Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Engineers are developing new ways to convert greenhouse gases to fuel

uc.edu

Post reply on HN
Print view View original

201–210 of 213 posts

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#201

Post by marcosdumay »

ncmncm wrote: post #181
tgsovlerkhgsel wrote: post #173

Earlier quoted context omitted.

> Current SF6 level (...) accounts for 10% of heat forcing. Source? This does not match what https://en.wikipedia.org/wiki/IPCC_list_of_greenhouse_gases says. In my naive mind, Methane seems like the it could be a good candidate for removal from atmosphere: If you could just get it to react with oxygen, it turns into water and the much less harmful CO2, so you don't have to sequester anything, and the reaction is exo…

https://en.wikipedia.org/wiki/Sulfur_hexafluoride#Greenhouse... : "the collective contribution of [SF6] and similar man-made halogenated gases has reached about 10 percent as of year 2020". But reading more closely, it seems the SF6 by itself is much less. The rest, I guess, must be CFCs and HFCs.

If you follow the citation, you get to this graph:

https://gml.noaa.gov/aggi/aggi.fig3.png

Those 10% are almost all CFC, then the next largest component is HCFCs and then HFCs, where SF6 is included. On the graph subtitle it's explained that SF6 is about 13% of the HFCs component.

Anyway, that's a large change from the last data I've found.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#202

Post by throwaway482423 »

ehsankia wrote: post #130
generalizations wrote: post #115

The problem, in general, is obtaining the CO2. Ironically, in industries where massive amounts of CO2 is needed (including biodiesel production from algae), one of the cheapest ways to get it is to just make it. Pulling it out of the air isn't feasible.

Pulling it out of the air isn't feasible. What about pulling it right where it's mostly produced (heavy polluting factories or electricity generators).

We do, but it's not without issue https://www.bbc.co.uk/news/explainers-58626935

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#203

Post by marcthe12 »

dTal wrote: post #83
dotancohen wrote: post #63

Earlier quoted context omitted.

There still must be some input of energy. From what I understand, the Sabatier reaction is really only viable from an environmental perspective if it is powered by some other non-carbon energy, such as solar or wind.

And if you have that surplus clean energy, you should spend it powering things that would otherwise be powered with fossil fuels - not trying to offset someone else's emissions. Carbon removal only makes sense in a world where nobody is burning any fossil fuels, and we're trying to lower atmospheric carbon. Lower, not offset.

Depends on the cause of emissions. A few are not for purely energy but involved in some kind of chemical reaction. Concrete and Metal extraction are 2 examples. Having a way to offset is important in a cheap manner. Metal extraction esp is a prob as carbon reacts with several metal oxides and reduces it releasing heat. Since it generates heat and creates the final product, it prob more efficient then the alternative electrolysis route.

But yes offsetting CO2 produced due to energy is a waste.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#204

Post by Aerroon »

gpm wrote: post #150
nielsole wrote: post #148

Earlier quoted context omitted.

Just remember that only the C part makes you lighter as the O2 comes from the air. So based on that number it's 375g/day (edit: it's 273g)

I get 273g/day? C is lighter than O. Also... this is a typical number for a typical lifestyle, I believe it can vary substantially if you exercise a lot. Also... I know nothing about wait loss, but surely a lot of the mass is in water?

As a sanity check: fat is around 9 kcal per gram. In a day you use around 2000 kcal of energy or 222 grams of fat. Protein and carbohydrates are around 4 kcal per gram.

The numbers are in the right ballpark.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#206

Post by roelschroeven »

gpm wrote: post #150
nielsole wrote: post #148

Earlier quoted context omitted.

Just remember that only the C part makes you lighter as the O2 comes from the air. So based on that number it's 375g/day (edit: it's 273g)

I get 273g/day? C is lighter than O. Also... this is a typical number for a typical lifestyle, I believe it can vary substantially if you exercise a lot. Also... I know nothing about wait loss, but surely a lot of the mass is in water?

> Also... I know nothing about wait loss, but surely a lot of the mass is in water?

Not really. Yes, you loose water (and its weight) when you e.g. sweat a lot when exercising, but it gets replaced when you drink. More generally your body keeps the amount of water more or less at the same level through intake (drinking, but also water in food), urinating and sweating. There are short-term variations, but besides exceptional circumstances on a day-to-day basis the amount of water in your body should be pretty constant.

Real weight loss is through loss of muscles (not preferable) or loss of fat.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#207

Post by fho »

lrem wrote: post #157
fho wrote: post #153

Earlier quoted context omitted.

Yep ... that's about two chocolate bars every kilometer ... and that has not really changed too much with newer motor generations as it is mostly a function of how much gas is used.

My current car uses about half of what the previous did though. Old Toyota Avensis 1.6, new Toyota Corolla 1.8 HSD.

Yep, engines definitely have improved over time. Still the Corolla is producing about 80 grams of CO² per km (which in Germany is the benchmark to get a E-plate).

So... Only about one chocolate bar per km.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#208

Post by fho »

henearkr wrote: post #166
fho wrote: post #111

Earlier quoted context omitted.

> 1kg of CO2/day which is crazy low if you put it in perspective and see that (gas powered) cars release about 0.2 kg of CO2 ... per kilometer.

Seems very low expressed like that, but actually it isn't because when you take your car you typically drive tens of kilometers.

You can easily walk tens of kilometers in a day. 10 km us basically nothing, 20 km would be somewhat taxing if you are unprepared ... But some (crazy) people are doing 100 km walks for "fun".

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#209

Post by AngryData »

makeitrain wrote: post #123
fho wrote: post #111

Earlier quoted context omitted.

> 1kg of CO2/day which is crazy low if you put it in perspective and see that (gas powered) cars release about 0.2 kg of CO2 ... per kilometer.

That's insane, I didn't realize it was that much. If we could see cars drop carbon turds on the road instead of venting it invisibly in the air we'd all be freaking out right now.

You could probably get a similar reaction if fossil fuel sales were given in the equivalent of trees or fuel crops. Someone might question running to the store just for donuts if they imagined burning half of a tree or 40 pounds of grain or something in the process, rather than just a bit of gasoline.

Re: Engineers are developing new ways to convert greenhouse gases to fuel

#210

Post by fho »

AngryData wrote: post #209
makeitrain wrote: post #123

Earlier quoted context omitted.

That's insane, I didn't realize it was that much. If we could see cars drop carbon turds on the road instead of venting it invisibly in the air we'd all be freaking out right now.

You could probably get a similar reaction if fossil fuel sales were given in the equivalent of trees or fuel crops. Someone might question running to the store just for donuts if they imagined burning half of a tree or 40 pounds of grain or something in the process, rather than just a bit of gasoline.

Honestly I was not even aware of that ... A quick search shows that a 100 yo birch tree stores only about 15 kg CO² ... So your half a tree seems to be in the right ball park.

Also ... CO² is bad ... but at least is non-toxic compared to some of the other side products.

Post reply on HN