They already run liquid cooling loops - compute density is way beyond what could circulate through air. Adding more pipes is probably trivial on the scale of datacenter expenses
Liquid cooling loops don't solve the problem of needing to reject the heat to the atmosphere outside of the building. It just makes it more efficient to transport the heat. At the grossest possible definition, a datacenter of N megawatts on Y acres of land is going to emit the same amount of heat whether it's air cooled equipment or liquid is used to take the heat to the outdoor heat exchanging equipment. On the scale of any very large datacenter the heat exchanging equipment is visible from aerial photos (and from space), take a look at google maps for some of the largest hyperscalers for examples.
I assume that "liquid cooling loop" has an endpoint outside of the building which hosts hardware. In this case it's exactly same problem - just make pipes longer.
Do you need many acres of land to host a heat exchanger?
Do you need many acres of land to host a heat exchanger?