Zhang Zhe and Rajasekhar Balasubramanian

Division of Environmental Science & Engineering

National University of Singapore

Conversion of Waste Cooking Oil to Biodiesel: Life Cycle Assessment

• 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

Use

PhaseEnd of Life

� 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

Original waste cooking oil 1.0638 L

Methanol used 0.2128 L

KOH used 8.511 g

Biodiesel Generated 1 L

�Material (Adapted from the laboratory experiment)

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 m3

� 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 = ∑ ×

i

ji eE

• i: different life stages

• Ei: the amount of sub-process used in that life

stage (Unit: L, kWh, etc.)

• ej: 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

� CO2 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

�Results and Discussion

� Conclusion

� Analysis Model