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Cryptocurrency and NFTs are all over the news right now, with grabby headlines about the megarich buying jpegs for millions of pounds, or how blockchain is going to change the world by decentralizing your hamster or something.
There’s no doubt it's big business: JPMorgan recently pegged the value of the NFT market at $7 billion , and TIME magazine is now accepting cryptocurrency for subscriptions.
But the other side of the headlines tells a different story, one about how this new technology is also killing the planet with carbon emissions, which come from the energy consumed by the intense calculations that underpin the whole thing.
I set myself a big challenge for the DesignSpark Air Quality Project – to investigate the real impact NFTs have on our air, and then to see what I could do to change it.
Most often, NFTs are associated with digital art, so my plan is to make a piece of NFT art that is not just carbon neutral, but actually uses blockchain technology to improve air quality.
There’s just one problem with this: I’m not a crypto guru. To me, a bitcoin is what you find in the washing machine if you don’t check your pockets before you do laundry. And an NFT? Doesn’t that mean network fault tolerance or something?
Step one in my project was to swat up on all the jargon and get up to speed. So if you’re a blockchain beginner like me, read on to find out what I discovered.
(Click on the headings to jump ahead )
- What is a blockchain?
- What's an NFT?
- What do you actually own?
- Why do some people think they’re bad for the planet?
- Are they right? How bad are they really?
- What’s being done? And is it enough?
- What am I going to do?
In short, it’s an account book. A really fancy account book.
The thing that makes it fancy is that it’s distributed, decentralised and cryptographically secure.
In the ordinary, non-blockchain world there’s usually just one copy of the account book and it’s ultimately controlled by a single person or organisation. If that person or organisation is a bad actor and decides to change the accounts, there’s limited opportunity for anyone to spot the foul play. Or, if the body controlling the accounts decides not to bother anymore, the whole record could just disappear.
With blockchains, everyone has a copy of the account book, and everyone can add to it. That’s the decentralised bit: no single party has total control over the ledger. For many people this is key to why blockchain is an important and revolutionary technology, it’s supposed to be accessible, transparent and democratic.
But if anyone can add to this account book, you need a way to check their addition is valid, and update everyone else’s copies. That’s where cryptography and consensus come in.
To understand this better, let’s take a look at what actually happens when you try and make a transaction on a blockchain network, like bitcoin for example.
Say you want to send some bitcoin to a friend. You open your wallet software, which is a bit like a banking app, and enter your friend’s wallet address, which is a bit like a bank account number, a way of identifying them on the network.
When you hit send, your requested transaction is broadcast to all the “nodes” on the network (computers that are running the blockchain software).
At any one time, there are a bunch of these pending transactions, so nodes group a selection of them into a “block” that they will try to add to the chain.
But first, the transactions must be verified – nodes check that they conform to the rules of the network, and that each transaction really came from the wallet address it appears to come from. This check relies on your public key, which is shared with everyone on the network, and your private key, which only you have access to. Messages encrypted with your private key can only be decrypted with your public key, so it’s easy to prove that your transaction really came from you.
And if you’re worried someone could guess your private key and impersonate you, fear not. It would take a supercomputer a billion years, so it’s very hard to fake a transaction.
Once the block is checked, a node must complete a difficult cryptographic puzzle that’s based on the transactions being added and some information about the previous block (that’s the chain part in blockchain). This is called proof-of-work and it’ll become important later.
The node that’s first to solve the puzzle broadcasts their solution to the other nodes on the network, which confirm the solution and update their copies of the ledger before starting to work on the next block.
They’re incentivised to do this because the node that proposed the next block gets a reward in bitcoins for doing so (as well as the transaction fees associated with the transactions in the block).
Part of the security comes from the fact that each new block is based on information from the previous block, so to change a transaction in the past would require rewriting the whole blockchain. Given that the puzzles are so difficult to solve, it would take an unfeasible amount of computing power to do that. And then you’d have to also compute any more blocks that had been added in the meantime, so you eventually have the longest chain, in order for all the other nodes to accept your version of the ledger as the real one.
If you had that much computing power, there are probably more lucrative things you could do with it.
So all in all, it’s pretty hard to steal cryptocurrency, which is another reason proponents think blockchains are so good.
And they come in different flavours. There are a few that have become popular – bitcoin and Ethereum being two of the biggest.
Although blockchains have been associated with currency, that’s not their only use. They can record a public ledger of anything, really. People have proposed using the technology for purposes as diverse as insurance, land registry, decentralised lending and more.
What’s an NFT?
It stands for “Non-Fungible Token”.
Well. That clears things up…
Tokens are digital assets that live on a blockchain – so bitcoins, for example, are a kind of token. Except one bitcoin is much like another bitcoin. They’re not individually special; if I swapped one of my bitcoins for one of your bitcoins, neither of us would be worse off. In other words, bitcoins are fungible tokens.
A non-fungible token on the other hand is unique, it can’t be swapped like-for-like with another. So an NFT is like a special, one-off digital asset.
Not all blockchains support them – bitcoin, the world’s most well-known blockchain, doesn’t support NFTs. Because blockchains are essentially just made of code, you can think of this as a bit like how some software runs on one operating system and not another.
The vast majority of NTFs being bought and sold today live on the Ethereum blockchain.
In fact, because blockchains are made of code, your tokens can execute code themselves, so NFTs can do clever things. Some can change depending on your wallet transactions or the weather. People have made self-replicating NFTs and all sorts.
Just like with other kinds of programming and technology, standards have developed, with the most well-known being ERC-721. This just defines a set of functions and properties the NFT code must have for it to be compliant. This structure guarantees the uniqueness of the tokens, as well as some other useful things.
What do you actually own?
In the simplest case, what you own is a certificate: a bit of code that lives on an immutable public ledger and is tied to your wallet address.
This bit of code usually has some attributes, or metadata, stored in it that points to something. So in the case of art, your token will often have a URI which points to a location where you can find a copy of the work. This could be an ordinary fileserver somewhere, or more usually an address on IPFS – a peer-to-peer file storage system.
There’s a lot of confusion over this, with plenty of media outlets reporting that art NFTs mean you own “the original copy” of a jpeg, which doesn’t really make sense – even on the artist’s own computer there are numerous “copies”, and when they upload the art to a server, it’s probably stored on thousands of machines simultaneously. You own a certificate that points to a copy of that work, marking you as the “owner”.
Some NFTs have the artwork baked into the code, but this is less common because it increases the computation that needs to be done on the blockchain, which also increases the transaction fees.
Although overall what you own is just a little piece of code, NFTs can stand-in for a lot more – individuals or companies can offer real-world benefits for owning one. My favourite example is probably the company that sold an NFT that gives the owner the chance to touch a tungsten cube once a year .
Nike even patented the idea of NFTrainers: “owners of ‘CryptoKicks’ will be able to intermingle or breed the digital shoe with another digital shoe to create ‘shoe offspring’ and have the offspring made as a new, tangible pair of shoes.” .
Why do some people think they’re bad for the planet?
As we saw earlier, adding a block to the chain requires all nodes in the network to work on cracking deliberately difficult cryptographic puzzles. All that computing power uses a lot of energy
By one recent estimate, Ethereum uses 23 Terawatt hours of electricity every year, which is close to the annual electricity consumption of Ireland .
That energy use comes with a carbon cost. And to break down how bad it is, it makes sense to try and work out the average emissions per transaction. This is hard to determine because different blocks store different numbers of transactions, and it’s impossible to know exactly what portion of the energy used comes from renewable sources.
The website Carbon.fyi looks at the spread of where network nodes are located and uses each country’s average split of renewable and non-renewable energy to come up with an estimate: 18.05 kgCO2 per transaction .
For context, the UK government says that the average per capita carbon footprint in the country is 6 tonnes of CO2 per year .
Framed this way, an Ethereum transaction might seem small, but we have to also take into account that a single NFT purchase can involve many transactions: bidding, cancelling bids, transferring ownership etc.
Obviously, this means the more NFTs you have, the worse for the planet, but what’s the average spread?
Since the Ethereum blockchain is a public record, anyone can explore it – so I picked a couple of wallet addresses and used the carbon.fyi calculator to estimate their specific carbon impact. The calculator scans the blockchain to look for the transactions associated with that wallet address to calculate its particular contribution.
I chose one wallet address active since 2018 that currently owned 559 NFTs on the Opensea marketplace and one wallet address that had been active since December 2021 and only had 2 NFTs. There was quite a significant difference. The first wallet had racked up a whopping 95,274 kg of CO2, nearly 16 times the UK annual average, while the second wallet came in at just 141 kg.
It goes to show how smaller amounts can add up quickly. Indeed, one artist who tried selling NFTs of his work in order to put the profits towards lowering the energy consumption of his studio had a nasty surprise when trying to calculate their impact: “I realized that those pieces, which had sold out in less than ten minutes, used more than 8,000kWh, more than my studio’s power consumption for the last two years.” 
Are they right? How bad are they really?
There’s no denying that the blockchains we’ve discussed use a lot of energy – but what portion of the network do NFTs occupy? On the Ethereum network, NFT related transactions only account for about 5-20% of the total .
So perhaps the rest of the network transactions, including job boards, social media networks, “DApps” and decentralised lending, should catch as much flack as NFTs.
Even if we’re just talking about art, the traditional art world isn’t without its vices: an often overlooked source of carbon emissions is the shipping of artworks to different galleries for temporary exhibitions, for example .
Another counterargument goes that NFTs shouldn't be counted as having any footprint, since the network would be running whether or not you’re making transactions on it – kind of like how a scheduled flight will still fly even if you don’t buy a ticket. That feels like flawed logic to me, since most people accept the idea of a flight as having a carbon footprint.
Even if our estimate for the carbon cost per transaction is rough, it makes sense to look at it in the context of other carbon costs – especially given that many ordinary things are “worse” than we think.
A 4-oz cheeseburger will set you back around 3.2kg CO2, and commuting 10 miles in bad traffic costs 16kg CO2 .
So if you drive to work most days and eat a cheeseburger a week, a few NFTs would be virtuous in comparison. And flying return from London to New York takes around 986 kg of CO2 per passenger , so a holiday to the States is much worse again.
