Dry residues from the prodn. of herbal plants (Mentha spicata L, Mentha rotundifolia L. and Rosmarinus officinalis L) were subjected to MeH fermentation at 37 degrees C. The av. content of MeH in the obtained biogas was 66%, CO2 32%, O-2 1% and H2S 500 ppm. The max. biogas productivity was about 300 m(3)/t.