Abstract
Over the years, natural gas has been promoted as a
clean-burning fuel, especially for transit buses. A
decade ago one could claim that natural gas buses deliver
significant emission benefits over diesel buses,
especially regarding particulate emissions. The spread in
nitrogen oxide emissions has always been significant for
natural gas engines, high for lean-burn engines and low
for three-way catalyst equipped stoichiometric engines.
With the introduction of US 2010 and Euro VI (effective
as of 2014) exhaust emission regulations, independent of
the fuel, the regulated emissions of all engines have
been brought close to zero level. This means that the
advantage of natural gas as a clean fuel is diminishing,
especially in a situation in which electric transit buses
are also entering the market. The motivation to use
natural gas could still be diesel fuel substitution and
to some extent, also reduction of greenhouse gas
emissions. However, looking at the full fuel cycle and
also taking into account methane leakages in various part
of the fuel cycle, natural gas is, at its best,
comparable to diesel regarding greenhouse gas emissions,
not better. One of the reasons for this is the low fuel
efficiency of spark-ignited gas engines compared to
diesel engines. To deliver an advantage regarding
greenhouse gas emissions, the efficiency of the gas
engines should be significantly improved. Alternatively
natural gas should be replaced with biogas. The paper
presents a comparison of diesel and natural gas buses for
regulated emissions, selected unregulated emission
components, greenhouse gas emissions and energy
efficiency.
| Original language | English |
|---|---|
| Article number | 2014-01-2432 |
| Number of pages | 11 |
| Journal | SAE Technical Paper Series |
| DOIs | |
| Publication status | Published - 2014 |
| MoE publication type | A1 Journal article-refereed |
| Event | SAE 2014 Commercial Vehicle Engineering Congress - Rosemont, United States Duration: 7 Oct 2014 → 9 Oct 2014 |
