Life cycle analysis of milking of microalgae for renewable hydrocarbon production

Botryococcus braunii is a unique microalga which can repeatedly produce the hydrocarbons after their non-destructive extraction - the process called milking. Botryococcus braunii hydrocarbons can be converted to high-quality fuel or used as other high-value products. In this study, we conduct the life cycle analysis of the milking process for renewable hydrocarbon production focusing on the GHG emissions, the fossil energy consumption, the freshwater consumption and the land use of the process. The total-CO2 emissions and the GHG emissions over 100-year time span for production of B. braunii hydrocarbons were estimated to be -0.39 kg CO2-eq/kg hydrocarbons and -0.90 kg CO2-eq/kg hydrocarbons, respectively. The fossil energy ratio of the process was found to be 1.04 MJ produced/MJ fossil energy consumed. The fresh water consumption of the process and the land use were estimated to be 1802 kg/kg hydrocarbons and 0.85m2/kg of hydrocarbons, respectively

Growth of microalgae on undiluted anaerobic digestate of piggery effluent with high ammonium concentrations

Anaerobic digestate of piggery effluent (ADPE) is extremely high in ammonia toxic to many microorganisms. Bioprospecting and nutrient enrichment of several freshwater and wastewater samples combined and further acclimation resulted in a mixed culture containing at least three microalgae species capable of growing on undiluted ADPE. Outdoor growth of the mixed culture using raceway ponds showed potential for up to 63.7 ± 12.1 mg N-NH4 + L −1 d −1 ammonium removal from the ADPE. The microalgal consortium was dominated by Chlorella sp. and was stable at between 800 and 1600 mg N-NH4 + L −1. Regulation of CO2 addition to the ponds to maintain a pH of 8 increased chlorophyll content of the microalgal consortium. Average microalgal biomass productivity of 800 mg N-NH4 + L −1 culture conditions during five weeks semicontinuous growth was 18.5 mg ash-free dry weight L −1 d −1. Doubling the ammonium concentration from 800 to 1600 mg N-NH4 + L −1 resulted in a 21% reduction of productivity, however the culture grown at 1600 mg N-NH4 + L −1 with the addition of CO2 by keeping pH at pH = 8 led to a 17% increase in biomass productivity

Life cycle analysis of milking of microalgae for renewable hydrocarbon production

Botryococcus braunii is a unique microalga which can repeatedly produce the hydrocarbons after their non-destructive extraction - the process called milking. Botryococcus braunii hydrocarbons can be converted to high-quality fuel or used as other high-value products. In this study, we conduct the life cycle analysis of the milking process for renewable hydrocarbon production focusing on the GHG emissions, the fossil energy consumption, the freshwater consumption and the land use of the process. The total-CO2 emissions and the GHG emissions over 100-year time span for production of B. braunii hydrocarbons were estimated to be -0.39 kg CO2-eq/kg hydrocarbons and -0.90 kg CO2-eq/kg hydrocarbons, respectively. The fossil energy ratio of the process was found to be 1.04 MJ produced/MJ fossil energy consumed. The fresh water consumption of the process and the land use were estimated to be 1802 kg/kg hydrocarbons and 0.85m2/kg of hydrocarbons, respectively

The role of turbulent coherent structures on microalgal mixing for nutrient removal in jet and paddlewheel raceway ponds

Outdoor studies were conducted on microalgae cultures in two raceway ponds (kept in constant motion with either jet or paddlewheel) with a flatbed to treat anaerobic digestion piggery effluent and to observe the characteristics of turbulence on microalgal mixing and growth. Acoustic Doppler Velocimeters (ADV) were deployed to record the instantaneous velocity components and acoustic backscatter as a substitution of microalgae concentration. The present research on microalgal mixing considers the effect of event-based turbulent features such as the widely known ‘turbulent bursting’ phenomenon. This is an important aspect, as turbulent coherent structures can result in microalgal mixing, which can lead to significant changes in microalgal growth. The experimental results presented in this paper of two contrasting environments of jet- and paddlewheel-driven ponds suggested that: (1) turbulent bursting events significantly contributed to microalgal mixing when paddlewheels and jets were used; (2) among four type of turbulent bursting events, ejections and sweeps contributed more to the total microalgal mixing; and, (3) a correlation was revealed using wavelet transform between the momentum and microalgal mixing flux when either jet or paddlewheel were used. Such similarities in jet and paddlewheel raceway ponds highlight the need to introduce turbulent coherent structures as an essential parameter for microalgal mixing studies

Developing food waste biorefinery: Using optimized inclined thin layer pond to overcome constraints of microalgal biomass production on food waste digestate

Diversion of food waste from landfill through anaerobic digestion is a sustainable form of energy production (biogas) and the waste effluent (digestate) can be utilised as nutrient supply for microalgae cultivation. However, digestate has very high nutrient concentrations and is highly turbid, making it difficult to utilize as a nutrient source with conventional microalgae cultivation systems. Here we compared the efficiencies of a conventional open raceway pond (ORWP) and an improved inclined thin layer photobioreactor (ITLP) for the utilization and treatment of food waste derived digestate by Chlorella sp. The ITLP improved on volumetric and areal productivities by 17 and 3 times over the ORWP, with values of 0.563 and 31.916 g m −2 day −1 respectively. Areal nutrient removal via microalgae biomass were 2359.759 ± 64.75 and 260.815 ± 7.16 mg m −2 day −1 for nitrogen and phosphorous respectively in the ITLP, which are 2.8 times higher than obtained in the ORWP. The ITLP’s superiority stems from its ability to support a much higher average biomass yield of 6.807 g L −1, which was 7 times higher than in the ORWP. Mean irradiance in-situ was higher in the ITLP, irradiance distribution and utilization by the culture in the ITLP was 44% more efficient than in the ORWP. Our results indicate that the ITLP is a far more productive system than conventional raceway ponds. This demonstrates that integration of ITLP microalgae cultivation using digestate has the potential to make digestate management yield net benefit in food waste biorefinery settings

