It seems that there are kelp forests right next to the driest desert on planet earth in Northern Chile.
I go back to my view that harvesting from a climax (kelp) forest implies increased carbon sequestration. I would guess that dragging kelp a few miles from the coast to the desert would imply a more or less permanent burial of the Carbon. I would also guess that sustainable harvesting of kelp would have moderate one off effect on the amount of carbon in the kelp forest where growth is limited by kelp shading kelp.
If so a huge flow of carbon out of the biosphere and into the dead dry desert could be managed for what I would guess is the modest cost of hauling the waste from agar production a few miles.
Kelp is currently harvested to extract agar (technically alginate) (beloved by molecular biologists but mostly used to make Ice cream slimy and I think the main ingredient in McDonald's thick shakes which contain no milk). I assume this leaves a lot of cellulose and other junk which is left to rot (an agar yield of over 50% of dry weight is big news kelp is, of course, wet being 80 to 90% water). It if were shipped and buried in the desert to rot over millenia that would make the world a cooler place.