Biomass & Combustion

Question 1

What are the chemical formulas of ethanol and methane?

Answer 1

Methane = CH4 
Ethanol = C2H60

Question 2

what % of incident solar is converted into biomass by plants?

Answer 2

0.5%

Question 3

whys is plant biomass conversion so low? ( up 7)

Answer 3

Sunlight falling at wrong times (not the growing season),

Land fertility inappropriate, poor or inappropriate water availability,

Only fraction of solar flux is incident on viable conversion surface (leaf),

Light, especially green part, is reflected,

Only a fraction has the correct wavelength to result in photosynthesis,

Only part of the photosynthesis results in carbohydrate production,

Some energy is used by plant to survive …without any growth.

Question 4

How much does the complete combustion of carbon and hydrogen release respectively?

Answer 4

32.8MJ/kg and 142.9mj/kg

Question 5

What’s the formula we can use to calcaulte energy relesed during cobustion?

Answer 5

= 32.8 x (mm C / Molar mass) + (142.9 x ( H - O/8)/Molar mass)

Question 6

what is meant by a short carbon cycle?

Answer 6

• energy/power generation refers to the sequestration of CO2 from the air by biomass over timescale measured in years
• followed by the release of the energy over a much shorter period
• cycle is then repeated making it renewable

Question 7

Why isn;t more of the biomass produced used?

Answer 7

• culture e.g. easier to burn fossil fuels
• lack of land to grow biomass
• more valuable use of land

Question 8

Why does methane have more energy per kg then diesel?

Answer 8

Methane, as it has a higher proportion of hydrogen to carbon atoms, and the oxidation of hydrogen produces more energy per kilogram than the oxidation of carbon