Utility of waste bio feedstocks as an energy source: Thermogravimetric Analysis and Kinetics of Sewage Sludge and Algal Biomass

Utility of waste bio feedstocks as an energy source: Thermogravimetric Analysis and Kinetics of Sewage Sludge and Algal Biomass

by: Bhavish Patel (presenting author)1, Carla Mae Pausta2, Tobias Borgmeyer3, María D. Ortíz-Álvarez4, Mohamed Tarik1, Luis Razon2, Aileen Huelgas-Orbecido2, Nestor A. Urbina-Suarez4, Andres F. Barajas-Solano4, Michael E. Perez-Roa4, Janeth Sanabria-Gomez5, Christian Ludwig1,3

1: Bioenergy and Catalysis Laboratory (LBK), Energy and Environment Research Division (ENE), Paul Scherrer Institut (PSI), Switzerland; 2: Department of Chemical Engineering, De La Salle University, Philippines; 3: Environmental Engineering Institute (IIE), School of Architecture, Civil and Environmental Engineering (ENAC), École polytechnique fédérale de Lausanne (EPFL), Switzerland; 4: Department of Environmental Sciences, Universidad Francisco de Paula Santander, Colombia; 5: School of Environmental & Natural Resources Engineering / Environmental Microbiology and Biotechnology Laboratory (Ciudad Universitaria Meléndez), eUniversidad del Valle, Colombia.

The use of biomass as an energy source remains a controversial topic with energy crops sometimes blamed for loss of arable land and increasing food prices. Given the importance of developing a balanced renewable energy source, sustainably, certain organic energy sources offer a promising outlook. With ample availability around the world, Sewage Sludge is an underutilized resource, which is usually disposed (sometimes untreated), or applied as a fertilizer. Considering the risk of increasing soil toxicity and pathogen levels, its direct use is not sustainable in the long run and thus requires pre-treatment adding to the costs. Similarly, advanced biomass such as algae can also be used to treat the liquid streams arising from these wastes where the cultivated biomass contain reclaimed minerals during the purification process. Similar to the Sewage Sludge, algal biomass grown in such streams cannot be used directly and would require treatment.

An alternative is to incinerate the sludge/algal biomass to reduce the volume, destroy pathogens, concentrate available minerals in the ash and most importantly generate energy along the way. As such, in this work, we present the feedstock characterization and the incineration kinetics, obtained via a Thermogravimetric Analyzer, of Sewage Sludge from the Philippines and Algal biomass cultivated in mining and domestic wastewater in Colombia. Experiments at ramp rates between 10-50˚C were conducted and the data processed using the Kissinger-Ahakira-Sunose, Flynn-Wall-Ozawa and the Friedman methods for calculation of the apparent activation energy. Furthermore, the results of on-line analysis of the eluted gases is also presented which was used to obtain a better understanding of the reactions.