Do you have any experience with CO2 pumps? I would like to know what pressure can inflate one 16g CO2 cartridge in tire.
I’m special interested in Duro Crux 29"x3,25", Surly Knard 29"x3" and King George 36"x2 21/4".
I have CO2 cartridges that I carry for emergency fixing of flats, and I’ve used them a couple of times. Two things: 1. expect to use at least two of the cartridges to fill the tire, 2. When you get home flatten the tire and refill it with regular air. Otherwise it will go flat quickly. For some reason, the CO2 bleeds out faster than regular air.
Just my personal experience. (This is with a 32" road tire, fixing flats that have occurred while out riding on paved surfaces. For some reason I’ve never had a flat while muni riding.) I now carry a very small conventional air pump along with the CO2 cartridges. (Belts and suspenders. 
)
Here’s a chart that may help. As Lance says, CO2 acts differently than air in a tire. CO2 dissolves readily in elastomers (tire rubber) so the initial pressure will decrease much more quickly than with air.
I always carry a proper pump. I would only use CO2 for racing. The Lezyne pumps are my favorite. The Micro Floor Drive HP comes in at 150g and is a really nice floor-style pump that fits in a camelback easily. If you want to go even lighter, the smaller pumps they sell come in around 80g. If you want faster pumping, they make high volume pumps for a weight penalty of about 20-50 grams, but they’ll still go up to 80 or 90 psi… more than enough for unicycle applications. All their bits are aluminum and gaskets are replaceable.
I carry the high volume version of the floor pump while I’m on the 36er. You’re not filling that thing up reasonably with CO2 cartridges. You’d have to use at least a handful of them.
It’s not worth getting stuck out on the trail for me.
Thank you for your answers. I thought I´ll use 16g cartridges on marathons because of fast inflate tire. I need minimum 3 pcs for Surly Knard… It’s not very good solution. Maybe I´ll use one 16g cartridge and then small aluminium pump.
According to this news, inflating a 29x3.0 tire to 20-22 psi requires 38g of CO2.
So with your initial requirements, you should be able to get about 10 psi out of a 16g CO2 cartridge.