In agriculture, a pulper is a machine designed to remove pulp (I.e. the soft flesh from agricultural produce). For example, in coffee growing the ripe, red cherries are picked from the coffee bushes and prior to fermentation and later drying the soft pulp needs to be removed (otherwise a potentially uncontrollable fermentation/rot will occur). In the case of coffee the pulping is normally done in a pulper that is either hand-cranked or engine-driven; the beans are emptied into an elevated hopper and then dropped through a narrow slot within which they come into contact with a rotating spiked drum that removes the pulp or flesh. Again in the case of coffee, the sticky beans that result from this process then have to be washed, fermented, washed again and dried prior to further processing (milling to remove the parchment) and then roasting.
In paper making, a pulper is a machine that produces pulp from cellulose fibres; this pulp can directly be used by a paper machine.