<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>nine_k</author><text>But there are CO₂-rich exhausts in chemical plants and power plants, with concentrations well above 50%. This is where the capture could work efficiently. These likely produce a sizable portion of the carbon dioxide surplus.&lt;p&gt;Capturing carbon from a jet engine will remain problematic, or slow. Maybe we should just grow more trees, extract solid carbon from them (by burning or otherwise), and bury it in old coal mines.</text><parent_chain><item><author>marshray</author><text>There really is very, very little carbon in the atmosphere, famously ~410 ppm. (Yes, that little bit is enough to absorb significantly more heat from the sun).&lt;p&gt;So, whatever capture system you use, you&amp;#x27;d need to move &lt;i&gt;a lot&lt;/i&gt; of air through in order to produce a small amount of something like liquid hydrocarbon fuel.&lt;p&gt;It will require thousands of times more air, by mass. Since the output fuel product is hundreds of times more dense, it would require a crazy large volume of air to extract the carbon necessary to fill a fuel tank.&lt;p&gt;A corn field combined with a methanol fermentation and distillation facility is an example of a machine that does that. Very large.</text></item><item><author>photochemsyn</author><text>If you can figure out how to get the carbon feedstock from the atmosphere at scale, why would anyone bother with refining a mixed muck coming out of the ground?  What we call &amp;#x27;petrochemistry&amp;#x27; today will be called &amp;#x27;aero-hydro-chemistry&amp;#x27; tomorrow.</text></item><item><author>PaulHoule</author><text>Hydrogen has numerous uses.  Petroleum refineries produce and consume hydrogen in numerous places, if they find they are steam reforming they could use green hydrogen instead, together with storing waste Carbon dioxide to green operations.&lt;p&gt;Even if we quit refining oil from the ground we will still be doing chemistry like petrochemisty with other feedstocks.</text></item><item><author>photochemsyn</author><text>Technically this is about evolving oxygen gas from water more than it is about the hydrogen end of the electrocatalytic reaction.  Since this is a cathode (2H+ + 2e- -&amp;gt; H2 gas) vs. anode process (2H2O -&amp;gt; 4H+ + 4e- + O2) linked up by a wire to close the circuit, you have two chemical processes to manage.  The oxygen-evolving one tends to be slower, i.e. rate limiting.  For an overview:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;sci-hub.se&amp;#x2F;10.1039&amp;#x2F;c9cs00607a&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;sci-hub.se&amp;#x2F;10.1039&amp;#x2F;c9cs00607a&lt;/a&gt;&lt;p&gt;Song, et al. (2020). &amp;quot;A review on fundamentals for designing oxygen evolution electrocatalysts.&amp;quot; Chemical Society Reviews.&lt;p&gt;&amp;gt;&amp;quot;Therefore, the OER is the key process that governs the overall efficiency of electrochemical water splitting. To date, IrO2 and RuO2 have been state-of-the-art OER catalysts. However, both of them are made of precious metals and the cost is high. Therefore, it is imperative to seek low-cost alternative materials that can effectively reduce the kinetic limitation of OER and improve the efficiency of water splitting.&amp;quot;&lt;p&gt;So, they discovered that the catalyst used at the OER end has some light-activation property, which is pretty interesting, i.e. they discovered a kind of photovoltaic electrocatalyst.  Whether it will prove to be industrially useful is anyone&amp;#x27;s guess.  There are similar systems but they&amp;#x27;re not very practical (i.e. they require high-energy UV):&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;physicsworld.com&amp;#x2F;a&amp;#x2F;light-activated-catalysts-make-nearly-perfect-water-splitters&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;physicsworld.com&amp;#x2F;a&amp;#x2F;light-activated-catalysts-make-ne...&lt;/a&gt;&lt;p&gt;As far as hydrogen-from-water tech, again it has three plausible large-scale cleantech industrial uses: ammonia from atmospheric N2, reduction of iron ore to sponge iron, and methane (and plausibly jet fuel) production from atmospheric CO2.</text></item></parent_chain></comment><story><title>Researchers generate hydrogen more efficiently from water</title><url>https://phys.org/news/2022-10-revolutionary-technique-hydrogen-efficiently.html</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>photochemsyn</author><text>Plants pull 100 gigatons of carbon out of the atmosphere every year and convert it to biomass (essentially, oxy-ammonia-hydrocarbons like sugars, proteins, fats, etc.).  