Green hydrogen will be the key driver in the decarbonization of cement and concrete, according to an upcoming report from Rethink Energy. But while hydrogen can replace the heavy heat needs of production, the chemically created emissions will need to be captured if these materials are ever to truly reach net zero.
As a rule, Rethink Energy has been firmly against carbon capture as a decarbonization solution across most industries. The technology has consistently been used as an excuse for the fossil fuel industry to continue with business as usual while investing in half-heated R&D into failing CCUS technologies that will never remove the full scope of a plant’s emissions.
Current flagship CCUS projects achieve far lower capture rates than the 85% figure that proponents like the IEA have suggested – the IEA has consistently overestimated the growth of CCUS capacity while underestimating renewables. The Petra Nova project in the US captures less than 40% of the flue gas from one of four coal-fired units, while the Boundary Dam project in Canada has an overall capture rate of 31%. Research from Stanford University has highlighted that in testing, current technologies achieved as little as 10.5% of CO2 removal over a 20-year period, with only 20% to 31% captured over 100 years.
Even the IEA has said that if all available solutions were to be deployed across value chains, 25% of total oil and gas methane emissions would remain unaddressed. Adding CCUS technologies to existing production techniques is also extremely costly, with premiums often outweighing those of emission-free processes.
In the steel sector, for example, the use of green hydrogen in the direct reduction of iron (DRI) followed by a renewables-powered electric arc furnace (EAF) can provide a full decarbonization approach above and beyond those suggested using existing coal-powered furnaces with speculative CCUS technologies.
However, while hydrogen, when burned, can displace some of the fossil fuel energy used in cement production, it cannot be used as an ingredient or reactant in the chemical processes required.
Behind steelmaking, cement production accounts for the second largest chunk of industrial emission across the globe – around 8% of greenhouse gas emissions. Today’s annual demand for 4.1 billion tons of cement requires constant kiln temperatures of 1,450 degrees Celsius to produce clinker – a core ingredient in modern Portland cement.
Low carbon options to generate heat at this temperature are limited; electrification of heat can only really be used for low temperature applications, and once you get to around 400 degrees Celsius both cost and technical barriers start to arise, as circuit components need to handle higher operating temperatures.
Operational advances in efficiency and reductions in coal consumption have already largely been implemented, resulting in an 8% reduction in emission intensity. The potential to use alternative fuels or materials like fly ash instead of clinker are limited by the decreasing availability of input materials.
There are several innovative approaches being pursued to lower its carbon intensity. One start-up is using a lower proportion of limestone in its cement, which results in fewer process and fuel emissions and also locks in additional CO2. Others are trying to reduce the temperature used to produce clinker from 1,450 degrees to 800 degrees, which would make it easier for renewable technologies like CSP to be used in production.
Over the past few years several companies and academics have been focusing on the use of hydrogen to provide the high-grade heat used in cement kilns, replacing the use of coal or natural gas. Work is ongoing on how to adapt the process to the different flame properties and heat dispersion from hydrogen combustion.
However, unless some separation and storage of CO2 is undertaken, only the CO2 produced by the coal can be avoided, which is only 36.5% of the total CO2. The calcination process of separating CO2 from the Calcium Carbonate is responsible for the remaining 63.5% of CO2 created chemically.
The process needs to be changed somewhat to make it easy for that CO2 to be syphoned off and captured. This is likely to be a much easier process than using Amines to scrub flue gases, as in coal plants, and therefore should be achievable at a relatively low cost, but as yet no-one has moved such a process to scale.
Once optimised for kiln heating, hydrogen burners can be paired with CCUS and other technologies, such as those being developed at the LEILAC project, to produce truly net zero cement and concrete.
Other techniques are also being developed for ‘Earth Friendly Concrete’ by Australian firm Wagners, which claims that it has around 70% less embodied CO2, saving 250 kilograms of CO2 per cubic meter. It is made from a binder consisting of industrial waste products, ground granulated blast furnace slag and pulverised fly ash with no Portland Cement.
Which route we end up using is primarily down to China, which uses around 57.4% of all cement, and produces around 53.7%. We believe this will be a complex series of partial outcomes, with areas with low cloud cover and high radiance trying out CSP and thermal storage for overnight 24/7 running of kilns, and in other areas, the use of hydrogen. Amid a surge of Chinese investment, however, the likely winner is hydrogen.
This will likely, however, be inspired by early pilot projects in Europe – such as initiatives from HeidelbergCement, that are already in operation in the UK – before hydrogen-ready facilities start being installed from 2024 onwards.
By 2035, clean cement produced using hydrogen will account for 32.1% of global supply, rising to 78.2% in 2050 when the sector’s total hydrogen demand will be close to 91 million tons per year, according to Rethink Energy’s upcoming hydrogen forecast.