Curing with heat and oxygen is the best way to remove hydrocarbons (fats, oils, alcohols) from tobacco.
Nicotine boils 247 degrees celcius, so it should be cured at a lower temperature than this.
Sunlight destroys the nicotine, and biodegradation may only destroy some of the [harmful] hydrocarbons.
Fire curing may introduce hydrocarbons to the tobacco.