[Digestion] Digestion Digest, Vol 19, Issue 16

Tue Jan 29 13:18:54 CST 2008

GAS POWERED BUSES A CLIMATE THREAT..............IS IT TRUEEE ?????

Gas powered buses are often launched as a cheaper alternative to
trolleybuses. However, they emit substances that are more harmful to
the climate than even diesel buses.

The world politicians efforts on combatting global warming is
concentrating on reducing carbon dioxide (CO2) emissions.

But is that really so important compared to methane (CH4)?

The 'relative greenhouse effect' of methane is estimated at about 17
times that of carbon dioxide. But it is true that the emissions of
carbon dioxide still are much greater than those of methane. So the
'historic' global warming effect that we have seen might be caused
largely by carbon dioxide.

However, the emissions of methane are increasing on a much faster rate
than those of carbon dioxide. It is no doubt that global warming in
the future more and more will be associated with methane.

In addition, the use of methane-containing fuels is even advocated by
environmental interests. The methane in the atmosphere come from a
variety of sources, among those most important are agriculture,
garbage dump sites, exploration of natural gas fields, pipelines for
natural gas, leakages from gas depots or gas filling stations,
emissions from end use of natural gas or biogas in household, industry
or vehicles.

The fact is that natural gas as well as 'biogas' contain 95-98%
methane. Environmental organisations use to promote the use of
'biogas' as an alternative to fossil fuels. However, the CH4 emissions
must be taken into consideration. 'Biogas' is often produced from
garbage or harvested grass that is anaerobically treated. If not
biogas was produced, some methane would anyhow be produced from the
dump site but the majority of the coal-containing compounds would be
transformed into other hydrocarbons or just carbon with time. So there
is a considerable net emission of methane (and also carbon dioxide) if
biogas is produced and used in vehicles. Still worse is of course the
use of natural gas in buses.

The use of natural gas - or biogas - in buses is usually associated
with significant emissions of methane due to that engines are tuned in
to reduce emissions of nitrogen oxides which otherwise would be a
problem for gas-powered vehicles. This is especially true for cold
starts and during city traffic conditions.

A Swedish study assesses the greenhouse effect of methane emissions
from biogas-powered vehicles to about 3 times the greenhouse effect of
carbon dioxide emissions from diesel-powered vehicles. Even if
considered the shorter average life of methane emissions compared to
CO2, the greenhouse impact from biogas buses seem to be far higher
than the greenhouse impact of diesel buses. Natural gas powered buses
are still worse since they also emit fossil CO2. More to read in
http://the-greenhouse-effect.blogspot.com/2006/06/is-methane-big-danger.html

This is thus a contradiction - that environmental organisations call
for the use of gas-powered vehicles when methane emissions might
become the most significant global warming problem in the future.

If we cannot control the methane buildup in the atmosphere there might
be more severe effects as methane is released from 'frozen' deposits
at sea bottom when the water warms up. The resulting greenhouse effect
might be much worse than what we are now discussing - there might be
an increase in global temperatures of 20-30 degrees C which in fact
has happened historically, last time during Eocene period som 55
million years ago when the North Pole had a climate with temperatures
about +20 degrees C and of course no ice.

So try to stop the methane emissions before it is too late. Use cheap
power from nuclear energy instead of natural gas or biogas wherever
feasible. Use electric trolley buses in cities with zero emissions
instead of experimenting with gas-powered buses.

was just wanted to rectify whether this news is true or not.

with regards
srinivas kasulla
Mumbai9869179601

On 1/29/08, digestion-request at listserv.repp.org
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>    1. Re: Solid Waste (francois chartier)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Tue, 29 Jan 2008 00:35:12 -0800 (PST)
> From: francois chartier <francoischartier at yahoo.com>
> Subject: Re: [Digestion] Solid Waste
> To: digestion at listserv.repp.org
> Message-ID: <731715.50193.qm at web50406.mail.re2.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
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> Hi all,
>
> As anyone experience in biogaz using solid waste? What
> type of digester, handling, etc.
> cheers
> Francois
>
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> End of Digestion Digest, Vol 19, Issue 16
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-- 
SRINIVAS KASULLA
M E D C/ M E S N
09869179601