1. Institute of Agricultural and Environmental Engineering, JTI, PO Box 7033, SE-750 07 Uppsala, Sweden
2. Department of Microbiology, Swedish University of Agricultural Sciences, PO Box 7025, SE-750 07 Uppsala, Sweden
3. SYVAB Himmerfjärdsverket, SE-147 92 Grödinge, Sweden
4. Department of Biotechnology, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark and Danish Technological Institute, Kongsvang Alle 29, DK-8000, Denmark