Virendra Kumar Vijay

Phycoremediation coupled production of algal biomass, harvesting and anaerobic digestion: Possibilities and challenges

Biogas produced from anaerobic digestion is a versatile and environment friendly fuel which traditionally utilizes cattle dung as the substrate. In the recent years, owing to its high content of biodegradable compounds, algal biomass has emerged as a potential feedstock for biogas production. Moreover, the ability of algae to treat wastewater and fix CO2 from waste gas streams makes it an environmental friendly and economically feasible feedstock. The present review focuses on the possibility of utilizing wastewater as the nutrient and waste gases as the CO2 source for algal biomass production and subsequent biogas generation. Studies describing the various harvesting methods of algal biomass as well as its anaerobic digestion have been compiled and discussed. Studies targeting the most recent advancements on biogas enrichment by algae have been discussed. Apart from highlighting the various advantages of utilizing algal biomass for biogas production, limitations of the process such as cell wall resistivity towards digestion and inhibitions caused due to ammonia toxicity and the possible strategies for overcoming the same have been reviewed. The studies compiled in the present review indicate that if the challenges posed in translating the lab scale studies on phycoremediation and biogas production to pilot scale are overcome, algal biogas could become the sustainable and economically feasible source of renewable energy.

Phycoremediation and biogas potential of native algal isolates from soil and wastewater

The present study is a novel attempt to integrate phycoremediation and biogas production from algal biomass. Algal isolates, sp. 1 and sp. 2, obtained from wastewater and soil were evaluated for phycoremediation potential and mass production. The estimated yield was 58.4 sp. 1 and 54.75 sp. 2 tons ha(-1) y(-1). The algal isolates reduced COD by >70% and NH3-N by 100% in unsterile drain wastewater. Higher productivities of sp. 1 (1.05 g L(-1)) and sp. 2 (0.95 g L(-1)) grown in wastewater compared to that grown in nutrient media (0.89 g L(-1) for sp. 1 and 0.85 g L(-1) for sp. 2) indicate the potential of algal isolates in biogas production through low cost mass cultivation. Biogas yield of 0.401-0.487 m(3) kg(-1) VS added with 52-54.9% (v/v) methane content was obtained for algal isolates. These results indicate the possibilities of developing an integrated process for phycoremediation and biogas production using algal isolates.

Algae mediated treatment and bioenergy generation process for handling liquid and solid waste from dairy cattle farm

In the present work four algae were tested for their biomass production potential in neat livestock wastewater. Chroococcus sp.1 was found to be the best for biomass production under controlled (2.13 g L(-1)) and outdoor conditions (4.44 g L(-1)) with >80% of nutrients removal. The produced biomass was then digested with cattle dung as cosubstrate. Interestingly, up to 291.83 ± 3.904 mL CH4 g(-1) VS fed was produced during codigestion studies (C/N ≈ 13.0/1). In contrast to this, only 202.49 ± 11.19 and 141.70 ± 2.57 mL CH4 g(-1) VS fed was recorded with algae (C/N ≈ 9.26/1) and cattle dung (C/N ≈ 31.56/1) alone, respectively. The estimated renewable power generation potential of the investigated coupled process was around 333.79-576.57 kW h d(-1) for a dairy farm with 100 adult cattle. However, further scale-up and testing is needed to make this process a reality.

Studies on the Drying Characteristics of Zingiber Officinale Under Open Sun and Solar Biomass (Hybrid) Drying

Drying characteristics of Zingiber officinale (Ginger) under the open sun and direct type natural convection solar biomass (hybrid) drying were studied. It has been observed that under open sun drying conditions, the drying rate depends on the product thickness and climatic conditions. The results have been drawn for both the summer (April-May, 2004) and winter (November-January, 2003–04) months of Delhi, in India. In the hybrid drier, the ginger, with a thickness of 0.008 m, dried in 33 hours in comparison to 96 hours in open-sun drying. The overall drying efficiency of the hybrid drier was found to be 18% and 13% under summer and winter climatic conditions respectively. The loss of volatile oil content of the ginger is less in hybrid drier in comparison to open sun drying. It was found that the average drying air temperature of 60°C with average air velocity of 0.6m/sec was sufficient for the drying of ginger in the hybrid drier. Ginger quality after drying is better and drying time is less in the hybrid drier in comparison to open-sun drying. The hybrid drier is a simple device, which can be manufactured with locally available materials and can be used for drying of other spices, vegetables and fruits etc.

Enhanced methane production from algal biomass through short duration enzymatic pretreatment and codigestion with carbon rich waste

Anaerobic digestion of algal biomass faces problems of low digestibility due to cell wall resistance and inappropriate carbon to nitrogen ratio. In the present work a short duration method involving fungal crude enzyme based pretreatment of algal biomass was disclosed. The effect of fungal crude enzymes on algal biomass was assessed qualitatively through visual and microscopic observations and quantitatively through measuring algal biomass solubilization. Up to 50% biomass COD solubilization was observed within 150 min of pretreatment under optimal conditions. Subsequent anaerobic digestion of pretreated algal biomass showed production of 324.38 mL CH4 g−1 VSfed as compared to 254.73 mL CH4 g−1 VSfed from untreated algal biomass. Interestingly, methane yield increased up to 413.89 mL g−1 VSfed when pretreated algal biomass was codigested with cattle dung. On the other hand, sugarcane bagasse had a negative effect on algal biomass codigestion due to its poor digestibility. Overall, the present attempt showed promising results by improving methane yield from algal biomass though pretreatment and codigestion.

