ABSTRACT
Heterotrophic microalgae Chlorella protothecoides, either as whole (H) or pre-treated by ultrasound method (HPU), were anaerobically digested to provide information on the light effect on the simultaneous production of biogas/methane and pigments, under conditions of continuous absence or presence of light. The simultaneous production of red pigments and biogas/methane was achieved by using continuous lighting, while under complete darkness only methane was obtained as anaerobic digestion’s product but with higher amounts; values of 36/68 (H and HPU) against of 115/150 mL methane (Hc and HPUc) were registered. Ultrasonic pre-treatment doubled the methane yield from 120 to 278 and 382 to 615 L CH4/kg VSIN (H vs HPU and Hc vs HPUc, respectively), confirming its positive effect on anaerobic digestion process. From the results, the permanent supply of light to the digestion units is necessary for the simultaneous production of biogas/methane, digestate flow and pigments.
