Research PaperEnergetic valorization of Nador lagoon algae and proposal to use it as a means of elimination of the eutrophication in this lagoon

•The red alga (Alsidium corallinum) produced the most biogas (85.23 ml/gVS).•The green alga (Chaetomorpha linum) produced the least biogas (22.23 ml/g VS).•The brown alga (Cystoseira barbata) ranked second place with 76.45 ml/gVS of biogas product.•The three lagoon-polluting algae are green energy producers.•We propose a new system which will halt eutrophication of this lagoon.

The Nador lagoon is one of the best lagoons in the Mediterranean, it currently suffers from eutrophication caused by algae proliferation. In this study, we valorised the three important algae that are responsible for pollution of the lagoon. We determine their potential of biogas production and green energy capacities and we studied their effects on anaerobic bacteria proliferation in digester. After 40 days of incubation in batch mode we observed the red alga (Alsidium corallinum) produced the most biogas with 85.23 ml/gVS, which is equivalent to 511 kWh/tVS of green energy, whereas the brown alga (Cystoseira barbata) ranked second place with 76.45 ml/gVS of biogas product, the equivalent to 458 kWh/tVS of green energy. But, the green alga (Chaetomorpha linum) produced the least biogas do not exceed 22.23 ml/g VS, so these algae produces the lowest amount of energy green 133 kWh/tVS. Thus, this red alga (Alsidium corallinum) were considered excellent substrate for anaerobic digestion. These results correlated with the anaerobic bacterial proliferation of the inoculum, where the two algae (Alsidium corallinum and Cystoseira barbata) led to a large proliferation of anaerobic bacteria, from 1.8 × 105 CFU/g to 61 × 105 CFU/g, followed by the green alga. Therefore, we consider these three algae (Alsidium corallinum, Cystoseira barbata, and Chaetomorpha linum) as an exploitable energy reservoir in Nador lagoon. Finally, we propose that a new system which will halt eutrophication of this lagoon, it comprising anaerobic digestion of these algae, be installed to produce green energy for a lagoon aerator to dissolve the atmospheric oxygen inside the lagoon.