生物塑料并非那么“绿色”

生物塑料并非那么“绿色”

Some bioplastics have a higher environmental footprint than certain petroleum-based plastics, research finds.

研究发现，一些生物塑料比某些由石油制成的塑料拥有更高的环境足迹。

Chemicals and energy needed to grow the crops that provide the raw materials for bioplastics create the larger footprint.

对那些为生产生物塑料而提供原材料的作物来说，供其生长的化学品和能量会留下更深的足迹。

Production of certain petroleum plastics is very efficient, leading to a relatively lower environmental footprint.

某些石油制塑料的生产效率极高，因此也有相对较低的环境足迹。

Plant-based plastics appeal to green-minded consumers thanks to their renewable origins, but their production carries environmental costs that make them less green than they may seem, research says.

研究称，由植物制成的塑料因其可更新利用的源料而吸引着那些怀有绿色环保理念的消费者们，但它们的生产所带来的环境代价却使得它们变得不那么“绿色”了。

"The main concern for us is that these plant-derived products have a green stamp on them just because they're derived from biomass," said study author Amy Landis of the University of Pittsburgh. "It's not true that they should be considered sustainable. Just because they're plants doesn't mean they're green."

研究作者，来自匹兹堡大学的Amy Landis说：“我们主要关心的是虽然这些源自植物的产品都有着一个‘绿色’的邮戳，但这仅仅是因为它们来源于生物质。其实它们并不是可持续的，仅凭它们植物的身份并不足以表示它们是‘绿色的’。”

The work, by Landis and others and published in Environmental Science & Technology, traces the full impact of plastic production all the way back to its source for several types of plastics.

Landis和其他作者的这一工作发表在了《环境科学与技术》上，他们详细追踪了几种类型的塑料从其生产源头到最终成品的过程中所造成的全面影响。

The technique considered each process's footprint for 10 different types of environmental impacts, from global warming potential to release of human carcinogens to smog to algae-choked lakes or eutrophication.

针对10种不同类型的环境影响，研究者们在工作中考虑了每一个过程所产生的足迹，从全球变暖的可能性到人类致癌物的释放到烟雾污染再到水藻富集的湖泊或是环境过营养化。

For bioplastics, the tracing incorporates, among other things, the environmental consequences of the chemicals and the energy required to grow the corn, soybeans or sugarcane that often comprise the plastics. For standard, petroleum-based plastics, the analysis includes the environmental impacts of extracting and refining the oil.

对于生物塑料而言，对其的追踪在其它事物中间囊括了化学品以及能源的环境后果，这些化学品与能源均是供那些通常用来生产塑料的谷物，大豆或甘蔗生长的必需品。而对于普通的基于石油而生产的塑料，对其的分析则包括了提取和纯化石油对环境造成的影响。

The researchers found that while making bioplastics requires less fossil fuel and has a lower impact on global warming, they have higher impacts for eutrophication, eco-toxicity and production of human carcinogens.

研究者们发现虽然生产生物塑料所需要的化石燃料较少，且对全球变暖的影响也相对较低，但是它们却比较多的影响着生物富营养化，生态毒性以及人类致癌物的产生等问题。

These impacts came largely from fertilizer use, pesticide use and conversion of lands to agricultural fields, along with processing the bio-feedstocks into plastics, the authors reported.

作者称，伴随着生物原料转变成塑料成品的整个过程，这些影响主要来自于化肥，杀虫剂的使用以及退地还耕的举措。

"I don’t want people to take away from this that biopolymers are bad. The problem is that there are problems with them," Landis said. "There is a lot of research going on to create biopolymers based on non-corn feedstocks," which would reduce these impacts, she said.

“我并不希望人们因此而认为生物聚合物都不好，它们只是自己遇到了麻烦，”Landis说，“当前有大量的研究在合成基于非谷物原料的生物高聚物，它们或许能降低这些影响。”

Using cellulosic sources of biomass, such as corn stalks, grasses, or woody plant parts would be better, agreed Michael Griffin of Carnegie Mellon University in Pittsburgh. "If instead of using something like corn, you move to something like cellulosic, that immediately gets you a reduction of impact. A lot of these cellulosic feedstocks use fewer chemicals and you get higher yield," he said.

而使用生物质的纤维原料，例如麦秸秆，草本或是木本植物的某些部分或许比较乐观，这也得到了匹兹堡卡内基梅隆大学的Michael Griffin的认同：“假如为了取代像谷物这样的原料，你会把注意力转移到像纤维素之类的物质上去，那立刻能让你降低影响。而许多这样的纤维原料仅消耗较少的化学品同时你又能得到更高的产出。”他如是说道。

Bio-based plastics face an uphill battle, because they are competing against a highly streamlined production process for petroleum.

生物塑料面临着一场正在升级的战争，因为它们正在与一个高效的石油生产过程竞争。

"It is an amazingly efficient process in getting petroleum from the ground and into a feedstock," Griffin said. "If you then take the petroleum feedstock and convert it very efficiently into the polymer, it can have a very low environmental footprint."

Griffin说：“从地表获得石油并将其转化成生产原料的效率非常之高。假如你到时能将得到的石油原料高效地转成高聚物，那么其只会具有非常低的环境足迹。”

One important limitation of the study is that the comparison did not include the relative impacts of disposal, Landis said, because the necessary data for these calculations was not available. This means bio-plastics did not get "credit" for being biodegradable, nor do certain types of petroleum plastic for being easily recyclable.

Landis说，他们研究的一个重要局限是在比较中缺少对废物处理的相对影响的调查，因为他们无法获取相关计算所必需的数据。这意味着生物塑料并没有得到其能生物降解的“学分”，同时也无法保证某些类型石油塑料制品能够轻易地循环掉。

"That could drastically change the ranking of these polymers," Griffin said.

Griffin说：“但这样可能彻底地改变这些高聚物在人们心中的地位。”

According to the study, polypropylene topped the team's list as having the least life-cycle impact. Polypropylene is used in a wide array of plastic products including textiles and medium-duty objects like remote controls, large plastic tubs or chairs.

根据研究，聚丙烯因其有着最短的生命周期影响而占据着研究小组名单的头把交椅。聚丙烯被广泛地用于一系列塑料制品中，这些制品包括纺织品和像遥控器这样的媒体工具，同时包括大型塑料盆或塑料椅子。

High-density polyethylene and low-density polyethylene were the second and third place polymers. These polymers are widely used for plastic bottles and bags.

高密度聚乙烯和低密度聚乙烯是在名单中排在二位和三位的高聚物。这些聚合物被广泛地应用于生产塑料瓶和塑料袋。

The biopolymer polyhydroxyalkanoate came next on the list. Polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were ranked last.

接下来轮到生物高聚物聚羟基脂肪酸酯。而聚氯乙烯(PVC)和聚对苯二甲酸乙二醇酯（PET)则排在了名单的最后。

But taking the rankings at face value has its limits, Griffin noted. The rankings weigh each environmental impact equally, but different manufacturers or consumers may have different priorities for what is most important, whether it be global warming potential or toxin release.

但Griffin注意到，仅凭其表面价值而排位是具有局限性的。排名虽然客观公正地权衡了每一项环境影响，但不同的生产商或消费者可能会有自己的侧重来决定什么是最重要的，比如是不是有着导致全球变暖的潜力或是会释放有害物质。

"They're important to different people," Griffin said. "People are going to make different decisions based on how they weigh things."

“它们对不同的人群非常重要，”Griffin说道，“人们会根据自身对事物的权衡做出不同的抉择。”