Understanding Carbon Emission numbers - and leading edge project seeding

[whole diary]

[grahame]

From Driver Knowledge Tests

One litre of petrol weighs around 740g but produces around 2.31kg of carbon dioxide when burned. A litre of diesel, which weighs around 840g, produces even more – 2.68kg of carbon dioxide. This CO2 is created in the combustion process in your engine and it’s a potent greenhouse gas.

"We have already saved 226kg of Carbon emission with electric charging delivered at Melksham Station Hub" - speaker at last night's Melksham Town meeting, in relation to the hub.  Sounds impressive, but what does that mean if we convert it?   226kgs is the burning of 84 litres of diesel.  Looking back, I recall filling up with between 40 and 45 litres of fuel - so (unless I have missed something), the charging done and proudly proclaimed is the equivalent of a couple of fill ups at your local 'petrol' station. Have I missed something?? I doubt it ... I have seen a car being charged, but it's rare compared to the times that I've seen the charger unused. And I am aware that a full charge of an electric car only takes you about a third of the distance of a tank of diesel. So perhaps half a dozen charges have been delivered.

Not necessarily any problem with the charging rate - one of the roles of a CIC^▸ (Community Interest Company ) (and come to that certain other bodies such as a parish council) is to be an enabler - bleeding edge rather than leading edge, taking an early loss or providing underutilised facilities.  Could say the same thing for the cycle hire; with six cycles available, there has been 100% availability every time I have been to the hub. Could also have said the same thing in 2013 when the train service went up from 2 to 8 each way per day.  We were given three years to get passenger journeys up from 18,000 to 108,000 - enabling, seeding by the DfT^» (Department for Transport - about) (big "Thank You"). Mind, we got up from 18,000 to 180,000 in just one year and hit the roof shortly thereafter with the train at peak time having no more space.

[broadgage]

Accurate figures for carbon emissions and savings therein are surprisingly difficult to come by and are often disputed.
In the case of the carbon saved by the EV charge point, it depends upon the carbon intensity of the electricity used, the ACTUAL carbon intensity of the grid not only varies minute to minute, but is in itself not accurately known due to imports of electricity.
Promoters of EVs generally claim zero carbon intensity by the purchase of indulgences to cover the electricity consumed.

On the other hand, the carbon intensity of diesel fuel and petrol is arguably a lot worse than the figures quoted. Determining the carbon contained in a liter of fuel, and the consequent carbon dioxide emissions of burning it is basic science and can be confirmed by experiment in a reasonably well equipped university research lab.
That however does not tell the whole story. Consider the fuel burnt in an oil refinery, and by the ships and other transport used in bringing the fuel to the user. Consider the losses by leakages and evaporation. And the often extravagant illumination of petrol filling stations.

All that may be reliably claimed in my view is that an EV is a lot greener than a fossil fueled vehicle, but is less green than walking or cycling.

[broadgage]

And considering the particular charge point in question, it is doubtful if any net benefit has YET been achieved. I consider it probable that at least 84 liters of fuel was consumed in transporting the equipment, materials, and the installation team to site.

Still a good thing though in my view for several reasons.
1) The equipment will hopefully remain in use for many years.
2) The carbon intensity of grid power is expected to decline.
3) Future use of the charge point is likely to increase.

And of course oil is largely imported and supplies are at the mercy of various unstable looking places. Electricity is largely produced within our own borders, and production can be expanded.

[eightonedee]

Forgive my ignorance,  but aren't carbon emissions also a function of the efficiency of the engine in which they are being run and the way in which the vehicle is being driven,  how well it is being maintained and other factors too?

Until we all started to get conscious of the adverse effects of other emissions in the last 6 or 7 years it seemed that there was considerable progress in reducing carbon emissions.

Does anyone know what assumptions are made by those publishing figures for saving carbon emissions as to the overall emissions standards of current traffic? Are the figures meaningful or indeed useful when most informed opinion is aware of
the need to reduce carbon emissions generally?

[eXPassenger]

The amount of CO2 produced per litre of fuel is fixed by chemistry.  The engine efficiency and driving style affect the distance travelled per litre of fuel and hence the amount of CO2 per mile.

[broadgage]

Forgive my ignorance,  but aren't carbon emissions also a function of the efficiency of the engine in which they are being run and the way in which the vehicle is being driven,  how well it is being maintained and other factors too?

Until we all started to get conscious of the adverse effects of other emissions in the last 6 or 7 years it seemed that there was considerable progress in reducing carbon emissions.

Does anyone know what assumptions are made by those publishing figures for saving carbon emissions as to the overall emissions standards of current traffic? Are the figures meaningful or indeed useful when most informed opinion is aware of
the need to reduce carbon emissions generally?

Carbon emissions are indeed related to engine efficiency and driving style, but are fixed per liter of fuel consumed.
More efficient engine=less fuel used and therefore less carbon emitted.
More prudent driving=less fuel used and therefore less carbon emitted.
Or put another way, carbon emissions per liter of fuel are fixed, BUT Carbon emissions per mile traveled are variable according to engine efficiency and driving style.

Carbon emissions per mile traveled can be estimated with reasonable accuracy by surveying a sample of drivers who are asked to submit odometer readings and fuel receipts.
And then cross checked by comparing total fuel sold with total vehicle miles traveled.
Vehicles sold secondhand or scrapped can be surveyed for age in years, and total miles run since manufacture.
Total fuel used can be corrected for the relatively small amounts of petrol used for boat engines, garden tools, generators and the like.

[Western Pathfinder]

Easily done with the available data from the mileage records from Mot tests and Gvt on the DVLA^▸ (Driver and Vehicle Licensing Agency) databases  just need some clever bod to set it up to run.....