Volunteering isn't bartering. Assuming you meant bartering...
It is not bartering in the strict meaning I guess, no. Still I did not mean bartering, I meant exactly what I said.
In exchange for nothing! That is what volunteering means!
Picture everybody doing this --or for starters, picture a small town doing this, so you can also get an idea of how it can spread to neighboring towns.
Consider this scenario: a bridge breaks, and needs to be fixed: it needs engineers, masons perhaps, other experts, workers, all that. Those are the the ones that are going to physically fix it. It may also need replacement material, which has a 'cost' (a monetary cost). Last, there is a bunch of politicians and burreaucrats that have to rule on the economics and whatnot and the rest of the 'administrative stuff' regarding the rebuilding of the bridge, which is a crowd that somehow has hypnotized everyone over the years into believing that their work is essential.
In this scenario, the town's experts volunteer time to do their best to fix the bridge. The town's best minds, via an emergent selection from the town itself, are on to it. People who have nothing direct to volunteer, volunteer snacks and entertainment for the people who do the work. Snacks get too many too soon, and the town has an excess that it can perhaps DONATE to a neighboring town (that is going through a similar 'bartering', if you want to call it as such, process) and that neighboring town may have an excess of bridge material (the material that has a 'cost') to DONATE to the town with the faulty bridge.
Where does money fit here? Nowhere. Where do burreaucrats fit here? Nowhere. Bridge gets fixed? Hell yes.
As long as people keep greed in check, this can work surprisingly well.