Potential use of algae for heavy metal bioremediation, a critical review

Algae have several industrial applications that can lower the cost of biofuel co24 production. Among these co-production applications, environmental and wastewater bioremediation are increasingly important. Heavy metal pollution and its implications for public health and the environment have led to increased interest in developing environmental biotechnology approaches. We review the potential for algal biosorption and/or neutralization of the toxic effects of heavy metal ions, primarily focusing on their cellular structure, pretreatment, modification, as well as potential application of genetic engineering in biosorption performance. We evaluate pretreatment, immobilization, and factors affecting biosorption capacity, such as initial metal ion concentration, biomass concentration, initial pH, time, temperature, and interference of multi metal ions and introduce molecular tools to develop engineered algal strains with higher biosorption capacity and selectivity. We conclude that consideration of these parameters can lead to the development of low-cost micro and macroalgae cultivation with high bioremediation potential

Larval development of the western school prawn Metapenaeus dalli Racek, 1957 (Crustacea: Decapoda: Penaeidae) reared in the laboratory

The six Naupliar, three Protozoea, three Mysis and first post-larval forms of the western school prawn Metapenaeus dalli Racek, 1957 were cultured in the laboratory. These stages were described in detail and compared to those of other metapenaeids. The ontogenetic development occurred in 12 days at 26°C, with both the growth rate and morphological patterns of development in M. dalli broadly following those recorded for other metapenaeids. Differences were found between M. dalli and other metapenaeids at corresponding stages of larval development, with these being the number, location and composition of individual setae and other minor spinal development

Effects of different light spectra on the growth, productivity and photosynthesis of two acclimated strains of Nannochloropsis sp.

Light (quantity and quality) is the main growth-limiting factor of photoautotrophic microalgae. The integration of selective permeable photovoltaic filters above microalgae cultivation systems has been proposed previously to improve both production efficiencies and economics. In order to optimize such system, we evaluated the growth and photosynthesis of two spectrally acclimated strains of Nannochloropsis sp. (MUR 266 and MUR 267) grown semi-continuously under different light spectra in this study. No significant differences in biomass productivity were observed between cultures acclimated under full blue (BL, 400-525 nm) and narrow blue (LEDB, 430-490 nm) light when compared to the positive control of white light (WL, 400-700 nm), while lower values were recorded under red (RL, 600-700 nm) and pink light (PL, 400-525, 600-700 nm) for both species. When compared to WL, the photosynthetic performance (Fq′/Fm′, αETR, ETRmax) of both species was higher under both BL and LEDB except for the Fq′/Fm′ of MUR 267 under LEDB. Chlorophyll a content was highest in cultures acclimated to RL while values tended higher under LEDB, RL and PL for MUR 267. Total lipid yield of both MUR 266 and MUR 267 was higher under BL and PL than WL. Based on the results of this study, theoretical modelling of the proposed photovoltaic-microalgae system indicate approximately 150-210 W m−2 of electricity could be potentially generated if only blue wavelengths (BL and LEDB) are selectively filtered from sunlight while converting the remaining unused spectrum of sunlight into electricity

Quantitative determination of ovarian development in penaeid prawns (Decapoda: Penaeidae)

We developed histological methods to increase precision in measuring oocyte size and, for the first time, quantify changes in oocyte composition during ovarian development in penaeids. Wild-caught female Metapenaeus dalli Racek, 1957 from the Swan-Canning Estuary, Perth, Western Australia were used as a model species to compare the novel method to traditional techniques. Morphological analysis showed that ovarian development in M. dalli occurs in five stages: immature, early maturing, late maturing, mature, and post spawning, which is consistent with other penaeids. Analysis of key morphometric parameters of length and Gonad Somatic Index (GSI) showed that GSI provided the strongest discriminators of ovarian development. Oogenesis was similar to qualitative descriptions of other penaeid prawns and most-closely related to previous descriptions of Metapenaeus affinis Milne Edwards, 1837. Comparisons between the novel perimeter tracing and traditional single linear methods for measuring oocyte dimensions showed that greater precision was achieved by tracing. This resulted in a 17-40% reduction in the confidence limits of the means for all cell types measured. A novel histological technique of examining oocyte composition was also developed. This technique allowed for the relationship between stages of ovarian development and proportion by volume of oocyte types to be determined. The difference in the proportions of cell types between each stage of ovarian development was found to be statistically significant, except between immature and post spawning females. The novel methods developed in this study provide new opportunities in the study of ovarian development in penaeids and possibly in other species

Sustainable conversion of light to algal biomass and electricity: A net energy return analysis

A substantial interest is growing in the cultivation of microalgae as a source of biofuel production, considering their relatively high lipid content, fast growth rates, use of alternative water sources, and growth on non-arable land. This paper conducts an energy life cycle analysis for a novel hypothetical hybrid energy system where the electricity required for microalgae cultivation is generated from semi-transparent PV panels to energise paddle wheels and light emitting diodes installed on raceway ponds. The combined system configuration allows for a full utilisation of the solar spectrum, while enhancing the photosynthetic productivity of microalgae cultivation and reducing the evaporation from raceway ponds. The findings of study for a hypothetical system installed in Western Australia show that the amount of land use substantially decreases by 43%, the productivity of microalgae cultivation increases by 75%, while the net energy return of the system remains significantly higher than one, in comparison with a microalgae cultivation system energised by grid electricity. Among a range of variables affecting the energy performance of the proposed system, the primary energy demand for PV panels and conversion efficiency of LEDs exert the highest impact on energy life cycle of the syste