The Cultivation of Lipid-Rich Microalgae Biomass as Anaerobic Digestate Valorization Technology—A Pilot-Scale Study

Marcin Dębowski,Aleksandra Rudnicka,Marta Kisielewska,Izabela Świca,Magda Dudek,Marcin Zieliński,Joanna Kazimierowicz

doi:10.3390/pr8050517

Abstract

The aim of the study was to determine the use of digestate from anaerobic digestion of dairy wastewater as a culture medium for microalgae to obtain bio-oil. The experiments were conducted at a small scale in a closed raceway pond. The efficiency of the microalgae biomass production, the digestate treatment efficiency as well as the content and properties of the bio-oil obtained from the microalgal cells were analyzed. The produced biomass concentration was about 3000 ± 10.5 mg dry biomass/L, with an average growth rate of 160 ± 6.6 mgdm/L·d. The efficiency of organic compound and nutrient removal was above 90%. The bio-oil content in the biomass was about 20%. Based on the results of the study, a concept for technical-scale technology was developed.

Highlights

Wastewater from dairy processing plants is characterized by a high content of organic compounds and nutrients; there is a potential of its use as a source of nutrients for microalgal biomass production [1]
The aim of the study was to determine the use of digestate from anaerobic reactor-treated dairy wastewater to grow mixed-culture microalgae
The efficiency of microalgae biomass growth, digestate treatment efficiency as well as the content and properties of bio-oil obtained from the microalgae cells were analyzed

Summary

Introduction

Wastewater from dairy processing plants is characterized by a high content of organic compounds and nutrients; there is a potential of its use as a source of nutrients for microalgal biomass production [1]. The raw wastewater contains too high a concentration of organic compounds, and is characterized by high turbidity and low transparency. When using raw wastewater as a culture medium for microalgae, the high concentration of organic compounds could enhance the growth of detrimental organisms, mainly bacteria, while the turbidity and its dark color could limit the availability of light and inhibit photosynthesis [4]. One of the methods is wastewater treatment in anaerobic reactors for partial organic compound removal and transformation of biogenic compounds into mineral forms that are absorbed by microalgae, as well as reducing turbidity and color [5]

Objectives

Methods

Conclusion