TE||On the plastic highway

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塑料公路

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On the plastic highway

塑料公路正在建造中

英文部分选自经济学人Science and technology版块

Recycling

回收

On the plastic highway

塑料公路正在建造中

Roadmakers are using waste to create harder-wearing surfaces

道路建设者正用废品建造更耐磨的路面

OF ALL the plastic produced since the 1950s, less than 10% has been recycled. The vast majority ends up being dumped, most of it in landfill. Some is left to litter the natural environment, where it can get into rivers and wash out into the sea (see following story). The plastic-waste problem will worsen before it gets better: some 380m tonnes of the stuff are likely to be made this year. That is more than three times as much as the 120m tonnes of bitumen produced annually, most of which goes into building the world’s roads.

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自上世纪50年代生产出塑料以来,回收的塑料总量仅占产出总量的不到10%。绝大多数的塑料最终被倾倒,大部分留在垃圾填埋区,还有些残留在自然环境中,继而进入河流,汇入大海。塑料污染问题还将继续恶化:今年产出的塑料废弃物预计将达到3.8亿吨左右,是每年主要用于道路建设的沥青产量——1.2亿吨的3倍还多。

There is a connection. Just as plastic is derived from petrochemicals, bitumen is produced as a by-product of refining oil. Both are polymers, which consist of long strands of molecules bound together firmly. It is this characteristic that makes plastic strong and contributes to its great longevity. Such features are also useful for road builders, who use hot bitumen to bind together aggregates made from broken rocks and stones, into what is commonly known as asphalt. All of which has got some people thinking: why not swap one polymer with another?

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塑料和沥青之间存在关联。塑料是石油化工产品的提取物,而沥青也是提炼石油的副产品,二者都是由紧密结合在一起的长链分子组成的高分子聚合物。正因为这个特性,塑料才能又强劲又耐用。对筑路公司来说,这些特点同样有用。他们把破碎的石块制成的碎料用热沥青粘连在一起,制成广为人知的柏油。于是有些人开始思考:为什么不换一种聚合物呢?

Recycled plastic is already used to make some products, such as guttering and sewage pipes. Now attention is turning to roads. On September 11th in Zwolle, a town in the Netherlands, a 30-metre bicycle track made from 70% recycled plastic and the rest from polypropylene was opened. It will be used to test a product called PlasticRoad, which is being developed by two Dutch firms—KWS, a road builder, and Wavin, a firm that makes plastic piping—in partnership with Total, a French oil-and-gas firm.

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回收塑料已被用于制作雨水槽,下水道管这样的产品,而现在关注的焦点转向道路。9月11号,一条70%由回收塑料,其余由聚丙烯做成的30米长自行车道在荷兰兹沃勒市投入使用。该自行车道将被用来测试一种叫“塑料道路”的产品,该产品由两个荷兰公司——KWS道路建筑公司和Wavin塑料管制作公司与法国道达尔油气公司合作研发。

PlasticRoad is prefabricated in a factory as modular sections. The sections are then transported to the site and laid end to end on a suitable foundation, such as sand. Because these sections are hollow, internal channels can be incorporated into them for drainage, along with conduis for services such as gas and electricity. For the Zwolle project, sections that were 2.4 metres long and 3 metres wide were used. These were fitted with sensors to measure things such as temperature, flexing and the flow of water through the drainage channels. A second pilot cycleway is being built in the nearby town of Giethoorn.

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“塑料道路”在工厂里预先制造成数个部分模块,之后将这些模块运输到项目现场,头尾连接平铺在适合的地基上(例如沙地)。因为这些模块是中空的,所以能嵌入用于排水和输送天然气与电力的导管。兹沃勒项目的模块长2.4米、宽3米,并装有传感器用于测量温度、变形度和经过排水管的水流流量等。另外,在邻近的杰胡恩市也修建了第二条试验自行车道。

Smart roads, too

智能公路

If all goes well, the inventors hope to develop the idea and make the sections entirely from recycled plastic. Paths, car parks and railway platforms could follow. Eventually, sections for use as actual roads are planned. These could contain sensors for traffic monitoring. In time, the circuits in the plastic roads might extend to assisting autonomous vehicles and recharging electric cars wirelessly.

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如果一切进展顺利,研发者希望更进一步,让模块完全用回收的塑料制成。小路、停车场和火车站月台亦可由这些模块拼接而成。最后,应用于实际道路的模块也在计划当中。这些道路可包含用于交通监控的传感器。到时候,塑料公路上的导管还可能协助自动驾驶和给电动车无线充电。

Prefabricated plastic roads should last two-to-three times longer than conventional roads and cost less, the companies claim, mainly because construction times would be reduced by almost two-thirds. Anti-slip surfaces could be incorporated, too, including crushed stones which are traditionally used to dress road surfaces. The sections, when replaced, can also be recycled. But engineers will be watching to see how the track stands up to wear and tear and if the hollow structure causes resonance, which would make such a road unduly noisy.

