Methane and hydrogen production from cotton waste by dark fermentation under anaerobic and micro -aerobic conditions

The dark fermentation (DF) of organic textile (e.g. cotton) wastes is discussed in this paper. The influence of micro-aeration on hydrogen and methane production is studied. Fermentation was carried out under the following conditions: load 5 g VSS/L (Volatile Suspended Solids), the pH was varied in the range from 6.23 to 7.8; oxygen was added in small quantities. The oxygen flow rates (OFRs) were varied between 1 and 4.6 mL/h. The highest yields of methane (0.78 L/g VSS) were obtained under anaerobic conditions and neutral pH (7.54), while the production of hydrogen (1.1 mL/g VSS) peaked under an oxygen flow rate of 4.6 mL/h and a pH value of 6.4. Hydrogen and methane yield and the peak days of their production from various substrates (such as cotton waste, sour cabbage, wheat straw, and potato wastes) were compared and discussed. Cotton waste is a potential source of methane, but is substantially less efficient than potato waste.