<p>I did some napkin math based on your data. At 4 tx/s and 8GW, that is 2GWs per transaction. 0.5kg/kWh is around 139kg/GWs. Thus each transaction is around 278kg. Looks like we reached the same answer. </p>

<p>But is this the carbon footprint of one Bitcoin transaction? To put it differently, if there was a global carbon tax, would it makes sense to charge for 278kg per transaction? Probably not. In fact, almost certainly most of the tax would just apply to the electricity bill of Bitcoin miners, which is split between hashing for the block reward and processing transactions.</p>

<p>There are <a href="https://www.blockchain.com/charts/n-transactions-per-block" rel="nofollow noreferrer">roughly 2000 transactions per block</a>. Each transaction costs roughly \$1. The block reward is 12.5 Bitcoins as of now. At \$8200 per Bitcoin, roughly <span class="math-container">$\$2000/(12.5\space\text{BTC} \times \$8200/\text{BTC} + \$2000)=0.0191$</span> or 2% of a miner's electricity bill goes to transaction processing. So perhaps it makes more sense to say that each transaction costs around <span class="math-container">$278\space\text{kg} \times 0.02=5.56$</span>kg of carbon.</p>

<p>So what about the rest of the carbon? In some sense, the main job that PoW does is preserving the integrity of existing token balances. The block reward is seniorage. This a similar principle to how central banks print more money and thus reduce the value of existing bank notes and coins. As of now <a href="https://www.blockchain.com/charts/total-bitcoins" rel="nofollow noreferrer">there are close to 18 million Bitcoin in existence</a>. Continuing with your carbon emission numbers, each Bitcoin holder that isn't transacting is then responsible for <span class="math-container">$((8/(18 \times 10^6)) \times 139) \times 0.98=0.000060542$</span>kg of carbon per second per Bitcoin or 5.23kg of carbon per day per Bitcoin.</p>

CC BY-SA 4.0
2019-10-04T15:15:09.720Z
Thanks, I like your approach of splitting the cost. I guess in the end it's a matter of how one defines the purpose of bitcoin.
Bernd Strehl
CC BY-SA 4.0
2019-10-03T13:55:47.757Z
2019-10-03T14:02:24.367Z
2019-10-03T14:02:24.367Z
Kent Shikama
<p>Out of personal interest I wanted to find out which carbon footprint one bitcoin transaction produces. Following I will present my calculation. The result surprises me and my question is <strong>Is this realistic? Did I make mistake?</strong></p>

<p><strong>Variables</strong></p>

<ul>
<li>Transaction throughput: <span class="math-container">$\approx 4\frac{tx}{s}$</span>  <a href="https://www.blockchain.com/de/charts/transactions-per-second?daysAverageString=7&amp;timespan=1year" rel="nofollow noreferrer">source</a></li>
<li>Bitcoin energy consumption <span class="math-container">$\approx 8.00GW$</span> <a href="https://www.cbeci.org/" rel="nofollow noreferrer">source</a></li>
<li>Carbon emission per <span class="math-container">$\approx \frac{0.5kg}{kWh}$</span> CO2 <a href="https://www.umweltbundesamt.de/themen/co2-emissionen-pro-kilowattstunde-strom-sinken" rel="nofollow noreferrer">germany</a> (Not sure if China is lower or higher here, since mining mostly happens in China)</li>
</ul>

<p><strong>Calculations</strong><br>
Transactions per hour: <span class="math-container">$4\frac{tx}{s} = 60*4\frac{tx}{m} = 60*60*4\frac{tx}{h} = 14.400\frac{tx}{h}$</span><br>
Energy Consumption per hour: <span class="math-container">$8.00GWh = 8 * 10^6kWh$</span><br>
Energy Consumption per transaction <span class="math-container">$\frac{8 * 10^6kWh}{14.400tx} \approx 555\frac{kWh}{tx}$</span><br>
Carbon footprint per transaction <span class="math-container">$555\frac{kWh}{tx} * \frac{0.5kg}{kWh} \approx 277\frac{kg}{tx}$</span></p>

<p>If the whole energy used for bitcoin was produced in germany one bitcoin transaction would have a carbon footprint of 277kg. If we take <a href="https://www.rensmart.com/Calculators/KWH-to-CO2" rel="nofollow noreferrer">Finland</a> for example with more reneweable energies (<span class="math-container">$\frac{0.113kg}{kWh}$</span>) it would be 77kg CO2. </p>

