An environmentally beneficial alterative to the incineration or land disposal of sewage sludge has been cooked up by researchers from the University of Cordoba, Spain. A new pyrolysis-based process converts the urban waste into activated carbon for use in gas treatment, energy storage and other applications.

Similar schemes have relied on high-cost activating agents that in turn pose increased environmental issues in terms of toxicity. The process detailed in the Journal of Environmental Management instead relies on potassium hydroxide, a relatively low cost and non-polluting compound. By reducing the amount of the agent used, the researchers have further improved the sustainability and economics of the sludge treatment train.

The treatment entails mixing dried sludge with the activating agent, after which a pyrolysis process carbonizes the residue, and a purification step removes certain minerals. In comparison with other techniques proposed or implemented for this purpose, the amount of activating agent used was reduced by at least 50% at a maximum temperature of 800° C. A process yield of 0.627 kg activated carbon/kg sewage sludge was documented.