Evaluation of the energetic valorization of the lagoon and Mediterranean algae (Caulerpa prolifera & Corallina elongata) by anaerobic digestion

Abstract

Morocco is characterized in the North-East by two aquatic ecosystems (the Mediterranean Sea and the Nador Lagoon).The latter is a reservoir of algal proliferation that worsens with the installation of localized pollution in the last decades. In this work, we have evaluated and compared the energy recovery of the two important algae (Caulerpa prolifera, Corallina elongata) that are abundant in these two ecosystems. Thus, we found that Caulerpa prolifera produces more biogas than Corallina elongata. Caulerpa prolifera shows a significant influence of mechanical pretreatment on anaerobic digestion, which is reflected in a decrease in biogas production from 30.4 ml/gTS to 12 ml/gTS. On the other hand, Corallina elongata has a low dependence on pretreatment which varies between 4.42 and 6.63 ml/g TS. Additionally, the digestion of this red alga leads to the disappearance of the bacterial arsenal in the digester so it reacts negatively on the efficiency of this process. Therefore, the energy recovery of Corallina elongata shows a significant influence of its chemical composition on the anaerobic digestion that is not in favor of this process. Based on the obtained results, the mixing test of these two algae in the same digester shows that it is not beneficial for a common valuation. The anaerobic digestion of Caulerpa prolifera with a particle size of 0.12 mm makes it possible to obtain a large production of biogas which allows a good valorization of this natural resource. Keywords: Anaerobic digestion, Algae, Biogas, Corallina elongate, Caulerpa prolifera