According to the International Energy Agency (IEA), the direct CO2 intensity of cement producton increased 1.8 per cent per year between 2015 and 2020. In contrast, three per cent annual declines to 2030 are necessary to get on track with the Net Zero Emissions by 2050 Scenario. Michael Nelson explores the ways in which the industry is attempting to overcome the challenges that this presents.
Heavy industry accounts for roughly 30 per cent of global emissions today, almost exclusively from the use of fossil fuels in production processes, or in combustion engines in the mobility sector. While some of these industries are paving their way towards electrification, such as road transportation, some harder-to-abate sectors cannot easily transition to electricity as a power source.
Usually, these industries require very high temperatures for their industrial processes. Alongside steel and chemicals, cement is one such industry in which the solutions to reduce emissions are more complex or are at a very early stage of development.
By itself, concrete accounts for eight per cent of carbon dioxide (CO2) emissions and, as a building material that will be integral to providing the infrastructure needed to drive the energy transition, it is essential that the industry finds a way to reduce its carbon footprint.
Alternative production methods
The Global Cement and Concrete Association (GCCA) recently released a roadmap, entitled ‘Our Concrete Future’, which outlines the industry’s vision for how cement and concrete will play a major role in building the sustainable world of tomorrow. This includes commitments to accelerate the reduction of CO2 emissions over the next decade to 2030 – by 25 per cent per cubic metre of concrete, and by 20 per cent per tonne of cement.
One of the ways they are hoping to achieve this is by increasing the use of clinker substitutions. Mikaela DeRousseau, data and methodology manager at Building Transparency, says that the manufacturing method for cement, a major element of concrete, is the reason why it is so carbon-intensive. Limestone and clay are heated to more than 1400 degrees Celsius in a kiln, and the release of carbon dioxide occurs as a result of a chemical reaction called calcination.
There are quite a few ways to reduce the carbon dioxide emissions from concrete mixtures, however.
“One method that is becoming more popular is to replace a portion of the cement with supplementary cementitious materials (SCMs) such as fly ash or blast-furnace slag,” explains DeRousseau. “These materials are industrial by-products from burning coal and steel production respectively.
“Additionally, the CO2 emissions from cement production can be reduced with energy efficiency improvements to cement production. For instance, higher efficiency cement kilns with preheater and precalciner technologies can reduce energy consumption compared to older and less efficient kiln technologies.
“Different types of cement, such as Type IL, are also being created. Type IL cement is on average 5 to 10 per cent lower-emitting than typical cement.”
Brimstone Energy is one such company making strides forward in reducing its carbon emissions. They have developed a process to produce cement with significantly lowered carbon dioxide emissions by using an alternative processing route, starting from non-limestone-based raw materials, which helps avoid calcination emissions. However, most technologies that aim to significantly cut greenhouse gas emissions from cement are in the pilot stage, and thus need to prove economic and technological feasibility.
Reducing reliance on fossil fuels
Further reductions will also mean limiting fossil fuel use at every point in the supply and production chain. Electrification is one of the methods which could help reduce emissions.
In their most recent report on the subject, the IEA highlights a number of recent projects that are exploring this possibility. In Sweden, cement producer Cementa, a subsidiary of HeidelbergCement, and energy producer Vattenfall are working together on the CemZero project to electrify cement production. The feasibility study, completed in early 2019, showed that electrified cement production is technically possible and likely cost-competitive with other options to substantially reduce emissions. The project is continuing with an investigation on how a pilot plant can be built.
Similarly, the ELSE project in Norway is investigating kiln electrification, while the UK Mineral Products Association is trialing fuelling kilns with a blend of biomass, hydrogen, and electrical plasma.
DeRousseau, however, does not see electrification as a viable solution.
“Despite opportunities for energy efficiency improvement, cement production is a very difficult process to decarbonise significantly. It is currently not feasible to switch cement production to use electricity or renewables, instead of the current fossil fuel usage, due to the high kiln temperatures required during clinkering.”
Given the difficulties in implementing electrification, the IEA outlines some alternative recommendations in their report. They say that energy and material efficiency should be accelerated, and can be achieved through collaborative efforts among industry, public sector, and research partners to share best practices on state-of-the-art technologies and to develop plant-level action plans that would increase the speed and scale of technology deployment. Ensuring efficient equipment operations and maintenance would also help guarantee optimal energy performance, as would the use of energy management systems.
Additionally, greater uptake of alternative fuels can be facilitated by redirecting waste from landfills to the cement industry, and by coordinating the supply of sustainably sourced biomass across sectors to enable cost-competitive access for cement production.
The role of CCUS
Although investment and research into alternatives to Portland clinker cement to reduce CO2 emissions is increasing, the GCCA roadmap concludes that they will likely have a limited role because of the lack of raw material at the required scale. Likewise, as has been discussed, transitioning to renewable sources of energy in order to power production processes is either at a very early stage of development or comes with multiple challenges.
Carbon capture, utilisation, and storage (CCUS), therefore, is seen as a vital component on the road to decarbonising the concrete and cement industries. CCUS encompasses methods and technologies to remove CO2 from the flue gas and from the atmosphere, followed by recycling the CO2 for utilisation and determining safe and permanent storage options.
According to the GCCA roadmap, CCUS pilots already have substantial momentum with live projects and announcements picking up pace in North America, China, India, and Europe. But there are significant hurdles to overcome before CCUS is adopted at larger scales.
DeRousseau says that, at present, the largest barrier to the adoption of CCUS technology in the cement industry is economical, due to large capital investments and increased operating costs. Stakeholders such as policymakers and the investment community will need to be engaged to help develop, de-risk and deploy the technology and infrastructure over time to help transform the industry worldwide.
The first step, argues DeRousseau, is transparency. “If more cement and concrete producers start reporting the greenhouse gas (GHG) emissions from their products via mix-specific, Type III Environmental Product Declarations (EPDs), then the construction industry will better understand the carbon impact of specifying a specific material. With this information, the industry can make more informed purchasing decisions and incentivise suppliers to compete on both cost and carbon emissions. The goal is to allow cement producers to find the most economically feasible method to reduce emissions, agnostic of technology, to drive down emissions.”
To that end, Building Transparency has developed their Embodied Carbon in Construction Calculator (EC3), which is the first free program that allows users to assess global supply chain data to set EPD requirements for their building projects, and set project-level embodied carbon reductions per material category. It can be implemented in both the design and procurement phases of a construction project to look at overall embodied carbon emissions.
More specifically, EC3 aids in enabling the specification and procurement of low-carbon material options, and allows users to search for products that meet their building materials’ performance requirements and to select the option with the lowest possible embodied carbon dioxide emissions. Tools such as this can help drive the production of low CO2 emissions products via basic supply and demand economics.
A complex journey ahead
Whilst the journey to reducing CO2 emissions from concrete and cement production is by no means straightforward, the GCCA roadmap points out that not all changes require investment, and some can even reduce costs by reducing the quantities of raw materials through improved design processes, use of reprocessed and recycled material, re-use of elements, and extending the lifetime of whole projects.
Design efficiency and utilising the benefits and versatility of concrete can result in less material being used, meaning that concrete and cement are not products that are produced, but they can also be crucial components in a circular economy.
With the introduction of a comprehensive policy framework, and collaboration between industry, policymakers, and governments, significant reductions in concrete and cement GHG emissions can be achieved.