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.
For the tea industry, cradle-to-gate could refer to either tea plantations or tea processing factories. If it's a contract tea plantation, tea leaves are considered a commodity, so cradle-to-gate refers to the emissions from planting tea seedlings to harvesting tea leaves in the plantation. If it's a tea farmer who both grows tea and processes it, then cradle-to-gate encompasses everything from planting tea seedlings through the tea processing stages, and may even include packaging the finished tea products.
Gate-to-Gate
This can be understood as a process occurring within an independent tea factory, from when raw materials are delivered through the factory gates until the finished products are transported out of the factory gates. The tea factory purchases fresh tea leaves (raw materials) from contracted tea farmers, produces finished or semi-finished products (goods) through tea processing operations. Finished products are packaged within the tea factory, while semi-finished products such as roughly processed tea still need to be sent elsewhere for stem removal or color sorting for refinement.
How are the stages of carbon footprint divided in Taiwan's tea industry?
The carbon footprint of Taiwanese tea products includes various greenhouse gas emissions from cradle to grave. However, how do we define which processes or stages need to be calculated for emissions? It is necessary to refer to the Carbon Footprint of Product-Product Category Rules (CFP-PCR) published by the Ministry of Environment. This document establishes a reference standard for similar product categories, defining the stages that generate carbon emissions and related assumptions. This article explains this based on the Ministry of Environment's Carbon Footprint of Product-Product Category Rules (CFP-PCR) for Tea, Version 4.0.
The Product Category Standard divides the life cycle scope of tea products into five stages:
Raw Material Acquisition: This includes carbon emissions from fertilizers, pesticides, consumables, and packaging materials used in tea leaf production; carbon emissions from energy resources used by agricultural machinery; transportation emissions from moving tea leaves from plantations to tea factories; and emissions from waste disposal.
Processing: First is the rough processing of tea, referred to as "primary processing" in the product category rules. For semi-fermented tea, this includes withering, pan-firing, rolling, and drying. Carbon emissions calculated include electricity usage in the tea factory and liquid petroleum gas combustion in pan-firing machines and Type A and B drying machines. Next is the tea refining stage, called "secondary processing," which includes stem removal, cutting, sorting, roasting, and blending. Finally, there is tea "packaging," which includes electricity used by vacuum machines. Overall, manufacturing stage emissions mainly come from energy resources (fuel and electricity) used by factory machinery, as well as emissions from waste transportation and processing.
Distribution and Sales: This covers emissions from transporting tea products to sales locations, including vehicle emissions. There may be several warehouses involved, all of which need to be defined. As for calculating emissions until the product reaches consumers' hands, since consumers are distributed throughout Taiwan, it's difficult to calculate accurately. Therefore, calculations typically only include transportation emissions from the tea factory to main sales points. Additionally, transportation scenarios need to consider factors such as distance, mode of transport, loading rate, ton-kilometers, average fuel consumption/cost, etc.
Consumption: The tea carbon footprint product category rules estimate consumer usage emissions through scenario assumptions. The scenario assumes a ratio of 3g of tea to 150ml of hot water, calculating the energy required to heat room-temperature water to boiling using electricity, liquefied petroleum gas, or natural gas. Since it's difficult to estimate how consumers will use the tea (they might cold-brew it or use different tea-to-water ratios), a uniform standard is established for calculating carbon emissions during the tea usage stage
Disposal: This also uses scenario assumptions, calculating the carbon emissions from tea waste disposal based on Taiwan's published ratios for common waste treatment methods: 1) incineration and 2) food waste recycling.
However, there are many differences in how product carbon footprints are defined across the lifecycle. Research from mainland China also divides tea carbon footprints into five stages, but with some differences in terminology and stage differentiation (Figure 3). This research includes the stages: 1. Cultivation 2. Processing 3. Packaging & Transport 4. Consumption 5. Disposal.
In this case study, the manufacturing stage only includes the rough processing and refining of tea leaves without packaging. Instead, packaging and distribution are classified in the same stage, possibly because the local tea industry chain often sells roughly processed tea before proceeding with standardized packaging. In contrast, Taiwan's product category rules include packaging in the manufacturing stage. Although packaging activities represent a very small proportion of the overall tea carbon footprint, calculating them in different stages still results in slight differences.
Overall, calculating the carbon footprint of tea may seem simple, but it actually requires substantial data on tea garden management, tea processing, and even transportation to calculate the complete greenhouse gas emissions throughout the tea life cycle, which are then uniformly converted to carbon dioxide equivalents to represent the carbon footprint. After calculating the tea's carbon footprint, one typically seeks to obtain a carbon footprint label issued by the Ministry of Environment. For this purpose, carbon footprint verification must first be obtained. Applicants need to follow the aforementioned carbon footprint product category standards and ISO 14067:2018 standard to write a report on carbon footprint inventory, which must present all information about scenario assumptions, emission activities, and carbon footprint calculations, including emissions related to electricity, liquefied petroleum gas, packaging materials, fertilizers, etc., as well as emissions from distribution and sales, usage stage, and waste disposal stage scenario assumptions, ultimately calculating the emissions per unit of product. After a third-party verification agency conducts data verification and issues a verification statement, one can apply to the Ministry of Environment for a carbon footprint label for tea products.
Other questions about the carbon footprint of tea?
Q: Which stage of tea products has a higher proportion of carbon footprint?
The carbon footprint proportions vary depending on different countries' tea garden management, manufacturing methods, use and disposal scenario assumptions, carbon footprint coefficients for fuels and electricity, and differences in manufacturing stages for various tea types (such as black tea, green tea, partially fermented tea). Therefore, the stage with a higher carbon footprint proportion may differ by region and tea type.
Q: Do different tea consumption methods also create different carbon footprints?
Tea consumption methods indeed affect the carbon footprint. Most studies assume consumers use boiling hot water to brew tea leaves, but cold brewing would result in a different carbon footprint. Western research shows that black tea with milk has a higher carbon footprint, while in Taiwan, hand-shaken drinks with various ingredients would make calculations even more complex.
Q: Can't tea plantations absorb some carbon dioxide?
Tea plantations can absorb carbon dioxide from the atmosphere. Research on green tea from mainland China includes calculations of carbon sequestration by tea plantations, which can reduce overall carbon emissions and lower the carbon footprint per unit of product. However, calculating the exact carbon sequestration of tea plantations requires more rigorous methodology.
Q: Does a carbon footprint label add value to tea products?
The impact of carbon footprint labels on adding value to tea products is not straightforward. Different tea garden operations and tea factory models, as well as items excluded when calculating carbon footprints, can all lead to differences in the final tea carbon footprint. For example, high mountain tea may have a higher carbon footprint, mainly due to the long distance of material transportation and high emissions during the transportation stage. However, because of differences in calculation methods among various operators, it is inappropriate to judge the quality of tea products based solely on the carbon footprint. It's important to note that tea carbon footprints need to be verified by third-party verification agencies before applying for a carbon footprint label from the Ministry of Environment, which represents a significant cost for businesses.
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