K. C. Das

Microalgae cultivation in a wastewater dominated by carpet mill effluents for biofuel applications

Industrial and municipal wastewaters are potential resources for production of microalgae biofuels. Dalton - the Carpet Capital of the World generates 100-115 million L of wastewater d(-1). A study was conducted using a wastewater containing 85-90% carpet industry effluents with 10-15% municipal sewage, to evaluate the feasibility of algal biomass and biodiesel production. Native algal strains were isolated from carpet wastewater. Preliminary growth studies indicated both fresh water and marine algae showed good growth in wastewaters. A consortium of 15 native algal isolates showed >96% nutrient removal in treated wastewater. Biomass production potential and lipid content of this consortium cultivated in treated wastewater were approximately 9.2-17.8 tons ha(-1) year(-1) and 6.82%, respectively. About 63.9% of algal oil obtained from the consortium could be converted into biodiesel. However further studies on anaerobic digestion and thermochemical liquefaction are required to make this consortium approach economically viable for producing algae biofuels.

Effect of low-temperature pyrolysis conditions on biochar for agricultural use.

The removal of crop residues for bio-energy production reduces the formation of soil organic carbon (SOC) and therefore can have negative impacts on soil fertility. Pyrolysis (thermoconversion of biomass under anaerobic conditions) generates liquid or gaseous fuels and a char (biochar) recalcitrant against decomposition. Biochar can be used to increase SOC and cycle nutrients back into agricultural fields. In this case, crop residues can be used as a potential energy source as well as to sequester carbon (C) and improve soil quality. To evaluate the agronomic potential of biochar, we analyzed biochar produced from poultry litter, peanut hulls, and pine chips produced at 400°C and 500°C with or without steam activation. The C content of the biochar ranged from 40% in the poultry litter (PL) biochar to 78% in the pine chip (PC) biochar. The total and Mehlich I extractable nutrient concentrations in the biochar were strongly influenced by feedstock. Feedstock nutrients (P, K, Ca, Mg) were concentrated in the biochar and were significantly higher in the biochars produced at 500°C. A large proportion of N was conserved in the biochar, ranging from 27.4% in the PL biochar to 89.6% in the PC biochar. The amount of N conserved was inversely proportional to the feedstock N concentration. The cation exchange capacity was significantly higher in biochar produced at lower temperature. The results indicate that, depending on feedstock, some biochars have potential to serve as nutrient sources as well as sequester C.

The influence of temperature and moisture contents regimes on the aerobic microbial activity of a biosolids composting blend

To understand the relationships between temperature, moisture content, and microbial activity during the composting of biosolids (municipal wastewater treatment sludge), well-controlled incubation experiments were conducted using a 2-factor factorial design with six temperatures (22, 29, 36, 43, 50, and 57 degrees C) and five moisture contents (30, 40, 50, 60, and 70%). The microbial activity was measured as O2 uptake rate (mg g(-1) h(-1)) using a computer controlled respirometer. In this study, moisture content proved to be a dominant factor impacting aerobic microbial activity of the composting blend. Fifty percent moisture content appeared to be the minimal requirement for obtaining activities greater than 1.0 mg g(-1) h(-1). Temperature was also documented to be an important factor for biosolids composting. However, its effect was less influential than moisture content. Particularly, the enhancement of composting activities induced by temperature increment could be realized by increasing moisture content alone.

Effects of stocking density and feeding rate on vermicomposting of biosolids

Abstract The double-pronged problem of quantity, and disposal of waste streams from a myriad of industries, is becoming increasingly acute, the world over. The use of earthworms as a waste treatment technique for such wastes is gaining popularity. This method is commonly known as vermicomposting. Compared to conventional microbial composting, vermicomposting produces a product that is more or less homogenous, with desirable aesthetics, with reduced levels of contaminants and tends to hold more nutrients over a longer period, without impacting the environment. Like in other related waste treatment techniques, certain parameters need to be established for the design of efficient and economical vermicomposting systems. Specifically, the focus of this study was to investigate and establish an optimal stocking density and an optimal feeding rate for the vermicomposting of biosolids, with paper mulch provided as bedding. A stocking density of 1.60 kg-worms/m 2 (0.33 lb-worms/ft 2 ) and a feeding rate of 1.25 kg-feed/kg-worm/day resulted in the highest bioconversion of the substrate into earthworm biomass. The best vermicompost was obtained at the same stocking density and a feeding rate of 0.75 kg-feed/kg-worm/day.

Effect of operating conditions of thermochemical liquefaction on biocrude production from Spirulina platensis

This study investigated the optimum thermochemical liquefaction (TCL) operating conditions for producing biocrude from Spirulina platensis. TCL experiments were performed at various temperatures (200-380°C), holding times (0-120 min), and solids concentrations (10-50%). TCL conversion at 350°C, 60 min holding time and 20% solids concentration produced the highest biocrude yield of 39.9% representing 98.3% carbon conversion efficiency. Light fraction biocrude (B(1)) appeared at 300°C or higher temperatures and represented 50-63% of the total biocrude. Biocrude obtained at 350-380°C had similar fuel properties to that of petroleum crude with energy density of 34.7-39.9 MJ kg(-1) compared to 42.9 MJ kg(-1) for petroleum crude. Biocrude from conversion at 300°C or above had 71-77% elemental carbon, and 0.6-11.6% elemental oxygen and viscosities in the range 40-68 cP. GC/MS of biocrude reported higher hydrocarbons (C(16)-C(17)), phenolics, carboxylic acids, esters, aldehydes, amines, and amides.

