Scenario analysis of life cycle greenhouse gas emissions of Darjeeling tea

Following water, tea is the second most consumed drink worldwide and has the peculiarity that not only its production but especially its preparation can be associated with considerable greenhouse gas (GHG) emissions. The aims of this study were to calculate the cradle-to-gate and cradle-to-grave product carbon footprint (PCF) of Darjeeling tea and to identify potentials to reduce GHG emissions along its life cycle. Therefore, various options for action and their impact on the PCF were modeled by using a scenario analysis.

To assess the PCF of Darjeeling tea, the method based on ISO/TS 14067 was used with some limitations. Besides one base scenario, alternative cradle-to-gate scenarios and different use profiles were modeled. The results were split in a cradle-to-gate and a cradle-to-grave perspective. For the cradle-to-gate phase a functional unit of one kilogram loose black Darjeeling tea was chosen, whereas for the cradle-to-grave phase one liter black Darjeeling tea that is prepared and ready to drink in Germany was seen as appropriate functional unit. Primary data for the present study has been collected from local farmers, manufacturers, and agents in Darjeeling, Kolkata, and Rotterdam. For secondary data, the database ecoinvent 2.2 was mainly used.

The cradle-to-gate PCF of 1 kg Darjeeling tea is between 7.1 and 25.3 kg CO₂e depending on the cultivation method, energy sources used, or mode of transportation. The cradle-to-grave PCF for 1 l organic Darjeeling tea is about 0.15 kg CO₂e. The largest share, 51 %, makes up the use phase, which is clearly dominated by the boiling of water. The variety of possible use profiles yields results of great breadth. It shows that the life cycle of organic Darjeeling tea transported by ship, depending on the preparation variants can cause emissions from 0.12 to 0.51 kg CO₂e/l tea.

The main reduction potentials for GHG emissions were identified in the process of water boiling, the intercontinental transport mode, and the cultivation method. Since the climate impact of tea strongly depends on the way in which it is prepared, the consumer has a decisive influence on the PCF. Therefore, in order to make a reliable statement about the climate performance of consumer goods such as tea, the whole life cycle must be considered.