The rapidly depleting fossil fuel reserves with rising greenhouse gas levels (GHGs) in the atmosphere necessitate exploring alternate sustainable energy options. Biofuels from microalgae are emerging as a viable renewable energy resource owing to their inherent characteristics of higher biomass and lipid yield per hectare compared to other terrestrial bioenergy feedstocks. In this context, the present communication highlights the prospects of microalgal biofuel and other value-added products produced in a decentralized microalgal biorefinery in the flood plains (gazani lands) of the west coast of India. The spatial extent of potential sites for diatom cultivation estimated in three districts along the Indian west coast was 1940 ha. The opportunities for establishing biorefineries using diatoms as renewable bioenergy feedstocks were investigated through species prioritization, seasonal availability, tolerance, and biochemical composition analyses. Nitzschia and Amphora sp. were prioritized for lab-scale productivity studies based on their tolerance and macromolecular composition. When cultivated in a prototype biofilms-based bioreactor designed using gravel stones as substrates, Amphora sp. yielded 16 times more productivity (0.56 g L^-1) than conventional shake flask cultures. Design of a diatom biorefinery and its mass budgeting considering 100 kg dry biomass yielded ~ 15 – 24 kg of biodiesel. Techno-economic assessment of biodiesel with value-added products of glycerol, biogas, and biofertilizer demonstrated a biodiesel production cost of 30.08 – 59.52 INR/kg of biodiesel. Harvesting cost in a hybrid mode using mechanized scrubbers and manual labour was estimated as 20 INR/kg of biomass.

Highlights

• Evaluate the potential of diatoms as a source of biofuel with value-added products.

• Biochemical composition and feedstock availability assessment across seasons.

• Design and implementation of prototype algal reactor.

• Economic feasibility assessment and mass budgeting of the diatom biorefinery.

• Promising scope for a diatom biorefinery along the Indian central west coast.

Keywords: diatoms; biofuel; bioreactor; microalgal refinery; techno-economic; lifecycle assessment; value-added products.

Abbreviations 

GDP	Gross Domestic Product	UCO	Used cooking oil
GHG	Greenhouse gas	FAME	Fatty Acid Methyl Ester
CO2	Carbon dioxide	HTL	Hydrothermal liquefaction
EBP	Ethanol blending programme	3G	Third generation
NBM	National biodiesel mission	ABE	Acetone-Butanol-Ethanol
SCO	Single cell oil	TAG	Triacylglycerol
ASP	Aquatic Species Program	ICTGEB	International Centre for Genetic Engineering and Biotechnology
MPB	Microphytobenthos	C5	Five carbon sugars
LC-PUFA	Long-chain polyunsaturated fatty acid	MI	Mission Innovation
DoE	Department of Energy	IOC	Indian Oil Corporation
EPS	Exopolysaccharides	IIT COD	Indian Institute of Technology Chemical Oxygen Demand
				ATS	Algal Turf Scrubbers	HRT	Hydraulic Retention Time
GoI	Government of India	QGIS	Quantum Geographic Information System
DBT	Department of Biotechnology	ISRO	Indian Space Research Organisation
ICT	Institute of Chemical Technology	NRDMS	Natural Resources Data Management System

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