Earlier quoted context omitted.
Transactions do not matter at all. The energy is used to mine blocks. The same energy is used whether the blocks contain transactions or are empty
Ok so there's no value for a transaction, but rather for a block. However,many miners compete for a block, is this accounted for or is the number an average for the winning miner?
reward_per_block * price = value_per_block
cost_per_hash * avg_hashes_to_find_block = cost_per_block
cost_per_hash is the cost of electricity and mining hardware . If value_per_block > cost_per_block, mining is profitable and more miners will join the network, increasing avg_hashes_to_find_block, until value_per_block == cost_per_block.
co2_emissions = avg_hashes_to_find_block * co2_per_hash.
So the emissions are a function of the price of bitcoin and the price of (electricity + mining hardware).