Anaerobic Digestion of Three Microalgae Biomasses and Assessment of Digestates as Biofertilizer for Plant Growth

Abstract

This study focused on the determination of biochemical methane potential of three different microalgae, Chlorella sp., Neochloris conjuncta, and Botryococcus braunii, and evaluation of the digestates as biofertilizers for corn growth. Biomethane Potential Test Unit consisting of twelve 2‐L flasks placed in temperature controlled water at 37°C was utilized. As Botryococcus braunii had the highest lipid content (9.54%), it also had the highest biochemical methane potential (290.63 N mL g−1 volatile solid). The digestates containing microalgae and inoculum were applied to corn plant with four application dosages (0 [control], 5, 10, and 15 t ha−1) based on dry mass. Results emphasized that the lowest dosage (5 t ha−1) of the digestates containing Chlorella sp. and inoculum (digested dairy manure with silage maize) increased plant dry weights by 9% and 23%, respectively. However, further increase in the dosages of the digestates containing Botryococcus braunii and Neochloris conjuncta resulted in a decrease of plant growth and nutrients uptake by corn plants from the soil. Results highlighted that increment of the dosages of the digestates containing Botryococcus braunii and Neochloris conjuncta led to a decrease of plant growth and nutrient uptake from soil. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13024, 2019