The article states that 1 kg of muscle mass burns an additional 25-50 calories; the high estimate would tranlate to an additional 11.4 Calories per pound of lean muscle mass added. Consequently, this value is very similar to a value of 13 Calories/pound that I determined by statistically analyzing the data from my lab at Baylor University. The most conservative estimate predicts that an extra pound of muscle burns only about 7 Calories/pound.
A value of 30-50 kcal/lb of lean muscle is unrealistic and untrue, though it is published a lot in popular media. Numbers this high do not make practical sense. For instance, suppose a typical male bobybuilder has 100 lbs of muscle mass (not including the bone, organs and other components of fat-free mass), the mythical numbers would suggest that his muscle alone is burning between 3000-5000 Calories a day. On top of that, organs burn far more Calories per pound than muscle, so based on popular dogma, the man above maybe about 6000 Calories/day. I've measure the metabolism of countless athetic men, and roughly 3000 total Calories per day would be high for an athletic man of this size.
When high values are provided in articles, they are not supported by scientific literature; however, articles that reference research always suggest lower number, which generally range between 5-15 Calories per pound of muscle. Another good article that addresses this topic is below:
Jean offers nutrition coaching for weight loss, muscle gain, or any of your personal goals at her office in the Alico building in downtown Waco, TX right in the heart of central Texas. She also offers personal training services at Ironhorse gym on the corner of Franklin and 17th, which is also very convenient to downtown Waco. Contact information can be found on her personal website.