High yield cultivation of marine macroalga Ulva lactuca in a multi-tubular airlift photobioreactor: A scalable model for quality feedstock

• Published in: Journal of cleaner production 2021-12, Vol.329, p.129746, Article 129746
• Main Authors: Savvashe, Prashant, Mhatre-Naik, Akanksha, Pillai, Gayatri, Palkar, Juilee, Sathe, Mayur, Pandit, Reena, Reddy, C.R.K., Lali, Arvind M.
• Format: Article
• Language: English
• Subjects: Airlift photobioreactor; Coastal agronomy; Macroalgae; Onshore cultivation; Renewable feedstock; Ulva lactuca
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2021.129746

Conventional off-shore and on-shore cultivation methods for marine macroalgae are both inadequate to pitch macroalgae as scalable renewable feedstock that can be grown across all coastal locations. With on-shore cultivation likely to be sustainable and preferred over eco-damaging open seas cultivation, new reactor systems need to be developed for on-shore cultivation of seaweeds at scale. The present work is an attempt to use the indigenously designed vertical multi-tubular air-lift photobioreactor system to grow Ulva lactuca through the entire year under natural conditions. Optimized operation of the 1000 L photobioreactor assembly demonstrated a year-round averaged productivity of 0.87 kg m−2.d−1 (fresh weight) implying 1800 ton.ha−1.y−1 feedstock production. Carbon dioxide supplementation (5%), optimized circulation velocity (0.25–0.35 m/s), and managing nitrogen supply (17 ppm), under natural light intensities (500–1400 μmol m−2.s−1) provided a year-round sustained and continuous production of Ulva lactuca biomass. The photobioreactor system designed as a modular, linearly scalable, and resilient system operates with low land and water footprints, and gives a multi-fold increase in renewable feedstock production compared to the conventional sea-based and other on-shore tank-based practices. For the video summary of this article, see the file in the supplemental data. [Display omitted] •Cultivation of Ulva lactuca biomass using airlift photobioreactors.•Demonstration of year-round outdoor cultivation of marine feedstock.•Continuous and consistent supply of food-grade Ulva lactuca biomass.•Demonstration of multi-fold improvement in aerial biomass production.•Proof of concept promoting and supporting coastal agronomy.