What were some possible alternatives to slave labor?

The Industrial Revolution brought about machine technology, which would have been a better alternative, because it would be operated by the machines, not by people.

Domestic slave workers perform a variety of household services for an individual or a family, from providing care and elderly dependents to house keeping, including cleaning and household maintenance. Other responsibilities may include cooking, laundry and ironing, shopping for food and undertaking other household errands. Such work has always needed to be done but before the Industrialrenovation and the advent of labour saving devices, it was physically much harder.