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制造方称,预先制造的塑料公路的寿命比传统公路长2-3倍,由于施工的时间减少了将近2/3,修路成本也有所降低。这种新式公路也可以添加防滑表面,比如一贯用于装点公路表面的碎石。模块替换时,旧模块也可以回收。但是,研发者仍在观测道路抗磨损程度如何,以及中空结构是否会导致共振,使公路上噪音过大。

An alternative method of using recycled plastic is to mix the material into hot bitumen when making asphalt. A road is about to be built this way on the campus of the University of California, San Diego, to test a number of specialist roadmaking plastics developed by MacRebur, a British firm. Each mix is produced from plastic that is not easily or cheaply recycled and so typically ends up in landfill, says Toby McCartney, who founded the firm in 2015 with a group of colleagues.

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再生塑料的另一种使用方式是将其混入热沥青之中,制得新型柏油。加利福尼亚大学圣地亚哥分校的校园内将使用这种新型柏油修筑道路,以对英国MacRebur公司研发出的筑路专用塑料进行测试。MacRebur公司于2015年成立,该公司创始人之一Toby McCartney表示,每一种混合材料都是由不易回收或廉价回收的塑料制成,而这些塑料通常最后都埋进了垃圾填埋场。

MacRebur cleans and sorts the plastic and then grinds the waste into flakes or pellets. The plan is for this part of the process to be carried out in the localities where roads are being laid or repaired, so that local waste is used to produce local roads. Each mix can contain 20 or so different polymers for specific surfaces. One mix, for instance, might be suitable for a bus lane that carries heavy loads. Another would provide some flexibility in an area of turning traffic, such as a roundabout, where lateral forces from vehicles’ wheels can stretch the surface causing it to tear. Extremes of heat and cold can also be adjusted for. And because the addition of plastic helps to seal up small holes, which allow water to get below the surface of a road and cause it to break up, the modified asphalt can help to prevent potholes.

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MacRebur公司将这些塑料进行清洁并分类,并将这些废塑料研磨成薄片或者颗粒。该计划的一部分是将这些材料用在道路铺设或修复的过程中,如此一来,便可实现废弃材料就地用于当地道路建设。每种混合物含有可用于特定表面的20种左右不同的聚合物。例如,其中一种混合物可适用于承载重载的公交车道;另一种则可以提高对应区域的道路韧性,用于容易因车轮侧向力拉伸而导致表面撕裂的环形交叉路口。极端冷热造成的问题也可因此改善。同时也因为加入了塑料材料,可以填堵道路上容易进水的小孔,使路面不易破裂,因此改性沥青可以防止道路坑洼出现。

The company’s plastic mixes have already been used in roads, car parks and airport runways in various parts of the world. One of the oldest projects is a stretch of road in Cumbria, in north-west Britain, which is extensively used by heavy lorries. This used to need resurfacing every six months or so, but with the addition of plastic it is still going strong after two years, says Mr McCartney. When resurfacing is needed, the material can be recycled again.

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该公司的塑料混合物已用于修筑世界各地的道路、停车场以及机场跑道。其中最早的道路项目位于英国西北部坎布里亚郡,该路段常有重型卡车驶过。McCartney表示,这段道路以往每6个月就要翻修一次,而添加了塑料材料的新路将在两年后仍强韧坚固。另外,翻新道路时,塑料材料还可以重新回收。

Cleaning and sorting plastic made out of multiple polymers can be relatively expensive, especially if it is used to make low-value products such as packaging. But using such plastic as a replacement for bitumen is cost-effective, claims Mr McCartney. As an example, he says that a tonne of bitumen might cost around £400 ($521) in Britain. A recycled-plastic additive for a standard road works out at £300-£350 a tonne. The additive would replace a proportion of the bitumen, so there are savings to be made. At present 5-10% of the bitumen is replaced by the additives, but this could be increased to 25%.

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McCartney先生说:对多种聚合物制造出的塑料垃圾进行清洁和分类是一项很昂贵的过程。尤其是用来制造低价值的产品,例如塑料袋。然而,如果废弃塑料能作为沥青的替代物,这将带来可观的经济效益。举个例子,一吨沥青在英国价值400英镑。把回收塑料加入到标准道路上,每吨的成本仅为300-350英镑。如果回收塑料代替沥青,可以结余出一部分开销。目前5%-10%的沥青可以换成回收塑料,但这一比例可以增加到25%。

Mr McCartney decided to develop specialist recycled-plastic additives after watching a practice sometimes employed in India to repair potholes. Plastic waste collected by pickers is piled into the hole and then set alight with diesel to form a molten mass. It is crude and polluting, but it provides a fix of sorts. A number of roads in India are also made by mixing chopped-up plastic into bitumen.

