Organic Waste Recycling

Biofuels production 203

Table 4.22 Quantities of biogas required for a specific applicationa

Quantity of gas required

Use Specification ft^3 /hr m^3 /hr

Cooking 2" burner 11.5 0.33
4" burner 16.5 0.47
6" burner 22.5 0.64
2"-4" burner 8-16 0.23-0.45
per person/day 12-15 0.34-0.42
Gas lighting per lamp of 100 4.5 0.13
candle power
per mantle 2.5-3.0 0.07
2 mantle lamp 5 0.14
3 mantle lamp 6 0.17
Gasoline or diesel
engineb

converted to

biogas, per hp

16-18 0.45-0.51

Refrigerator per ft^3 capacity 1.0-1.2 0.028-0.034
Incubator per ft^3 capacity 0.4-0.7 0.013-0.020
Gasoline 1 liter 47-66c 1.33-1.87c
Diesel fuel 1 liter 53-73c 1.50-2.07c
Boiling water 1 liter 3.9d 0.11d
a Compiled by NAS (1977)
bBased on 25 percent efficiency
c Absolute volume of biogas needed to provide energy equivalent of 1 L of fuel
d Absolute volume of biogas needed to boil off 1 L of water

Table 4.23 Approximate solubilitya of CO 2 in waterb

Pressure Temperature oF (^0 C)
Atm kg/cm^2 32 (0) 59 (10) 68 (20) 86 (30) 104 (40)
1 1.03 0.40 0.25 0.15 0.10 0.10
10 10.3 3.15 2.15 1.30 0.90 0.75
50 51.7 7.70 6.95 9.00 4.80 3.90
100 103 8.00 7.20 6.60 6.00 5.40
200 207 - 7.95 7.20 6.55 6.05
a Solubility is expressed as kg CO 2 per 100 kg H 2 O
bAdapted from Nonhebel (1964)

NaHCO 3 is the precipitate form which can be removed from the solution.
Lime or Ca(OH) 2 is readily available in most areas and is low-cost. The
reaction of CO 2 removal in lime solution is

Ca(OH) 2 + CO 2 ĺ CaCO 3 ↓ + H 2 O (4.19)