Evaluation of microalgae cultivation using recovered aqueous co-product from thermochemical liquefaction of algal biomass

This study characterized the ACP stream from the TCL of Spirulina and evaluated its potential as a nutrient source for cultivation of microalgae. TCL of 100 g of dry Spirulina resulted in 40% BioOil and 429.80% ACP. The ACP was found to have high nitrogen (16,200 mg L(-1)), phosphorus (795 mg L(-1)), potassium (11,260 mg L(-1)) and secondary and micronutrients. Growth media were prepared using ACP as sole nutrient source in deionized water at 0.2%, 0.33%, 1%, and 10% v/v concentration and compared with a standard growth medium (BG 11) for algal cultivation. Chlorella minutissima was grown in these media for 12 days and monitored for biomass concentration, total chlorophyll and lipids. Biomass productivities with the ACP added media at 0.2% and 0.1% concentration were 0.035 and 0.027 g L(-1) d(-1), respectively, compared to 0.07 g L(-1) d(-1) in BG 11.

Biomass Production Potential of a Wastewater Alga Chlorella vulgaris ARC 1 under Elevated Levels of CO2 and Temperature

The growth response of Chlorella vulgaris was studied under varying concentrations of carbon dioxide (ranging from 0.036 to 20%) and temperature (30, 40 and 50°C). The highest chlorophyll concentration (11 μg mL–1) and biomass (210 μg mL–1), which were 60 and 20 times more than that of C. vulgaris at ambient CO2 (0.036%), were recorded at 6% CO2 level. At 16% CO2 level, the concentrations of chlorophyll and biomass values were comparable to those at ambient CO2 but further increases in the CO2 level decreased both of them. Results showed that the optimum temperature for biomass production was 30°C under elevated CO2 (6%). Although increases in temperature above 30°C resulted in concomitant decrease in growth response, their adverse effects were significantly subdued at elevated CO2. There were also differential responses of the alga, assessed in terms of NaH14CO3 uptake and carbonic anhydrase activity, to increases in temperature at elevated CO2. The results indicated that Chlorella vulgaris grew better at elevated CO2 level at 30°C, albeit with lesser efficiencies at higher temperatures.

Biochars impact on soil moisture storage in an Ultisol and two Aridisols

Abstract Biochar additions to soils can improve soil-water storage capability; however, there is sparse information identifying feedstocks and pyrolysis conditions that maximize this improvement. Nine biochars were pyrolyzed from five feedstocks at two temperatures, and their physical and chemical properties were characterized. Biochars were mixed at 2% wt wt−1 into a Norfolk loamy sand (Fine-loamy, kaolinitic, thermic Typic Kandiudult), a Declo silt loam (Coarse-loamy, mixed, superactive, mesic xeric Haplocalcid), or a Warden silt loam (Coarse-silty, mixed, superactive, mesic xeric Haplocambid). Untreated soils served as controls. Soils were laboratory incubated in pots for 127 days and were leached about every 30 days with deionized water. Soil bulk densities were measured before each leaching event. For 6 days thereafter, pot-holding capacities (PHC) for water were determined gravimetrically and were used as a surrogate for soil-moisture contents. Water tension curves were also measured on the biochar-treated and untreated Norfolk soil. Biochar surface area, surface tension, ash, C, and Si contents, in general, increased when produced under higher pyrolytic temperatures (≥500°C). Both switchgrass biochars caused the most significant water PHC improvements in the Norfolk, Declo, and Warden soils compared with the controls. Norfolk soil-water tension results at 5 and 60 kPa corroborated that biochar from switchgrass caused the most significant moisture storage improvements. Significant correlation occurred between the PHC for water with soil bulk densities. In general, biochar amendments enhanced the moisture storage capacity of Ultisols and Aridisols, but the effect varied with feedstock selection and pyrolysis temperature.

Biomass and bioenergy production potential of microalgae consortium in open and closed bioreactors using untreated carpet industry effluent as growth medium.

Improved wastewater management with beneficial utilization will result in enhanced sustainability and enormous cost savings in industries. Algae cultivation systems viz. raceway ponds, vertical tank reactors (VTR) and polybags were evaluated for mass production of algal consortium using carpet industry (CI) untreated wastewater. Overall areal biomass productivity of polybags (21.1 g m(-2)d(-1)) was the best followed by VTR (8.1 g m(-2)d(-1)) and raceways (5.9 g m(-2)d(-1)). An estimated biomass productivity of 51 and 77 tons ha(-1)year(-1) can be achieved using 20 and 30 L capacity polybags, respectively with triple row arrangement. Biomass obtained from algal consortium was rich in proteins (approximately 53.8%) and low in carbohydrates (approximately 15.7%) and lipids (approximately 5.3%). Consortium cultivated in polybags has the potential to produce 12,128 m(3) of biomethane ha(-1)year(-1). To be economically viable, the capital expenditure for polybag reactors needs to be reduced to

An efficient system for carbonation of high-rate algae pond water to enhance CO2 mass transfer

10 m(-2) for bioenergy/biofuel production.