Utilization of microalgae for Enhanced CO2 Sequestration in a photo bioreactorIntroduction: One of the major causes of global warming is the increase in concentration of the carbon dioxide gas in the atmosphere. CO2gas emissions have gradually increased. Do to the Industrial Revolution with the use of fossil fuel. One of the most promising and benign technologies to sequester CO2is the biological sequestration of the gas. The approach in this work is to evaluate the global rates of carbon dioxide sequestration in photo bioreactor using a culture of chlorella vulgaris cultivated in a synthetic medium. The focus will be on the measurement of CO2 sequestration rates in liquid and gas phases, O2 release rates , carbon fixation into biomass ,and the effect of photoperiod cycles (day/night) during the batch cultivation .

Carbon dioxide emissions rates:

Carbon dioxide emissions are derived from burning fossil energy and the concentration of CO2 in the atmosphere has increased around 40% since the beginning of the industrial revolution. The United States, Euro Area, and Japan produce almost 75 percent of the CO2 emissions from all high-income countries. However, about half of the total global CO2 emissions come from the developing world, particularly from China, the Russian Federation, and India. China's share of global emissions has risen from 11 to 20 percent between 1990 and 2005.

The graph shows various countries and their levels of CO2 emissions per capita. Also indicates the difference from high income to low income nations on CO2 output. Central to any study of climate change is the development of an emissions inventory that identifies and quantifies a countrys primary sinks of greenhouse gas. Emissions are not usually monitored directly, but are generally estimated using models. Some emissions can be calculated with only limited accuracy. Emissions from energy and industrial processes are the most reliable (using energy consumption statistics and industrial point sources). Some agricultural emissions, such as methane and nitrous oxide carry major uncertainties because they are generated through biological processes that can be quite variable.Carbon dioxide removal(CDR): CDR methods refer to a number of technologies which reduce the levels ofcarbon dioxidein the atmosphere.Among such technologies arebio-energy with carbon capture and storage,direct air capture,ocean fertilizationandenhanced weathering.CDR is a different approach to removing CO2from the stack emissions of largefossil fuelpoint sources, such aspower stations, as this reduces emission to the atmosphere but cannot reduce the amount of carbon dioxide already in the atmosphere. It is by some regarded as a branch of geo engineering,while other commentators regard CDR as a form ofcarbon capture and storage.

One of the Chemical methods to remove CO2includes liquid solvents and solid sorbents. Once these substances become fully loaded with CO2, they are isolated from the main gas stream and exposed to higher temperatures or lower pressures to release the CO2 and regenerate their capacity for CO2 removal.

Chlorella vulgaris is a single celled type of green algae. It survives in water purely thanks to photosynthesis, and it needs only carbon dioxide, water and sunlight to survive.Chlorella vulgaris shows promises as a biomass fuel and as a natural food coloring agent. Because the algae grows rapidly in light and dark places with a minimum amount of nutrients Chlorella vulgaris can be produced at low cost. Some patients taking Chlorella vulgaris have experienced an allergic reaction marked by chest pain or tightness, trouble breathing and hives. Chlorella vulgaris can also cause nausea and make people more sensitive to sunlight.

About Experiment:

The strain chlorella vulgar is chosen in this study. All experiments will be conducted at room temperature (25c) in a bioreactor of 4 liter fed with of culture medium inoculated with chlorella vulgaris to give a starting concentration of 0.1 mg/L. The experiments will be performed in mode glass bubble column photo bioreactor equipped with a gas inlet at the bottom and an outlet at the top. The culture will be continuously bubbled with air with known rate using a 3 scc (Standard Cubic Centimeter) pore size sparger. The reactor will be continuously illuminated by six white light lamps controlled by an automated system to simulate a circadian cycle.For analytical procedures gas chromatography (GC) will be used to determine the carbon dioxide and oxygen concentration in air streams. The concentration of carbon dioxide dissolved in the liquid phase will be evaluated by a dynamic method.The medium:

An inorganic salts medium was used to culture freshwater algae called bold's Basel medium (BBM). BBM is used at the University of Reading for culturing chlorella vulgaris which is the algae were using in the lab. This medium is recommended by the culture centre of algae and protozoa, Cambridge for culturing such organism.Preparing BBM:

At first 12 different stocks containing salt, iron, minerals and different nutrients should be prepared separately in different flasks using distilled water. To prepare 1 Liter of BBM different volumes from each stock of the 12 stocks prepared earlier need to be added in a 1 Liter conical flask. To complete the 1 Liter volume needed distilled water is added. Then the flask must sealed probably and then heated in an oven to sanitize the medium.

Stock solution no.Chemical nameFormulaWeight (g)Distilled water (ml)

1di-potassium hydrogen orthophosphate

K2HPO41.875250

2Potassium

di-hydrogen orthophosphate

KH2PO44.375250

3Magnesium sulphate

MgSO4.7H2O1.875250

4Sodium nitrate

NaNO36.25250

5Calcium chloride

CaCl2.2H2O0.625250

6Sodium chloride

NaCL0.625250

7EDTA tetrasoduim salt

Potassium hydroxideEDTA Na4KOH5.000

3.100100

8Ferrous sulphate

Sulpharic acid conc.

(wt per ml = 1.84 g)FeSO4.7H2O

H2SO40.498

0.1 ml100

9Boric acid

H3PO31.142100

10Zinc sulphate

ZnSO4.7H2O0.35325

11Manganese chloride

MnCl2.4H2O0.05825

12Capric sulphate

CuSO4.5H2O0.06325

Taking the following volumes based on preparing 1 liter of BBM:

From stock 1 6 10 ml

From stock 7 9 1 ml

From stock 10 12 0.1 mlStock solutions 1 6 maybe stored for up to 3 months 7 12 maybe stored for up to 12 months from preparation, or all maybe stored indefinitely autoclaved or sterilized. All solutions can be stored at room temperature in the dark. If precipitation occurs in any stock solution it should be renewed regardless of expiry date. Each stock solution should be labeled with:

Name of chemical:

Solution number:

Date of preparation:

Operator's initials:

Expiry date:

BBM containers should be labeled with :

Date of preparation:

Operator's initials:

Ph: