Sewage 'mud' could mean greener cement

The “mud” left over from waste water treatment could help cement producers reduce their carbon footprints, according to new research from Spain’s Rovira i Virgili University (URV).

The cement industry is one of the most contaminating in terms of carbon dioxide emissions. The process of making cement also produces dioxins, furans and heavy metals, all of which are harmful to the environment and human health.

The URV researchers says the solid waste produced by water treatment plants in large cities could be used as an alternative fuel in cement production. They tested the method at a cement plant in Vallcarca (Catalonia), which has been producing cement for more than 100 years, and confirmed it is “the best option for getting rid of mud that would have had to be dumped elsewhere, while also powering the plant.”

“As this mud is already waste, burning it does not enter into the atmospheric CO2 emissions assigned to each country under the Kyoto Protocol,” said José Luis Domingo, lead author of the study and director of URV’s Toxicology and Environmental Health Laboratory.

Up to 20% of the fossil fuel energy used at the Catalan plant has now been substituted for the fuel from waste water treatment plant mud.

From an economic point of view, the researchers will not say that cement plants could increase their profits by using this method, but they do point out, “They will not have to pay anything to exceed their agreed emissions.”

The cement plant experiment led to a 140,000-tonne reduction in CO2 emissions between 2003 and 2006, and will have limited the potential deaths from exposure to chemical pollutants, according to the researchers. In addition, their study finds that using this “green fuel” would reduce the cancer rate by 4.56 per million inhabitants.