how much fossil fuels are used for fuel, compared to other things?

[UndercoverElephant]

Google isn't helping me, does anybody know?

What proportion of fossil fuels currently being extracted are actually burned as opposed to turned into fertiliser and other petrochemicals which ultimately aren't burned? Or do all of them eventually end up as CO2, some way or another? And is there a trend for this? Is the proportion increasing or decreasing?

Can we extract fossil fuels and use them in ways that don't increase climate change?

[BritDownUnder]

I would suggest that you first take a 'helicopter view' of what fossil fuels actually are, in particular oil. Then look into organic chemistry which is all about the (almost) unique properties of carbon as an element being able to form stable and strong chemical bonds with other atoms thereby being able to form an almost infinite variety of carbon atom chain molecules which could contain on carbon atom or one million carbon atoms linked together in chains or rings. What fuel it is depends on the number of carbon atoms in the chain (C4 has 4 carbon atoms and is butane gas)



Then you need to understand the differences between coal, oil and natural gas and their relative eases of use in the chemical industry.

From now on I am just going to talk about oil but there are or have been whole chemical industries based on natural gas and coal as well. What happens in an oil refinery is that first of all fractions of many different molecules consisting of varying numbers of carbon atoms are separated based on their boiling points. After that some further work is done modifying molecules by adding hydrogen or splitting longer chain molecules apart resulting in smaller molecules that are more useful as fuels.

This nice little graphic shows where a typical 42 gallon barrel of oil goes to...



So about 85% to fuels (and residues such as petroleum coke etc) which get burnt and 13% to (I would presume) ethane/ethene gases which are two carbon atom containing molecules which form the feedstock of nearly all plastic industry.

Note that different times of year and changing profitability will affect the refining ratio.

So at least 80% of a barrel will get burnt but if there is demand more ethane will get produced by cracking gasoline or diesel to produce more ethane gas for plastics. It's anyone's guess how much plastic gets recycled but I would guess less than 50% of plastic gets recycled each cycle.

Fertiliser is mainly made from the methane in natural gas.

[UndercoverElephant]

I would suggest...

Thanks for the very helpful reply.

[adam2]

AFAIK, the two main non fuel uses of gas and oil are fertilizer manufacture and plastics manufacture.

Ammonia based fertilizer is made from hydrogen and atmospheric nitrogen, the hydrogen is commonly from natural gas. The carbon from the natural gas is released into the air as carbon dioxide, or captured for industrial and other uses and then released into the air.

Plastic manufacture ties up the carbon content possibly for centuries, until the plastic is either burnt or decomposes.

Both processes are complex with considerable ancillary fuel used for heating, cooling, handling and other processing, this could be renewably generated electricity, but probably is fossil fuel.

[PS_RalphW]

One by product of oil distillation is tar, which is used on roads worldwide. This needs periodic replacement, due to wear and oxidation. The top level is sometimes scraped off and some of the scrapings are burned to provide heat to melt the replacement tar so it can be laid

In a post fossil fuel world roads will need a major redesign.

[clv101]

Yeah, roads are in issue! It's also interesting how little choice you get regarding how much petrol, diesel, tar etc you get out of a barrel of oil. If for example we completely electrified transport, virtually eliminating demand for petrol and significantly reducing demand for diesel - what do we then do with the light fractions? You can't build a road from petrol!

[BritDownUnder]

A knowledge of organic chemistry is quite useful to gain an understanding of a lot of modern products but without an advanced degree I think it is hard to make a career out of it.

A lot of roads in Australia are gravel roads and others are made of concrete (not just around bridges but quite long lengths of motorways especially modern ones) so alternative surfaces do exist.

I could not find figures of the amount of natural gas used for ammonia production but one site did say it was about 20% of industrial natural gas demand and 5% of industrial coal demand, presumably mostly in China, although 60 years ago the UK chemical industry was based almost completely around coal and not natural gas.

[BritDownUnder]

Yeah, roads are in issue! It's also interesting how little choice you get regarding how much petrol, diesel, tar etc you get out of a barrel of oil. If for example we completely electrified transport, virtually eliminating demand for petrol and significantly reducing demand for diesel - what do we then do with the light fractions? You can't build a road from petrol!

There's probably a way to turn short chain hydrocarbons such as petrol into longer chain ones such as tar. I used to make quite a lot of tar like materials during my organic chemistry reactions on a regular basis.

Believe it or not petrol was once a waste product of oil refining hence why someone invented the spark ignition engine to use all this waste product.

You do get a choice of the petrol produced but it involves organic chemistry, complexity, investment and energy so much more than just distillation.

[mr brightside]

One by product of oil distillation is tar, which is used on roads worldwide. This needs periodic replacement, due to wear and oxidation. The top level is sometimes scraped off and some of the scrapings are burned to provide heat to melt the replacement tar so it can be laid

In a post fossil fuel world roads will need a major redesign.

Tar and chip, the preferred way to bollocks up an otherwise decent road.

[BritDownUnder]

A nice Youtube video all about the history of gasoline.

[Vortex2]

Google's Bard (which has improved greatly recently) says:

The proportion of fossil fuels burned varies from country to country. For example, in the United States, fossil fuels accounted for 80% of primary energy consumption in 2021. In China, fossil fuels accounted for 77% of primary energy consumption in 2021. And in India, fossil fuels accounted for 65% of primary energy consumption in 2021.

[BritDownUnder]

Very good but the question asked in the post was what proportion of fossil fuels are burnt rather than being used for other things like plastics and ultimately what proportion end up as CO2. The title was less clear. Your Bard answer came out as what proportion of primary energy came from fossil fuels as opposed to hydro, nuclear, wind, hydro etc and didn't mention what proportion went to making plastics and chemicals. I feel a Sankey diagram coming.

Would be interesting to compare how Bard and ChatGPT understand the question.

I recall the Dalai Lama used to give an answer by saying "bad question". Maybe AI should ask for clarification now and then.

[adam2]

Believe it or not petrol was once a waste product of oil refining hence why someone invented the spark ignition engine to use all this waste product.

You do get a choice of the petrol produced but it involves organic chemistry, complexity, investment and energy so much more than just distillation.

Indeed, in the early days of crude oil refining the desired products were mainly lamp oil, called paraffin in the UK, and lubricating oils for steam driven machinery.
Early petroleum derived lamp oils had a very poor safety record with many fires resulting. In order to get the greatest yield of saleable lamp oil, from the crude oil, some of the lighter fractions, more akin to petrol, were included in the lamp fuel. This resulted in a fuel with a dangerously low flash point.
An early and still extant regulation requires a minimum flash point for lamp oil/paraffin/kerosene.

Petrol CAN be used for illumination, but only in a purpose designed lamp, NEVER in a lamp designed intended for lamp oil.