But, why? Regarding your farmer example, there are examples throughout history of farming that fed many without the involvement of currency or the paying off of debt. Take a look into syndicalized Spain if you ever get a chance (~1936-1939). Farms were collectivized and worked on by volunteers, distributions done by need with some bookkeeping to track how many people were in certain regions. Worked pretty well until the communists decided it needed to be centrally controlled and kicked out the anarchists!

Everyone always starts every future speculation assuming capitalism, or at least, currency. Isn't it worth challenging these core baseline assumptions? At the very least, the other ground is well covered, so we might come up with a little more interesting.