Can I heat with…

Your plant needs heat when the temperature is too low. NOT when you are doing laundry. And, heat from a clothes dryer is very uncontrollable. You could very easily damage your plants. Just get an inexpensive space heater.

That air is contaminated, I would never use it. There is plenty of small heaters for begining of grow. Deeper you will go, stronger light you will need. There is no light without heat. Usually my light do all of heating during day time, for night I still put heaters on timer. Cheap controller costs like 20 quid,buy one, plug heater to it and all worries with that bit will be forgotten. You will spent max 50£ on all heating regulating and control units and it will work and last forever. All the Best !

Dryer as in washing machine and clothes dryer?? I absolutely would not, full stop. That air going into the potential grow room aka coming out of the dryer is crazy humid/moist and filled with particulate matter that would get trapped in the buds. Part of that unwanted matter would be smells and chemicals from dryer sheets or sent booster beads, that shits wack. You would also need to worry about lint and micro fibres getting in the resin. Don't want that lacing your buds. The bigger issue though is this, if it's a gas powered dryer you have, it needs to be vented outside for potential carbon monoxide gas buildup. If it was being being vented indoors you could cause some serious harm. Over all not a great idea if its that kinda of dryer. Plus you can put a filter on a dryer vent it would cause even more issues with the dryer itself. even a hair dryer is still dumb and a large fire hazard. Just get a mini space heater or a few 100w incandescent bulbs. They mainly produce heat. Happy Growing