Abstract
High volumes of lipid extracted microalgal biomass residues (LMBRs) are expected to be produced upon commencement of biodiesel production on a large scale, thus necessitating its value addition for sustainable development. LMBRs of Chlorella variabilis and Lyngbya majuscula were employed to substitute the nitrogen content of recommended rate of fertilizer (RRF) for Zea mays L. The pot experiment comprised of 10 treatments, i.e., T1 (No fertilizer); T2 (RRF-120 N: 60 P2O5: 40 K2O kg ha−1); T3 to T6—100, 75, 50, and 25% N through LMBR of the Chlorella sp., respectively; T7 to T10—100, 75, 50, and 25% N through LMBR of Lyngbya sp., respectively. It was found that all LMBR substitution treatments were at par to RRF with respect to grain yield production. T10 gave the highest grain yield (65.16 g plant−1), which was closely followed by that (63.48 g plant−1) under T5. T10 also recorded the highest phosphorus and potassium contents in grains. T4 was markedly superior over control in terms of dry matter accumulation (DMA) as well as carbohydrate content, which was ascribed to higher pigment content and photosynthetic activity in leaves. Even though considerably lower DMA was obtained in Lyngbya treatments, which might have been due to the presence of some toxic factors, no reduction in grain yield was apparent. The length of the tassel was significantly higher in either of the LMBRs at any substitution rates over RRF, except T6 and T7. The ascorbate peroxidase activity decreased with decreasing dose of Chlorella LMBR, while all the Lyngbya LMBR treatments recorded lower activity, which were at par with each other. Among the Chlorella treatments, only T5 recorded significantly higher values of glutathione reductase activity over RRF, while the rest were at par. There were significant increases in carbohydrate and crude fat, respectively, only in T4 and T3 over RRF, while no change was observed in crude protein due to LMBR treatments. Apparently, there was no detrimental effect on soil properties, suggesting that both the LMBRs can be employed to reduce the usage of chemical fertilizers, thus promoting maize crop production in a sustainable manner.
Highlights
The effect of climate change due to the incessant burning of fossil fuels is being felt across the globe (Ghosh, 2012) which has necessitated the search for alternate sources of cleaner energy (Ghosh et al, 2007; Ghosh, 2014)
All the treatments employing lipid extracted microalgal biomass residue (LMBR) from Lyngbya were at par with recommended rate of fertilizer (RRF) with respect to plant height at all the days of observations, except T8 at 60 days after sowing (DAS); there was no change in the number of nodes due to any of the treatments
The length of the tassels formed by applying either of the LMBRs at any of the substitution rates was markedly higher than that formed under RRF (P < 0.05), except that in the treatments employing the lowest level of LMBR from Chlorella and the highest level of that from Lyngbya, where were at par
Summary
The effect of climate change due to the incessant burning of fossil fuels is being felt across the globe (Ghosh, 2012) which has necessitated the search for alternate sources of cleaner energy (Ghosh et al, 2007; Ghosh, 2014). In the last few years, there has been intensive research on microalgae as it is an attractive feedstock for biofuel production (Chisti, 2007). Microalgae have been reported to have much higher primary productivity as compared to other terrestrial plants having biofuel potential (Mata et al, 2010). Processes for conversion of microalgal oil to biodiesel have already been developed (Mishra et al, 2012) and it is expected that once the microalgal cultivation technology is sufficiently optimized, adequate feedstock would be available from large scale cultivation for biofuel production. Lipid is extracted from microalgal biomass through suitable solvent and converted to biodiesel through trans-esterification process. A huge amount of de-oiled microalgal biomass remains left
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