What's the carbon footprint of brewing a cup of tea?
You might think that tea is just an agricultural product and probably doesn't have much carbon emissions, perhaps only from the machinery used in tea processing or the slight carbon emissions from burning gas when boiling water for tea. However, the carbon footprint of tea is more complex than you might imagine.
To understand the carbon footprint of tea, one must grasp the concept of "product carbon footprint life cycle". Firstly, although it's called a "carbon" footprint, it actually includes emissions of various greenhouse gases, not just carbon dioxide. Different greenhouse gases have different Global Warming Potentials (GWP). This can be understood as their ability to cause the greenhouse effect compared to carbon dioxide. For example, methane (CH4) has a GWP value of about 28, meaning that emitting 1 kg of methane is equivalent to the greenhouse effect caused by 28 kg of carbon dioxide (CO2). In other words, emitting 1 kg of methane equals 28 kg of carbon dioxide equivalent (CO2e). Finally, the impact of all greenhouse gases is expressed in terms of carbon dioxide equivalent (CO2e).
Additionally, we need to understand the concept of a product's "life cycle". First, we must determine which stages need to be calculated in this cycle, what relevant emissions need to be calculated in these stages, and which emissions can be excluded. In Taiwan, the carbon footprint life cycle of tea products includes cradle-to-grave, which means from tea tree planting to the disposal of tea waste. Why is it called a cradle? You can think of it as a newborn baby sleeping in a cradle. For products, it refers to the raw materials needed for production. The raw material for tea making is simply the tea leaves harvested from tea trees. The tea tree might initially be a seed or a cutting, and we also need to include emissions from fertilizers and materials used in tea garden management. The grave, as you might guess, is the endpoint of the product. Just as humans are buried in coffins and then in graves after death, products will eventually become waste. For tea products, besides packaging waste, the used tea leaves from brewing also generate carbon emissions during waste treatment. The disposal of tea product waste is the endpoint.
Cradle-to-Grave: From tea seedling growth to tea waste disposal.
Cradle: Refers to the starting point of raw materials. Why use a cradle? It's like a newborn baby sleeping in a cradle.
Producing a product requires raw materials. The raw material for tea making is simply the fresh tea leaves harvested from tea trees, which come from tea gardens. The tea tree initially might be a seed or a cutting.
Grave: Refers to the endpoint of the product. Compared to the cradle? After death, people lie in coffins and are then buried in graves.
The used tea leaves after brewing, the process of disposing of tea leaves may also generate carbon emissions. When the tea product is discarded and finally disappears, that's the endpoint.
The cradle-to-grave product carbon footprint life cycle is the most complete. The cradle is just the starting point, and there are many greenhouse gas emission activities in the subsequent processes. For example, after the tea seedlings grow, various tea garden management activities are needed. During this period, there are emissions from the burning of agricultural machinery, nitrous oxide (N2O) emissions from fertilizer application, or electricity use of equipment in tea factories and gas use in drum-type roasting machines during the tea-making stage. Additionally, it extends to the packaging and transportation of tea products, to consumers boiling water to brew tea, and finally to the disposal of used tea leaves, which completes the full life cycle. In short, from planting tea trees to disposing of used tea leaves, all related carbon emissions are included in the tea product's carbon footprint life cycle, but some items can actually be excluded.
Cradle-to-Gate: From tea seedling growth to tea leaf harvesting in the garden, or from tea seedling growth to the output of tea products in the tea factory.
Gate: Refers to the cut-off point for emissions. For the tea industry, cradle-to-gate could be the tea garden or the tea factory. If it's a contracted tea garden, fresh tea leaves are a product, so cradle-to-gate would be the process (and emissions) from planting tea seedlings to harvesting fresh tea leaves in the garden. If it's a tea farmer who both grows tea and processes it, then cradle-to-gate would be from planting tea seedlings, through the tea-making process, and even to packaging it into a tea product.