Unfortunately the laws of thermodynamics will get in the way. Cannabis farming uses electricity to build organic chemicals and outputs waste heat at 40°C; bitcoin mining uses electricity to solve equations and outputs waste heat at 40°C. There's not really any way to use the waste products of one as an input to the other.
A CPU/ASIC can be seen as an electrical heater with extra steps. So why not heat up your plants with your CPU. The energy flow is: power plant -> CPU -> greenhouse -> the atmosphere
I remember seeing some talk about a company creating ASIC blocks to heat houses but grows afaik don't generally need more heat the lights and everything creates enough heat for the plants.
Just imagine that one scene from the Snatch! where Lincoln instead of a fianite tries to fend off a golden-painted manhole cover that the Pikies convinced him was a Bitcoin :)
Edit: Oh God, it's actually an actual thing that already exists: [1]
So I think it's more Lock, Stock, and Two Smoking barrels - with the big Bitcoin penny being used to smash in people's heads along the way -
"hey, why's there so much blood on this thing?"
"you don't wanna know"
"I do want to know Tom, I do - enlighten me, where did all this blood come from? Wait a minute, is that hair and bits of brain down here? You don't normally see that kind of thing on coinage of the realm Tom"
on edit: formatting, and made dialog more Ritchiean.
