Question

Determine the amount of air required to compost 7 tons of solid wastes using in vessel composting systemwith forces aeration. Assume that the composition of the organic fraction of the MSW to be composted is given by C₆₀H₁₀₀O₄₀N. Assume that:

a.       Moisture content or organic fraction of MSW:25%

b.      Biodegradable volatile solids = 0.60 x TS

c.       Air contains 21% oxygen and the specific weight of air is 1.2 kg/m³ at 20 ^oC.

Answer 1

1. Determine the mass of biodegradable volatile solids in 7 tons of solid waste

Biodegradable volatile solids = 0.60 x TS  

   Moisture content or organic fraction of MSW:25%

TS(TOTAL SOLIDS ) = 75%

  mass of biodegradable volatile solids (BVS)= 0.6*0.75*7*1000 kg = 3150kg

2.Determine the amount of oxygen required for decomposition of 1 kg of BVS

C₆₀H₁₀₀O₄₀N + 64.25 O2 → 60.0 CO2+ 48.5 H2O + N

Molecular wt of C₆₀H₁₀₀O₄₀N =1474g

Molecular wt  64.25 O2 = 2056g

O2 required =2056/ 1474 = 1.39 kgO2 /kgBVS

3.Determine the total amount of air required for 7 ton of MSW, containing 3150 kg of BVS, as determined in Step 1

Air Required= (3150kg*1.390)/(0.21*1.2kg/m³)= 17375m³