Enhancement of CO2 biofixation and lipid production by Chlorella vulgaris using coloured polypropylene film

Chlorella vulgaris was cultivated with light at different wavelengths (λmax) and irradiation intensities (I) by applying a coloured tape (CT) as a simple, inexpensive light filter. C. vulgaris was cultivated in a standard medium using blue (CTB), green (CTG), red (CTR), yellow (CTY) and white (CTW) CT to filter the light, as well the unfiltered light (U). The influence of λmax and I on specific growth rate (μ), nutrient removal efficiency (% RE of total nitrogen, TN, and phosphorus, TP), CO2 fixation rate (RC) and lipid productivity (Plipid) were evaluated. The highest biomass concentration Xmax of 2.26 g L−1 was measured for CTW with corresponding μ, TN and TP RE, RC and Plipid values of 0.95 d−1, 92% and 100%, 0.67 g L−1 d−1 and 83.6 mg L−1 d−1, respectively. The normalised μ and Plipid for U were significantly lower than in CTW of 33–50% and 75%, respectively. The corresponding non-normalised parameter values for CTB were significantly lower at 0.45 d−1, 0.18 g L−1, 15% and 37%, 0.03 g L−1 d−1 and 1.2 mg L−1 d−1. Results suggest a significant impact of I and λmax, with up to a 50% increase in growth and nutrient RE from optimising these parameters

The cost benefit of algal technology for combined CO2 mitigation and nutrient abatement

The use of microalgae culture technology (MCT) for mitigating CO2 emissions from flue gases and nutrient discharges from wastewater whilst generating a biofuel product is considered with reference to the cost benefit offered. The review examines the most recent MCT literature (post 2010) focused on the algal biomass or biofuel production cost. The analysis reveals that, according to published studies, biofuel cost follows an approximate inverse relationship with algal or lipid productivity with a minimum production cost of $1 L−1 attained under representative conditions. A 35–86% cost reduction is reported across all studies from the combined harnessing of CO2 and nutrients from waste sources. This compares with 12–27% for obviating fertiliser procurement through using a wastewater nutrient source (or else recycling the liquor from the extracted algal biomass waste), and 19–39% for CO2 fixation from a flue gas feed. Notwithstanding the above, economic competitiveness with mineral fuels appears to be attainable only under circumstances which also feature: a) The inclusion of cost and environmental benefits from wastewater treatment (such as the energy and/or greenhouse gas emissions benefit from nutrient and CO2 discharge abatement), and/or a) Multiple installations over an extended geographic region where flue gas and wastewater sources are co-located

Impact of CO2 concentration and ambient conditions on microalgal growth and nutrient removal from wastewater by a photobioreactor

The increase in atmospheric CO2 concentration and the release of nutrients from wastewater treatment plants (WWTPs) are environmental issues linked to several impacts on ecosystems. Numerous technologies have been employed to resolves these issues, nonetheless, the cost and sustainability are still a concern. Recently, the use of microalgae appears as a cost-effective and sustainable solution because they can effectively uptake CO2 and nutrients resulting in biomass production that can be processed into valuable products. In this study single (Spirulina platensis (SP.PL) and mixed indigenous microalgae (MIMA) strains were employed, over a 20-month period, for simultaneous removal of CO2 from flue gases and nutrient from wastewater under ambient conditions of solar irradiation and temperature. The study was performed at a pilot scale photo-bioreactor and the effect of feed CO2 gas concentration in the range (2.5–20%) on microalgae growth and biomass production, carbon dioxide bio-fixation rate, and the removal of nutrients and organic matters from wastewater was assessed. The MIMA culture performed significantly better than the monoculture, especially with respect to growth and CO2 bio-fixation, during the mild season; against this, the performance was comparable during the hot season. Optimum performance was observed at 10% CO2 feed gas concentration, though MIMA was more temperature and CO2 concentration sensitive. MIMA also provided greater removal of COD and nutrients (~83% and >99%) than SP.PL under all conditions studied. The high biomass productivities and carbon bio-fixation rates (0.796–0.950 gdw·L−1·d−1 and 0.542–1.075 gC·L−1·d−1 contribute to the economic sustainability of microalgae as CO2 removal process. Consideration of operational energy revealed that there is a significant energy benefit from cooling to sustain the highest productivities on the basis of operating energy alone, particularly if the indigenous culture is used

