Question

Calculate the emissions reductions if a coal-fired power plant is converted to wood pellets. The biomass burned by the power plant is fully regrown but 19% of the harvest is consumed during processing of the biomass. Furthermore, the transportation of wood and wood pellets from source to power plant requries 273 litres of diesel per ton of wood pellet delivered. Treat the diesel as pure cetane and the wood pellets are pure carbohydrate chains.

Fuel Properties

-Calorific value of coal: 31 GJ/t

-Carbon content of coal: 90%

-Calorific value of wood pellets: 16 GJ/t

-Density of cetane: 0.82 kg/l

Calculate the % savings (e.g if coal emitted 200 units of CO₂ and the biomass plant had a net emission of 120 units, then the % savings would be (200-120)/200 = 40%

Give the answer in %, rounded to the nearest +/- 1 %

Answer 1

Solution:-

Let us assume that 1 ton of coal & 1 ton of wood pellet over user

For coal,

Amount of energy released by having 1 ton of coal = 31GJ

90% of coal has carbon being converted to CO₂ and this amounts to 900 kg.

For wood pellet,

Amount of wood collected from forest = 1 ton

Amount of wood consumed during processing = 0.19 ton

Amount of wood available for burning = 0.81 ton

Amount of energy released = 12.96 GT

Amount of fuel used for transportation = 273 L

Amount of CO₂ produced from octone = 0.82 kg/L x 273L x 84.9/100 = 190kg