Your empty cuppa could capture carbon
Your empty cuppa could capture carbon
你喝完的空杯或许能捕捉碳排放
Humanity has littered the sky with the refuse of fossil fuel use, releasing enough CO2 to change the planet’s climate. We are also chucking incredible sums of carbon in the form of plastics into landfills and into the environment around (and inside of) us. What if cleaning up one of these problems could also help clean up the other? A new study led by Ruth Ebenbauer at Aarhus University experiments with this idea by upcycling discarded polystyrene into (part of) a material commonly used in carbon-capture systems.
人类因使用化石燃料而向天空排放了大量废弃物，释放的二氧化碳足以改变地球气候。同时，我们还将海量的碳以塑料的形式丢弃到垃圾填埋场以及我们周围（甚至体内）的环境中。如果解决其中一个问题能有助于解决另一个问题，会怎样呢？奥胡斯大学（Aarhus University）的露丝·埃本鲍尔（Ruth Ebenbauer）领导的一项新研究对此进行了实验，通过将废弃的聚苯乙烯升级再造，使其成为碳捕捉系统中常用材料的一部分。
Adding amines
添加胺类物质
This material is based on amines—a simple chemical group that conveniently acts like a sponge for CO2. An amine will grab CO2 molecules when exposed to them, but let go of the CO2 when heated or depressurized, leaving it ready to go again. The first “CO2 scrubbers” tried in smokestacks used amines dissolved in water to do this, but solid amines are used in all kinds of carbon-capture systems now because they require less energy. These solid materials—often made into granules similar to the activated carbon in a water filter—have high surface area and high porosity, so the amines can efficiently partner up with CO2 molecules.
这种材料基于胺类物质——这是一种简单的化学基团，可以像海绵一样方便地吸收二氧化碳。当胺类物质接触到二氧化碳分子时会将其捕获，而在加热或减压时又会释放二氧化碳，从而使其能够循环使用。最初在烟囱中尝试的“二氧化碳洗涤器”使用溶解在水中的胺类物质，但现在各类碳捕捉系统都倾向于使用固体胺，因为它们能耗更低。这些固体材料通常被制成类似于滤水器中活性炭的颗粒，具有高表面积和高孔隙率，使胺类物质能高效地与二氧化碳分子结合。
Currently, these materials are all derived from fossil fuels. There are two components: the amine groups themselves, and something else that provides a structure for them to sit within. The research team’s idea was that polystyrene could be a great fit for that structural component. Polystyrene has been used for Styrofoam and for solid items like eating utensils or the clear portion of a CD case. Less than 1 percent of it is recycled in the US, while Europe manages a slightly less awful 10 percent.
目前，这些材料均源自化石燃料。它们由两部分组成：胺基本身，以及为胺基提供附着结构的载体。研究团队认为，聚苯乙烯非常适合作为这种结构组件。聚苯乙烯常用于制造泡沫塑料，以及餐具或CD盒透明部分等固体物品。在美国，聚苯乙烯的回收率不足1%，而欧洲的情况稍好，回收率约为10%。
The upcycling process has two chemical steps. The first attaches bromine atoms to aromatic rings in the polystyrene, using gold as a catalyst. The second step introduces a two-carbon form of amine (a common ingredient in a wide array of products) and a copper catalyst, which swaps amine groups in where the bromine atoms were. Some of the amine groups hang out solo, while others link with each other to help create the porosity within the solid.
升级再造过程包含两个化学步骤。第一步是以金为催化剂，将溴原子连接到聚苯乙烯的芳香环上。第二步引入一种双碳形式的胺（许多产品中的常见成分）和铜催化剂，将胺基置换到原先溴原子的位置。部分胺基保持独立，而另一些则相互连接，从而帮助在固体内部形成孔隙。
The researchers tested this process with a few plastic objects, including Styrofoam, food packaging, a fork, a CD case, and a Lego base plate (which has another chemical component). They found that the material they produced performed well in the carbon-capture cycle, both at the extremely high CO2 concentration of a smokestack and the lower concentration of ambient air.
研究人员利用几种塑料制品测试了这一过程，包括泡沫塑料、食品包装、叉子、CD盒和乐高底板（含有其他化学成分）。他们发现，所生产的材料在碳捕捉循环中表现良好，无论是在烟囱中极高浓度的二氧化碳环境下，还是在环境空气中较低浓度的环境下，均能有效运作。
Fine tuning
微调
The researchers also found that they could control the material’s properties along the way. They could tune the amine content up or down, as well as adjusting the proportion that made porosity-building linkages instead of CO2-grabbers. Since the amine-containing starting material they used was ultimately fossil-fuel derived, they also tested turning a couple other kinds of synthetic materials into amines instead. Past research has shown a few pathways to do this, but those give you slightly more complicated forms of amines that may not be as reactive.
研究人员还发现，他们可以在过程中控制材料的特性。他们可以调高或调低胺含量，并调整用于构建孔隙的连接结构与用于捕捉二氧化碳的基团之间的比例。由于他们使用的含胺起始材料最终仍源自化石燃料，他们还测试了将其他几种合成材料转化为胺类物质。过去的研究展示了一些实现途径，但那些方法产生的胺类形式较为复杂，反应活性可能不如前者。
In this case, they used these amines in an upcycling reaction on urethane foam mattress material and decorative building trim. This worked, producing carbon-capture material made completely from waste, but the chunkier amine groups made from waste didn’t perform as well. Its capacity for CO2 was lower, and it failed to sponge up CO2 from ambient air. But the polystyrene still held up its end of the bargain, and there’s a flexible blueprint here.
在此次实验中，他们将这些胺类物质用于聚氨酯泡沫床垫材料和建筑装饰线条的升级再造反应中。实验成功了，生产出了完全由废料制成的碳捕捉材料，但由废料制成的较大胺基团表现稍逊。其二氧化碳容量较低，且无法从环境空气中吸收二氧化碳。不过，聚苯乙烯的表现依然稳健，这为我们提供了一个灵活的蓝图。
With the right source and process for amines, carbon-capture material could be entirely produced from the flood of plastics going into landfills. And even if it’s only half produced from plastics, that would still be improvement. This could both provide a market to redirect some of the plastic waste and technically reduce the carbon footprint of carbon capture (although the vast majority of its footprint is the energy required to run the process.) Carbon capture isn’t a license to keep using fossil fuels. It’s an additional action we can take to rein in atmospheric CO2 more quickly. And the more sustainably you can run that process, the better it is.
只要找到合适的胺类来源和工艺，碳捕捉材料就有可能完全由进入垃圾填埋场的塑料废弃物制成。即使只有一半由塑料制成，也是一种进步。这不仅能为塑料废弃物提供一个再利用的市场，还能从技术上减少碳捕捉过程本身的碳足迹（尽管其大部分足迹来自运行该过程所需的能源）。碳捕捉并不是继续使用化石燃料的许可证，而是我们为了更快控制大气中二氧化碳含量而采取的额外行动。而且，该过程运行得越可持续，效果就越好。