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2.
Environ Sci Pollut Res Int ; 31(12): 17760-17777, 2024 Mar.
Article in English | MEDLINE | ID: mdl-37648915

ABSTRACT

The share of solar energy in the energy mix has become a major concern, and the global effort is to increase its contribution. Photovoltaic technology is an environment-friendly way of electricity production compared to fossil fuels. Currently, third generation of solar cells with a maximum average conversion efficiency of 20% has been achieved. Asia is an emerging market for photovoltaic technology, and it has recorded the highest installation capacity for 2018 (280 MW), 2030 (1860 MW), and 2050 (4837 MW). Meanwhile, Asia is estimated to be the highest producer of PV waste by 2040, with 5,580,000 metric tons of waste volume. Solid waste management is already a big environmental issue in South Asian countries, and untested landfilling of solar cells can further increase the burden. This review emphasizes the end-of-life scenario of solar cells in developing South Asian countries. Solar cell waste is hazardous e-waste that can lead to environmental and health impacts if not managed properly. It consists of metals with market value, which can be waste or gold, depending on its management. The study finds that recycling is the economically and environmentally effective waste management option for solar cells in South Asia. This paper reviews the deficiencies in the existing solar cell waste management framework in South Asian countries. Moreover, practical implications are presented for designing an effective waste management plan for solar cells in South Asian countries. Strong legislation, sufficient recycling infrastructure, and high stakeholders' interests are required to resolve this environmental concern.


Subject(s)
Waste Management , Recycling , Asia , India , Solid Waste , Asia, Southern
3.
Bioresour Technol ; 219: 228-238, 2016 Nov.
Article in English | MEDLINE | ID: mdl-27494104

ABSTRACT

The technical feasibility of long term anaerobic mono-digestion of two brown seaweeds, and co-digestion of both seaweeds with dairy slurry was investigated whilst increasing the organic loading rate (OLR). One seaweed was natural (L. digitata); the second seaweed (S. Latissima) was cultivated. Higher proportions of L. digitata in co-digestion (66.6%) allowed the digester to operate more efficiently (OLR of 5kgVSm(-3)d(-1) achieving a specific methane yield (SMY) of 232LCH4kg(-1)VS) as compared to lower proportions (33.3%). Co-digestion of 66.6% cultivated S. latissima, with dairy slurry allowed a higher SMY of 252LCH4kg(-1)VS but at a lower OLR of 4kgVSm(-3)d(-1). Optimum conditions for mono-digestion of both seaweeds were effected at 4kgVSm(-3)d(-1). Chloride concentrations increased to high levels in the digestion of both seaweeds but were not detrimental to operation.


Subject(s)
Biofuels , Bioreactors , Seaweed , Waste Management/methods , Dairying , Industrial Waste , Methane/biosynthesis
4.
Bioresour Technol ; 216: 219-26, 2016 Sep.
Article in English | MEDLINE | ID: mdl-27240238

ABSTRACT

Ascophyllum nodosum, an abundant Irish brown seaweed, shows significant seasonal variation in chemical composition and biogas production. The polyphenol content is shown to be a more important factor in biogas production than ash content. High polyphenol content in summer months adversely affected biogas production; suggesting two potential harvest dates, March and October. A. nodosum harvested in October showed a relatively low level of polyphenols (2% of TS) and ash (23% of volatile solids), and exhibited a specific methane yield of 215LCH4kgVS(-1), which was 44% of theoretical yield. The highest yield per wet weight of 47m(3)CH4t(-1) was achieved in October, which is 2.9 times higher than the lowest value (16m(3)CH4t(-1)), obtained in December. The gross energy yield of A. nodosum based on the optimal biogas production can achieve 116GJha(-1)yr(-1) in October.


Subject(s)
Ascophyllum/chemistry , Ascophyllum/metabolism , Biofuels , Methane/metabolism , Ireland , Polyphenols/analysis , Polyphenols/metabolism , Seasons , Seaweed/chemistry , Seaweed/metabolism
5.
Bioresour Technol ; 209: 213-9, 2016 Jun.
Article in English | MEDLINE | ID: mdl-26970924

ABSTRACT

Biomethane produced from seaweed may be used as a transport biofuel. Seasonal variation will have an effect on this industry. Laminaria digitata, a typical Irish brown seaweed species, shows significant seasonal variation both in proximate, ultimate and biochemical composition. The characteristics in August were optimal with the lowest level of ash (20% of volatile solids), a C:N ratio of 32 and the highest specific methane yield measured at 327LCH4kgVS(-1), which was 72% of theoretical yield. The highest yield per mass collected of 53m(3)CH4t(-1) was achieved in August, which is 4.5 times higher than the lowest value, obtained in December. A seaweed cultivation area of 11,800ha would be required to satisfy the 2020 target for advanced biofuels in Ireland, of 1.25% renewable energy supply in transport (RES-T) based on the optimal gross energy yield obtained in August (200GJha(-1)yr(-1)).


Subject(s)
Biofuels , Laminaria/metabolism , Methane/biosynthesis , Seasons , Seaweed/metabolism , Carbon/analysis , Carbon/metabolism , Conservation of Energy Resources , Ireland , Laminaria/chemistry , Nitrogen/analysis , Nitrogen/metabolism , Seaweed/chemistry
6.
Bioresour Technol ; 205: 118-25, 2016 Apr.
Article in English | MEDLINE | ID: mdl-26820925

ABSTRACT

Algae may be fermented to produce hydrogen. However micro-algae (such as Arthrospira platensis) are rich in proteins and have a low carbon/nitrogen (C/N) ratio, which is not ideal for hydrogen fermentation. Co-fermentation with macro-algae (such as Laminaria digitata), which are rich in carbohydrates with a high (C/N) ratio, improves the performance of hydrogen production. Algal biomass, pre-treated with 2.5% dilute H2SO4 at 135°C for 15min, effected a total yield of carbohydrate monomers (CMs) of 0.268g/g volatile solids (VS). The CMs were dominating by glucose and mannitol and most (ca. 95%) were consumed by anaerobic fermentative micro-organisms during subsequent fermentation. An optimal specific hydrogen yield (SHY) of 85.0mL/g VS was obtained at an algal C/N ratio of 26.2 and an algal concentration of 20g VS/L. The overall energy conversion efficiency increased from 31.3% to 54.5% with decreasing algal concentration from 40 to 5 VS g/L.