<p>For reference: A single flight form Hamburg to Munich (600km, aprox. 1h) is 161kg <a href="https://co2.myclimate.org/de/portfolios?calculation_id=2641900" rel="nofollow noreferrer">myclimate</a>. The compensation of 277kg CO2 is roughly $6.50 with <a href="https://www.atmosfair.de/en/offset/fix" rel="nofollow noreferrer">atmosfair</a>.</p>

<bitcoin>
CO2 footprint per bitcoin transaction
Bernd Strehl
# CO2 footprint per bitcoin transaction

(Asked by: username_0 on 2019-10-03)

Out of personal interest I wanted to find out which carbon footprint one bitcoin transaction produces. Following I will present my calculation. The result surprises me and my question is **Is this realistic? Did I make mistake?**

**Variables**

* Transaction throughput: $\approx 4\frac{tx}{s}$ [source](https://www.blockchain.com/de/charts/transactions-per-second?daysAverageString=7×pan=1year)
* Bitcoin energy consumption $\approx 8.00GW$ [source](https://www.cbeci.org/)
* Carbon emission per $\approx \frac{0.5kg}{kWh}$ CO2 [germany](https://www.umweltbundesamt.de/themen/co2-emissionen-pro-kilowattstunde-strom-sinken) (Not sure if China is lower or higher here, since mining mostly happens in China)

**Calculations**  
Transactions per hour: $4\frac{tx}{s} = 60\*4\frac{tx}{m} = 60\*60\*4\frac{tx}{h} = 14.400\frac{tx}{h}$  
Energy Consumption per hour: $8.00GWh = 8 \* 10^6kWh$  
Energy Consumption per transaction $\frac{8 \* 10^6kWh}{14.400tx} \approx 555\frac{kWh}{tx}$  
Carbon footprint per transaction $555\frac{kWh}{tx} \* \frac{0.5kg}{kWh} \approx 277\frac{kg}{tx}$

If the whole energy used for bitcoin was produced in germany one bitcoin transaction would have a carbon footprint of 277kg. If we take [Finland](https://www.rensmart.com/Calculators/KWH-to-CO2) for example with more reneweable energies ($\frac{0.113kg}{kWh}$) it would be 77kg CO2.

For reference: A single flight form Hamburg to Munich (600km, aprox. 1h) is 161kg [myclimate](https://co2.myclimate.org/de/portfolios?calculation_id=2641900). The compensation of 277kg CO2 is roughly $6.50 with [atmosfair](https://www.atmosfair.de/en/offset/fix).

**Tags:** bitcoin


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## 1 answers

### Answer by username_1 on 2019-10-03. Score: 3 | Accepted answer

I did some napkin math based on your data. At 4 tx/s and 8GW, that is 2GWs per transaction. 0.5kg/kWh is around 139kg/GWs. Thus each transaction is around 278kg. Looks like we reached the same answer.

But is this the carbon footprint of one Bitcoin transaction? To put it differently, if there was a global carbon tax, would it makes sense to charge for 278kg per transaction? Probably not. In fact, almost certainly most of the tax would just apply to the electricity bill of Bitcoin miners, which is split between hashing for the block reward and processing transactions.

There are [roughly 2000 transactions per block](https://www.blockchain.com/charts/n-transactions-per-block). Each transaction costs roughly \$1. The block reward is 12.5 Bitcoins as of now. At \$8200 per Bitcoin, roughly $\$2000/(12.5\space\text{BTC} \times \$8200/\text{BTC} + \$2000)=0.0191$ or 2% of a miner's electricity bill goes to transaction processing. So perhaps it makes more sense to say that each transaction costs around $278\space\text{kg} \times 0.02=5.56$kg of carbon.

So what about the rest of the carbon? In some sense, the main job that PoW does is preserving the integrity of existing token balances. The block reward is seniorage. This a similar principle to how central banks print more money and thus reduce the value of existing bank notes and coins. As of now [there are close to 18 million Bitcoin in existence](https://www.blockchain.com/charts/total-bitcoins). Continuing with your carbon emission numbers, each Bitcoin holder that isn't transacting is then responsible for $((8/(18 \times 10^6)) \times 139) \times 0.98=0.000060542$kg of carbon per second per Bitcoin or 5.23kg of carbon per day per Bitcoin.

> **Comments:**
> **username_0**: Thanks, I like your approach of splitting the cost. I guess in the end it's a matter of how one defines the purpose of bitcoin.  

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