Humans pull about 6 gigatons of carbon out of the ground each year and pump it into the atmosphere.&lt;p&gt;The reason this cycle doesn&amp;#x27;t exhaust the atmospheric pool, of course, is that animals and fungi (more the latter) break down biomass into CO2 and release it back into the atmosphere.&lt;p&gt;That&amp;#x27;s not what I&amp;#x27;d call &amp;#x27;very very little carbon&amp;#x27;.</text><parent_chain><item><author>marshray</author><text>There really is very, very little carbon in the atmosphere, famously ~410 ppm. (Yes, that little bit is enough to absorb significantly more heat from the sun).&lt;p&gt;So, whatever capture system you use, you&amp;#x27;d need to move &lt;i&gt;a lot&lt;/i&gt; of air through in order to produce a small amount of something like liquid hydrocarbon fuel.&lt;p&gt;It will require thousands of times more air, by mass. Since the output fuel product is hundreds of times more dense, it would require a crazy large volume of air to extract the carbon necessary to fill a fuel tank.&lt;p&gt;A corn field combined with a methanol fermentation and distillation facility is an example of a machine that does that. Very large.</text></item><item><author>photochemsyn</author><text>If you can figure out how to get the carbon feedstock from the atmosphere at scale, why would anyone bother with refining a mixed muck coming out of the ground?  What we call &amp;#x27;petrochemistry&amp;#x27; today will be called &amp;#x27;aero-hydro-chemistry&amp;#x27; tomorrow.</text></item><item><author>PaulHoule</author><text>Hydrogen has numerous uses.  Petroleum refineries produce and consume hydrogen in numerous places, if they find they are steam reforming they could use green hydrogen instead, together with storing waste Carbon dioxide to green operations.&lt;p&gt;Even if we quit refining oil from the ground we will still be doing chemistry like petrochemisty with other feedstocks.</text></item><item><author>photochemsyn</author><text>Technically this is about evolving oxygen gas from water more than it is about the hydrogen end of the electrocatalytic reaction.  Since this is a cathode (2H+ + 2e- -&amp;gt; H2 gas) vs. anode process (2H2O -&amp;gt; 4H+ + 4e- + O2) linked up by a wire to close the circuit, you have two chemical processes to manage.  The oxygen-evolving one tends to be slower, i.e. rate limiting.  For an overview:&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;sci-hub.se&amp;#x2F;10.1039&amp;#x2F;c9cs00607a&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;sci-hub.se&amp;#x2F;10.1039&amp;#x2F;c9cs00607a&lt;/a&gt;&lt;p&gt;Song, et al. (2020). &amp;quot;A review on fundamentals for designing oxygen evolution electrocatalysts.&amp;quot; Chemical Society Reviews.&lt;p&gt;&amp;gt;&amp;quot;Therefore, the OER is the key process that governs the overall efficiency of electrochemical water splitting. To date, IrO2 and RuO2 have been state-of-the-art OER catalysts. However, both of them are made of precious metals and the cost is high. Therefore, it is imperative to seek low-cost alternative materials that can effectively reduce the kinetic limitation of OER and improve the efficiency of water splitting.&amp;quot;&lt;p&gt;So, they discovered that the catalyst used at the OER end has some light-activation property, which is pretty interesting, i.e. they discovered a kind of photovoltaic electrocatalyst.  Whether it will prove to be industrially useful is anyone&amp;#x27;s guess.  There are similar systems but they&amp;#x27;re not very practical (i.e. they require high-energy UV):&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;physicsworld.com&amp;#x2F;a&amp;#x2F;light-activated-catalysts-make-nearly-perfect-water-splitters&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;physicsworld.com&amp;#x2F;a&amp;#x2F;light-activated-catalysts-make-ne...&lt;/a&gt;&lt;p&gt;As far as hydrogen-from-water tech, again it has three plausible large-scale cleantech industrial uses: ammonia from atmospheric N2, reduction of iron ore to sponge iron, and methane (and plausibly jet fuel) production from atmospheric CO2.</text></item></parent_chain></comment><story><title>Researchers generate hydrogen more efficiently from water</title><url>https://phys.org/news/2022-10-revolutionary-technique-hydrogen-efficiently.html</url></story>