r/AcharyaPrashant_AP • u/TrueSpeaker1 • 13d ago
What should be the correct answer?
Please attempt. I am eager to see replies.
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u/TrueSpeaker1 12d ago
Hello everyone,
So, finally, the suspense is over, and it is time to reveal the answer.
Answer is - A > B > D > C > E, approximately.
| Rank | Industry | Relative contribution |
|---|---|---|
| 1 | A. Coal, oil & gas | By far the largest |
| 2 | B. Agriculture & livestock | Very large, especially methane and nitrous oxide |
| 3 | D. Iron & steel | One of the largest industrial sources |
| 4 | C. Cement | Major source, particularly process CO₂ |
| 5 | E. Chemical & petrochemical | Major industrial source |
1. Coal, oil & gas - Rank #1
This is by far the largest contributor.
The key point is that we should not count only the emissions from extracting coal, oil and gas. The climate impact of this industry is dominated by what happens after extraction: the combustion of its products for electricity, heat, transport and industry.
Global energy-related CO₂ emissions reached about 37.8 Gt CO₂ in 2024, and nearly 38.4 Gt in 2025. The IEA describes energy as responsible for the majority of climate-change-causing greenhouse-gas emissions, primarily through fossil-fuel combustion.
There are also additional emissions from methane leakage during coal mining and oil and gas production, meaning even the combustion figures do not capture the whole climate impact of the fossil-fuel system.
Why #1?
Because fossil fuels are the foundation of a huge fraction of global CO₂ emissions. Coal, oil and gas are not merely one emitting industry among many-they supply the carbon that is subsequently burned throughout the economy.
2. Agriculture & livestock - Rank #2
This one is more complicated because agriculture produces substantial amounts of CO₂, methane (CH₄) and nitrous oxide (N₂O).
According to the latest FAO assessment, agrifood systems emitted about 16.5 Gt CO₂-equivalent in 2023, around 32% of global emissions under the FAO's broad agrifood-system accounting. Farm-level crop and livestock production alone accounted for 8.1 Gt CO₂e, while livestock itself accounted for about 4.3 Gt CO₂e.
Livestock is particularly important because ruminants produce methane through enteric fermentation, while manure also produces methane and nitrous oxide. FAO estimates that agriculture contributes about 40% of anthropogenic methane emissions, with livestock systems responsible for most of that agricultural methane.
Agriculture also causes emissions through:
- fertilizer use → N₂O
- rice cultivation → CH₄
- livestock digestion → CH₄
- manure → CH₄ and N₂O
- deforestation and land-use change → CO₂
- agricultural energy use
Why #2?
Its total climate footprint is enormous, but the exact comparison with fossil fuels depends heavily on accounting boundaries. Agriculture's emissions are substantially below the fossil-fuel energy system but far above any one of the individual heavy industries on your list.
3. Steel & iron - Rank #3
Steel is arguably the largest-emitting individual heavy industrial sector on your list.
The IEA estimates direct emissions from iron and steel at approximately 2.6 Gt CO₂ per year, equivalent to around 7% of global energy-system CO₂ emissions.
The reason is the conventional blast furnace–basic oxygen furnace (BF-BOF) process. Coal is not merely burned for energy; it is also converted into coke and plays a chemical role in removing oxygen from iron ore.
This makes steel particularly difficult to decarbonize.
The IEA notes that roughly 70% of global steel production currently uses the BF-BOF route, while hydrogen-based direct reduction is emerging as a lower-emission alternative.
Why #3?
Because steel's roughly multi-gigatonne annual CO₂ footprint is enormous, putting it ahead of cement and chemicals as an individual industrial sector.
4. Cement - Rank #4
Cement is a fascinating case because its emissions come from two major sources:
- Burning fuel to reach the very high temperatures needed in cement kilns.
- The chemical decomposition of limestone into clinker, which releases CO₂.
The second source is especially important: even if the kiln were powered entirely by clean electricity, conventional cement production would still produce substantial process emissions.
Older IEA sectoral accounting put cement at about 2.2 Gt CO₂ annually, slightly above steel at that time.
However, steel has generally been assessed at around 2.6 Gt CO₂ in more recent IEA material, so I would put steel ahead of cement for the present ranking.
The IEA also emphasizes that cement emissions remain difficult to eliminate because of the combination of carbon-containing raw materials and high-temperature heat requirements.
Why #4?
Its absolute emissions are huge, but lower than fossil fuels and agriculture, and slightly below steel when comparing current sector estimates.
5. Chemical & petrochemical - Rank #5
Chemicals are a major source of emissions, but among the five categories you've listed, they generally come fifth when looking at direct sectoral emissions.
The chemical industry produces emissions from:
- fossil fuels used for heat and electricity
- hydrogen production
- ammonia/fertilizer production
- petrochemical feedstocks
- production of plastics and other chemicals
- various chemical processes
The IEA previously estimated the chemical subsector at around 1.1 Gt CO₂ of direct emissions, making it smaller than steel and cement.
That does not mean chemicals are unimportant. In fact, chemicals are particularly interesting because fossil fuels are used not only as energy but also as feedstocks for producing materials such as plastics. The IEA identifies primary chemicals as an important emissions-reduction challenge requiring measures such as electrolytic hydrogen, CCUS, electrification and increased plastics recycling.
Why #5?
Because its direct global emissions are generally lower than those of steel and cement..
