Which bag should you use? - Luka Seamus Wright and Imogen Ellen Napper

譯者: Lilian Chiu 審譯者: Melody Tang

You’ve filled up your cart and made it to the front of the grocery line

你已經裝滿購物車，輪到你結帳了，

when you’re confronted with yet another choice:

此時你面臨了另一個選擇：

what kind of bag should you use?

你應該要用哪一種袋子？

If you’ve seen the images of plastic bags strewn across the ocean,

如果你曾經看過塑膠袋 散在海洋裡的影像，

it might seem obvious that plastic is bad for the environment.

那應該很明顯，塑膠對環境不好。

Surely a paper bag or a cotton tote would be the better option.

當然紙袋或棉布袋 會是比較好的選項。

But is that really true?

但，真的是如此嗎？

Each of these three materials has a unique environmental impact

這三種材料都有其 對環境的獨特影響，

that’s determined by its carbon footprint,

決定因素包括它們的碳足跡、

its potential to be reused and recycled, and its degradability.

可再利用和回收的可能性， 以及可自然分解的程度。

So, to get the full story on these grocery bags

所以，為了完整了解這些購物袋，

we need to look at how they’re made,

我們必須了解它們 如何被製造、被使用，

how they’re used, and where they ultimately go.

以及最終會到哪裡去。

Let’s start with plastic.

從塑膠開始。

The typical thin and flimsy plastic bag is made of high-density polyethylene,

典型的輕薄塑膠袋 是用高密度聚乙烯製成，

commonly known as HDPE.

即一般所知的 HDPE。

Producing this material requires extracting petroleum from the ground

製造這種材料會需要從地底粹取石油

and applying extreme heat.

再用極高溫加熱。

The resulting polymer resin is then transported

產生出來的聚合樹脂 接著會和其他原料

alongside additional ingredients like titanium oxide and chalk

如氧化鈦及白堊一起運送

to a bag manufacturing plant.

到袋子製造工廠。

Here, coal powered machines melt the materials down

在這裡，靠煤運轉的機器

會將材料熔解並製做成塑膠片，

and spin them into sheets of plastic,

which are then folded into bags.

接著塑膠片會被折疊成袋子。

By the time a bag reaches its final destination,

等到袋子抵達最終目的地時，

it’s contributed an estimated 1.6 kg of carbon dioxide to the atmosphere.

總共會排放大約 1.6 公斤

二氧化碳到大氣中。

That’s the same amount of carbon a car produces,

這和一台汽車行駛 6 公里多

driving a little over 6 kilometers.

所排放的碳量相同。

But the alternatives actually possess a much larger carbon footprint.

但其他替代選項的碳足跡實際上更高。

Paper is made from wood pulp,

紙是用木漿製成，

and when you account for the carbon cost of removing trees from their ecosystems,

如果你把將樹木從其生態系統中 砍除的碳成本也算進來，

a single paper bag can be responsible for about 5.5 kg of carbon dioxide.

單單一個紙袋就會造成

約 5.5 公斤的二氧化碳。

Meanwhile, growing cotton is an extremely energy and water intensive process.

而種植棉花的過程 要消耗大量能源和水。

The production of a single cotton tote

製造一個棉布袋

emits an estimated 272 kg of carbon dioxide.

估計排放約 272 公斤的二氧化碳。

When we compare carbon footprints, plastic bags are the clear winner.

如果比較碳足跡， 很明顯塑膠袋會勝出。

But environmental impact is also determined by how the bag is used.

但如何使用袋子也會決定 袋子對環境造成的影響。

Reusing or recycling these bags

重覆使用或回收這些袋子

significantly offsets their environmental toll

可以減少對新生產的需求，因而

by reducing demand for new production.

大大抵消它們對環境的不良影響。

To quantify that offset, we can divide the bag’s carbon footprint

一種將抵消效果量化的方式

是把袋子的碳足跡除以 它被重覆使用的次數。

by the number of times it’s reused.

For example, if a typical paper bag is reused three times,

比如，如果一般的紙袋 可以重覆使用 3 次，

it has a lower net impact than a single-use plastic bag.

它的淨影響就會比 一次性塑膠袋更低。

The carbon footprint of a cotton tote can similarly be lowered,

同理，如果一個棉布袋 能重覆使用 131 次，

if it’s reused 131 times.

它的碳足跡就會比較低。

Of these three options, durable cloth totes are most likely to be reused.

在這三個選項當中，耐用的布袋 最有機會被重覆使用。

Evidence shows paper bags are quickly discarded due to their tendency to tear.

證據顯示紙袋容易被撕破 因此很快就會被丟棄。

This issue plagues HDPE plastic bags as well.

HDPE 塑膠袋也有這個麻煩。

But even when they’re made to avoid tearing,

但，就算有防撕破設計，

their widespread availability makes it easy to treat them as single-use items.

因為太容易取得， 往往用完一次就丟。

Fortunately, researchers estimate that 40% of HDPE bags

幸運的是，研究者估計， 約 40% 的 HDPE 袋

are reused at least once for throwing out waste.

在被丟棄前都有被 重覆使用至少一次。

Recycling these bags also offsets their carbon footprint,

回收這些袋子也能 抵消它們的碳足跡，

but it’s not universally possible for each material.

但並非世界各地 都能回收每一種材料。

Many countries lack the infrastructure to efficiently recycle plastic bags.

許多國家缺乏有效回收 塑膠袋的基礎設備。

Cotton totes are perhaps even more difficult to breakdown and process,

也許棉布袋還更難分解和處理，

but since they’re often reused for long periods,

但因為它們通常會被長期重覆使用，

they’re still least likely to end up in landfills.

它們會淪落到掩埋場的 機率仍然最低。

Whenever these bags aren’t recycled,

只要這些袋子沒有被回收，

the third factor in calculating environmental impact comes into play:

在計算對環境的影響時 就要考量第三個因素：

degradability.

可分解性。

Since HDPE bags are heat-resistant and insoluble,

因為 HDPE 袋耐熱且不會溶解，

they stick around long after we’re done with them.

我們不用之後，它們還會留存很久。

Partially broken down plastic can circulate in ecosystems for centuries.

部分分解的塑膠能在 生態系統中循環數世紀。

Cotton on the other hand degrades substantially in a matter of months,

另一方面，大體上， 棉只要幾個月就會分解，

and paper bags break down completely in just 90 days.

紙袋在 90 天內就能完全分解。

So, which bag should you use?

所以，你該用哪種袋子？

It turns out the most environmentally friendly bags

結果發現，對環境最友善的袋子

have features of several materials we've discussed.

具有前述幾種材料的特性。

They’re durable and reusable, like cotton, but made of plastic,

它們和棉一樣很耐用、 可重覆使用，卻是用塑膠做的，

which has a lower carbon footprint than cotton or paper.

塑膠的碳足跡比棉或紙都還要低。

These sturdy shopping bags consist of polyester, vinyl and other tough plastics,

這些耐用的購物袋成份包括聚酯、

乙烯基，及其他結實的塑膠，

and are already used worldwide.

全世界都已經在使用它們。

Most importantly, they should last a lifetime—

最重要的是，它們應該能用一生——

making them the best option for the planet, and your groceries.

對地球以及對你的雜貨而言， 它們都是最佳選項。