Waste not, want not: Fueling green cement

Pile of shredded waste rubber in front of rotary cement kiln used as alternative fuel

How many people do you think there will be on Earth by 2050? According to the United Nations (UN), it’s likely to be around 9.7 billion. Just imagine how much waste 9.7 billion people will generate!

This matters to the building materials industry, and it’s easy to see why. People need houses and infrastructure, which in turn need concrete and cement. However, all this building comes at a cost to the planet.

So, how can we address these key issues that are so important to our future?

Industry impact

The majority of carbon dioxide (CO2) emissions created by the cement industry come from two processes: heating the kilns, and the calcination of the principal calcium carbonate raw material (limestone).

In the manufacture of ordinary Portland cement (OPC) with 95% clinker, heating the rotary kiln using fossil fuels accounts for 38% of CO2 emissions per ton of cement produced. We need to work out ways to bring down the energy consumption and emissions of this process.

The case for waste

Luckily, one reason the human population is so successful is that we’re great at problem-solving. It’s predicted that waste generation will grow 70% by 2050 (thanks to all those extra people) – which sounds like a big problem. But what if it could be put to good use? Well, some clever problem-solving humans have already found a way to use waste as an alternative fuel source!

Close up of man holding shredded municipal waste in front of rotary cement kiln used as alternative fuel

Alternative fuels are already used within the cement industry. In addition, replacing fossil fuels with waste-derived fuels cuts emissions significantly. Burning waste as a fuel source is great for everyone, both communities and manufacturers, as the waste becomes productive instead of costing money to destroy or store it. The use of pre-existing infrastructure saves further resources, as the resulting heat from incineration is useful rather than wasted energy in a municipal plant.

And of course, manufacturers save money too – after all, who wouldn’t want to replace expensive fossil fuels with a resource people can’t wait to give away?

Enabling the switch

Convinced yet? There’s just one potential stumbling block.

Waste-derived alternative fuels tend to be highly variable in their material composition. They can have different moisture contents, particle size distributions, or even include toxic elements such as mercury, thallium, or cadmium – all of which could result in undesirable effects on the cement process, as well as possibly illegal or harmful emissions. This doesn’t mean these fuels shouldn’t be used, but they must be carefully controlled to ensure a stable fuel stream, maintain safety, and avoid environmental damage.

The best way to control the fuel stream and monitor its composition? Materials analysis – preferably fast and accurate to keep your operations running efficiently and enable maximum value.

Inside your analytical toolbox

X-ray fluorescence (XRF) is one key technique for highly accurate and reproducible elemental characterization (and combines well with other methods too!). The Epsilon 4 is a great example of a compact XRF spectrometer that has integrated solutions for both solid and liquid waste-derived fuel samples, including sludge, wood, rubber, plastics, and more. This accommodates common materials ranging from biomass to oil, rice husk, and tyres.

The Epsilon 4 also works with the OMNIAN software, a standardless analysis program that quantifies elements from fluorine to americium when no matrix-specific standards are available – perfect for alternative fuel applications, where samples may be very inconsistent or even unidentified. 

For continuous process control (depending on the materials you’re analyzing), you can also opt for pulsed fast and thermal neutron analysis (PFTNA) with an instrument like the CNA Pentos cross-belt analyzer. The CNA measures bulk material on a belt without the need for sampling, and returns results in real time to enable immediate corrections where necessary. The CNA Pentos can also be deployed in other areas of the cement plant – in fact, it’s so popular with our building materials partners that we created an industry-specific Cement edition!

Greener cement for a cleaner world

It’s true that the future holds both challenges and opportunities for all of us – especially in the building materials industry. But with smart solutions and innovative tools, we can work not only to build the world of tomorrow, but make it a cleaner, greener place too.

Blog written by Murielle Goubard, Wednesday, 24th May 2023 – (Malvern Panalytical)


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