V.V. Tyagi

A novel method to harvest Chlorella sp. via low cost bioflocculant: Influence of temperature with kinetic and thermodynamic functions

In this study, harvesting efficiency (HE) of bioflocculant (egg shell) was observed with variation in flocculent concentrations (0-100mgL-1), temperature (30°C, 35°C 40°C, 45°C and 50°C) and variable contact time (0-50min). It was found maximum (≈95.6%) with 100mgL-1 bioflocculant concentration whereas influence of temperature was also observed with optimized concentration of bioflocculant (100mgL-1) at 40°C (≈98.1%) and 50°C (≈99.3%), in 30min of contact time. Significant changes in algal cell structures were also analyzed after exposure to various temperatures with microscopy, SEM (Scanning electron microscopy) and EDS (Energy dispersive X-ray spectroscopy) images with and without bioflocculant. The experimental data was found to be a good fit with pseudo-second order kinetic model. The thermodynamic functions such as ΔG (Gibbs free energy), ΔH (enthalpy), ΔS (entropy) were also determined. The negative value of ΔG and positive value of ΔH and ΔS shows the spontaneous and endothermic nature of flocculation process.

Microalgal cultivation for value-added products: a critical enviro-economical assessment

The present review focuses on the cultivation of algal biomass for generating value-added products (VAP) and to assess their economic benefits and harmful environmental impact. Additionally, the impact of bioreactor designs on the yield of microalgal biomass for VAP is also considered. All these factors are discussed in relation to the impact of microalgae production on the bio-economy sector of commercial biotechnology.

Microbial fuel cells: a sustainable solution for bioelectricity generation and wastewater treatment

ABSTRACT A microbial fuel cell (MFC) is an advance device to contend with three-dimensional problems of fossil fuel-based energy production with high-cost and pollution-generating units. It is an emerging technology of wastewater treatment with energy production. It has the potential to utilize wastewater as feed substrate for microorganisms and to generate bio-electricity. MFCs can also applied in carbon capture, bioremediation, biosensing, bio-hydrogen production and desalination. In this review, the major focus is on treatment of wastewater integrated with bio-electricity production by MFC. Information about various designs of MFC, electrode materials, important process parameters (pH, temperature, etc.) and the most recent integrated technology of MFC with natural water bodies (hybrid MFCs) is also reviewed. This technology holds promise for a clean and green environment, and its successful applications provide a new outlook for engineers and scientists.

Solar Photovoltaics (PV): A Sustainable Solution to Solve Energy Crisis

Although sun is the source of all forms of energy including the energy contained in fossil fuels, the term “solar energy” is meant the energy obtained directly from sun’s radiation. Solar photovoltaic (PV) is the most promising of all the active solar energy technologies. This technology is affordable and the source of this energy is inexhaustible. Moreover, it is the cleanest source of energy developed so far, thereby establishing it as a sustainable solution to solve energy crisis. This chapter presents a succinct picture of the solar PV technology along with classification and application areas. The status of the technology maturity and energy–exergy and economic aspects of PV technology has also been addressed.

Algae-Based Biohydrogen: Current Status of Bioprocess Routes, Economical Assessment, and Major Bottlenecks

This chapter reviews the bioprocess routes for algal-based biohydrogen production. Important factors such as pH, nutrients, light, immobilisation, substrates, inoculums, and reactors have been taken as prime objectives in this study. Highlights associated with economical stresses and major bottlenecks (in R&D and for commercialization) with biophotolysis (BP) and dark fermentation (DF) process routes are also reviewed with respect to the last 10 years of research-based data. The environmental benefits of biohydrogen economy in general are also reviewed very briefly to achieve a sustainable, economic, and viable evaluation of the bioprocesses. Hence, this study provides an overview of the better options available in algal-based biohydrogen production from lab scale to commercial scale.