The objective of this study was to determine the optimum rate of palm oil sludge for Ganoderma mushroom (Ganoderma lucidum (Fr.) Karst) cultivation. Different concentrations of palm oil sludge (5-20% by dry weight) were mixed with rubber sawdust and used to grow the Ganoderma mushroom in plastic bags. Growth rate of the mycelia, number of basidiocarp, cap diameter, thickness of pileus and yield were compared with the control (not supplemented) and with 5% rice bran (standard formula). The results showed that use of 5% palm oil sludge was optimal for Ganoderma cultivation. Yield when grown on 850 g/ bag of rubber sawdust with 5% palm oil sludge, 2% Ca( OH) 2 and 0. 2% Mg( SO4) was 74. 82 g/ bag (B.E.=22.01%), which does not differ significantly from that with 5% rice bran in the sawdust (66.31 g/bag, B.E.=19.50%).
