Abstract

Municipal wastewater treatment plants generatelarge amounts of sludge after a set of unit processes. The sewagesludge is an important resource for energy production becauseof its high level of biodegradability. Sewage sludges aregenerally made of non-toxic and biodegradable organiccompounds mixed with a small fraction of non-toxic and toxicinorganic compounds having a very low biodegradability. Thelarge fraction of biodegradable matter constitutes a pool forgreen/clean energy to be used for industrial and domesticapplications. The generated energy can also be used in thewastewater treatment plant. Currently, fossil fuels are leadingthe energy world, however, they are being depleted and areconsidered to be among the main causes contributing to climatechange and global warming. Domestic sewage sludge can beconverted sustainably into bio-hydrogen and bio- methane.This conversion is achievable through anaerobic digestion,combustion, pyrolysis and gasification. With regard to the lastthree conversion processes, the organic and inorganic toxiccompounds are eliminated. Production of biogas from sewagesludge is being undertaken worldwide on small, medium, andlarge scales. However, hydrogen production from sludge is stilldeveloping. There is an existence of substantial knowledge inthis field, the production of hydrogen and biogas from sewagesludge is gaining interest. This study analyses variouspossibilities of sewage sludge conversion into clean energy. Theanalysis focuses on the technology strengths, weaknesses andgaps to be improved in future studies.