ABSTRACT
Microalgal biorefineries have been recognized as an economically appealing and potentially sustainable opportunity for the production of a host of value-added products and have recently gained prominence as a key to the realization of a bioeconomy. One of the significant drivers of bioeconomy is the attainment of a carbon-neutral economy, and to this end, lifecycle assessment-based appraisal of alternative products and processes is expected to play a significant role. Numerous lifecycle assessment studies have identified the processes upstream of biomass processing (including cultivation, harvest, drying and dewatering) to be the hotspots of environmental impacts, as these processes typically entail high energy demand. Since all of these processes are an integral part of any microalgal biorefinery (except for the fact that a few technologies can process biomass slurry), these stages of the biomass supply chain deserve significant attention. The availability and analysis of various technological interventions, alternative strategic designs, processing routes and residue valorization endeavors have all led a highly uncertain picture of microalgal biorefineries. Nonetheless, the problem of plenty has also led to process designs with unprecedented energy returns, greenhouse gas savings and appealing values for other sustainability indicators. Selection of an ideal strain(s), optimization of growth and biomass composition, utilization of waste streams of nutrients and water with a maximum degree of recycling, improving energy use efficiency at various stages, development of wet biomass extraction and processing routes, and appropriate valorization strategies are expected to help the realization of an environmentally and economically appealing biorefinery.
