December 2023

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.

就茶產業來說搖籃到大門可能是茶園，也可能是製茶廠。如果是契作的茶園，茶菁是個商品，所以說搖籃到大門，就是種植茶苗到茶園收穫茶菁這個過程(的排放量)；如果是兼具茶園種植與製茶的茶農，那搖籃到大門，就是從種植茶苗，到製茶過程，甚至還包含自行包裝成茶葉產品。

大門到大門(Gate-to-Gate)

可以理解成一個獨立的製茶廠內發生的過程，從將原料送進製茶廠大門，到做成產品載離製茶廠大門。製茶廠從契作的茶農買進茶菁(原料)，經過製茶的操作後生產出成品或半成品(商品)，成品會在製茶廠內包裝，半成品如粗製茶，還需要將粗製茶送到別的地方進行挑梗或色選機進行精緻。

台灣的茶葉碳足跡區分為哪些階段呢？

台灣的茶葉產品碳足跡包含從搖籃到墳墓的各項溫室氣體排放，然而到底如何界定哪些過程或階段需要計算排放量呢？必須要參考環境部公布的碳足跡產品類別標準(Carbon Footprint of Product-Product Category Rules, CFP-PCR)，此份文件將相似產品類別建立一個參考標準，內容會界定產生碳排放的階段，以及相關的假設，本文以環境部碳足跡產品類別規則(CFP-PCR)-茶(tea) 第4.0版作為說明(圖2)。(註：另有環境部較新版之咖啡豆與茶葉 (Coffee Beans and Tea)第1.0版也可以參考，不過參雜咖啡豆的碳足跡較不易理解。)

產品類別標準將茶葉產品之生命週期範圍分為五個階段：

一、原料取得：包含茶園生產茶菁過程中使用的肥料、農藥、耗材、包裝材料的碳排放、農業機具使用的能資源產生的碳排放、將茶菁從茶園運到茶廠過程中的運輸排放，此階段也包括廢棄處理的排放。

二、製造：首先是茶葉的粗製，產品類別規則稱為「一次加工」，以部分發酵茶來說，包含茶葉萎凋、炒菁、揉捻、烘乾，需計算碳排量不外乎是茶廠的用電碳排量、以及炒菁機、甲種乾燥機與乙種乾燥機燃燒液化石油的碳排量；然後，進入茶葉精製階段，產品類別規則稱為「二次加工」，包含揀梗、裁切、選別、焙火、拼配；再來，進行茶葉的「包裝」，這部分包括真空機用電。整體來說，製造階段的碳排放，主要是廠內機運具使用能資源(燃料與電力)的排放量，另外還有一些廢棄物的運輸與處理過程的碳排放。

三、配送銷售：將茶葉商品運輸到銷售據點，運輸車輛的排放量，中間可能有好幾個倉儲，這些都需要界定。至於銷售到消費者手上是否也需要計算呢？由於消費者分布在台灣各地，實際上很難準確計算，所以通常僅計算到從茶廠到主要銷售點的運輸排放。此外需考量有關運輸距離、運輸方式、裝載率及載重噸公里、 平均耗油量/油價(費)等方式來訂定運輸情境，再進行計算。

四、使用：此份茶葉碳足跡產品類別規則，以情境假設的方式來預估消費者使用茶葉的碳排量。情境假設每3g茶葉需以150ml熱水沖泡為比例，計算以電力或液化石油氣、天然氣方式將常溫水加熱到沸騰需要的能量。因為也難估計消費者如何飲用，有可能是冷泡，有可能茶水比不同，所以只好制定統一的標準供茶葉商品計算茶葉使用階段的碳排量。

五、廢棄處理：也是採情境假設的方式，以台灣公佈一般常見垃圾處理的方式1.焚化 2.廚餘回收 之比率計算，泡完茶後廢棄物處理的碳排量。

不過在定義產品碳足跡生命週期的方式也有許多差異，中國大陸的研究也同樣把茶葉碳足跡分成五個階段，但在用詞與階段的區分上有些差異(圖3)。此篇研究各階段包含1.種植(Cultivation) 2.製造(Processing) 3. 包裝與配送(Packaging & Transport) 4. 使用(Consumption) 5. 廢棄處理(Disposal)。

此案例的製造階段僅包含茶葉的粗製與精製並不含包裝，而是將包裝與配送歸類在同個階段，可能是因為當地的茶產業鏈大多會將粗製茶賣出，再進行統一的包裝，而台灣的產品類別規則將包裝涵蓋在製造階段。雖然包裝的活動在整體茶葉碳足跡比例非常小，但由於計算在不同階段，還是會有些許的差異。

整體來說，茶葉碳足跡的計算看似簡單，但實際上需要在茶園管理、製茶，甚至是運輸方面都有相當的數據基礎，才能計算出完整茶葉生命週期的溫室氣體排放量，再統一轉換成二氧化碳當量來表示碳足跡。計算完茶葉的碳足跡後，通常會想取得環境部核發的碳足跡標籤。為此，首先需要取得碳足跡的查證，申請者需要依循上述碳足跡產品類別標準與ISO 14067:2018標準，撰寫一份關於碳足跡盤查的報告，也就是必須呈現有關情境假設、排放活動行為與計算碳足跡的所有資訊，包含電力、液化石油氣、包材、肥料等相關的排碳量，以及配送銷售、使用階段、廢棄物處理階段的情境假設之排放量，最終算出每單位產品的排碳量。經由第三方驗證機構進行數據查證並核發查證聲明書後，即可向環境部申請茶葉產品的碳足跡標籤。

其他關於茶葉碳足跡的問題？

Ｑ茶葉商品哪個階段的碳足跡比例比較高？

不同國家的茶園管理、製造方式、使用與廢棄情境假設、燃料與電力的碳足跡係數，以及不同茶葉種類（如紅茶、綠茶、部分發酵茶）在製造階段都有較大的差異。因此，碳足跡比例較高的階段可能因地區和茶葉種類而異。

Ｑ飲茶方式也會造成碳足跡的不同？

飲茶方式確實會影響碳足跡，大多數研究假設消費者使用沸騰的熱水沖泡茶葉，但如果以冷泡的方式碳足跡就會有所不同。西方研究顯示，加入牛奶的紅茶碳足跡較高，而在台灣，手搖飲料加入各種配料，若要計算也就會更為複雜。

Ｑ茶園難道不行吸收一些二氧化碳嗎？

茶園是可以吸收大氣中的二氧化碳，中國大陸的綠茶研究就包含了茶園的碳匯量計算，這可以減少整體的碳排量，從而降低單位產品的碳足跡，但實際上如何計算出茶園的碳匯量需要更嚴謹的方法學。

Ｑ碳足跡標籤有利於茶葉產品加值嗎？

碳足跡標籤對茶葉產品加值的影響並不簡單，不同的茶園經營與茶廠模式，以及計算碳足跡時排除的項目，都可能導致最終茶葉碳足跡的差異。例如，高山茶的碳足跡可能較高，主要是因為物資運輸距離長，運輸階段的排放量大。然而，因為各業者計算上的差異，所以僅憑碳足跡的高低來判斷茶葉產品的優劣並不適當。必須注意的是，茶葉碳足跡需要經過第三方驗證機構的查證，才能申請環境部的碳足跡標籤，這對於業者來說是不小的成本。

歡迎聯繫TRIT討論