A method for simultaneous bioflocculation and pretreatment of algal biomass targeting improved methane production

A novel method for simultaneous bioflocculation and pretreatment of algae is revealed. The method includes bioflocculation of precultured algae (Chroococcus sp.) using a pellet forming filamentous fungus (Aspergillus lentulusFJ172995) resulting in nearly 100% harvesting within 6 h without addition of any nutrient or carbon source at the optimized fungal/algal (F/A) ratio of 1 : 3. The algal–fungal interactions require a metabolically active fungus with opposite charge. The bioflocculation process is replicable at the reactor scale under continuous aeration. A simple incubation of harvested algal–fungal pellets under controlled conditions was associated with significant cellulase production (>0.4 FPU mL−1 ) by the fungus leading to soluble sugar release (≈ 360 mg L−1) from algal cells. As a result, >54% enhancement in digestibility and a marked increase in methane production (up to 50%) from algal–fungal pellets during anaerobic digestion were noticed. The invented method is a unique process of its kind and has potential application in algae based biofuel production including biomethane, biohydrogen and biodiesel as well as in the extraction of other valuable compounds from microalgal biomass.

The Design, Development and Performance Evaluation of Thermoelectric Generator(TEG) Integrated Forced Draft Biomass Cookstove

Abstract The new developments in cookstove design have been made for better usage of sustainable energy and reducing the worse impact of climate change on environment. A cookstove is a combustion device which liberates lot of heat energy during cooking. In the recent developed design of TEG integrated forced draft biomasscookstove, the liberated waste heat energy is utilized for generation of electricity with the help of a thermoelectric generator. A power of 5W is achievedthrough the thermoelectric generator. The generated electricity is stored in a Li-ion battery and used further for running a 12Vd.c. fan, lighting a LED light, and charging a mobile phone. The novelty in charging a Li-ion battery is to run a fan for domestic biomass cookstovefor cleaner combustion. The fan is also used for cooling one side of TEG through heat sink for improving electrical performance of TEG and thus improving the combustion of the cookstove. This cookstove has been deployed in the rural areas to check its usability, viability, electrical and thermal performance under the umbrella of clean combustion.

Anaerobic technology harnessed fully by using different techniques: Review

In todays energy demanding life style, there is need for new sources of energy which are renewable as well as eco-friendly because the climate change is one of the biggest challenges for mankind. Many countries initiated production and distribution of several renewable energy technologies to solve the energy problem in rural areas. In India, the per capita energy consumption is 400 KWH per annum, while 350 kgoe per capita primary commercial energy consumption and about 80% of total rural energy consumption comes from non-commercial energy like firewood, agricultural waste, dry cow dung cakes. Among several technologies the anaerobic digestion technology, has been proved to be viable and emerged as a promising technology because biomass is available as domestic resources in India (biomass availability in India is of 150 million MT per annum), require less capital investment and per unit production cost as compare to other renewable energies. The another major issue is to reduce the emission of greenhouse gasses and this could be solved by anaerobic digestion technology (1 kg biomethane is equivalent to the reduction of 25 kg CO2) with various advantages like; replace the fossil fuels, reduce or eliminate the energy footprint of waste treatment plants, reduce methane emission from landfills, replace the industrially produced chemical fertilizers etc. Recent life cycle assessment studies have demonstrated that biogas derived methane (biomethane) is one of the most energy efficient and environmentally sustainable way of replacement of fossil fuels in both heat and power generation. In anaerobic digestion other than its merits, certain constraints are also associated with it. Most common among these are the low gas production in winter, low gas production from agricultural residues, large hydraulic retention time and digester design etc. Therefore, need of different techniques to remove its various limitations to achieve optimized gas production and helpful for rural areas. This paper reviews the various techniques, which could be used to solve the constraints occur during the gas production and harnessed fully anaerobic technology.

Characterization of leaf waste based biochar for cost effective hydrogen sulphide removal from biogas

Installation of decentralized units for biogas production along with indigenous upgradation systems can be an effective approach to meet growing energy demands of the rural population. Therefore, readily available leaf waste was used to prepare biochar at different temperatures and employed for H2S removal from biogas produced via anaerobic digestion plant. It is found that biochar prepared via carbonization of leaf waste at 400 °C effectively removes 84.2% H2S (from 1254 ppm to 201 ppm) from raw biogas for 25 min in a continuous adsorption tower. Subsequently, leaf waste biochar compositional, textural and morphological properties before and after H2S adsorption have been analyzed using proximate analysis, CHNS, BET surface area, FTIR, XRD, and SEM-EDX. It is found that BET surface area, pore size, and textural properties of leaf waste biochar plays a crucial role in H2S removal from the biogas.

Design and testing of thermoelectric generator embedded clean forced draft biomass cookstove

This paper signifies a method of development of a forced draft biomass cook stove for off-grid rural areas where the technology of thermoelectric generator has been implemented for electricity generation. The thermoelectric generator is a semiconductor device that converts heat energy directly to electrical energy. The thermoelectric generator is positioned on outer wall of the cook stoves combustion chamber. The biomass, that is burnt inside the combustion chamber heats one side of the thermoelectric generator. The temperature difference between the two sides of the thermoelectric generator causes for electricity generation. The electricity generated from the thermoelectric generator is used to run a DC fan. The excess energy generated from the thermoelectric generator is stored in a rechargeable battery. The energy from the battery is used for multipurpose applications like lighting a LED lamp, charging a mobile phone battery and kick starting of the fan when the temperature of the flame is low during ignition period. The main purpose of the DC fan is to supply air inside the combustion chamber to increase fuel-to-air ratio and to achieve a cleaner fuel burning by reducing harmful emissions. The fan also cools one side of the thermoelectric generator to produce greater temperature difference. The temperature difference between the two sides of the thermoelectric generator is directly proportional to electricity generated. The performances of the 25 stove were evaluated on the basis of feedback from the stove users.