<P><B>Highlights</B></P><P>► Co-production of ethanol and fertilizer from a red seaweed, <I>Kappaphycus alvarezii</I>. ► Best yields for saccharification was ca. 28% (w/w). ► Eighty percent of the reducing sugar generated was converted to ethanol. ► A petrol vehicle was successfully run with E10 gasoline made from this bioethanol.</P> <P><B>Abstract</B></P><P>The present study describes production of bio-ethanol from fresh red alga, <I>Kappaphycus alvarezii</I>. It was crushed to expel sap – a biofertilizer – while residual biomass was saccharified at 100°C in 0.9N H<SUB>2</SUB>SO<SUB>4</SUB>. The hydrolysate was repeatedly treated with additional granules to achieve desired reducing sugar concentration. The best yields for saccharification, inclusive of sugar loss in residue, were 26.2% and 30.6% (w/w) at laboratory (250g) and bench (16kg) scales, respectively. The hydrolysate was neutralized with lime and the filtrate was desalted by electrodialysis. <I>Saccharomyces cerevisiae</I> (NCIM 3523) was used for ethanol production from this non-traditional bio-resource. Fermentation at laboratory and bench scales converted ca. 80% of reducing sugar into ethanol in near quantitative selectivity. A petrol vehicle was successfully run with E10 gasoline made from the seaweed-based ethanol. Co-production of ethanol and bio-fertilizer from this seaweed may emerge as a promising alternative to land-based bio-ethanol.</P>