New insights on improved growth and biogas production potential of Chlorella pyrenoidosa through intermittent iron oxide nanoparticle supplementation

In the present work, the effect of α-Fe(2)O(3)-nanoparticles (IONPs) supplementation at varying doses (0, 10, 20 and, 30 mg L(−1)) at the intermittent stage (after 12th day of growth period) was studied on the growth and biogas production potential of Chlorella pyrenoidosa. Significant enhancements in microalgae growth were observed with all the tested IONPs doses, the highest (2.94 ± 0.01 g L(−1)) being at 20 mg L(−1). Consequently, the composition of the biomass was also improved. Based on the precedent determinations, theoretical chemical oxygen demand (COD(th)) as well as theoretical and stoichiometric methane potential (TMP, and SMP) were also estimated. The COD(th), TMP, SMP values indicated IONPs efficacy for improving biogas productivity. Further, the biochemical methane potential (BMP) test was done for IONPs supplemented biomass. The BMP test revealed up to a 25.14% rise in biogas yield (605 mL g(–1) VS(fed)) with 22.4% enhanced methane content for 30 mg L(−1) IONPs supplemented biomass over control. Overall, at 30 mg L(−1) IONPs supplementation, the cumulative enhancements in biomass, biogas, and methane content proffered a net rise of 98.63% in biomethane potential (≈ 2.86 × 10(4) m(3) ha(−1) year(−1)) compared to control. These findings reveal the potential of IONPs in improving microalgal biogas production.