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垃圾回收的工作原理

How Recycling Works

I don’t know about you, but I take recycling for granted.
我觉得垃圾回收是理所当然的 你觉得呢?
You finish your drink,
当你喝完饮料
and you just toss the plastic bottle into a bin marked “Recycling”.
把瓶子扔到标有“可回收”的垃圾箱里
Then, something happens to it,
然后 它会被进行相应处理
and you’re told it’s good for the environment,
然后有人会告诉你这样做有益于保护环境
and then you feel good
然后你会感觉很不错
because you’re saving the planet in your own small way by not throwing that bottle into the garbage.
因为只要不随意丢弃饮料瓶 你就为拯救地球出了一份力
But how does recycling really work?
但是垃圾回收到底是什么原理呢?
What happens to that plastic, or that can, or that piece of paper
那些被我扔进带箭头的垃圾桶的塑料 铝罐和纸
I toss into that little bin with the arrows on it?
究竟会经历什么呢?
Recycling is, basically, the process of collecting waste materials and
基本上 回收就是收集废弃物
breaking them down into building blocks that can be turned into new products.
将它们分解后 重新做成其它物品
Since each material is made of different things,
因为每种材料都是由不同成分制成的
it needs to be broken down in its own way.
所以要用不同的方法来分解它们
Paper, for instance, becomes wood fibres,
比如 纸 会被分解成木质纤维
but glass is just crushed into tiny pieces.
而玻璃只能被压成碎片
And, since 1973,
并且 自1973以来
scientists and engineers have been working on the best ways
在“材料回收厂”中 科学家和工程师一直致力于研究出最佳方式
to separate clean and processed recyclables at”Material Recovery Facilities”.
可以分解出干净 可再加工的可回收物
They’re also known as”MRFs”, for short,
他们也被简称为“MRFs”
which is a much more awesome and fun name
这个名字听起来更加酷炫有趣
that we will be using from now on.
我们从现在开始叫它“MRFs”
There are, typically, two kinds of MRFs:
通常 MRFs有两种类型
“Single Stream Recycling Plants” and”Dual Stream Recycling Plants”.
“单流循环回收工厂”和“双流循环回收工厂”
Dual Stream Recycling means that the curb-side bins are split into two categories:
双流循环回收指把路边垃圾箱分为两种
“Mixed Paper” and”Everything Else”.
“混合纸”和“其他垃圾”
These two categories are kept separate in the truck,
在垃圾车里这两种垃圾也要分开
dumped into two separate piles, and offloaded onto two separate conveyor belts.
倒进两个不同的垃圾桶 然后转移至两条不同的传送带
Single Stream Recycling, on the other hand, means exactly that.
另一方面 单流循环回收意味着
Everything is thrown into the same recycling bin
任何垃圾都可以扔到同一个垃圾回收箱里
and sorted later by a combination of people and high-tech machines.
然后在人类和高科技机器的合作下被分类
Less than half of all Material Recovery Facilities use this method,
虽然只有一小半的材料回收工厂会使用这种方法
but that number is growing.
但数量一直在增长
So here’s how it works: almost anything can be recycled,
其原理是:几乎所有东西都可以被回收
but some materials,
但是有一些材料
like computers, batteries and light bulbs are too complex,
如电脑 电池和灯泡太复杂
too large, or contain too many toxins,
太大 或者含有太多有毒物质
to properly recycle at any given MRF.
因此不能在MRF中合理地回收
If they show up in the recycling pile,
如果它们出现在回收堆里
they’re either thrown away or
它们要么会被扔掉
taken to different, specialised facilities.
要么会被带到不同的 特殊的工厂
Single Stream Recycling focuses on five different kinds of waste: Paper,
单流循环回收主要处理五种不同的垃圾
steel, glass, aluminium, and plastic.
纸 钢铁 玻璃 铝以及塑料
As they make their way through the plant,
垃圾进入工厂后
each of these materials is separated from the mixture,
这五种垃圾被从混合物中分离出来
and is processed.
然后被重新加工
The paper and the cardboard come first,
先是纸和硬纸板
thanks to a series of rubber, star-shaped wheels
通过一系列橡胶制成的 星状的
called”Rotary Screen Separators”.
被称为“旋转筛分离器”的转盘
With the help of blown air pushing them along,
由鼓风系统推动它们前进
the cardboard and paper ride the wheels at a 45° incline,
硬纸板和纸以45度倾斜角搭上转盘
up to a higher conveyor belt,
传送到更高的传送带上
while the more three-dimensional, heavier objects,
而更立体的 更重的物体
like containers and bottles, fall through the gaps in the wheels
像容器和瓶子 会从转盘的间隙掉下去
and land back on the main conveyor belt.