But perhaps it makes more sense to compare NFTs with other digital things.
Not looking so good… But then again, the little things do add up. For example, the UK could reduce its carbon footprint by 16,433 tonnes of carbon a year if everyone sent one less “thank you” email .
Thinking about cryptocurrency in general, what about making the comparison with traditional banking?
A group of nonprofits in 2020 discovered that the top banks in the world have given $2.7 trillion to fossil fuel companies since 2015 . Although perhaps this isn’t so relevant until we start getting our pensions in bitcoin.
Another study claims that traditional banking uses twice as much energy as bitcoin, when you take into account the overheads of running bank branches and online banking . But considering far more money is exchanged traditionally than through bitcoin, surely that’s to be expected?
Bitcoin and other blockchains do have a secret weapon though – a single transaction could theoretically contain up to 32,256 “outputs”, which would need to be split into 32,256 separate transactions in traditional banking. Plus, you could argue that it’s hard to compare traditional banking and bitcoin because traditional banking relies on other services and providers, whereas blockchain technologies are self-contained.
It’s easy to tie yourself in knots with this kind of reasoning – I briefly considered trying to work out the carbon cost of writing this article, how many google searches I did, the electricity I used…
In summary, the whole issue is thorny and it’s hard to make a like-for-like comparison, since everything depends on how you frame it.
There are certainly some artists who are making a living from their art in a way they weren’t able to before NFTs, and there is certainly some wild speculation afoot. But it’s not as though these things aren’t present in traditional art markets, and there are plenty of other carbon vices that aren’t as maligned as NFTs despite being just as bad for our air.
Ultimately, at the moment cryptocurrency definitely isn’t *good* from a carbon perspective, but if it turns out to provide benefits, there’s certainly room for this nascent technology to green-up. In fact, there are already some plans being set in motion.
What’s being done? And is it enough?
A surprising amount, really.
First off, there are plenty of projects involving the purchase of carbon offsets, by individual auctions and NFT marketplaces alike. For example, earlier this year NFT marketplace Nifty Gateway held an auction including eight carbon-negative NFTs, backed by 500 tons of CO2 offsets . Superrare and Zora, two other marketplaces, have also bought carbon offsets.
Marketplace NiftyGateway went one better and pledged to become totally carbon negative. But this announcement, as well as the net-negative auction, garnered a mixed reaction, with critics saying that relying on carbon offsets doesn’t fully solve the problem, and ignores the more fundamental issues with the tech .
A more thorough and long-term solution, then, might be to change the way the technology works.
Remember earlier when we talked about proof-of-work, where the network nodes all work on solving the difficult cryptographic puzzle? Well, it turns out there’s another way to add your blocks to the chain, and it’s called proof-of-stake.
Instead of having the nodes compete, a node is selected at random to add the next block. The other nodes then perform the much less computationally intensive task of checking that this block is sound.
The nodes still get a reward for adding a block, or verifying a proposed block, but in this system, the thing that prevents foul play is each node’s “stake”. Nodes front some cryptocurrency to participate and are essentially fined if they try to add dodgy blocks or confirm a block that doesn’t check out.
Crucially, proof-of-stake could cut a network’s energy consumption by more than 99% .
Proof-of-stake might hold other benefits too – some believe it even makes networks more secure .
One blockchain that already uses Proof of Stake is Flow, which underpins a popular series of NFT collectables called NBA Top Shot. And OpenSea, one of the biggest NFT marketplaces, has begun working on support for Flow. Tezos is another proof-of-stake network, which recently launched its own NFT marketplace.
In fact, for a while now, Ethereum itself has been on the path towards transitioning to poof-of-stake. It’s just been taking a bit longer than hoped. (The changeover was meant to happen in 2017.)
But according to Justin Drake of the Ethereum Foundation: “There’s essentially zero chance that we’re not going to eventually have proof-of-stake. It’s just a matter of when, and I would be absolutely shocked if it didn’t happen in 2022” .
You can see a comparison of the energy consumption of different blockchains here: https://docs.google.com/spreadsheets/d/1nEIFuu9oUVxtsQHgUZck-YhMD9xKXzl5AyD-Jj2j3lM/edit#gid=882144635
What am I going to do?
I’m going to need to think hard and tread carefully. I’ve got some decisions to make – like which blockchain I deploy my artwork on, and exactly how it’s structured.
I could make art on a greener blockchain, but if I want to sell it for a higher price so that the proceeds could, for instance, go towards planting trees, I might be better off with a larger marketplace.
There’s no doubt that Ethereum is the biggest player in the NFT space: at the moment, around 97% of NFT transactions are taking place on this network .
And Opensea is probably the best-known marketplace. Although most of their NFTs are Ethereum based, they do also support Polygon and Klatyn…
I’m certainly looking forward to trying to create, buy and sell my first NFTs, especially after reading a BBC article with the encouraging title “Buying a pink NFT cat was a crypto nightmare”.
I hope you’ll all join me in part 2, where I’ll be jumping into the code and starting to craft my (hopefully) eco-friendly NFT.