二氧化碳和水就能造出航空燃料？

A way of combining atmospheric CO2 and water to make aircraft fuel.MOST PEOPLE who think about such things agree that replacing fossil fuels with renewable electricity, either directly or indirectly, is the best way to decarbonise industry, transport and the heating and cooling of buildings.But there are some holdout areas where this is hard.Cement is one.Aviation is another, because batteries are too heavy and hydrogen (which could be made using renewable electricity) too bulky to do the job easily.Hydrocarbon aviation fuels are thus likely to be around for a while.But such fuels need not be fossil.They might be synthesised from the CO2 exhaust of various industrial processes.And a study just published in Nature, by Aldo Steinfeld of ETH Zurich, a technological university in Switzerland, and his colleagues, shows how they might literally be plucked from thin air.Dr Steinfeld and his team devised and tested a system that, in essence, reimagines the natural process of photosynthesis.Plants take in atmospheric CO2 and water and, with sunlight providing the energy, turn those raw materials into organic molecules.And that is exactly what Dr Steinfeld has done.

一种将大气中的二氧化碳和水结合起来制造飞机燃料的方法大多数人都同意这一点——直接或间接地用可再生电力取代化石燃料是工业、交通以及建筑供暖和制冷的脱碳最佳方式。但也有一些领域难以做到脱碳。水泥行业就是其中之一。航空领域是另一个，因为电池太重，氢（可以用可再生电力制造）需要的体积太大，难以实现。因此，碳氢化合物航空燃料可能会存在一段时间。但这些燃料不一定是化石燃料。它们可以从各种工业过程排放二氧化碳合成。瑞士苏黎世理工大学的阿尔多·斯坦菲尔德和他的同事们刚刚在《自然》杂志上发表的一项研究展示，它们是如何从稀薄的空气中提取燃料的。斯坦菲尔德博士和他的团队设计并测试了一个系统，从本质上说，它可以重新想象光合作用的自然过程。植物吸收大气中的二氧化碳和水，并通过阳光提供能量，将这些原材料转化为有机分子。这正是斯坦菲尔德博士所做的。

The process has three stages.The first absorbs CO2 and water from the atmosphere using a so-called direct-air-capture device made by Climeworks, a spin-off of ETH founded by two of Dr Steinfelds students that made the news recently by opening a demonstration carbon-capture-and-storage system in Iceland.There, however, the CO2 is reacted with basalt rock to dispose of it. Dr Steinfeld’s system makes use of it.The second stage is the clever bit.It employs concentrated sunlight to heat a material called cerium oxide which, when so heated, reacts with both CO2 and water.The reaction with CO2 creates carbon monoxide.The one with water creates hydrogen.In both cases the by-product is oxygen, which is vented into the atmosphere.But a mixture of carbon monoxide and hydrogen is a familiar one to industrial chemists.

这个过程分为三个阶段。第一个阶段是利用Climeworks制造的名为“直接捕获空气装置”从大气中吸收二氧化碳和水。博士的两学生最近在冰岛展示了“碳捕获和存储系统”，已成为新闻。（Climeworks是ETH的一个分支，ETH是由斯坦菲尔德博士的两名学生创建的。）然而，在那里，二氧化碳与玄武岩发生反应，将其转化。斯坦菲尔德博士的系统利用了它。第二个阶段是是很有巧思的。它利用集中的阳光加热一种叫做氧化铈的物质，当这种物质被加热时，它会与二氧化碳和水发生反应。与二氧化碳的反应产生一氧化碳。有水的产生氢气。在这两种过程下，副产品都是氧气，氧气被排放到大气中。但是工业化学家对一氧化碳和氢气的混合物并不陌生。

It is called syngas, and is widely used as a raw material to make other things.The third part of the process is therefore to turn the syngas into organic molecules.For the hydrocarbons that make up aviation fuel an industrial chemist would normally turn to what is known as the Fischer-Tropsch process.For their demonstrator, the team chose another route, which led to methanol rather than hydrocarbons.But the general idea is the same.

它被称为合成气，是被广泛用作制造其他东西的原料。因此，该过程的第三阶段是将合成气转化为有机分子。对于构成航空燃料的碳氢化合物，工业化学家通常会采用费托合成的方法。对于他们的示范者，团队选择了另一条路线，这样可以产生甲醇而不是碳氢化合物。但总体思路是一样的。

The teams demonstration rig, which they installed on the roof of ETHs Machine Laboratory Building, had a typical yield of 32ml of pure methanol per seven-hour day—tiny, but a clear proof of principle.A back-of-the-envelope calculation suggests that substituting the world’s aviation-fuel market entirely in this way would need 45,000km2 of suitably insolated land.

That sounds a lot, but is equivalent to about 0.5% of the area of the Sahara Desert.Air-captured aviation fuel would certainly need its path to market smoothed by appropriate carbon taxes on the fossil variety, and possibly other measures.But Dr Steinfelds rig does seem to have demonstrated a credible and potentially scalable way to go about making the stuff.

该团队的演示装置安装在ETH机器实验室大楼的屋顶上，其产量为每7小时32毫升纯甲醇，虽然量很小，但这是一个明确的原理证明。粗略计算表明，以这种方式完全替代世界航空燃料市场需要4.5万平方千米的适当日照土地。这听起来很多，但仅相当于撒哈拉沙漠面积的0.5%。通过对化石燃料征收适当的碳税，再加上可能采取的其他措施，空气中捕获的航空燃料进入市场的道路肯定会变得平坦。但是斯坦菲尔德博士的设备似乎已经证明了一种可靠的、潜在的可扩大规模化的方法来制造这些东西。