The production of biogas using algal biomass in comparison to
some terrestrial plants is shown in Table 4.
Biogas is produced through the anaerobic transformation of
organic matter present in the biodegradable feedstock such as
marine algae, which releases certain gases like methane, carbon
dioxide, and traces of hydrogen sulfide. The anaerobic conversion
process involves basically four main steps. In the first step, the
insoluble organic material and higher molecular mass compounds
such as lipids, carbohydrates, and proteins are hydrolyzed into soluble
organic material with the help of enzyme released by some
obligate anaerobes such as Clostridia and Streptococci. The second
step is called as acidogenesis, which releases volatile fatty acids
(VFAs) and alcohols through the conversion of soluble organics
with the involvement of enzymes secreted by the acidogenic bacteria.
Further, these VFAs and alcohols are converted into acetic acid
and hydrogen using acetogenic bacteria through the process of acetogenesis,
which finally metabolize to methane and carbon dioxide
by the methanogens