is to capture the process emissions from cement production by re-engineering the process flows of a traditional calciner, heating the limestone indirectly in a steel vessel. This enables the capture of pure CO2 and requires no chemical reagents or additional concentration processes.

Carbon Storage

Carbon sequestration involves placing anthropogenic CO2 emissions in underground geological formations for permanent storage. For successful storage, this process requires deep, porous layers of rock, capped by several layers of impermeable rock.

Depleted oil and gas reservoirs and deep saline aquifers are typically used, so this practice is only possible in areas with suitable conditions and hence not equally applicable or economically viable globally.

The North Sea is an example of a suitable location for CO2 storage, due to its geology and the existing infrastructure from a mature oil and gas industry in the region. Norcem, in collaboration with Heidelberg Cement, is piloting a project that takes advantage of this by implementing the industry’s first CCS facility at its Brevik plant in Norway.

The post-combustion CO2 capture technology will allow for 400,000t of CO2 to be captured per year, representing approximately 50% of the plant’s emissions. This will then be transported by pipeline and injected into underground reservoirs beneath the North Sea.

Carbon Usage

Carbon dioxide has many uses, including in chemicals, polymers, fertilisers, and synthetic fuels, as well as carbon curing of special concrete and aggregates. However, according to the Carbon Capture Institute, even the most mature technologies are currently only in demonstration phases, with fertilisers and enhanced oil recovery constituting the largest markets.

One area which could be particularly promising for the cement industry is new technology being developed that enables CO2 to be used in building materials.

WCA member Solidia has developed a low-lime, low-energy cement that is currently being produced by LafargeHolcim. In addition to reducing both process and thermal CO2 emissions at the cement kiln, this cement rapidly carbonates when exposed to CO2. 

Mineral CO2 sequestration is a naturally occurring process, whereby compounds present in the earth’s crust react with atmospheric CO2 to form stable carbonates, such as calcium carbonate (limestone). The ubiquitous presence of calcium, magnesium and iron in the earth’s crust offers the potential for mineral CO2 sequestration to rival the physical storage of CO2 in geological formations, and thus play a major role in reducing atmospheric CO2 levels.

When you take into account emissions at the cement kiln and CO2 consumed during carbonation, Solidia’s cement offers a 60% reduction in carbon footprint compared with ordinary Portland cement. The new cement has been used in precast applications in the USA, Canada and the UK, and in ready-mix applications in the USA.

California-based company Blue Planet has developed technology to obtain CO2 from any emission source without the need for concentration or purification. A pilot plant due to start operation this year will take CO2 directly from the flue gas of a natural gas power plant at very low concentration. The CO2 is then reacted with calcium oxide, derived from demolition waste or industrial by-products, to produce synthetic aggregates which are 40% CO2 by weight.

Similarly, in the UK Carbon8 Systems has developed an accelerated carbonation technology process to react CO2 with calcium and magnesium salts in industrial thermal residues to form solid carbonates, which produce low density synthetic aggregates.

Barriers to CCUS:

Current barriers to CCUS are primarily economic: implementing this at scale generally requires government subsidies, with CO2 used for enhanced oil recovery being the only viable business case at present.

The EU CEMCAP project (part of Horizon 2020) has suggested that CCUS processes may add 90% to the cost of cement production, with other estimates being even higher. Recent announcements by Principles for Responsible Investment, as well as several other investment analysts, suggest that future carbon pricing policies may have a substantial impact on both the cost of cement and the market capitalisations of cement producers.

Worldwide, 85% of CO2 emissions are currently unpriced, and therefore there is little incentive for companies to invest in CCUS. Carbon pricing will need to recognise the additional operating cost of CCUS before we can expect large scale investment from the industry.

Some pioneers, such as WCA member Dalmia Cement, have set the goal of being carbon negative by 2040; their roadmap to achieving this includes carbon capture, utilisation and carbon sequestration. Nevertheless, they are still more the exception than the rule.

In the meantime, through sharing best practices, WCA supports its members in taking the steps they can today to reduce their emissions, by improving energy efficiency, utilising alternative fuels and optimising the use of cementitious materials in their operations.

World Cement Association


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