The objective of this study was to screen nine annual or perennial novel plants for biogas production cultivated in years 2007-2010 in Finland. The most promising novel plants for biogas production were found to be brown knapweed, giant goldenrod and Japanese millet producing 14-27 t total solids/ha and 4000-6100 Nm(3) CH4/ha. The specific methane yields of all studied plants varied from 170 to 381 Nm(3) CH4/t volatile solids (VS), depending on harvest time and plant species. Co-digestion of brown knapweed with cow manure in continuously stirred tank reactor was investigated and the highest methane yield was 254 NL CH4/kg VS, when the share of brown knapweed was 50% in the feed VS (organic loading rate (OLR) 2 kg VS/m(3)/d). The cultivation managements and sustainability of novel plants for biogas production have to be investigated. (c) 2013 Elsevier Ltd. All rights reserved.