Energetic analysis of draught animal hay harvest: an alternative look at cellulosic biomass.

For most of human history, biomass has been the primary energy input for society. Concerns regarding climate change, resource depletion and energy security have prompted renewed interest in the use of biomass as an energy source. Draught animals, in addition to being a traditional means of utilizing biomass, can be used to harvest biomass. Data from oxen-powered haying at Green Mountain College in Vermont show an energy return on energy invested (EROI) of 5.93 for pelletized grass, with 80% of the energy input being renewable. Comparisons with other draught animal hay harvesting systems suggest that this performance is mediocre. Modest goals for system improvements could raise the EROI to over 10. Due to their competitive energy efficiency and low capital requirements, draught animals deserve more serious examination as a renewable energy source.