Comparison of horse and tractor traction using emergy analysis

Horse traction in the context of Sweden 1927 and tractor traction in the context of Sweden 1996 were compared in terms of their resource requirements. Flows of energy, material and service from the environment and the economy were identified for the two traction-producing systems, The environmental work and human activity involved in generating necessary inputs for the systems were evaluated on a common basis, using emergy analysis. The main difference between the systems was found in their energy signature. Sixty percent of the horse inputs were renewable, compared with only 9% renewable inputs for the tractor. Ecological technology was replaced by mechanical technology. This represented a shift from a technology that was maintained and driven by mainly locally-generated qualities and driven on local flow-limited renewable sources to a technology controlled and supported by non-local processes and driven on non-renewable sources. A decrease in available fuels and minerals might cause a change in the choice of technology and ecological technology might then be reintroduced into our society as a whole and not only into the agricultural sector. Evaluating management strategies that consider direct and indirect requirements for natural resources from the economic system and 'free' natural resources from the environment currently requires a method able to integrate both. Emergy analysis provides that ability. (C) 2002 Elsevier Science B.V. All rights reserved.