Very little smoke; exhaust is drafted outside with a fan through a horizontal or vertical vent pipe.
A passive system requiring a vertical chimney so that smoke can rise and flow outside.
Find 40-pound bags of pellets at home centers and hardware and grocery stores in cold climates. Dealers will also deliver pellets by the ton.
You may be able to harvest your own hardwood, but it must be properly seasoned. It's also sold by the bundle at stores or by the cord from tree-care pros.
Bags of pellets should be kept indoors to guard against moisture infiltration.
Wood can be stacked outside under cover and away from the house to prevent damage from termites.