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在印度看到当地人用回收塑料修补孔洞后,McCartney先生决定开发专门的回收塑料添加物。废弃塑料被填入到孔中,然后将其用柴油燃烧加热熔化,得到一团熔化后产物。这一过程粗放又污染环境,但是却提供了一种可行的修补方式。在印度,很多道路都是采用把零散的塑料垃圾混入到沥青中这一方法铺设完成的。

Australia is another country that is starting to recycle plastic into roads. Earlier this year a 300-metre stretch was completed in Rayfield Avenue, Craigieburn, a suburb of Melbourne, using a substance called Plastiphalt. This consisted of recycled material from more than 200,000 plastic bags and packaging, 63,000 crushed glass bottles and toner from 4,500 printer cartridges. All this was blended into 50 tonnes of reclaimed asphalt to create a total of 250 tonnes of road-building material. The road will be monitored to see how it performs.

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另一个开始把塑料回收利用到道路上的国家是澳大利亚。今年,一段300米长、使用塑料沥青的道路在墨尔本市郊克莱基伯恩区的雷菲尔德路(Rayfield Avenue)铺设完成。该段路中包含的回收材料有:20万个塑料包装袋、6.3万个碎玻璃瓶以及4,500个打印机墨盒的调色剂。所有这些混合到50吨再生沥青中,制成了250吨道路建筑材料。该段道路的未来运行情况将受到专门监测。

Stuart Billing of Downer, a firm involved in constructing the road, said that the cost of using the recycled materials was comparable with building a road in the usual way. But the road is expected to last a lot longer and prove better at coping with heavy traffic.

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参与修路的Stuart Billing of Downer公司声明,使用回收塑料的成本堪比平时造路的成本。但是,使用回收塑料造出来的道路预计有更长的使用寿命,并且面对庞大的车流量有更好的耐久度。

Officials in Craigieburn reckon that the amount of rubbish used to construct the road, all of which was diverted from landfill, is equivalent to what Rayfield Avenue’s residents would have put into their recycling bins over the past ten years. One of the biggest complaints to local councils is about the state of the roads, especially potholes. Households in Australia and elsewhere might well do more sorting and recycling of plastic if they knew it could result in a smoother drive.

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克莱基伯恩官方认为,把所有造路用到的填埋垃圾翻出来,其总量相当于雷菲尔德大街上的居民过去十多年间放入垃圾回收箱的垃圾的总和。民众向当地议事厅反映的最严重的问题之一就是道路条件,尤其是路上的坑。澳大利亚,乃至世界其他地方的居民可能会对塑料垃圾做更多的分类和回收,前提是他们知道这些垃圾可以使道路变得更加平顺。

翻译组:

Frank,男,小硕,经济学人的死侍

Muyi,文产小研,经济学人初段读者

Helga,女,笔译民工,经济学人爱好者

校核组:

Nikolai,男,小硕, science追随者

Vambie,女,互联网民工,经济学人粉丝

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观点|评论|思考

本次观点由Xingyi独家奉献

Xingyi,男,小硕,经济学人爱好者

四五年前的一个冬天,我在泰东的春武里府游玩的时候遇到了一次大暴雨,海浪甚是汹涌澎湃。而冲上沙滩的就是一堆堆的白色垃圾。那时候一位长住于此的英国大妈就和我抱怨,每次起风都让她很扫兴,整个海滩变得非常恶心。看着那些垃圾,真的有点为自己为人类而羞愧。

白色垃圾飘在海上就无国界了,本期的经济学也有一篇文章介绍,于此我就不赘述。而今天这篇文章谈的是垃圾的回收,好事,但我个人觉得还有许多问题。

首先是垃圾分类问题,回收的塑料各式各样,很难保证所有垃圾都是同类物质,具有接近的物理特性。其次就是受热膨胀系数的差异了,不同物质的膨胀系数不同,路面温度变化后极有可能出现各种裂缝。同时,高分子聚合物的受热膨胀系数较大,可能会对设计造成更高的要求。

高分子一般有体形高分子和线性高分子之分。线性高分子热塑性强,体形高分子的热固性更强。不严谨地说,热塑性意味着加热后易变形,热固性就是受热能维持原样。如何使道路能在夏天暴晒的同时承受高吨位车辆的压力,将是对塑料道路的新挑战。

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