"Bob Hobden" wrote in message
...

"Andy wrote in message

That's no real issue and can easily be removed. I quite like to
see
a certain amount of lichens on roof tiles. It makes them look more
interesting.....


Apparently lichens only grow in places of low atmospheric pollution,
so it's a good indicator of air quality, as well as any aesthetic
benefit.

but is the same true about moss? In fact, are moss and lichen
synonymous?
I know that lichens are rarer than they once were.

Actually, since the Clean Air Act came into
force (yes I remember that!) the
pollution has reduced drastically. Most came
from coal fires and those of us
of a certain age will remember those horrid
yellow filthy smogs every winter
in the good old days. Whilst most pollution
still comes from the home, central heating etc,
vehicle pollution has made drastic reductions too in
recent years, in fact the pollution from cars is a
reversing trend despite
more and more on the roads.

Pollution from homes: oil, gas and electricity generation, is approx 42%, so
clamping down on this is very productive. The MicroGen Stirling elec/gas
boiler will make a big impact here. The coming minimum 86% boiler
efficiency is welcome too and will make an impact. EU regulation on gas
burners, which are very clean anyhow, are tightening too.

Vehicles "are" a very large polluters, especially when they are concentrated
in cities, where masses of people live. Great progress is being made on
pollution from homes, in insulation standards, boiler efficiency , etc, yet
there appears no immediate solution to the filthy car. Technology is there
to make boilers very efficient and very clean burning, at no great cost,
also by increasing insulation standards, a homes emissions can be
drastically reduced. This can be done right now and people wonder why it is
not being implemented. The car? Well apart from taxing larger engines, not
much at all can be done. There are some advanced concept engines around,
but the big corps have not yet taken up these ideas, tending not wanting any
change at all.

Cars are even dirtier until the engine and exhaust is hot. So, in many
cases, when the car is used to go to Safeway or the school run, the thing is
hardly up to temperature before being switched off. In this period they
pollute heavily. The current piston internal combustion engine needs
totally replacing.



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