Liquid nitrogen is a byproduct? I thought it is normal commercial product. It can be produced with liquid oxygen, but don't they use LN to recover energy used to freeze air? Not reusing LN and just dumping it would be like wasting 80% of energy.<p>> Owners will typically have to replace the nitrogen every seven to 10 days, depending how much they use it.<p>100L tank of LN "soaks up" about 8kWh of energy when heating from liquid to -10C, so like a heat pump transferring 200W for 5h/day for 8 days. Not that much. 100L of LN costs about $3000 where I live, 8kWh of electricity costs about $2, no one sane would use LN2 instead of electricity.