1. Process Engr., Organic Waste Systems n.v., Dok Noord 4, B-9000 Ghent, Belgium. E-mail: pvdv66@hotmail.com
2. Grad. Student, Laboratory for Microbial Ecology and Technology (LabMET), Ghent Univ., Coupure Links 653, B-9000 Ghent, Belgium.
3. Prof., Laboratory for Microbial Ecology and Technology (LabMET), Ghent Univ., Coupure Links 653, B-9000 Ghent, Belgium. E-mail: willy.verstraete@rug.ac.be
4. Assoc. Dir., Proter&Gamble Eur. Tech. Ctr., Temselaan 100, B-1853 Strombeek-Bever, Belgium. E-mail: feijtel.t@pg.com
5. Sr. Envir. Engr., Procter&Gamble Eur. Tech. Ctr., Temselaan 100, B-1853 Strombeek-Bever, Belgium. E-mail: schowanek.d@pg.com