Intermediate Agricultural Machines Energy Efficiency: The Example of Harvesting and Threshing

The article compares fifteen different methods used to harvest and thresh wheat, from traditional manual solutions, to animal traction machines to modern combine harvesters. For each methodology, individual productivity in terms of field area worked in a unit of time by each individual operator, and specific productivity, in terms of field area worked per unit of energy are calculated. These parameters are related to the power available for each operator involved in the process, whether deriving from their muscles, animal prime mover or heat engine. The analysis shows that increasing individual power increases productivity, although with a reduced gradient at high powers. On the other hand, low power solutions are up to ten times more energy efficient, confirming that intermediate technologies can be an appropriate solution with a view to sustainability.