In Iceland, CO2 Sucked From The Air Is Turned To Rock

徐晶晶

At the foot of an Icelandic volcano， a newly- openedplant is sucking carbon dioxide from the air and turning itto rock， locking away the main culprit behind global warming.

Orca， based on the Icelandic word for“energy”， doesits cutting- edge work at the Hellisheidi geothermal powerplant in southwest Iceland.

It is the world’s largest plant using the direct air capturetechnology （DAC）， which is the least developed of thecarbon removal technologies. Climeworks， a Swiss start-upthat has just built the plant， is not deterred.

By pulling CO2 from ambient air， the plant is differentfrom more traditional types of carbon capture and storage（CCS） projects at highly-polluting industrial smokestacks.

Fans in front of the collector draw in ambient air andrelease it， largely purified of CO2， through ventilators at theback.

Project manager Lukas Kaufmann said“very selectivefilter material inside our collector containers”catch carbondioxide.

“As soon as the filter is full， we close it off， and thenwe heat it up to around 100 degrees Celsius”to separate thepure gas， Kaufmann added.

Dissolved in fresh water， the gas is then injected underhigh pressure into the basalt rock between 800 and 2，000metres underground.

The solution fills the rock’s cavities and the solidification process begins -- a chemical reaction turning it to calcifiedwhite crystals that occurs when the gas comes in contactwith the calcium， magnesium and iron in the basalt.

It takes up to two years for the CO2 to petrify.

The carbon dioxide would only be re-released into theair if the rock were to heat up to very high temperatures， asin a volcanic eruption， Didier Dalmazzone， head of thechemistry laboratory at French engineering school ENSTAParis， told AFP.

The volcanic activity level here is considered low， withthe last eruption 1，900 years ago.

The Orca plant， which cost $10- 15 million to build，can suck up around 4，000 tonnes of CO2 per year.

The amount is tiny by global standards. Climate modellingsuggests the world needs to eliminate several billiontonnes per year by 2050.

CCS is one of the methods advocated by experts to limitglobal warming to 1.5 degrees C from pre-industrial levelsby 2100. That is the bar seen as the only way to preventcatastrophic global warming.

CCS methods capture CO2 before it enters the atmosphere，pulling it immediately from highly-concentrated industrialpollution zones.

But the direct air capture （DAC） process， like the onein Iceland， aims to capture past emissions already in the atmosphere.

However， the DAC method is in its early days and ishampered by the small concentration of CO2 in the atmosphere.

Orca has to process two million cubic metres of air tocapture just one tonne of CO2 -- a costly process that requireslarge amounts of energy， though Climeworks wouldnot divulge any details.

在冰岛的一座火山脚下，一家新开的工厂正在吸收空气中的二氧化碳并将其转化为石头，把全球变暖的元凶囚禁起来。

这家名为Orca（源自冰岛语，意思是“能源”）的工厂在冰岛西南部的赫利舍迪地热发电站开展这一尖端工作。

该工厂是全世界使用直接空气捕集技术的最大工厂，直接空气捕集技术是各种除碳技术中最不成熟的一种。尽管如此，开办这一工厂的瑞士初创企业Climeworks并没有被吓退。

这家吸收周围空气中二氧化碳的工厂和比较传统的碳捕获与存储项目不同，后者被用于捕获高度污染的工业烟囱废气。

该工厂的收集器在通过前端的风扇吸入周围空气后，会去除空气中的大部分二氧化碳，然后通过尾端的排气扇将净化后的空气排出。

项目经理卢卡斯·考夫曼说，“收集器内部容器中精度很高的过滤物质”会捕获二氧化碳。

考夫曼说：“一旦过滤器满了，我们就会关闭入口，然后将其加热到100摄氏度”以分离出二氧化碳。

二氧化碳在淡水中溶解后就會通过高压注入地下800米到2000米深的玄武岩中。

溶液填满岩石的缝隙，凝固过程就开始了。当二氧化碳接触到玄武岩中的钙、镁和铁，就会产生化学反应，转变成钙化白色晶体。

让二氧化碳石化需要两年时间。

法国国立高等先进科技学校（法国的一家工程学院）的化学实验室主任迪迪尔·达尔马佐内告诉法新社说，只有在岩石被加热到温度极高的时候（比如在火山喷发的情况下），二氧化碳才有可能被重新释放到空气中。

据认为，这里的火山活动水平很低，上一次火山喷发是1900年前。

耗资1000万至1500万美元（约合人民币6400万到9600 万元）建造的Orca 工厂每年可吸收约4000吨二氧化碳。

按照全球标准来看，这个数量是微不足道的。气候模型显示，2050年前，全球每年需要去除几十亿吨二氧化碳。

为了防止灾难性的全球变暖，专家认为唯一的途径就是在2100年前将全球升温幅度控制在比工业化前水平高1.5摄氏度以内。碳捕获与存储技术是专家提倡的除碳方式之一。

碳捕获与存储技术是在二氧化碳进入大气前捕获二氧化碳，将其立即抽离工业集中污染区。

但是冰岛的这种直接空气捕集方法旨在捕获过去排放到大气中的二氧化碳。

但是，直接空气捕集技术还不成熟，而且还面临大气中二氧化碳浓度太低等障碍。

Orca工厂要处理200万立方米的空气才能捕获1吨二氧化碳，这一过程要耗费大量能源，不过Climeworks公司没有透露关于成本的任何细节。

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