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.

在冰島的一座火山腳下，一家新開的工廠正在吸收空氣中的二氧化碳并將其轉化為石頭，把全球變暖的元兇囚禁起來。

這家名為Orca（源自冰島語，意思是“能源”）的工廠在冰島西南部的赫利舍迪地熱發電站開展這一尖端工作。

該工廠是全世界使用直接空氣捕集技術的最大工廠，直接空氣捕集技術是各種除碳技術中最不成熟的一種。盡管如此，開辦這一工廠的瑞士初創企業Climeworks并沒有被嚇退。

這家吸收周圍空氣中二氧化碳的工廠和比較傳統的碳捕獲與存儲項目不同，后者被用于捕獲高度污染的工業煙囪廢氣。

該工廠的收集器在通過前端的風扇吸入周圍空氣后，會去除空氣中的大部分二氧化碳，然后通過尾端的排氣扇將凈化后的空氣排出。

項目經理盧卡斯·考夫曼說，“收集器內部容器中精度很高的過濾物質”會捕獲二氧化碳。

考夫曼說：“一旦過濾器滿了，我們就會關閉入口，然后將其加熱到100攝氏度”以分離出二氧化碳。

二氧化碳在淡水中溶解后就會通過高壓注入地下800米到2000米深的玄武巖中。

溶液填滿巖石的縫隙，凝固過程就開始了。當二氧化碳接觸到玄武巖中的鈣、鎂和鐵，就會產生化學反應，轉變成鈣化白色晶體。

讓二氧化碳石化需要兩年時間。

法國國立高等先進科技學校（法國的一家工程學院）的化學實驗室主任迪迪爾·達爾馬佐內告訴法新社說，只有在巖石被加熱到溫度極高的時候（比如在火山噴發的情況下），二氧化碳才有可能被重新釋放到空氣中。

據認為，這里的火山活動水平很低，上一次火山噴發是1900年前。

耗資1000萬至1500萬美元（約合人民幣6400萬到9600 萬元）建造的Orca 工廠每年可吸收約4000噸二氧化碳。

按照全球標準來看，這個數量是微不足道的。氣候模型顯示，2050年前，全球每年需要去除幾十億噸二氧化碳。

為了防止災難性的全球變暖，專家認為唯一的途徑就是在2100年前將全球升溫幅度控制在比工業化前水平高1.5攝氏度以內。碳捕獲與存儲技術是專家提倡的除碳方式之一。

碳捕獲與存儲技術是在二氧化碳進入大氣前捕獲二氧化碳，將其立即抽離工業集中污染區。

但是冰島的這種直接空氣捕集方法旨在捕獲過去排放到大氣中的二氧化碳。

但是，直接空氣捕集技術還不成熟，而且還面臨大氣中二氧化碳濃度太低等障礙。

Orca工廠要處理200萬立方米的空氣才能捕獲1噸二氧化碳，這一過程要耗費大量能源，不過Climeworks公司沒有透露關于成本的任何細節。

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