Subject(s)
Cyanobacteria/metabolism , Ethanol/metabolism , Fatty Acids, Volatile/biosynthesis , Hydrogen/metabolism , Laminaria/metabolism , Biofuels , Biomass , Carbohydrates/chemistry , Carbon/metabolism , Fatty Acids, Volatile/metabolism , Fermentation , Glucose/metabolism , Mannitol/metabolism , Microalgae/metabolism , Nitrogen/metabolism , Seaweed/metabolism
7.
Bioresour Technol ; 193: 488-97, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26163759

ABSTRACT

Fermentative hydrogen from seaweed is a potential biofuel of the future. Mannitol, which is a typical carbohydrate component of seaweed, was used as a substrate for hydrogen fermentation. The theoretical specific hydrogen yield (SHY) of mannitol was calculated as 5 mol H2/mol mannitol (615.4 mL H2/g mannitol) for acetic acid pathway, 3 mol H2/mol mannitol (369.2 mL H2/g mannitol) for butyric acid pathway and 1 mol H2/mol mannitol (123.1 mL H2/g mannitol) for lactic acid and ethanol pathways. An optimal SHY of 1.82 mol H2/mol mannitol (224.2 mL H2/g mannitol) was obtained by heat pre-treated anaerobic digestion sludge under an initial pH of 8.0, NH4Cl concentration of 25 mM, NaCl concentration of 50mM and mannitol concentration of 10 g/L. The overall energy conversion efficiency achieved was 96.1%. The energy was contained in the end products, hydrogen (17.2%), butyric acid (38.3%) and ethanol (34.2%).


Subject(s)
Ethanol/metabolism , Fatty Acids, Volatile/biosynthesis , Hydrogen/metabolism , Mannitol/metabolism , Seaweed/chemistry , Ammonia/analysis , Biofuels/analysis , Fermentation/drug effects , Hydrogen-Ion Concentration , Mannitol/pharmacology , Metabolic Networks and Pathways/drug effects , Nitrogen/analysis , Sodium/pharmacology , Solubility , Waste Disposal, Fluid
8.
Bioinformation ; 9(14): 725-9, 2013.
Article in English | MEDLINE | ID: mdl-23976829

ABSTRACT

Bacillus thuringiensis is an insecticidal bacterium whose chitinolytic system has been exploited to improve insect resistance in crops. In the present study, we studied the CBP24 from B. thuringiensis using homology modeling and molecular docking. The primary and secondary structure analyses showed CBP24 is a positively charged protein and contains single domain that belongs to family CBM33. The 3D model after refinement was used to explore the chitin binding characteristics of CBP24 using AUTODOCK. The docking analyses have shown that the surface exposed hydrophilic amino acid residues Thr-103, Lys-112 and Ser-162 interact with substrate through H-bonding. While, the amino acids resides Glu-39, Tyr-46, Ser-104 and Asn-109 were shown to have polar interactions with the substrate. The binding energy values evaluation of docking depicts a stable intermolecular conformation of the docked complex. The functional characterization of the CBP24 will elucidate the substrate-interaction pathway of the protein in specific and the carbohydrate binding proteins in general leading towards the exploration and exploitation of the prokaryotic substrate utilization pathways.

9.
Enzyme Microb Technol ; 52(2): 105-10, 2013 Feb 05.
Article in English | MEDLINE | ID: mdl-23273279

ABSTRACT

Integrated storage and pre-treatment (ISP) combines biopreservation of moist material under airtight conditions and pre-treatment. Moist wheat straw was inoculated with the biocontrol yeast Wickerhamomyces anomalus, the xylan degrading yeast Scheffersomyces stipitis or a co-culture of both. The samples and non-inoculated controls were stored at 4 or 15 °C. The non-inoculated controls were heavily contaminated with moulds, in contrast to the samples inoculated with W. anomalus or S. stipitis. These two yeasts were able to grow on wheat straw as sole source of nutrients. When ethanol was produced from moist wheat straw stored for four weeks at 4 °C with S. stipitis, an up to 40% enhanced yield (final yield 0.15 g ethanol per g straw dry weight) was obtained compared to a dry sample (0.107 g/g). In all other moist samples, stored for four weeks at 4 °C or 15 °C, 6-35% higher yields were obtained. Thus, energy efficient bio-preservation can improve the pre-treatment efficiency for lignocellulose biomass, which is a critical bottleneck in its conversion to biofuels.


Subject(s)
Biofuels , Debaryomyces/metabolism , Ethanol/metabolism , Pichia/metabolism , Plant Stems/metabolism , Preservation, Biological/methods , Triticum/metabolism , Biomass , Coculture Techniques , Fermentation , Fungal Proteins/metabolism , Hot Temperature , Humidity , Lignin/metabolism , Plant Stems/drug effects , Plant Stems/microbiology , Saccharomyces cerevisiae/metabolism , Sulfuric Acids/pharmacology , Temperature , Triticum/drug effects , Triticum/microbiology
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