Figure 3: Biological efficiency (percentage ratio of fresh mushrooms weight over the dry weight of the respective substrate) for four mushroom species growing on seven cultivation substrates (TPOMW: raw two-phase olive mill waste; cTPOMW: composted two-phase olive mill waste). Values (%) from four species were pooled and results are expressed as means ± standard errors of means, . Lack of letters in common indicates statistically significant differences (Gabriel’s -test, ) among the substrates examined.