A technoeconomic assessment of microalgal culture technology implementation for combined wastewater treatment and CO2 mitigation in the Arabian Gulf

A technoeconomic assessment (TEA) has been conducted of the feasibility of large-scale application of microalgal culture technology (MCT) to the combined mitigation of CO2 emissions from flue gases and nutrient discharges from wastewater in the Arabian Gulf. The assessment has incorporated the selection of the algal species and MCT technologies, the extent of nutrient removal, and the biomass/biofuel production rate. The cost benefit of the abatement of pollutants (in the form of CO2 and nutrient discharges) was included by assigning appropriate credits to these contributions. The overall economic viability was quantified as the break-even selling price (BESP) of the generated biocrude, taken to be the price at which the product must sell to cover the operating expenditure (OPEX). Based on available information and optimal operational conditions, the BESP was calculated as being $0.544 per kg biomass, equating to$0.9 L−1 for the extracted biocrude, the credited items contributing ˜14% of this figure. The BESP was found to be most sensitive to the algal growth rate μ, the BESP changing by ±24% in response to a ±20% change in μ. Whilst the terms of reference of the study are limited to OPEX contributors, the potential for sustainability associated with the innately reliably high levels of natural light in the Gulf region appear to provide auspicious circumstances for large-scale implementation of MCT. For emerging economies with a comparable climate but without a mineral oil-based economy a greater financial benefit from the proposed scheme would arise

Bioreactor for microalgal cultivation systems: strategy and development

Microalgae are important natural resources that can provide food, medicine, energy and various bioproducts for nutraceutical, cosmeceutical and aquaculture industries. Their production rates are superior compared to those of terrestrial crops. However, microalgae biomass production on a large scale is still a challenging problem in terms of economic and ecological viability. Microalgal cultivation system should be designed to maximize production with the least cost. Energy efficient approaches of using light, dynamic mixing to maximize use of carbon dioxide (CO2) and nutrients and selection of highly productive species are the main considerations in designing an efficient photobioreactor. In general, optimized culture conditions and biological responses are the two overarching attributes to be considered for photobioreactor design strategies. Thus, fundamental aspects of microalgae growth, such as availability of suitable light, CO2 and nutrients to each growing cell, suitable environmental parameters (including temperature and pH) and efficient removal of oxygen which otherwise would negatively impact the algal growth, should be integrated into the photobioreactor design and function. Innovations should be strategized to fully exploit the wastewaters, flue-gas, waves or solar energy to drive large outdoor microalgae cultivation systems. Cultured species should be carefully selected to match the most suitable growth parameters in different reactor systems. Factors that would decrease production such as photoinhibition, self-shading and phosphate flocculation should be nullified using appropriate technical approaches such as flashing light innovation, selective light spectrum, light-CO2 synergy and mixing dynamics. Use of predictive mathematical modelling and adoption of new technologies in novel photobioreactor design will not only increase the photosynthetic and growth rates but will also enhance the quality of microalgae composition. Optimizing the use of natural resources and industrial wastes that would otherwise harm the environment should be given emphasis in strategizing the photobioreactor mass production. To date, more research and innovation are needed since scalability and economics of microalgae cultivation using photobioreactors remain the challenges to be overcome for large-scale microalgae production

Modelling and Optimization of Combined Wastewater Treatment and CO2 Bio-fixation in a Batch Algal Photobioreactor

The research focuses on investigation and optimization (using Box Behnken design) of the key parameters of CO2 gas concentration, light intensity, temperature, feedwater nutrient concentration, and wastewater origin (municipal primary and secondary, and petroleum industry) on photobioreactor algal growth parameters. A mathematical model is provided for predicting algal growth. Finally, the influence of light wavelength on algal growth is investigated. The outcomes can be used to inform design and operation of large-scale algal cultivation systems

