**4. Algal bio-refinery based production**

Algal biorefinery approach aims to promote harvesting of several value-added products from the algae feedstock, towards economic and environmental effectivity of algal based technology. There are plenty of the research efforts has been made to harness the algal biomass to produce biofuel, biofertilizer, biodiesel, pharmaceutical products as well as for wastewater remediation. The industrial production of the biofuel through algal biomass utilizing different photobioreactors could be possible to burden off the current energy demand. The basic process of biodiesel production through bio-refinery is explained in **Figure 3**. Additionally, the nutrient qualities such as carbohydrates, proteins, nitrogen, phosphorous, potassium and other nutrients of the algal biomass can also be utilized as nutrient feed for animal as well as for fish etc. The algal dry biomass composition contains up to 46% Carbon (C), 10% Nitrogen (N) and 1% Phosphates (P) and 1 kilogram (kg) of dry algal biomass utilizes up to 1.7 kg carbon dioxide (CO2) (Hu et al., 2008). The algal biomass after remediation of wastewater having vast potential as biofertilizer. The N,P and K content in microalgae algae biomass varies from 7 to 9%, 1–2% and 0.1–1%, respectively [5, 13]. The algal biomass can also be used as biofertilizer in agro-ecosystems. The algal biomass not only provides essential nutrients to the agricultural crops but also significantly contribute to improve the soil carbon and soil fertility [5, 13]. Sharma et al. [5] in a study conducted on the impact of algae biomass as manure on the nitrate leaching reported that microalgal manure are slow releasing in nature and less leaching of nitrate as compared to chemical fertilizer was observed, so application of microalgae biomass

#### **Figure 3.**

*A conceptual process (Biorefinery based) for producing microalgae biofuels for better economy.*

also results in reduction of nitrate leaching from agricultural fields as compared to chemical fertilizer, hence prevent eutrophication of the water bodies. Thus based on the available literature and recent research it can be concluded and put forward that algal biorefinery is one of the most promising cutting-edge economic alternative of existing traditional technologies to cater the environment through direct reduction of the primary and/or secondary pollutants as well as sustainable solution for essential required developmental process.