然后落到主传送带上
That cardboard and paper is sorted by workers
瓦楞纸板和纸张
who remove any remaining contaminants, or stray plastics,
通过人工分类把其中的残留污染物和塑料碎片除去
and separated the materials into bins for newspaper,
然后把它们按材料分别投入装废旧报纸的桶
mixed paper, and corrugated cardboard.
装混合纸桶和装瓦楞纸的桶
Paper is made out of two basic ingredients:
纸由两种基本材料组成
cellulose fibres from wood, and water.
木质纤维 还有水
So, to recycle it,
所以回收纸
you need to break it down to those two component parts
需要分解出这两种成分
and let it reform.
然后把它们重新组合
Plus, there are contaminants,
另外 回收纸里还有些杂质
like ink and dirt, that need to be filtered out.
比如墨水和污垢需要被过滤掉
So, first, the paper is compacted, baled,
首先 纸张被压缩打包
sent to a mill and placed in a hot water bath.
然后被送到工厂放进一个热水池
This bath quickly breaks the paper down into tiny strands of cellulose fibre,
这个池子快速将纸分解成细小的纤维素纤维
creating a mushy substance called”pulp”, basically,
产生“纸浆”这种糊状物质
wet, lumpy paper.
也就是湿的 块状的纸
That pulp is still dirty though,
这时纸浆还是脏的
so it’s forced through screens that filter out any remaining residues,
所以要通过滤网过滤掉纸浆中所有剩余残渣
like glue or bits of plastic.
比如胶水或塑料碎片
It’s then sent to the”De-inker”,
然后纸浆再被送到“脱墨池”
which is another bath containing air bubbles
是另一种池子 里面含有气泡
and soap-like chemicals called surfactants
和与肥皂相似的化学物质-表面活性剂
that separate the paper from the ink.
将纸从墨水中分离出来
Air bubbles carry the ink up to surface,
气泡把墨水带到水面
while the pulp, which is heavier, sinks to the bottom.
更重的纸浆下沉到底部
That pulp, now clean, can be formed into new paper products.
此时的纸浆非常干净 可以被重新做成纸
You might have even eaten from a recycled cereal box this morning.
今天早上 你吃的东西可能就是用再生纸燕麦盒装的
Meanwhile, back at the MRF,
我们再回到MRF
anything that didn’t make it up the rotary separator enters another sorting line.
那些没能通过旋转分离器的垃圾被放到另一个分类线上
What’s left on the conveyor belt is moved through a”cross-belt magnet”,
留在传送带的东西通过“交叉带磁铁分拣系统”被移走
which is a high-powered magnet that attracts iron-containing metals, mostly steel.
它是一个磁性很强的磁铁 吸引含铁金属 大多数是钢
Aluminium gets left behind because aluminium isn’t usually magnetic.
铝会被留在传送带上 因为铝不具有磁性
Steel isn’t all that hard to recycle,
钢不是很难回收
it’s just crushed and baled and sent to foundries where it’s melted down.
它只需要被压缩和包装 然后送到铸造厂熔化
After that, it’s ready to be mixed with new steel
在那之后 它会合成新的钢铁
and refashioned into cans, or cars, or beams, or anything else made of steel. So,
以及重新制成罐头罐 汽车 横梁或者任何铁制品
now all we have left at the MRF are glass, aluminium, and plastic.
因此 最后留在MRF的都是玻璃 铝和塑料
They’re separated using an”Air Classifier”,
它们通过空气分离器被分解
which is a fan that pushes lighter goods,
空气分离器是用来分离更轻物体的风扇
like aluminium and plastic,
像铝和塑料
toward a higher conveyor belt,
会被吹到更高的传送带
while allowing glass, which is heavier, to fall down to a lower conveyor belt.
而较重的玻璃则落到较低的传送带
Then the glass takes a ride through a”Rolling Drum”.
然后玻璃会通过一个“滚筒”
It’s shattered into pieces and filtered through sieve-like screens that
被压成碎片 然后通过筛网过滤
ensure that no glass piece is larger than 5cm wide.
筛网可以确保通过的玻璃片直径小于5cm
Those glass pieces are then sorted by colour:
这些玻璃碎片会按照颜色分成:
clear, brown, and green.
透明的 棕色的和绿色的
The different colours are important.
不同的颜色很重要
They make recycling tricky because they’re permanent.
颜色不同使回收变得很棘手 因为颜色是永久性的
Glass is made of silica,
玻璃的成分是二氧化硅
plus a bunch of other ingredients, depending on the colour,
根据不同颜色还会添加其他成分
that’s been melted by high heat and then rapidly cooled.
玻璃经过高温熔化后快速冷却
Around 60% of all the glass in the U.S. is clear,
在美国 将近60%的玻璃是透明的
it’s the easiest glass to make because it’s just silica, limestone and soda ash.
