<P><B>Abstract</B></P> <P>This paper analyses the improved energy and environmental performance of the biomethanation of a mixture of sheep manure (20% by weight) and cheese whey (80% by weight) in a reactor of 2 L capacity containing 2 g of charcoal in the form of a fixed bed with respect to the same process but without the charcoal in the reactor (control experiment). The results show an increased methane production of 27.05% and a reduction of the H<SUB>2</SUB>S content in the biogas of 34.7%, over those obtained in the control experiment. These marked improvements of the biomethanation process are attributable to the content of highly electropositive metals such as K and Ca in the charcoal which, because chemical reactions, can increase the pH of the medium and thus favour the processes of methanogenesis and sulphate reduction. Charcoal would act as a bacteriological adherent promoting the biomethanation of the organic waste materials used in the study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The biomethanation of sheep manure and cheese whey is studied. </LI> <LI> Charcoal is used as a bacteriological adherent in the biomethanation. </LI> <LI> Bioreactions are carried out for 168 days without inhibition. </LI> <LI> The production of CH<SUB>4</SUB> increases by 27.05%. </LI> <LI> The content of H<SUB>2</SUB>S in the biogas is reduced by 34.7%. </LI> </UL> </P>