The nonparametric method of data envelopment analysis (DEA) was used to investigate the energy efficiency and CO 2 emission of barley farm in Hamedan province of Iran. The method was used based on eight energy inputs including human labor, machinery, diesel fuel, fertilizers, farmyard manure, biocide, electricity and seed energy and single output of barley yield and technical, pure technical, scale and cross efficiencies were calculated using CCR and BCC models. The results showed that the average values of technical, pure technical and scale efficiency scores of farmers were 0.788, 0.941 and 0.833, respectively. Also, energy saving target ratio for barley production was calculated as 11.45%, indicating that by following the recommendations of this study, about 2,865 MJ ha -1 of total input energy could be saved with the same constant level of barley yield. Moreover the contribution of chemical fertilizer input from total saving energy was 34.88% which was the highest share followed by diesel fuel (25.88%) and electricity (20.89%) energy inputs. On one hand, optimization of energy use improved the energy use efficiency, energy productivity and net energy by 12.94%, 15.55% and 6.16%, respectively. On the other hand, total greenhouse gases (GHG) emission was 885.56 kg CO 2eq ha -1, which indicated that, the total CO 2 emissions can be reduced by 11.06%.
