Pyrolysis gasification of dried sewage sludge in a combined screw and rotary kiln gasifier

Supercritical Water Gasification of Municipal Sludge: A Novel Approach to Waste Treatment and Energy Recovery

“…Incineration-derived slag, for example, still contains all of the heavy metals, up to 30% of the original hazardous organic compounds, and additional secondary combustion compounds (Dogru et al, 2002;Fytili & Zabaniotou, 2008). Most contemporary thermal options are prohibitively costly due to high capital investment and increasingly stringent, air-quality permitting and compliance standards (Chun et al, 2011;Fytili & Zabaniotou, 2008). Thermal destruction also meets with considerable, unfavorable public opinion due to the air-borne release of metal emissions and harmful gases (Abbas et al, 1996;Adegoroye et al, 2004;Lavric et al, 2006).…”

“…Ocean dumping was a preferred sludge disposal method for the last couple of centuries (Chun et al, 2011;Snyder, 2005), but it was banned in the 1990s by both U.S. and international law due to the high level of harmful pollutants in the sludge and the adverse effect on marine organisms (Abbas et al, 1996;Costello & Read, 1994;Harrison et al, 2006;Snyder, 2005). The loss of ocean-dumping drove most municipalities to embrace either agricultural land application or thermal destruction (viz., incineration) as their primary sludge-disposal routes, with a small percentage using landfilling or composting (Lavric et al, 2006).…”

“…Modeling, predicting, and defining these thermodynamic mechanisms is difficult, and there is no straightforward explanation in the literature for SCW reaction kinetic mechanisms (Azadi & Farnood, 2011;Bermejo & Cocero, 2006b;Bernardi et al, 2010;Hodes et al, 2004;Lu et al, 2010). The assumed, basic reaction kinetics are represented by the formulas (3-8) listed below (Chun et al, 2011;White et al, 2011):…”

“…Numerous researchers and institutions have noted that in order to fully evaluate sludge safety and risks, it is necessary to go well beyond the EPA's minimalist, chemical analyses and actually combine those with genuine ecotoxicological criteria (Abbas et al, 1996;Chun et al, 2011;Leiva et al, 2010;McBride, 2003;NASNRC, 1996NASNRC, , 2002Nature, 2008;Oleszczuk, 2008;Snyder, 2005;Tollefson, 2008). There is even growing concern that in the very near future, traditional management options will be unable to handle the increasing sludge quantities (Bernardi et al, 2010).…”

“…The facilities are designed to collect, remediate, and dispose of human and commercial wastes within an established regulatory framework (Chun et al, 2011;Demirbas, 2011b;Fytili & Zabaniotou, 2008;Svanström et al, 2004;USEPA, 2009). Sewage that enters wastewater treatment facilities gets processed and separated into two products.…”