Depends on how hard you go at it, and what your eating habits are like.
If you ride for 30 minutes/day, at a level of effort that gets you sweaty and winded, it can use up a decent amount of calories - which certainly can help with weight loss.
But if you're overeating badly, 30 minutes won't be enough to to let you lose any weight.
Likewise, 30 minutes of just casually turning the pedals won't use up any important amount either.
Depends on how hard you ride. If you're only pootling around - not many. If you're getting sweaty and winded, as much as 400.
The degree of resistence will determine how much. You would have to account for your weight, the weight of the bike, the surface you're riding on, the material, density and texture of the tires you're riding on, the angle of the surface you're riding on...It's subjective, so has no one right answer.
Riding a bike is good for your cardio and will give you great legs. It may help you gain a flat stomach as well depending on how long you ride and how fast.
about 50-60 psi for uphill riding
Chemistry has been involved in the production of pretty much every part of the bike. All from the paint to refining the metals the bike is made of.
Ice is slippery, right?
Pretty much all of them.
I don't think it will do much except flatten the grass and kill it.
Depends entirely on how much riding the person does, and what the person would have done otherwise. If the person is riding a bicylce instread of using an motorized vehicle, then some CO2 will be saved. If the person is riding instead of walking, then there's no difference.
about 150
No single answer, depends on how much money you want to spend and what kind of riding you want to do.
There's no single answer to that, it depends on how much money you want to spend and what kind of riding you want to do.