A closed-loop algal biomass production-platform and biorefinery from renewable sources of N and P and intensive recycling of reagents into nutrients

MARIA EUGENIA SANZ SMACHETTI; LARA SANCHEZ RIZZA; MAURO DO NASCIMENTO; CAMILA DENISE CORONEL; LEONARDO CURATTI

San Luis

Congreso; XIII Congreso Argentino De Microbiología General SAMIGE; 2018

Asociación Civil de Microbiología General

Microalgae and cyanobacteria are increasingly considered a promising alternative to conventional crops as feedstock for food and feed and biofuels, mainly because of a much higher photosynthetic productivity. One of the drawbacks of this technology is the very large demand of N and P fertilizers that must be supplied to realize algal production potential.In this study we provide proof-of-concept for a closed-loop algal production platform and biomass biorefinery for ethanol at the expense of atmospheric N2 and P from bone meal. N2 is assimilated in a N2-fixing cyanobacterium?s biomass that accumulates very high levels of protein (60 % w/w). Water extraction of this biomass produced an organic fertilizer, which as a sole source of nutrients, sustained mixotrophic growth to very high yields of a microalga that accumulated high levels of carbohydrates (60% w/w). The algal biomass was saccharified in the presence of H2SO4 and this acidic condition was secondary used to release soluble PO43- from different P-sources, including bone meal, as a renewable P-source. After increasing the pH with KOH and Mg(OH)2, the resulting preparation was fermented with yeast to quantitatively produced ethanol at about 90 % of its theoretical yield. The resulting fermentation vinasse, supplemented with P, was efficiently recycled as a sole source of macronutrients for the cultivation of the N2-fixing cyanobacterium?s biomass to complete one production cycle. Water recycling and co-production of residual biomass as feed are also shown.This closed loop-algal production platform brings concepts of circular economy into the field of microalgae biomass biorefineries. It basically produces ethanol and feed grade-like biomass at potentially high yields at the expense of atmospheric CO2 and N2, and mostly P from food industry waste (bones). Nevertheless, the overall procedure still needs to be subjected to techno-economic and environmental performance analyses for a more realistic comparison to alternative processes.