Conversion of Waste Cooking Oil to Biodiesel: Life Cycle Assessment

Conversion of Waste Cooking Oil to Biodiesel:
Life Cycle Assessment
Zhang Zhe and Rajasekhar Balasubramanian
Division of Environmental Science & Engineering
National University of Singapore

• To compare the life cycle emission of carbon
dioxide and particulate matter (PM) from
biodiesel (generated from waste cooking oil) and
diesel
• To gain insights into
biodiesel’s life cycle impacts on
the environment

What is Life Cycle Analysis?
• It is an investigation and evaluation of the environmental
impacts of a given product caused by its existence.
• It measures the whole life cycle of the
product
Raw Material
Production
Process
End of Life
Use
Phase

Importance of Life Cycle Analysis
• The environmental impact generated from all
the processes is analyzed, not only the
manufacture or end use process
• Gain overall understanding
about a product’s entire
environmental impact

Life Cycle of Petroleum Diesel
Shipping
with
Ocean
Tanker
Emissions
Life Cycle of Waste Cooking Oil Biodiesel
Emissions

• Process
• Transesterification

Material (Adapted from the laboratory experiment)
Original waste cooking oil
Methanol used
KOH used
Biodiesel Generated
1.0638 L
0.2128 L
8.511 g
1 L

To represent the industrial practice, the following data
obtained from a research done by U.S. National Biodiesel
Board were used for the analysis.
Energy Use
Electricity
0.0502 kWh
Natural Gas 0.02581 m 3

Applications developed for the life cycle analysis
• Entire life cycle is broken down into different life stages of
the product.
• Each life stage is further broken down to sub-processes.
• The environmental impact from each sub-process
is analyzed.
• The integration of all the environmental impact is the
life cycle impact.

∑ Life Cycle Emission = E i
× e j
• i: different life stages
i
• E i : the amount of sub-process used in that life
stage (Unit: L, kWh, etc.)
• e j : emission factors associated with each sub-process
(Unit: kg/L, kg/kWh)

Taking diesel as example, analysis model was used:
• Stages:
o Crude Oil Drilling in Middle East
o Transportation to Singapore with Ocean Tankers
o Refinery
o Transportation to Retail Stations
o End Use
• Sub-processes:
o Diesel, combusted in industrial boiler
o Electricity, at grid
o Gasoline, combusted in equipment
o Natural gas, combusted in industrial boiler
o Residual fuel oil, combusted in industrial boiler

All the final results are based on the same
comparison basis: 1 MJ of energy that can be derived
from the fuel

CO 2 emission comparison (95.27 % reduction)

1. End Use
2. Refinery
3. Transportation to
Singapore: 8000 km
4. Drilling

1. Energy Use
During Production
2. Methanol and
KOH

Only consider about production and transportation stages.
58.96% Reduction

PM emission comparison (46.95% reduction)

44.60% Reduction

Used to measure the life cycle energy input (except end use phase)
40.57 % reduction

Biodiesel’s (from waste
cooking oil) life cycle
emission of carbon dioxide
and particulate matter is
much lower than that from
diesel
The life cycle analysis indicates that the use of biodiesel as
an alternative (automotive) fuel is acceptable from the
environmental point of view.

• To simulate industrial production process
• To obtain first-hand data of the resource usage

Data Source: National Renewable Energy Laboratory (NREL)
Database, experiment

Other Data Sources
• Saudi Arabia Emission Factor: CO2 Emissions from Fuel
Combustion. 2009 ed, International Energy Agency
• Singapore Emission Factor: Information on Emission
Factors 2010. National Energy Efficiency Committee
• Emission Factor for KOH: Korea LCI Database
Information Network. Korea Environmental Industry &
Technology Institute

Cost Aspects
• Most of waste cooking oil exported
• Supply of WCO cannot meet the
designed capacity
• Currently producing with cost
• Can only achieve break-even with an
increase of WCO supply by 80%

Life Cycle Analysis
Objectives
System Boundaries
Experiment to Produce Biodiesel
Analysis Model
Results and Discussion
Conclusion