A bioassimilation and bioaccumulation model for the removal of heavy metals from wastewater using algae: New strategy

A mathematical model for bioassimilation (BS) combined with bioaccumulation (BC) has been conducted to determine the removal and recovery of heavy metals (HMs) from wastewater using green algae. Response Surface and Box Benken Methodology (BBM) combined with best-fit simulation were used to determine ultimate uptakes. Results revealed that the percentages of HM removal (% RE r) and recovery (%HMc) are correlated with algal growth under the studied conditions. The developed mathematical model accurately predicts the % RE and HMc based on BS and BC mechanisms. Although the biosorption process exhibited higher metals uptakes than BS, the latter had a better affinity for the removal of different metals. The combined BS and BC mechanisms achieved 73 % and 69 % of Cu2+ and Pb2+removals, respectively, with the BC process is 6 folded higher than BS. Comparable percentage removal ? 74 % was observed for Cd2+, with 99 % of the removal was based on BC. The %HMc from aqueous and solid phases out of the hydrothermal liquefaction (HTL) process was estimated at 56.5 %. Mathematical modeling of the combined BS with BC processes provides an efficient and robust tool for predicting and forecasting the performance of HMs removals and recovery via algae process.Scopu

The cost benefit of algal technology for combined CO2 mitigation and nutrient abatement

The use of microalgae culture technology (MCT) for mitigating CO2 emissions from flue gases and nutrient discharges from wastewater whilst generating a biofuel product is considered with reference to the cost benefit offered. The review examines the most recent MCT literature (post 2010) focused on the algal biomass or biofuel production cost. The analysis reveals that, according to published studies, biofuel cost follows an approximate inverse relationship with algal or lipid productivity with a minimum production cost of $1 L−1 attained under representative conditions. A 35–86% cost reduction is reported across all studies from the combined harnessing of CO2 and nutrients from waste sources. This compares with 12–27% for obviating fertiliser procurement through using a wastewater nutrient source (or else recycling the liquor from the extracted algal biomass waste), and 19–39% for CO2 fixation from a flue gas feed. Notwithstanding the above, economic competitiveness with mineral fuels appears to be attainable only under circumstances which also feature: a) The inclusion of cost and environmental benefits from wastewater treatment (such as the energy and/or greenhouse gas emissions benefit from nutrient and CO2 discharge abatement), and/or a) Multiple installations over an extended geographic region where flue gas and wastewater sources are co-located.Scopu

Enhancement of CO2 biofixation and lipid production by Chlorella vulgaris using coloured polypropylene film

Chlorella vulgaris was cultivated with light at different wavelengths (λmax) and irradiation intensities (I) by applying a coloured tape (CT) as a simple, inexpensive light filter. C. vulgaris was cultivated in a standard medium using blue (CTB), green (CTG), red (CTR), yellow (CTY) and white (CTW) CT to filter the light, as well the unfiltered light (U). The influence of λmax and I on specific growth rate (μ), nutrient removal efficiency (% RE of total nitrogen, TN, and phosphorus, TP), CO2 fixation rate (RC) and lipid productivity (Plipid) were evaluated. The highest biomass concentration Xmax of 2.26 g L−1 was measured for CTW with corresponding μ, TN and TP RE, RC and Plipid values of 0.95 d−1, 92% and 100%, 0.67 g L−1 d−1 and 83.6 mg L−1 d−1, respectively. The normalised μ and Plipid for U were significantly lower than in CTW of 33–50% and 75%, respectively. The corresponding non-normalised parameter values for CTB were significantly lower at 0.45 d−1, 0.18 g L−1, 15% and 37%, 0.03 g L−1 d−1 and 1.2 mg L−1 d−1. Results suggest a significant impact of I and λmax, with up to a 50% increase in growth and nutrient RE from optimising these parameters.This work was made possible by the support of a National Priorities Research Programme (NPRP) grant from the Qatar National Research Fund (QNRF), grant reference number NPRP 6-1436-2-581. The statements made herein are solely the responsibility of the authors.Scopu