Biogas is one essential renewable energy source which can replace natural gas after its purification. Biogas is produced
from different biomass materials though the anaerobic digestion process. Algae are considered as a feedstock
for biogas production, which does not compete with food production and does not need large areas of
arable land and fresh water resources.
In order to improve the biogas production, pre-treatment techniques have been investigated to disrupt the structure
of algae increasing the availability of substrates. In this paper, a review of these pre-treatment methods is
presented. Pre-treatment methods are categorised into mechanical, ultrasound and micro-wave, thermal, chemical,
biological and combined groups. The effect of the application of each of the studied techniques on the biogas
yield and the energy balance is discussed. A comparison of the used techniques is carried out, and discussed