In this research the use of a macroalgae waste, algae meal, from the Agar-Agar industry is studied as precursor of activated carbon. Algae meal has a high carbon and nitrogen content, low ash content and absence of heavy metals. Activated carbons were prepared by KOH chemical activation by conventional and microwave heating system. The precursors studied were: algae meal and the carbonized waste obtained by pyrolysis at 750 C in previous works of energy use of this marine biomass waste. The nature of the precursor, the influence of the activation temperature and KOH/precursor weight ratio were investigated and discussed. Furthermore the effect of conventional and microwave activation, was studied. The best activated carbons were obtained by conventional activation using algae meal as precursor. Under appropriate activation conditions it is possible to obtain adsorbent materials with S-BET surface areas and pore volume as high as 2118 m(2)/g and 1.14 cm(3)/g respectively. Microwave activation favours the development of ultramicroporosity whereas medium-size micropore and mesopore formation was predominant in the material obtained by means of the electrical conventional furnace. Converting this macroalgae waste in activated carbon could solve environmental problems since a considerable portion of this residue is disposed of by landfill. (C) 2014 Elsevier B.V. All rights reserved.