Energy consumption and GHG emissions of GTL fuel by LCA: Results from eight demonstration transit buses in Beijing

doi:10.1016/j.apenergy.2010.03.029

Applied Energy

Volume 87, Issue 10, October 2010, Pages 3212-3217

https://doi.org/10.1016/j.apenergy.2010.03.029 Get rights and content

Abstract

Gas-to-liquids (GTL) as an alternative to diesel is considered to be one of the technical options to reduce petroleum consumption in the on-road transportation sector. Between May and August 2007, a joint demonstration program by Tsinghua University, Beijing Transit, Cummins Corporation and Shell Corporation was carried out in Beijing. The program focused on the supply systems and vehicle use of GTL fuel. The demonstration fleet was formed by four transit buses fueled with GTL and four with diesel. It was demonstrated that GTL has good compatibility with diesel in terms of fuel supply system and vehicle use. This paper compares the energy consumption and GHG emissions of diesel and GTL fuel supply chains by life cycle analysis based on demonstration results. The results indicate GTL’s large range (reported 54–70%) in synthesis efficiency, as the key factor in determining energy consumption and GHG emissions within the GTL fuel supply chain. For the probable case (GTL synthesis efficiency: 65%), the life cycle energy consumption and GHG emissions of GTL fuel are 42.5% and 12.6% higher than that of diesel. For two sensitivity analysis cases (GTL synthesis efficiency: 54% and70%), energy consumptions are 74.2% and 31.2% higher and GHG emissions are 27.3% and 7.4% higher than that of the diesel fuel supply chain. If the efficiency of the GTL synthesis process is improved to 75%, then the GHG emissions level of the GTL fuel supply chain can be reduced to the same level as the diesel fuel supply chain.

Introduction

With the rapid increase of vehicle stock in China, oil consumption and GHG emissions associated with on-road transportation are rising dramatically [1]. Increasing petroleum demand by the on-road transportation sector in China has raised the import dependence of petroleum from 19.7% in 1995 to 51.3% in 2008 [2]. Technology options for vehicles and fuels are in urgent need to establish a stainable and low-carbon transportation energy supply system.

Gas-to-liquids (GTL) as an alternative to diesel is considered to be one of the technology options to reduce petroleum consumption of on-road transportation [3]. GTL technology is recovering and enjoying growth due to recent technology and catalyst advancements. Current forecasts estimate that the world’s GTL capacity could increase from 35,000 B/D to 1–2 million B/D by 2015 [4].

Between May and August of 2007, a joint demonstration program by Tsinghua University, Beijing Transit, Cummins Corporation and Shell Corporation was carried out in Beijing. The demonstration fleet was made up of four transit buses fueled with GTL. Four buses fueled with traditional diesel were also included for comparison purposes. This paper analyzes the demonstration results regarding energy consumption and the associated GHG emissions of diesel and GTL fuel supply chains using life cycle assessment methods.

Section snippets

Model and system boundary

The LCA analysis section of this study is based on the well-to-wheels (WTW) analysis module of the Tsinghua-CA3EM (China Automotive Energy, Environment and Economy Model) model [5], [6], [7], which is an integrated computerized model that includes a specialized module for China’s automotive energy supply and demand balance calculation and analysis. The model is based on China’s national conditions and integrates the widely known and used transportation energy micro-level computing GREET model

GTL supply

All the GTL fuel consumed by the demonstration buses was supplied by Shell Corporation’s Malaysia plant. The GTL fuel was first shipped from Malaysia to Tianjin harbor by ocean tanker, and then distributed to Beijing’s Looan fuel storage site by road tankers. A dedicated refueling truck was used to fuel the four GTL transit buses.

Given that the tanks were previously used for storage of regular diesel fuel, the oil tank for GTL storage was treated using a mild cleaning procedure beforehand to

Demonstration buses

The vehicles evaluated were manufactured by the Chinese company King Long with Euro III common rail diesel engines by Cummins. All eight demonstration buses were the same model as described in Table 3. The 11.5-m long transit buses were chosen for the demonstration because this type of bus (by dimensions and engine type) represents most of the Beijing transit bus fleet. All buses were nine months old and have been in operation since 26 June 2006. The odometer readings ranged from 35,800 to

Diesel and GTL supply

The traditional diesel supply chain is very efficient since this fuel supply chain has dominated on-road transportation fuels for a long time. In this study, the diesel fuel chain starts with crude oil extraction in the mid-east. After extraction, the crude oil is transported by sea tanker to China where gasoline, diesel and LPG are produced in refineries. Diesel is then distributed by pipeline or trucks. The efficiencies of each stage are presented in Table 5 and all of them are based on

Discussion

Several studies have been conducted to address the energy efficiency and GHG emissions of diesel and GTL fuel chains, as presented in Fig. 6 (only for probable cases assumed for each study).

The two cited studies are based on car platforms with significantly higher fuel economy, making life cycle energy consumption and GHG emissions of both diesel and GTL fuel chains lower. For these three studies, energy consumption of GTL fuel chains are 42.9%, 28% and 42.5% higher than diesel fuel chains. GHG

Conclusion

(1)
GTL’s supply system is compatible with the traditional diesel supply system. It is demonstrated that, with proper procedure, GTL fuel can be stored and supplied by the same infrastructure as diesel fuel.
(2)
The use of GTL fuel is compatible for use in diesel vehicles. No modifications are needed when fueling a diesel bus with GTL fuel. The fuel economy of GTL transit buses is slightly lower (1%) than diesel buses.
(3)
GTL synthesis efficiency is the key factor to determine the energy consumption and GHG

Acknowledgements

The project is co-supported by Beijing Transit, Cummins Corporation and Shell Corporation. The authors would like to thank Dr. Xunmin Ou of Tsinghua University, Dr. Kristin. B. Zimmerman of GM and Dr. Michael Wang of Argonne National Laboratory for their generous help.

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Energy consumption and GHG emissions of GTL fuel by LCA: Results from eight demonstration transit buses in Beijing

Abstract

Introduction

Section snippets

Model and system boundary

GTL supply

Demonstration buses

Diesel and GTL supply

Discussion

Conclusion

Acknowledgements

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