[pf] liquid fuels for cars - CO2 and pollutant emissions.

· There are 5 liquid fuels (a 6th is kerosine) currently used in cars, in
various places around the world.

-1. gasoline, with more or less in the way of additives, some of which
increase the octane (which allows a higher compression to be used, raising
efficiency);

-2. diesel fuel, which explodes (as these all do, since they're used in
internal combustion -IC- engines) simply because it's compressed enough -
no spark plugs;

-3. methane, CNG, Compressed Natural Gas: currently the best way of
carrying hydrogen around with you, since it has only one carbon atom to
every 4 hydrogens, and much less CO2 is produced than with other fuels.
However, it's not actually a liquid, and it can only be kept in
thick-walled tanks under very high pressure - not a problem, except for
very light cars (like our old Mini);

-4. propane, LPG, Liquid Petroleum Gas: kept in relatively lightweight
tanks under small pressure (from the liquid's evaporation in the tank -
sometimes not enough, in winter). That's C2H6- almost as good as CNG (2 x
CH4 = 2C + 8H), and more energy per kg (or pound) than CNG, which
translates into a longer range per fill;
             and lastly for cars:
-5. the alcohols, methanol (CH3-OH: "wood alcohol"- it evaporates quickly
at summer temperatures) and ethanol (C2H5-OH: the one in vodka and other
spirits and liqueurs), which is - I think still - made by fermenting the
sugar you get by converting the starch in corn, etc. Here's a news item:
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
http://www.planetark.org/dailynewsstory.cfm?newsid=9472&newsDate=9-Jan-2001
  is:
Farmers fear Clinton decision on California ethanol
USA: January 9, 2001
WASHINGTON - US corn growers on Monday said they were worried President
Bill Clinton would scuttle a huge new market for ethanol in California by
granting the state a waiver from federal requirements for oxygen content in
fuel.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 That refers, not to 100% ethanol (though the old Indy race cars,
"fuelers", used to use it), but to various proportions from 5% through 15%
(common) to 85% ethanol, the rest being gasoline. I think it /can/ be mixed
with diesel too.

· All can be (and are being) carried around in cars, and can be "reformed"
(broken apart) to give the hydrogen that fuel cells need to produce the
electricity used in the electric drive motors. The CNG is the best (the
least CO2 produced), though for fuelling the fuel-cells for motorised
bicycles and very light-weight cars, cylinders of LPG would be chosen.

{· A 7th fuel for stationary applications (inc. very large-cells) is LNG,
Liquified Natural Gas (methane), but that needs extreme cooling to keep it
liquid, so including the deep-cold refrigeration the whole system is very
heavy.}


· None of what I've said so far refers to one of the main reasons
politicians are concerning themselves with these various fuels: "emissions"
- actually emissions of _pollutants_ like nitrogen and sulphur oxides etc,
the "side effects" of exploding the fuel with air in internal combustion
engines.

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At 23:08 28/2/2001 +1300, Jeremy Hall wrote to GreenViews-NZ, with Subject:
[GV]LPG question :-

Does anyone know if (and if so by how much) LPG is more environmentally
friendly than [gasoline/]petrol in terms of:

- ozone depleting emissions;
- global warming effects [mainly CO2, from transport]; 
- smog generation?

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

At 09:15 1/3/2001 +1300, Brent Efford <brent.efford@techmedia.co.nz> wrote:

Yes - my information (supplied through Rockgas, admittedly) is that LPG has:

- 10% - 15% less CO2 emissions than petrol
- only marginally less than diesel (due to the latter's higher thermal
efficiency)
- about half the carbon monoxide (CO) c.f. petrol
- 20% of the oxides of nitrogen c.f. petrol
- about 10% of the particulates c.f. a Euro-2-standard diesel engine
- about 15% of the air toxics (1,3-Butadiene, acetaldehyde, benzene, etc)
of [the] gasoline [suited to] vehicles fitted with catalytic converters.

The above applies to LPG used in internal combustion engines. If used in
external combustion engines, such as the Capstone gas turbines in the
Christchurch hybrid electric shuttle buses, emissions are even lower ("too
low for our instruments to measure" according to a Chch City Council
manager I spoke to).

I can round up more info if it would be really useful - but not just at the
moment.

Brent Efford
TechMedia Services
Transport 2000 NZ
PO Box 2626, Wellington 6015, New Zealand
Ph 04 801 9331, Fax 04 801 9344
www.techmedia.co.nz

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· Brent didn't answer Jeremy's question about ozone-depleting emissions; to
get 15 kilometres up, i.e. to reach the ozone layer, the
ozone-depleting-molecules have to be stable enough not to be reacted-with
by the large amount of oxygen we have in the Earth's atmosphere (~20%),
which isn't true of fuels and fuel byproducts. They are much too reactive
to get up to the ozone layer; that's /why/ they produce smog.

David.
(David MacClement) davd@ihug.co.nz 
http://www.geocities.com/davdd.geo/index.html#top
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