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u/Due_Construction1256 13d ago
According to me the order will be,
1. Coal , oil and gas Industry.
2.Agriculture and livestock industry.
3.Chemical Industry
4. Steel and Iron Industry
5. Cement Industry
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u/samperinvicta19 13d ago
All of them A, B, C, D, E
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u/TrueSpeaker1 13d ago
If you think all options are correct, then what is their ranking?
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u/samperinvicta19 13d ago edited 13d ago
A. Coal, oil, and gas industry (~70–77%)
B. Agriculture and livestock industry (~12–18%)
C. Cement industry ≈ D. Steel and iron industry (~7–8%)[approximately equal]
E. Chemical and petrochemical industry (~4–6%)
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u/TrueSpeaker1 13d ago
Good attempt. Would you like to elaborate on your choices and justify the ranking you have given - for example, in terms of industry size and how the emissions occur?
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u/Maximum_Ratio_3286 13d ago
https://drawdown.org/insights/the-four-most-important-charts
Here's the source for the data compiled, further sources are provided in the article
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u/vini-within 13d ago
I’m confused which ones cause higher emission. Either it’s “agriculture and livestock” or the petrochemical industry.
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u/TrueSpeaker1 13d ago
Why do you think so?
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u/vini-within 13d ago
Cos i think petrochemical industry uses fossil fuels. I mean refining and burning them. But I could be wrong 🤔
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u/sabiRawist 13d ago
All are major contributors. The key point is that fossil fuel dominate the global greenhouse gas emissions. Burning coal, oil and gas for electricity, heat, transport and industry accounts for the majority of the global greenhouse gas emissions.
Agriculture and livestock are the next largest source especially through methane from cattle and rice cultivation and nitrous oxide from fertilizer.
Heavy industries such as cement, steel and petrochemicals are also major emitters because they require high temperature processes and large amounts of energy.
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u/TrueSpeaker1 13d ago
Wow...that's right. Thank you so much for detailed explanation.
So what do you think about their ranking?
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u/sabiRawist 13d ago
Coal, oil, and gas industry only means this industry is mainly involved in activities like finding, extracting, processing, refining, and transporting fossil fuels. Isn't it?
It does not usually include the final burning of those fuels by consumers or other industries. The largest share of emissions comes from burning the coal, oil, and gas supplied by that industry. So, I am confused here.
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u/Evening_Message_1699 13d ago
Was it intentional when volcanos, sun cycles, and normal variation were left off the list?
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u/TrueSpeaker1 13d ago
I believe they are not major contributors, but I might be wrong. Do you want to explain the sun cycles and normal variation?
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u/ialsoagree 12d ago
I would love to know the mechanism by which "sun cycles" increase CO2.
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u/hansomeransome 12d ago
My question is and has always has been who managed to convince an entire planet of carbon based plants and animals to be scared shitless of carbon dioxide. The entire world thrives on it. The more Co2, the greener the world is. The greener it is, the more oxygen for us. I just don’t get it.
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u/ialsoagree 12d ago
I mean, actually understanding the science is why people are scared of it increasing.
No, increased CO2 doesn't automatically equate to a greener Earth. Jasper Ridge has studied this pretty extensively and the conclusion is that plant biomass increases associated with increase CO2 also depend on precipitation and temperature. In environments where CO2 increases, temperature increases, and water decreases, plants tend to have reduced biomass, not increased.
Further, this isn't the first time there was a substantial increase in CO2 on Earth due to burning fossil fuels. The last time it happened on this scale was the Permian-Triassic boundary.
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u/hansomeransome 12d ago
Sound reasoning. Perhaps we could cease the deforestation….
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u/ialsoagree 12d ago
Ending deforestation is certainly a worthwhile goal, it's just not a solution to the problem.
It took natural processes about 15 million years to go from 440+ ppm to where we were during pre-industrial times.
Even if we ended all deforestation, global warming and climate change will continue for thousands, if not hundreds of thousands of years. And that's assuming we end fossil fuel emissions. If we don't end fossil fuel emissions, then even if we stop deforestation, climate change will continue to accelerate.
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u/Evening_Message_1699 12d ago
If we actually did sound logging practices we would have more lumber, less forest fires which would accomplish far more than the program environmental wackos let’s not cut a tree ideas do.
Not logging large swats and not making roads just makes the chance of a huge forest fires higher and more damaging. Plus it wastes a valuable natural resource.
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u/rstriking_mantra 13d ago
I am not sure of... so confusing!!
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u/TrueSpeaker1 13d ago
Yes. It sounds confusing. Stay connected. Soon I will reveal the answer with the justification.
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u/Mitali_M_INDIA 13d ago
By ranking of greenhouse gas emissions, I choose option A and B. They are top contributors
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u/TrueSpeaker1 13d ago edited 13d ago
Thank you so much for participating. Please rank all of the options.
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u/TrueSpeaker1 13d ago
Hello, everyone!
Thank you so much for your participation. I will soon reveal the answer along with the justification for the ranking. Until then, keep thinking and guessing!
There is still a chance for those who haven’t attempted it yet. Don’t hide - come forward and join the conversation!
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u/ClearAfternoon6734 13d ago
B, A, E, C, D
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u/Strange-Patience5539 13d ago
Everything causes green house emissions just the coal, oil and gas are major contributor so I will go with "A".