Biomass growing stocks, harvesting productivity and costs of energy production, were studied in thinnings of Quercus pyrenaica. Eleven forest sites were selected in coppices located in Castilla y Leon (Spain). Three systems were employed for harvesting: a mechanised whole tree harvesting (WTH) system, which included chipping at landing; a fully mechanised cut-to-length (CTL) harvesting system for firewood; and a semi-mechanised CTL system with manual felling and bunching. Three WTH trials had a hauling off 34.7 -44.1 oven-dried tonnes (odt) ha(-1). In contrast, only 11.6-30.0 odt ha were obtained in the other eight CTL trials. Biomass weight equations for stems and whole trees were fitted. Worker operations were time-studied using software designed by the authors. The WTH system reached maximum productivity rates of 3.9 oven-dried tonnes per productive hour (odt h(-1)) for the felling and bunching operation and 6.9 odt h(-1) for the forwarding operation. The mechanised CTL harvesting method achieved a productivity range of 1.3 -0.5 odt h(-1) for the harvesting operation. Furthermore, the average forwarding productivity was 7.3 odt h(-1). Motor-manual felling and crosscutting in the CTL system accomplished a productivity range of 0.7-1.9 odt h(-1). Manual bunching resulted in similar values. The lowest firewood unit cost for trees with 10 cm of diameter at breast height (DBH) was 62.0 (sic) odt(-1) using a semi-mechanised CTL system. Under similar conditions, this cost was 85.2 (sic) odt(-1) for the mechanised CTL system. Finally, the cost corresponding to chips at landing from WTH sites (average DBH = 10 cm) was 65.3 (sic) odt(-1). (C) 2013 Elsevier Ltd. All rights reserved.