Solid Waste-to-Ethanol Process Offers Lower Life Cycle Energy Use than Corn- or Cellulosic-Ethanol Production
Researchers from the University of Toronto and Michigan State University have concluded that ethanol derived from municipal solid waste (MSW) can deliver a life cycle total energy use per vehicle less than that of corn-ethanol and cellulosic-ethanol (derived from energy crops).
The team modeled a municipal solid waste (MSW)-to-ethanol facility that employs dilute acid hydrolysis and gravity pressure vessel technology and estimated the life cycle energy use and air emissions. The researchers also assumed the ethanol was used in an E85 blend.
Compared to extant life cycle assessments of gasoline, corn-ethanol, and energy crop-cellulosic-ethanol fueled E85 vehicles, the team found that the life cycle total energy use per vehicle mile traveled for MSW-ethanol is less than that of corn-ethanol and cellulosic-ethanol. Energy use from petroleum sources for MSW-ethanol was also lower than for the other fuels.
MSW-ethanol use in vehicles reduces net greenhouse gas (GHG) emissions by 65% compared to gasoline, and by 58% when compared to corn-ethanol. Relative GHG performance with respect to cellulosic ethanol depends on whether MSW classification is included or not.
In an evaluation of waste management alternatives, the team found that MSW-ethanol production will result in net fossil energy savings of 397-1,830 MJ/MT MSW compared to net fossil energy consumption of 177-577 MJ/MT MSW for landfilling. However, landfilling with landfill gas (LFG) recovery either for flaring or for electricity production results in greater reductions in GHG emissions compared to MSW-to-ethanol conversion.
The research appears online in Environmental Science & Technology.
“Environmental Implications of Municipal Solid Waste-Derived Ethanol”; Youssouf Kalogo, Shiva Habibi, Heather L. MacLean, and Satish V. Joshi; Environ. Sci. Technol., ASAP Article 10.1021/es061117b S0013-936X(06)01117-5