Treatment and recycle of harvested microalgal effluent using powdered activated carbon for reducing water footprint and enhancing biofuel production under a biorefinery model

Valorization of Chlorella thermophila biomass cultivated in dairy wastewater for biopesticide production against bacterial rice blight: a circular biorefinery approach

Biopesticides offer a sustainable and efficient alternative to synthetic pesticides, providing a safer and more eco-friendly solution to pest management. The present work proposes an innovative approach that integrates crop protection and wastewater treatment using thermophilic microalgal strain Chlorella thermophila (CT) cultivated in nutrient-rich dairy wastewater as a growth medium. The microalgae was cultivated mixotrophically and was able to reduce both organic carbon as well as nutrient load of the dairy wastewater efficiently. The integrated circular biorefinery approach combines biomass cultivation, extraction of biopesticide compounds, and conversion to biocrude. The antimicrobial activity of the biopesticidal extracts against Xanthomonas oryzae and Pantoea agglomerans, the causative agent of bacterial rice blight, is assessed through in vitro studies. The biomass extract obtained is able to inhibit the growth of both the above-mentioned plant pathogens successfully. Mass spectroscopy analysis indicates the presence of Neophytadiene that has previously been reported for the inhibition of several pathogenic bacteria and fungi. Several other value-added products such as linoleic acid and nervonic acids were also been detected in the microalgal biomass which have extremely high nutraceutical and medicinal values. Furthermore, the study investigates the potential for co-production of biocrude from the biorefinery process via hydrothermal liquefaction. Overall, the findings of this present work represent an innovative and sustainable approach that combines wastewater treatment and crop protection using microalgal biomass.

Dairy wastewater treatment using Monoraphidium sp. KMC4 and its potential as hydrothermal liquefaction feedstock

Monoraphidium sp. KMC4 was cultivated mixotrophically for simultaneous treatment of dairy wastewater and biomass production. The KMC4 was cultivated with varying chemical oxygen demand concentrations of simulated synthetic dairy wastewater. Monoraphidium sp. KMC4 outperformed in 50% strength with biomass concentration of 1.47 g L^-1. A significant change in biomass of 3.69 g L^-1 was achieved after maintaining the pH of algal culture. The nutrient consumption promoted microalgal growth in the form of biomass productivity (122 mg L^-1 day^-1), accumulation of carbohydrate (28.73±1.6 wt%), protein (48.50±1.3 wt%), and lipid (20.29±2.3 wt%). This strain showed efficacious performance in treating simulated synthetic dairy wastewater obtaining biomass for various applications. The algal biomass derived from wastewater reported a significant volatile matter content and higher heating value. The biomass demonstrates satisfactory thermal degradation behavior which reveals its feasibility as feedstock for thermochemical conversion to biocrude. The integration of biomass production in high-scale raceway pond along with biocrude production is a promising pathway toward the generation of green energy for replacing traditional fossil fuels..

Current trends in the pretreatment of microalgal biomass for efficient and enhanced bioenergy production

Biofuels from microalgal biomass is among some of the promising sustainable energy technologies that can significantly replace the dependence on fossil fuels worldwide due to potentiality to lower CO₂ emissions. Nevertheless, the extraction of biomolecules for biofuel generation is inhibited by the rigidity of the cellular structure of microalgal biomass. Various pretreatment strategies have been evaluated for their efficacy in microalgal cell wall disruption to enhance microalgal bioenergy production. However, the efficiency of the pretreatment methods depend on the particular species being treated due to the inherent variability of the composition of the cell wall. This paper reviews pretreatment strategies (mainly novel physical, chemical and physicochemical) employed in bioenergy generation from microalgal biomass, address existing constraints and provides prospects for economic and industrial-scale production. The authors have also discussed the different pretreatment methods used for biodiesel, bioethanol, and biohydrogen production.