Cement production is responsible for around 5% of global CO2
emissions. The European industry constitutes around 10% of global
cement production and is therefore a key industry under EU targets to
reduce emissions. The burning of fuels such as petroleum coke or coal
in the calcination process that turns limestone into clinker, causes
emissions of CO2 to the atmosphere. Almost twice as much CO2
is actually produced by the calcination reaction itself. Since the
basic chemistry cannot be changed, the industry has had to find other
ways to reduce the CO2 output. Nevertheless, emerging
innovative products like the carbon negative cement Novacem, based on
magnesium silicate, might reduce the energy consumption during the
manufacturing process and push innovation in the ‘green’ low-carbon
segment of the building materials sector.
In Europe, in order to reduce energy consumption and CO2 emissions, the industry is focusing on increasing the use of clinker substitutes in cement, the use of alternative fuels and energy efficiency measures. The new research assessed the cost-effectiveness of several other energy efficiency measures, including modifications to the reaction chamber (kiln), recycling waste heat and carbon capture and storage (CCS) of CO2 from the waste gases. Cost-effectiveness was estimated using a computer model to calculate how long it would take for the savings from each measure to match the cost of the initial investment, known as the Pay Back Period. The model individually assessed 477 kilns in 294 production facilities within the European Cement Association (CEMBUREAU). For some measures, the Pay Back Period was less than a year. This included converting kilns from traditional ‘wet’ facilities to ‘dry’ facilities, which require half as much energy.
When all measures with Pay Back Periods of less than two years were considered, total energy consumption (across all cement facilities) decreased by 9.2%. This figure was 10.8% for Pay Back Periods of less than three years, and 15% for Pay Back Periods of less than 9 years. CO2 emissions were reduced by 3.4% for processes with Pay Back Periods of less than two years, and up to 5% for Pay Back Periods of less than 9 years. The energy efficiency gap, that is, the lack of deployment of all potential improvements at hand, independent of the decision criterion considered (the payback period, the net present value or the internal rate of return) requires a condusive policy environment that combines support for both technology development and its deployment.
The results also demonstrate that recycling waste heat is close to being cost-effective as the market price of electricity will affect the decision on investment. The project’s required minimum electricity price to make a worthwhile investment would be €0.08 per kWh.
Cement production could be an ideal candidate for CCS, since the concentration of CO2 in the waste gases is very high. But at present, CCS is far from being cost-effective (this is dependent on factors such as electricity and CO2 allowance prices) and is not expected to be available before 2025. The urgency of climate change action means that there is little ground for further delaying implementation of at least the most cost-effective measures. First steps could include encouragement for phasing out ‘wet’ facilities, say the researchers. The use of alternative raw materials and fuels and the decrease of clinker to cement ratio are also likely to influence the industry in the future.
To learn more about low-carbon technology innovations in the cement industry, please see: http://setis.ec.europa.eu/
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