NOVELTY - Fatty acid methyl esters (FAME), produced from naturally floating marine microalgal mats or thick layers of settled marine microalgae formed during cultivation in solar salt pans or its mixture, is claimed.    USE - The FAME is useful in a regular unmodified diesel vehicle as B20 blend or biodiesel under full load condition and complying emission requirements (claimed).    ADVANTAGE - The method provides a low cost option for generating marine microalgal biomass by harvesting naturally occurring mats of such algae in sustainable manner. The thermotolerant Chlorella sp. is found to be cultivable in open solar salt pans even in hot summer conditions with high biomass productivity and good lipid content. Only minimum nutrient and energy inputs are required for cultivation of the biomass. The biomass is readily harvestable. Only the useful portion of lipids suitable for biodiesel production is selectively extracted with the help of non-polar solvent. The simple methods are used to refine the raw oil obtainable with non-polar solvent extraction and thus the oil is readily processed into high quality biodiesel. The methyl ester obtained from marine microalgal sources can be utilized even under neat condition (B100) to run a regular diesel vehicle without any engine modification.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for production of engine worthy fatty acid methyl ester for use as biodiesel comprising: collecting naturally occurring microalgal mats consisting of Microspora sp. and Cladophora sp. or cultivated Chlorella variabilis to obtain algal biomass; sun drying the biomass to residual moisture level of 5-10%; pre-treating the biomass by steam blast or osmotic shock to disrupt the cell wall; extracting lipid from algal biomass using hexane as a solvent or optionally with diesel where the fuel is to be used in blend form to obtain raw oil; stripping off the hexane and treating resultant raw oil with fullers earth or optionally treating the extract directly with fullers earth to remove phospholipids, pigments and other impurities; filtering to remove suspended solids and treating the oil extract further to reduce free fatty acid (FFA) content, if required to obtain refined oil; undertaking alkali-catalyzed trans-esterification of refined oil, separating the FAME, and purifying it further to obtain engine worthy FAME.