这种玻璃制作简单 因为它仅包含二氧化硅 石灰岩和苏打粉
But, clear glass can sometimes cause the substance inside to degrade
但是 盛在透明玻璃里的东西有时会发生降解
due to light exposure from the sun.
主要原因是太阳的照射
Beer, for example, has a light-sensitive chemical called”isohumulone” inside of it
比如 啤酒里面含有一种叫“异葎草酮”的化学成分 它对光很敏感
that breaks down into free radicals when struck by ultraviolet light.
当紫外线直射 它会被分解成自由基
The side effect of this reaction is a skunky smell and some carbon monoxide.
这种反应的副作用是产生一股臭鼬味和一氧化碳
Generally, not what you’re looking for in a beer.
总之 就是不该在啤酒里的东西
That’s why we have brown and green glass,
所以就有了棕色和绿色玻璃
which act like sunglasses and protect the contents from UV rays.
它们就像太阳镜一样 可以防止紫外线直射内部
But they also have ingredients in them to make them that colour,
但是它们本身含有使其呈现这种颜色的成分
like nickel, iron, and sulphur.
像镍 铁和硫磺
This means that the brown and green colours can’t be removed from glass,
这意味着棕色和绿色不能从玻璃移除
so the need to be recycled separately.
因此需要分开回收
Once the glass is all separated, it’s crushed into tiny pieces, called”cullet”.
一旦玻璃分拣完成 就会被压成细小的碎片–“玻璃渣”
These cullets melt at a lower temperature than new glass,
这些碎玻璃的熔点低于新玻璃
because the ingredients and have already been mixed and fused together when that glass was initially made.
因为新的玻璃制作之初 那些成分已经混合在一起了
Back at the MRF, we’ve only got aluminium and plastic left.
回到MRF 现在只有剩下铝和塑料了
We are almost done.
回收工作接近完毕
Aluminium can be separated from the plastic using a machine called an”Eddy Current Separator”.
铝可以用一种叫做“涡流分离器”的机械装置从塑料中被分拣出来
It’s a big drum with a spinning rotor that contains magnetic poles,
它是一个有磁性的飞速旋转的大滚筒
which creates a really strong, magnetic field called an”induction field”.
一个可以创造出“感应场”的强大磁场
Remember how I said that aluminium isn’t magnetic?
还记得我说过铝不具备磁性吗?
Well, that is true, most of the time.
在通常情况下铝不具备磁性
This induction field is so powerful that it causes electrons in a conductor, like aluminium,
但这个感应场的磁性非常强大 能使导体产生电子 比如铝
to create their own magnetic field.
创造出它们自己的磁场
The two fields repel each other and the
这两个磁场相互排斥
aluminium is pushed away to a different conveyor belt,
于是铝被推到另一个传送带
while the plastic continues on.
而塑料会继续前移
Like steel, there isn’t much to do
像铁一样 不需要其他处理步骤
when it comes to making the aluminium reusable.
铝就可以被重复利用
It’s shredded, washed, and turned into chips,
它被粉碎 清洗 然后变成铝片
which are melted in a large furnace, and poured into moulds.
在一个大火炉里熔化后被倒入模具里
These moulds are shipped to manufacturers, where they’re melted again,
这些铝模会被运送到制造商那里再次熔化
and rolled out into thin sheets that can be cut, and bent, and shaped into new products,
并滚压成可裁剪的 可弯曲的 可塑成新产品的薄片
like cans, and licence plates, and aluminium foil.
像罐头 牌照和铝箔
So now all we have left is the plastic.
现在就省下塑料了
It turns out the plastics are made of one of six different kinds of chemicals,
塑料由这六种化学物质其中之一制成
which correspond to the numbers 1 through 6,
分别对应到数字1至6
that you’ll see on the bottom of that soda bottle, or yoghurt container.
你在苏打瓶或者酸奶瓶的底部会看到这些数字
Sometimes, you’ll also see a”7″,
有时候你会看到一个数字“7”
but that just means it’s made of any one of the less popular types.
但是那只是表明它是由其他不常见的类型制成的
Each kind of plastic has a different molecular structure,
每种塑料都有一种不同的分子结构
which determines the physical properties of the plastic.
分子结构决定了塑料的物理性质
It also means that some plastics are a lot easier to recycle than others.
这也意味着一些塑料比其他塑料更容易回收
Plastic is made out of long, carbon chains. Usually,
塑料由长的碳链组成
the hydrocarbon molecules are extracted from fuels,
通常 碳氢化合物分子是从燃料中提取出来的
like crude oil, or natural gas,
像原油 天然气
then linked up, forming big, repeating structures called”polymers”.
然后它们会连接起来 组合成一个巨大循环往复的“聚合物”的链条
Take PET, for example, which corresponds with code number 1.
