Objective. This study estimates the life cycle CO2(LC-CO2)of the melon fruit(variety: Ams melon)grown in non-heated greenhouses in Choshi, Chiba Prefecture. We specified the highest emission stage and process of the LC-CO2 and clarified the reason of that. Our result was compared with the LC-CO2 of melons grown outdoors and the hybrid calculation method using an I-O table.
Method. The functional unit is the weight of CO2 emission per kilogram of melon, otherwise known as its “carbon footprint(CFP)”. The lifecycle of a melon is classified into five stages, which can be divided into eight processes. LC-CO2 is calculated as the total amount of CO2 emitted from each process.
Results and discussion. The estimated result of LC-CO2 of the melons produced in Choshi was 1,226.3 g-CO2eq/kg. The following is the result obtained from the five lifecycle stages. 1)The raw materials procurement stage: 806.5 g-CO2eq(component ratio: 65.8%), 2)the production stage: 262.0 g-CO2eq(21.4%), 3)the distribution and selling stage: 58.7 g-CO2eq(4.8%), 4)the operation and maintenance stage: 67.1g-CO2eq (5.5%), and 5)the disposal and recycling stage: 32.0 g-CO2eq(2.6%). As results of the comparison of the hybrid calculation method at the condition of heated greenhouse using fossil fuels and long transportation, our results are 1)the raw materials procurement stage over 80% of the total amount of LC-CO2 by the burning of fossil fuels, 2)the transportation process of the distribution and selling stage over 60% of the total amount of LC-CO2 by using air transportation, and 3)our estimation result at the same conditions(heating by fossil fuels and air transportation)are almost 4 times against the hybrid calculation method.
Conclusions. Most of the CO2 is emitted from the field preparing process in the raw materials procurement stage, especially from the fertilizer, e.g. chemical and organic, which accounts for 45.8% of the total melon LC-CO2. And in our comparison research of the growing processes between outdoor and greenhouse farming, the greenhouse melons show about 10% higher LC-CO2 than melons grown in outdoors. This result indicates the importance of greenhouse lifespans, and the recycling of greenhouses components.
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