Interpretations

Graph 1 (Amount of Gas Produced) shows how much gas in millilitres was produced by each varying amount of copper and the sulphur deficient media.  This gas was generated over 10 days.  In the graph and table, it can be seen how every media generated hydrogen –even if it was little- except the control bottle which did not indicate hydrogen through the burning splint test. In the presence of hydrogen the burning splint test creates a loud “pop” sound; the control bottle did not show a presence of hydrogen. Knowing that algae can only produce hydrogen in an anaerobic environment it is possible to say that the environment within the control bottle never turned into anaerobic because there was no limiting condition on the algae to prevent them from photosynthesizing and producing oxygen.

Out of the different copper concentrations it can be seen that each increasing amount of copper produced more hydrogen than the last amount. The greatest amount of hydrogen generated was from the 1.6 ppm of copper, which produced 102 ml of hydrogen. However the next amount of 2.0 ppm copper produced even less than the 0.8 ppm Cu concentration and a possible reason for this would be it damaged the algae more than the other amounts. This means 1.6 ppm of copper turned out to be the most effective to make the algae produce the largest amount of hydrogen.

The sulphur deficient method still produced more than the 1.6 ppm of Cu. The sulphur deficient method produced 115.6 ml of hydrogen which is only 13.6 ml (2.51%) more than the most effective copper method. The downside which is clearly observed from looking at the bottle is the yellow tinge which indicates the algae are dieing compared to the greener color of the copper and control (most healthy).

Graph 2 (Gas produced by Percentage) shows how the results of the two trails (which were different amounts of water) produced consistent results and how 1.6 ppm Cu was the most effect in both trails.

Analysis and Discussion

After 10 days the largest amount of hydrogen produced from the copper (1.6 ppm) method was 102 ml. Knowing that 1.5 litres of water (algae) can produce 102 ml of hydrogen several calculations can be done to see how a larger scale of this project may look like.

This means for every litre of algae, 68 ml of hydrogen is produced every 10 days or 6.8 ml everyday. In one year you could produce 2482 ml of hydrogen. Using this information various other amounts of hydrogen produced per litre of algae water can be calculated. This graph shows various amounts of gas that can be produced if this were to be scaled up.

(fig 8-1) Amount of Algae vs Gas in One Year

 

 After 10 days, the amount of hydrogen produced from the sulphur deficient method was 115.6 ml.

This means for every litre of the sulphur deficient algae, 77 ml of hydrogen is produced over 10 days, or 7.7 ml per day. In one year you could produce 2810.5 ml of hydrogen.

Copper Addition vs. Sulphur Depletion

The major difference between the two methods is that when depleting the algae of sulphur they begin to die after a few days and the production of hydrogen stops. While with adding copper the algae are eventually able to repair and regenerate, they are able to start photosytem II synthesis again and then stop producing hydrogen. It has been found that the sulphur deficient method produces more hydrogen than the copper method but is unfavourable because the algae die. The copper method produces less hydrogen (but still comparable amounts), however the fact that the algae lives provides a great advantage. With the ability of the algae to live, a cycle of hydrogen production with a cycle of growth can be made by adding copper every time the algae stop producing hydrogen.  This type of system would be efficient because the algae will not need time to grow “from scratch” like the sulphur method.