Browsing by Author "Premaratne, M"

Now showing 1 - 6 of 6

item: Conference-Full-text
Assessment of the potential of co2 sequestration from cement flue gas using locally isolated microalgae
(IEEE, 2020-07) Wijayasekera, SCN; Cooray, BY; Premaratne, M; Ariyadasa, TU; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Carbon dioxide (CO2) emissions are rapidly escalating due to industrialization and urbanization worldwide, resulting in many long-term adverse effects such as global warming. Industrial flue gases which contain 3-30% CO2 (v/v) are a major constituent of global CO2 emissions. Employing microalgae for biological fixation of CO2 from flue gas is a prospective strategy for the reduction of CO2 emissions since microalgae have the capability of utilizing inorganic carbon to rapidly generate biomass via photosynthesis. In the current study, the locally isolated microalgal strains Chlorella sp. and Desmodesmus sp. were employed to assess the CO2 sequestration potential from simulated flue gas, comparable to the emissions from the cement industry. The gross calorific values (GCVs) were determined to evaluate the potential of employing microalgal biomass for co-firing processes. Desmodesmus sp. showed the highest CO2 tolerance, as it exhibited a biomass productivity and CO2 fixation rate of 1.17 g L-1 and 0.26 g L-1 day-1 respectively under undiluted flue gas (15.50% CO2). However, the GCVs of Chlorella sp. biomass were higher than Desmodesmus sp. biomass under all flue gas dilutions. Nonetheless, the GCVs of Desmodesmus sp. were in the range of 23.277-24.202 MJ/kg, comparable to biomass typically used in co-firing applications.
item: Article-Full-text
Cultivation of microalgae in palm oil mill effluent (POME) for astaxanthin production and simultaneous phycoremediation
(Elsevier, 2021) Fernando, JSR; Premaratne, M; Dinalankara, DMSD; Perera, GLNJ; Ariyadasa, TU
Haematococcus pluvialis and Chromochloris zofingiensis are freshwater microalgae exploited to produce the high-value carotenoid, astaxanthin. Nonetheless, a copious amount of freshwater is consumed for microalgae cultivation, thereby raising concerns regarding sustainable astaxanthin production. Characterization of palm oil mill effluent (POME) obtained from a commercial facility in southern Sri Lanka revealed high concentrations of total nitrogen (TN), total phosphorous (TP) and low concentrations of heavy metals, thus showcasing the potential of POME as an alternative growth media for astaxanthin production. Hence, H. pluvialis and C. zofingiensis were cultivated in 2.5%, 5.0% and 7.5% POME with the aim of producing astaxanthin, reducing freshwater consumption, and simultaneous phycoremediation. H. pluvialis exhibited better adaptability to higher POME concentrations, with its maximum astaxanthin yield (22.43 mg/L) achieved in 7.5% POME, whilst reducing specific freshwater consumption for astaxanthin production by 43%. However, only moderate performance in phycoremediation was achieved, with removal of 50.9% chemical oxygen demand (COD), 49.3% total nitrogen and 69.4% total phosphorous at rates of 3.95 mg/L/d, 0.50 mg/L/d and 0.11 mg/L/d respectively. The heavy metal content in biomass was within permissible limits. Characterization of astaxanthin-extracted residual biomass of H. pluvialis revealed possible applications as protein-rich animal feed or feedstock for biofuel production. Results indicated that POME generated in Sri Lankan palm oil mills has the potential to be utilized for large scale production of microalgal astaxanthin. Nevertheless, pilot-scale experiments, product toxicology evaluation and techno-economic feasibility studies are required prior to implementation of large-scale POME-integrated astaxanthin production facilities.
item: Article-Full-text
Cyanobacteria pigment production in wastewater treated for heavy metal removal
(Elsevier, 2023-11) Thevarajah, B; Nishshanka, GKSH; Premaratne, M; Wasath, WAJ; Nimarshana, PHV; Malik, A; Ariyadasa, TU
Cyanobacterial pigments have an evolving market demand as natural colorants with numerous health benefits and diversified applications. Nevertheless, scaling up cyanobacterial pigment production to meet the market demand is economically unsustainable due to the high upstream processing costs, notably associated with the supply of nutrients during cyanobacteria cultivation. Thus, utilization of wastewater as alternative nutrient sources for cultivation is a potential method to enhance the economic viability and sustainability of pigment production. In wastewater-integrated cyanobacteria cultivation, nutrients are assimilated to produce biomass simultaneous to bioremediation. Nonetheless, the toxic heavy metals present in wastewater may accumulate in cyanobacteria and adversely affect biomass valorization. Therefore, the use of suitable heavy metal removal techniques is essential prior to integration of wastewater with the upstream process of cyanobacterial pigment production in view of improving product safety. Accordingly, the current review discusses primary literature on pigment biosynthesis and heavy metal accumulation in cyanobacteria cultured in wastewater and details physicochemical, electrochemical, and biological treatment methods available for heavy metal removal from wastewater prior to cyanobacteria cultivation. The suitability of heavy metal removal methods is analyzed with respect to various technical and economic aspects, including selective heavy metal removal, minimizing nutrient loss, and incremental capital/operating costs. Moreover, future perspectives in the research domain are discussed, with emphasis on the requirement for techno-economic assessments, life cycle analysis, product safety assessment, and public perception. Thus, the current review comprehensively analyses strategies for heavy metal removal from wastewater prior to its integration with the upstream process of cyanobacterial pigment production.
