We calculated the total amount of CO2 produced to make one batch of biodiesel 20 L (18.3 kg).
Step 1: Find current/amperage (I) and voltage (V) of equipment used at each unit operation. Assume 120 V from wall outlet. Calculate power (P), in Watts, as:
P = IV
*If wattage of a piece of equipment is given, P = IV is not needed.
Step 2: calculate kilowatts, as:
kW = P (in watts) / 1000
Step 3: Calculate kilowatt hours (kWh), as:
kWh = P (in kW) x time equipment is used for a unit operation (in hours)
Step 4: Convert kWh to CO2 emissions:
1 kWh = 0.39 kg CO2 (US) = 0.31 kg CO2 (North Carolina)
Result = CO2 emissions to make 20 L of biodiesel:
| Water washed biodiesel* | 8 kg |
| Distilled biodiesel | 14 kg |
Additionally:
20L of biodiesel produces 7.2 x 10^8 J of energy when combusted, as:
= 9427 cal/g (4.184 J/cal) x 18,300 g
And, the total electrical energy used to make 20L of biodiesel can be calculated as: J = W/s, and there are 3600 sec/hr.
Energy ROI = energy return on energy invested = J “to burn” / J “to make”
| Biodiesel energy by calorimetry | 9427 cal/g |
| Total energy in 20 L biodiesel | 7.2 x 10^8 J |
| Total energy to make 20 L biodiesel (water washing to finish) | 7.3 x 10^7 J |
| Total energy to make 20 L biodiesel (distilling to finish) | 1.6 x 10^8 J |
| Energy ROI (water wash) | 9.9 x |
| Energy ROI (distillation) | 4.5 x |