There are two types of shredders available - automatic and manual. Automatic shredders are faster and less strenuous for the operator. On the other hand, they need electricity and are more expensive to operate.
Manual shredders are equipped with a crank, which is rotated when shredding and suitable for occasional use. This makes manual machines unsuitable for the large amounts of material, because it is rather tedious. On the other hand, the advantage is it can function without electricity and comes at a lower purchase price.