Pyrolysis characteristics of a macroalgae solid waste generated by the industrial production of Agar–Agar

• Valorization of a macroalgae industrial waste by pyrolysis.
• Energy use of the char, bio-oil and bio-gas obtained in the pyrolysis.
• The char is a good precursor for obtaining activated carbons.
• Gas fraction has a significant amount of syngas.

A biomass solid waste (algae meal) generated by the industrial production of Agar–Agar was used as a pyrolysis precursor for this work. The optimal pyrolysis conditions for obtaining energy from the fractions generated (char, oil and gas), and for preparing adsorbent materials from the char were established. Chemical analysis of the algae meal showed that its high carbon, hydrogen and nitrogen content together with its low ash content make it a potential precursor of activated carbons. The optimal pyrolysis conditions were selected by means of thermogravimetric analysis and a study of the carbonization process of the algae meal. These conditions were: final temperature: 750 °C; heating rate: 5 °C/min, time at final temperature: 60 min; flow of inert gas (N2): 150 ml/min. The char obtained from the pyrolysis process presents properties that make it suitable as a solid fuel and as a precursor of activated carbon. Analysis of the oil fraction by the chromatographic technique (GC–MS) showed compounds such as phenols, pyrroles and furanes. The gas fraction had a high syngas content enhancing its high heating value.