
Research group finds way to turn plastic waste products into jet fuel - curtis
https://phys.org/news/2019-06-group-plastic-products-jet-fuel.html
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blacksqr
The paper's abstract is intriguing, and kind of buries the lead. The waste
plastic angle is a bit of a headline-grabbing red herring. The authors claim
they can turn straight-chain hydrocarbons into aromatic ring molecules, which
I believe traditionally has been very hard. There's nothing special about
waste plastic as a source of straight-chain hydrocarbons, they could be
obtained from a variety of biomass sources.

Traditionally the only economical source of aromatic molecules has been
distillation of petroleum. An economical way to turn biomass-derived simple
hydrocarbons into aromatics could be revolutionary, as a path for making fuel
as well as a range of other high-value compounds, like phenolic plastic resin.

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dTal
Nice achievement, but I just don't see the environmental angle. The article
implies that this might help solve the ocean plastic problem, but the plastic
in the ocean isn't the plastic we carefully collected - it's the plastic that
"got away". We won't be turning that into jet fuel any time soon.

And of course, taking the larger view, plastic is still made from fossil oil.
Making it profitable to burn it is not going to help CO2 levels. The CO2
problem is larger than the ocean plastic problem, and even if we could turn
ocean plastic into jet fuel - it's probably a bad trade.

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chr1
If there was a use for collected plastic, a lot less of it would "get away",
currently most of collected plastic ends up in landfills anyway. Burning jet
fuel obtained from plastic would not decrease CO2 level, but it would not
increase it either, as there is lots of other jet fuel to burn.

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dTal
If it were profitable to turn plastic into jet fuel, that would imply that
plastic-derived jet fuel is cheaper. If the price of jet fuel goes down, more
gets burned.

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chr1
By that logic you can argue that banning plastic bags will decrease the use of
oil, making it cheaper for those who want to burn it. Or that buying tesla
makes oil cheaper and in some other place more of it gets burned. In all of
these cases the effect is tiny.

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dTal
It's a question of supply and demand. If your final goal is to burn less oil,
then you want to 1) reduce the supply and 2) reduce the demand. Buying Tesla
reduces demand: good. Turning plastic to oil increases supply: bad.

Your plastic bag example is interesting because I think it's accurate - having
plastic compete with combustion as a use for crude oil is _good_ from an
emissions standpoint, because when the wells run dry, less of it will have
been burned.

(Plastic bags are indeed a bit of a silly example because there's so little
plastic in them - we ban them because they cause disproportionate
environmental harm)

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DigitalVerse
As a few people have pointed out, this feels a lot like an attempt at solving
one environmental problem (proliferation of waste plastic) by exacerbating
another environmental problem (burning more fossil fuels). But if it took off,
it could potentially serve as something of an intermediary step between our
fossil fuel economy and a renewables-based economy. After all, the switch from
horses to automobiles took 50 years.
([https://thetyee.ca/News/2013/03/06/Horse-Dung-Big-
Shift/](https://thetyee.ca/News/2013/03/06/Horse-Dung-Big-Shift/),
[https://www.mnn.com/green-
tech/transportation/blogs/horses-h...](https://www.mnn.com/green-
tech/transportation/blogs/horses-horsepower-rocky-transition)) A similar shift
to renewables could easily take as long or longer.

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SamBam
Exactly. From a carbon/global warming sense, this is actually _worse._

Plastic is carbon that never went into the atmosphere. It's actually nicely
stored away, wildlife effects aside. Once you burn it, it's like you were
burning oil.

~~~
twertwtwetqew
Oil in the ground is also carbon that wasn't in the air.

If the amount of jetfuel consumed stays the same, the amount of CO2 going into
the air stays about the same. Could slightly increase or decrease depending on
the processes' efficiency compared to the marginal oil producers' efficiency.

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techno_modus
Adidas is producing millions of its shoes using ocean plastic:
[https://mymodernmet.com/adidas-parley-sustainable-
fashion](https://mymodernmet.com/adidas-parley-sustainable-fashion) (and these
shoes can be then turned into jet fuel).

~~~
bkrn
I think at this point they've moved to just "intercepting" plastic before it
makes its way into the ocean. From the parley website:

"In remote areas, we establish systems to intercept plastic waste before it
ends up in landfills, gets burned, buried or tossed into rivers or oceans."

So still might be more interesting than the recycled water bottles everyone
else is sourcing but maybe disingenuous for them to be using the "ocean
plastic" language still.

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Iamgroot1992
Love this idea but as another user has pointed out, it's the plastic that
'gets away' that we should be concerned about. Similarly, microplastics in the
ocean are - and will continue to be - a massive problem. A great concept, but
sadly only one cog in a very confusing machine.

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3327
The only question that matter is net yield of energy per energy expended vs
cost.

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roca
No it's not. Converting renewable energy into liquid fuels is valuable in
itself.

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pjc50
There are already different processes for this, including a rather nice one
developed by the US Navy which takes CO2 directly from the ocean.
Unfortunately it can't avoid being more expensive than fossil liquid fuels,
which is why we have to campaign against exploration and drilling.

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dmos62
The article is vague. It says that the process recovers 100% of energy from
plastics they tested. What plastics did they test? Also, there isn't a
discussion on energy efficiency of the process.

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kwhitefoot
How effective is it at converting plastic contaminated with food waste. The
vast majority of plastic from my household is food packaging which is really
quite expensive to decontaminate.

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twertwtwetqew
Turning plastic into fuel is probably the only practical way to re purpose it.

Food, different feed-stock, ect, are all small details when you're operating
at high T needed to cleave bonds to make fuel. Cleaved bond -> food molecule
is no longer food

Recycling never cleaves any bonds, so the food is still there causing
problems.

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perfunctory
This is the kind of project the fossil industry would invest in. What we need
instead is industry transformation away from fossils to renewables.

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empath75
Isn’t this just burning more fossil fuels?

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bloak
If some of the jet fuel comes from plastic waste instead of from the ground
that might result in burning less fossil fuel, compared to the situation in
which the plastic waste goes into landfill. However, as long as people are
still burning coal to make electricity (which still happens in China, India,
Australia, ....) I suspect that even less carbon would be released into the
atmosphere if the plastic waste were burnt in a power station rather than
turned into jet fuel.

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empath75
How much would be released if it were just put into landfills?

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bloak
No idea, really, but generating electricity by burning plastic might release
less carbon than from burning coal because the plastic contains hydrogen as
well as carbon. It depends, no doubt, on the type of plastic and the
efficiency with which it can be burnt while avoiding the release of nasty
chemicals.

It's not at all obvious to me what's best: landfill, burn, or recycle. But
government policy should be based on a proper analysis of those options. I
have the impression that government is mostly just compromising between what
industry lobbyists are asking for, in order to maximise their profits, and
what the ignorant public are asking for, in response to fashion and
irrationality. Let's hope that somewhere some sensible civil servants are
quietly doing the right sums.

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amelius
> generating electricity by burning plastic might release less carbon than
> from burning coal because the plastic contains hydrogen as well as carbon

Can we get the same effect from burning coal while adding external hydrogen?

