energy flow in conventional dairy farms with emphasis on co2 emission from electricity generation and use of technical equipment and machines

introduction energy is one of the most important commodities that make up a large proportion of international trade. among all the countries in the world, iran is known as semi-industrial developing country which is rich in energy such as non-renewable energy in particular fossil fuel. use of energy affects the environment in various forms of pollution. in the agricultural sector, the fao report states that livestock production has a major contribution to the world’s environmental problem (sutton et al., 2011). materials and methods this study analyzes energy flow and greenhouse gas emission in conventional dairy farms in mazandaran province. the required data for this study was collected by conducting interviews and filling up questionnaires from 26 cattlemen. from the questionnaires, information on five inputs such as labor, livestock feeding, diesel fuel, electricity and technical equipment and machines as well as milk product for 159 dairy cattle was collected. finally, energy productivity, efficiency and emissions of greenhouse gases were calculated for methane (ch4), nitrous oxid (n2o) and carbon dioxide (co2). results and discussion the results indicated that total energy which has been used to produce one liter of milk was 27.745 mega jul. livestock feeding and fuel were energy inputs that has been extensively consumed. in this relation, 47.4% and 28.5% of the total energy consumption were drawn from the livestock feeding and fuel, respectively. in the study conducted by sainz (2003), livestock feeding with 70% of the total energy consumption was also found as the largest input in terms of consuming energy. technical equipment with 22.8% of the total energy consumption was found the third place. a low proportion (0.8%) of the total energy consumption was drawn from labor. electric power with 0.5% of the total energy consumption was placed at the last. energy efficiency was measured at 0.257. the proportion of renewable and non-renewable energy in one-litter milk production was measured by 48.2% and 51.8%, respectively. the total greenhouse gas emitted toproduceone litter of milk is equal to 0.622 kg of carbon dioxide that is higher than the amount of carbon dioxide generated from dairy farms in the united states (sainz, 2003), but lower than the amount produced by dairy farms in portugal (castanheira et al., 2010). for the european countries, the average of greenhouse gas emission generated from dairy farms was calculated about 0.45 carbon dioxide equivalent. technical equipment, machines and fuel with generating 0.45 and 0.16 kg of carbon dioxide equivalent were the most contribution to greenhouse gas emission. according to the calculations, the two inputs emitted 72.3% and 25.7% of the total greenhouse gas emission in producing one litter of milk. only 2% of the total greenhouse gas emission that is equal to 0.012 kg of carbon dioxide equivalent was created from electricity generation. in the united states, diesel fuel and electricity with a contribution of 27% to 40% of the total greenhouse gasemissions were realized as the most polluted inputs. furthermore, in ireland and britain, the diesel fuel and electricity with producing 0.03 and 0.002 of carbon dioxide equivalent were realized as the most polluted inputs for producing one litter of milk. this suggests that diet re-formulation with special consideration to the output is an effective solution to the problem mentioned above. considering technical equipment and fuel as the most pollutant inputs, transferring equipment from natural gas consumption to diesel consumption decreases both energy consumption and negative-environmental externalities. conclusion considering that the livestock feeding has the largest amount of energy consumption, thedairy cow feed formulation should be considered as the most important concern. in relation to diesel fuel, replacement of natural gas with diesel fuel can reduce greenhouse gas emissions at a large extend