比如说PET 对应代码1
It’s made of a polymer called”polyethylene terephthalate”,
它是由“聚对苯二甲酸乙二醇酯”聚合物组成的
which has rings of carbons separated by chains of carbons,
它有分离的碳链
some of which have single and double bonds, to oxygen atoms.
相对于氧原子而言 一些含有单键和双键
Those rings and double bonds don’t give PET much flexibility,
那些环和双键无法给PET太多的灵活性
so the polymers tend to pack closely together, and are harder to melt.
所以聚合物会很紧密地聚合在一起 更难被熔化
Since PET will soften at temperatures more than a hundred degrees below that high melting point,
因为PET在高于100度 低于熔点的温度软化
it’s easy to reshape, without damaging its molecular structure.
所以它很容易重塑 不需要破坏它的分子结构
That’s pretty helpful when you’re trying to recycle it.
在回收时 这种特性非常有用
Then there’s code number 3, PVC,
然后是代码3 聚氯乙烯
which is made of a polymer called”polyvinyl chloride”.
它是由一种叫“聚氯乙烯”的聚合物组成的
It’s a strong and durable plastic
它是一种强韧耐用的塑料
often used in piping or in bottles of shampoo.
常用来制作成管道或是洗发水瓶
It’s also known as”the poison plastic”
它也被称为“有毒塑料”
because, when it’s melted,
因为当它熔化时
it can release a corrosive and toxic gas called, yeah, hydrochloric acid.
会释放出一种腐蚀性的有毒气体 叫做盐酸
Most of the time,
大多数时候
recycling PVC involves grinding into a powder at a specialised plant,
回收后的PVC在一间专门的工厂被磨成粉末
and then mixing it with additives so that it can be reused.
这些粉末里加入添加剂就可以被再次利用
But you definitely do not want
但是你绝对不想
it contaminating the rest of your plastic,
让它污染其他的塑料
which is just one reason why all the different kinds
这也是所有不同种类的塑料
of plastic are separated at the MRF.
要在MRF分拣的原因之一
More importantly, separating plastics by types preserves their special properties.
更重要的是 按类别分解塑料能够保留它们的特性
For example, PET is harder to shatter,
比如说 PET更难粉碎
while PVC is more resistant to harsh chemicals.
而PVC对刺激性化学品更有抵抗性
In most plants, the separation is done using human sorters but,
大多数工厂均通过人工分拣
in newer plants, there are infrared sensors
但在新型工厂 会用红外线分类器
that identify the plastics based on the spectrum of light they reflect.
它通过塑料反射出的光进行分拣
Since each type of polymer reflects light differently,
因为每种聚合物反射的光不同
the sensors can identify which plastic is which.
分类器可以识别出每种塑料的类别
Once identified, little puffs of air blast those plastics onto different conveyor belts.
一旦识别出来 气流会把塑料吹到各自类别的传送带上
Depending on the MRF’s capabilities, plus other factors, like market demands,
根据MRF的产能以及如市场需求等其他因素
some of these plastics are recycled, while others are thrown away.
一些塑料被回收 而另一些被扔掉
Take”expanded polystyrene”, for example,
比如“发泡聚乙烯”
which you know as”Styrofoam”.
也就是大家知道的“泡沫聚乙烯”
While it can technically be recycled, it’s not particularly practical,
尽管从技术角度能被回收 但不是特别实用
because a truck full of lightweight, air-filled Styrofoam
因为一卡车又轻又膨松的泡沫塑料
doesn’t melt down into a lot of polystyrene.
并不能够熔化成大量的聚苯乙烯
But soda bottles, which are made of PET plastic,
但是由PET塑料组成的苏打水瓶
are recycled at almost all MRFs.
几乎都能在MRF回收
They can be melted down, mixed with new plastic,
它们被溶解后可以和新的塑料混合
and used to create things like clothing, and carpet,
然后用来生产衣服 地毯之类的物品
or even to fill pillows.
甚至可以填充枕头
So that soda bottle you just recycled
所以被回收的苏打水瓶
Some day, you might end up wearing it.
也许某一天就会穿在你身上
Thanks for watching this SciShow Infusion, which was
感谢收看本期SciShow Infusion
brought to you by our patrons on Patreon,
本期节目由Patreon上的赞助商提供
who make SciShow possible for free for everybody.
在他们的支持下 SciShow才能向每个人都免费
If you want to help us keep making videos like this,
如果你想帮助我们继续制作这类视频
you can go to Patreon.com/SciShow, and don’t
你可以登陆Patreon.com/SciShow
forget to go to YouTube.com/SciShow, and subscribe.
还有不要忘记在YouTube上订阅
[Outro Music]
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该视频主要讲了回收垃圾的基本过程

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视频来源

https://www.youtube.com/watch?v=b7GMpjx2jDQ

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