Well, I for one aren't inclined to just take their word for it. First off, polymerising atmospheric compounds is extremely energy intensive, no matter how you slice it. It's simple and utterly unavoidable thermodynamics. It's not a question of the process, it's the fact that moving the necessary electrons into the higher energy states needed to form the new bonds requires a set minimum input of energy. It's a fundamental law of physics, there's no way around it.
Not only that, but the fact that they're using microbes can only means it's going to be far more energy intensive in practice than is thermodynamically required. Microbes, like all other living things, need energy just to stay alive. Then of course, the energy that does go towards producing proteins and carbs isn't going to be anywhere near 100% efficient. So yeah, I would be extremely surprised if the power to weight ratio of this stuff isn't through the fucking roof. Add to that the fact that the electricity that goes into powering this machine comes from the grid, which in Finland is only around 25% renewable, and it'll likely be a couple of orders of magnitude more expensive and environmentally unfriendly than the equivalent energy cost of producing the fertalisers, pesticides and fuel needed to grow the same mass of food.
I know this is just speculation on my part, and I for one would love to see someone check the actual numbers involved, but again, this is largely why these "things from air" processes fail miserably. I'll believe that this will be the one to buck the trend when I see some actual proof.