In 2008, Safeway has converted all its trucks to bio-diesel B20 which is a mixture of 20% of bio-diesel produced from soybean and 80% of diesel in volume. It claimed that 34,000 tons of CO2 emissions were saved per year.
EPA recently characterized the CO2 emission reduction for biofuel . B100 Biodiesel from soybean represents a reduction of 57% of CO2 emissions compared to traditional Diesel (from 100 kg CO2/mmBtu for diesel to 43 kg CO2/mmBtu).
The energy contained in bio-diesel is 126kBtu/Gal, and in diesel 139kBtu/Gal.
a. What are the emissions in kg CO2/Gal of Diesel and Bio-diesel (in kg CO2/Gal)?
CO2/Gal of Diesel = 100.0.139 = 13.9 kg CO2/Gal of Diesel
CO2/Gal of Bio-diesel = 43.0.126 = 5.4 kg CO2/Gal of Bio-diesel
b. What are the emissions of B20 (in kg CO2/Gal)?
Each gallon of B20 contains 0.8 gallon of Diesel and 0.2 gallon of Bio-diesel therefore the emissions of B20 are CO2/Gal of B20 = 0.8.13.9 + 0.2.5.4 = 12.2 kg CO2/Gal of B20
c. What is the energy contained per gallon of B20 (in kBtu/Gal)?
Similarly:
Energy/Gal of B20 = 0.8.139 + 0.2.126 = 136.4kBtu/Gal of B20
d. What are the emissions of B20 (in kg CO2/mmBtu)?
CO2/mmBtu of B20 = 12.2/136.1000 = 89 kg CO2/mmBtuof B20
e. The energy required by the trucks being the same with B20 and Diesel, what was the energy required by Safeway's trucks annually (in mmBtu/y)?
Safeway's trucks saved 34,000 tons of CO2 annually by switching to B20, the energy required by the Safeway trucks is therefore:
Energy/year = 34,000/(100-89).1000 = 3.2 106mmBtu/year
f. What was the annual Diesel consumption by Safeway's trucks (in Gal/year)?
Consumption/year of Diesel = 3.2 106/0.139 = 23 106 Gal/y
g. What is the annual Bio-Diesel consumption by Safeway's trucks (in Gal/year)?
Consumption/year of B20 = 3.2 106/0.136 = 24 106 Gal/y
Consumption/year of Bio-Diesel = 0.2.24 106 = 4.7 106 Gal/y
h. Knowing that the yield of Soybean is 53 Gal/acre per year, what soybean acreage is required to run all Safeway's trucks on Biodiesel (in Acre)?
Soybean acreage = 89,300 Acres = 361 km2