Sorry, this is not a get rich quick scheme but it sure is a good story about tackling climate change. Within the building materials industry the cement segment is one of the largest and certainly is present in almost every country on earth. Cement manufacturing is very energy intensive and the industry recognized as a significant contributor to total global CO2 greenhouse gas emissions calculated at 5% in 2012.
Producing a ton of cement requires 4.7 million BTU of energy, equivalent to about 400 pounds of coal, and generates nearly a ton of CO2.
A brief simplified description of cement manufacturing will help put into context the point of this blog:
- Limestone, clay and other ingredients are ground and combined in a homogenous mix
- The mixed material goes through a calcination process where large rotary kilns heat the material to 1400 degrees C to transform it into clinker. Flame temperatures of 2000 C are needed to reach the constant 1400+ C
- Clinker is ground an mixed with gypsum to make cement
The cement industry is understandably interested in moving away from using fossil fuels and finding different energy sources for production from a cost and emission mitigation point of view. This is where SRF – Solid Recovered Fuel comes into play.
SRF is defined as: ‘solid fuel prepared from non-hazardous waste to be utilised for energy recovery in incineration and co-incineration plants and meeting the classification and specification requirements laid down in EN15359 (Standard from the European Standardisation Committee).’
First, waste that can not be sorted or recycled is pre-ground. Inert material, metal, and chlorine residuals are removed using various sorting methods: mechanical, optical, and ventilation. After granulation, the fuel is quality controlled.
You may also see the term RDF or ‘refuse derived fuel’ that are calorific wastes but have no specific definition and quality may vary. SRF can be seen as a more refined version of RDF with specific standards.
Benefits of using SRF in Cement Manufacturing
Jan Theulen’s article ‘Cement Kilns: A Ready Made Waste to Energy Solution?’ in Waste Management World states:
“In a typical cement kiln some 200 tonnes per hour of sintering material passes the burner(s). The ashes of the fuel used to heat the kiln drops into the glowing material and reacts with the hot minerals to become an integral part of the end-product – clinker.
This clinker is then ground into cement. For such a kiln the fuel mix (both coal and waste derived fuel) might be around 30 tonnes per hour (tph) and produce some 20% ashes. This means that 6 tph of ashes are integrated into the 200 tph sintering material. Through this process, both the thermal and mineral value of waste is to 100% utilised by the cement kiln.
As the cement operator knows upfront the quantity and quality of this 3% addition by the fuel ashes to the sintering material, they will adapt the raw material mix accordingly.”
SITA UK is a recycling and resource management company whose paper ‘A Guide to Solid Recovered Fuels’ points out:
“Using solid recovered fuel instead of coal helps to preserve natural resources and emissions. SFR is helping cement producers to achieve a fuel substitution rate of over 79 per cent, significantly reducing the impact of their operations have on the environment.
Materials that would otherwise be landfilled are put to good use as a sustainable fuel and SRF reduces the need to mine virgin coal deposits and import into the UK.
The environment and economic benefits of using SRF are significant:
- Reduced reliance on expensive, finite fossil fuels
- Reduced carbon footprint and increased sustainability performance
- Reduced environmental impact through lower emissions at the cement plant
- Security of supply and quality of SRF
- High calorific value – one tonne of coal is equivalent to approximately one and a half tonnes of SRF”
Usage of SRF in Cement Manufacturing
There are many factors that impact the ability to manufacture SRF in different regions of the world starting with recycling programs and sorting facilities. The chart below is from 2010 but shows that Europe and North America are leading the way but is expected to expand in other regions of the world.
Use of non-hazardous waste materials to reduce environmental concerns in the cement industry is clearly in the best interests of us all.
If you are interested in cement and other Building Materials topics please consider joining the international SAP Forum for Building Materials 2016, which will take place July 7-8 at the SAP headquarters in Walldorf, Germany.