algae

Question 1

Brown Alage

Answer 1

burned to obtain the ash for use in the manufacture of glass, this fell into decline when other ways of producing NaOH were found

Iodine was also found in brown algae

Question 2

Open pond systems

Answer 2

Less efficient when compared with closed photobioreactors.

• Evaporation losses make a net contribution to cooling, it may also result in significant changes to ionic composition of the growth medium with detrimental effects on algae growth.
• Temperature fluctuations due to diurnal cycles and seasonal variations are difficult to control in open ponds.
• Potential CO2 deficiencies due to diffusion into the atmosphere may result in reduced biomass productivity due to less efficient utilisation of CO2.
• Poor mixing by inefficient stirring mechanisms, may result in poor mass CO2 transfer rates causing low biomass productivity.
• Light limitation due to top layer thickness may also incur reduced biomass productivity.
• However, enhancing light supply is possible by reducing layer thickness; using thin layer inclined types of culture systems, and improved mixing can minimise impacts to enhance biomass productivity.

Question 3

Open Saline Pond production in Australia

Answer 3

• achieved production rates of 50 tonnes per hectare per year, over half of which is converted to oil.
• high production rates are expected to increase at the new pilot plant due to the even better climatic conditions in Karratha.”
• The first stage is costing $1.5 million and further funding is being sought for future stages estimated to cost between $5-10 million.
• Professor Borowitzka says the cost of producing biofuel from algae has already dropped from $12 a kilo to below $4 in the past year, but the aim is to get it down to less than $1 a kilo.

Question 4

High algae biomass production rates are achievable with open pond systems.

Answer 4

Inconsistencies in production rates reported.

Jiménez et al. extrapolated an annual dry weight biomass production rate of 30 tonnes per hectare using data from a 450 m2 and 0.30 m deep raceway pond system producing biomass dry weight of 8.2 g m−2 per day in Malaga, Spain.

Using similar depth of culture, and biomass concentrations of up to 1 g l−1, Becker estimated dry biomass productivity in the range of 10–25 g m−2 per day.

However, the only open pond system for large-scale production that has achieved such high biomass productivity is the inclined system developed by Setlik et al. In this system, a biomass concentration of higher than 10 g l−1 was achieved, with extrapolated productivity of 25 g m−2 per day.

Weissman and Tillett operated an outdoor open pond (0.1 ha) in New Mexico, USA, and attained an average annual dry weight biomass production rate of 37 tonnes per hectare with a mixed species culture (four species), highest yields were confined to the 7 warmest months of the year

Question 5

Closed Algae systems

Answer 5

• tubular
• flat plate
• column photobioreactors

Question 6

Closed Photo-bioreactor Technology

Answer 6

Microalgae production based on is designed to overcome some of the major problems associated with the described open pond production systems.

Pollution and contamination risks with open pond systems, preclude their use for the preparation of high-value products for use in the pharmaceutical and cosmetics industry.

Permit culture of single-species of microalgae for prolonged durations with lower risk of contamination.

Higher cell mass productivities attained hence harvesting costs can also be significantly reduced.

However, the costs of closed systems are substantially higher than open pond systems

A.P. Carvalho, L.A. Meireles and F.X. Malcata, Microalgal reactors: a review of enclosed system designs and performances, Biotechnology Progress 22 (6) (2006), pp. 1490–1506.

Question 7

Oil extraction from algae

Answer 7

Oil extraction from algae is one of the more costly processes which can determine the sustainability of algae-based biodiesel.

Question 8

Enzymatic extraction

Answer 8

Enzymatic extraction uses enzymes to degrade the cell walls with water acting as the solvent, this makes fractionation of the oil much easier. The costs of this extraction process are estimated to be much greater than hexane extraction.

Question 9

Osmotic shock

Answer 9

Osmotic Shock is a sudden reduction in osmotic pressure, this can cause cells in a solution to rupture. Osmotic shock is sometimes used to release cellular components, such as oil.

Question 10

Ultrasonic-assisted Extraction

Answer 10

Ultrasonic extraction can greatly accelerate extraction processes. Using an ultrasonic reactor, ultrasonic waves are used to create cavitation bubbles in a solvent material, when these bubbles collapse near the cell walls, it creates shock waves and liquid jets that cause those cells walls to break and release their contents into the solvent

Question 11

How to make algae oil more economical.

Answer 11

Processing improvements
Large-scale cultivation techniques
Harvesting equipment/techniques
Extraction techniques
Fixed (heterogeneous) catalysts

Develop additional co-products
PUFAs (“omega-3s”)
Nutraceuticals
Animal feed
Additional alternative fuels (e.g., ethanol)

Question 12

LCA comparison of algae oil vs other Biofuels

Answer 12

In comparison to conventional energetic crops,

High photosynthetic yields of microalgae significantly reduce land and pesticide use but not fertilizer needs.

Production, harvesting, and oil extraction induce high energy consumption, which can jeopardize the overall energetic balance.

If the algal biodiesel is not really environmentally competitive under current feasibility assumptions, there are several improvement tracks which could contribute to reduce most of its impacts.

A large-scale production can be seriously considered under the achievement of the following improvements: the choice of microalgal species maintaining high lipid and low protein contents with sustained growth-rates (e.g., low-N culture, strain selection, or modification), the setup of an energetically efficient extraction method, and the recovery of energy and nutrients contained in the oilcake.

Question 13

What is responsible for deterioration of algal culture performance and biomass yield

Answer 13

Grazing zooplankton, or so called predators
This Hazard of predator contamination is so great that sustainable cultivation of many
algal crops of economic interest –– has not been possible.Contamination during the initial inoculation and early growth period

Fluctuating climatological conditions:-
Overheating
Nutrient changes
pH