Abstract In this study, data envelopment analysis (DEA) approach was utilized for optimizing
required energy and comparing greenhouse gas (GHG) emissions between efficient and inefficient
units for watermelon production in Guilan province of Iran. For this purpose, two models including
constant returns to scale (CCR) and variable returns to scale (BCC) were applied to determine efficiency
scores for watermelon producers. Based on the results, the average of technical, pure technical
and scale efficiency was computed as 0.867, 0.957 and 0.906, respectively. Also, 36 and 71
watermelon producers were efficient based on CCR and BCC models, respectively. The total optimum
energy required and energy saving were calculated as 34228.21 and 6000.77 MJ ha1, respectively.
Moreover, the highest percentage of energy saving belonged to the chemical fertilizers with
76.62%. The energy use efficiency of optimum units was determined as 1.52 and this rate increased
about 18% when compared with existing farms. Also, the energy forms including direct, indirect,
renewable and non-renewable energy improved about 15%, 15%, 10% and 15%, respectively. Furthermore,
total GHG emissions of efficient and inefficient farms were found to be about 869 and
1239 kgCO2eq. ha1, respectively. Biocides had the highest difference of GHG emissions between
efficient and inefficient farms. Finally, it can be said that applying the DEA approach can reduce