item: Conference-Full-text
Investigation of the effect of solar irradiation and temperature on h. pluvialis production in photobioreactors under outdoor cultivation in Sri Lanka
(IEEE, 2021-07) Perera, M; Muthunayaka, K; Madushanka, D; Liyanaarachchi, VC; Premaratne, M; Ariyadasa, TU; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
The complicated and varying weather conditions and contamination from fungi, protozoa, and bacteria are major problems associated with outdoor microalgae cultivation. In this study, outdoor microalgae cultivation was investigated in a 3.2 L vertical tubular photobioreactor in Moratuwa, Sri Lanka. During December, when both the solar irradiation and temperature were high, the water spray system in combination with two agro shading nets (each with a shading rate of 40-50%) could effectively reduce the temperature to 2±2 0C and control solar irradiation below 13500 lux. Under an initial biomass density of 0.2875 g/L and an atmospheric air flow rate of 1 vvm, Haematococcus pluvialis showcased a maximum biomass accumulation of 0.45 g/L and the maximum productivity of 20 mg/L/day. In addition, the reactor system and its design exhibited good performance, implying a potential scale-up opportunity. However, operation under outdoor conditions showed slightly poorer performance due to the light inhibition effect.
item: Article-Full-text
Nitrogen-limited cultivation of locally isolated desmodesmus sp. For sequestration of CO2from simulated cement flue gas and generation of feedstock for biofuel production
(Elsevier, 2021) Premaratne, M; Liyanaarachchi, VC; Nishshanka, GKSH; Nimarshana, PHV; Ariyadasa, TU
Biological CO2 sequestration from flue gas using microalgae has emerged as a promising alternative to conventional carbon capture technologies, since it concurrently generates valuable biomass which can be utilized to produce biofuels. In the current study, the locally isolated microalga Desmodesmus sp. was utilized for sequestration of CO2 from gas mixtures simulating undiluted cement flue gas (1x), and cement flue gas diluted by two-fold (1/2x), four-fold (1/4x) and eight-fold (1/8x). The current study aimed to assess the feasibility of maintaining high CO2 sequestration rates in nitrogen-limited culture media while simultaneously producing biomass rich in target metabolites for biofuel production. Accordingly, Bold’s Basal Medium (BBM) and BBM with three times the standard nitrate concentration (3N-BBM) were employed as culture media for nitrogen limited and nitrogen replete experiments respectively. The highest CO2 fixation rates were demonstrated in undiluted flue gas containing 15.50% CO2. Moreover, the average CO2 fixation rate of Desmodesmus sp. over the 8-day cultivation period (0.21 ± 0.02 g/L/d) was not significantly reduced in nitrate limited media (BBM). Nitrate limited cultivation in undiluted flue gas enhanced the accumulation of carbohydrates in microalgae (32.44 ± 0.45% and 327.65 ± 23.39 mg/L), although the increment in lipid content was not as significant as expected (41.54 ± 1.13% and 419.57 ± 31.52 mg/L). Biodiesel properties of microalgal lipids were within the limits of the ASTM D6751–12 standard. Higher heating values of microalgae biomass were in the range of 21.97–23.17 MJ/kg. Nonetheless, pilot scale studies using actual flue gas are essential prior to microalgal biofuel production and simultaneous CO2 sequestration.
item: Conference-Full-text
Sustainable cultivation of haematococcus pluvialis for the production of natural astaxanthin
(IEEE, 2021-07) Nishshanka, SH; Liyanaarachchi, VC; Premaratne, M; Ariyadasa, TU; Nimarshana, V; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Haematococcus pluvialis is a microalga with the ability to accumulate high quantities of astaxanthin. However, the large freshwater footprint and the requirement of external nutrient supply are issues in its commercial-scale cultivation. In the present study, synthetic dairy wastewater was employed as an alternative culture media for H. pluvialis under varying light intensities to determine the best lighting conditions for biomass and astaxanthin accumulation. The highest biomass concentration ( 1.359±0.013 g/L ) and astaxanthin concentration ( 20.783±0.105 mg/L ) was achieved in the culture supplied with 3250 lux light intensity during the growth stage. Nevertheless, the highest specific growth rate ( 0.0625±0.000 /day) and cellular astaxanthin content (1.696±0.007%) were observed in the culture supplied with 4000 lux during the growth phase. It was also observed that the total lipid content of cultures did not vary significantly with light intensity. Moreover, it was observed that total lipid content of residual H. pluvialis decreased significantly after astaxanthin extraction. Nonetheless, H. pluvialis showcased considerable potential of nutrient removal efficiency, achieving over 90% reduction of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP). Thus, it could be speculated that cultivation of H. pluvialis under moderate light intensities could yield astaxanthin and lipid-rich biomass simultaneous to phycoremediation.