It could be a scene from science fiction. Towering over dark, mossy lava fields are stacks of noisy machines the size of shipping containers, domes, and zig-zagging silver pipes. Found 30km (19 miles) southwest of Iceland’s capital Reykjavik, this is the world’s largest direct air capture (DAC) facility. Called Mammoth, it has been developed by Swiss firm Climeworks. It has been running for two months, sucking global-warming carbon dioxide (CO2) out of the air, then storing it deep underground where it turns to stone. Twelve collector containers are now installed, but in the coming months 72 of them will circle the large processing hall. “That will enable us to capture 36,000 tons of CO2 every year,” Climeworks’ chief commercial officer, Douglas Chan, tells the BBC. The idea is to reverse emissions that have already been pumped into the atmosphere. Each collector unit has a dozen powerful fans, which, every 40 seconds, can suck up enough air to fill an Olympic swimming pool. “The technology relies on sucking in lots and lots of air, slowing it down so that the filter can capture it, and then venting the air back out the end,” says Mr Chan.
这可能是科幻小说中的场景。黑暗、长满青苔的熔岩原上高耸着一堆堆噪音很大的机器，它们有集装箱大小、圆顶和锯齿状的银管。该设施位于冰岛首都雷克雅未克西南 30 公里（19 英里）处，是世界上最大的直接空气捕获 (DAC) 设施。它被称为 Mammoth，由瑞士公司 Climeworks 开发。它已经运行了两个月，从空气中吸收导致全球变暖的二氧化碳（CO2），然后将其储存在地下深处，在那里它会变成石头。现已安装 12 个收集容器，但在接下来的几个月中，其中 72 个收集容器将环绕大型加工车间。 Climeworks 首席商务官 Douglas Chan 告诉 BBC：“这将使我们每年捕获 36,000 吨二氧化碳。”这个想法是扭转已经被排入大气中的排放。每个收集器单元都有十几个强大的风扇，每 40 秒就可以吸入足够的空气来填充一个奥林匹克游泳池。 “这项技术依赖于吸入大量的空气，减慢空气的速度，以便过滤器能够捕获空气，然后将空气从末端排出，”陈先生说。
CO2 only makes up a tiny proportion of the atmosphere (0.04%), so capturing it requires a lot of electricity. For Mammoth that electricity comes from a neighbouring geothermal power plant, so, while operating, the plant is emissions free. Once full, the collection chambers are flushed out with hot steam, which is piped into the processing hall. Inside the hall, Mr Chan points out two enormous balloons overhead, which together hold a single tonne of CO2. That captured CO2 is then mixed with fresh water, in an adjacent tower. “It’s almost like a shower,” explains Dr Martin Voigt, from Icelandic firm Carbfix, which has developed a process to turn CO2 into stone. “From the top, water trickles down. The CO2 is coming up, and we dissolve the CO2.” Hidden inside two white, igloo-like domes nearby are injection wells, where the CO2-laden water is pumped more than 700m underground.
二氧化碳仅占大气的一小部分（0.04%），因此捕获它需要大量电力。对于猛犸象来说，电力来自邻近的地热发电厂，因此，该发电厂在运行时是零排放的。一旦装满，收集室就会用热蒸汽冲洗，然后通过管道输送到加工车间。在大厅内，陈先生指着头顶上的两个巨大气球，它们总共容纳了一吨二氧化碳。然后，捕获的二氧化碳在相邻的塔中与淡水混合。 “这几乎就像一场淋浴，”来自冰岛 Carbfix 公司的 Martin Voigt 博士解释道，该公司开发了一种将二氧化碳转化为石头的工艺。 “水从上面流下来。二氧化碳正在上升，我们要溶解二氧化碳。”附近的两个白色冰屋状圆顶内隐藏着注入井，富含二氧化碳的水被泵送到地下 700 多米深处。
“This is a fresh basalt here,” says Dr Voight, showing me a lump of black rock taken from a recent volcanic eruption, and riddled with tiny holes. “You can see there's a lot of porosity.” Iceland has an abundance of volcanic basalt, and this bedrock acts like a storage reservoir. When the carbon meets other elements found in the basalt, a reaction kicks off and it solidifies, locking it away as carbonate minerals. “Here you can see a lot of these pores are now filled with whitish specks,” says Dr Voight, handling a sample of drilled out rock. “Some of these are carbonate minerals. They contain the mineralised CO2.” The process is quick, claims Dr Voight enthusiastically. “We're not talking about millions of years.” “Around 95% of the CO2 was mineralised within two years in the pilot project. This is incredibly fast. On geological timescales at least.”
“这是一块新鲜的玄武岩，”沃伊特博士说道，他向我展示了一块从最近的火山喷发中取出的黑色岩石，上面布满了小孔。 “你可以看到有很多孔隙。”冰岛有丰富的火山玄武岩，这种基岩就像一个储水库。当碳遇到玄武岩中的其他元素时，就会发生反应并凝固，将其锁定为碳酸盐矿物。 “在这里你可以看到很多孔隙现在都充满了白色斑点，”沃伊特博士说，他正在处理钻出的岩石样本。 “其中一些是碳酸盐矿物。它们含有矿化二氧化碳。”沃伊特博士热情地声称，这个过程很快。 “我们不是在谈论数百万年。” “在试点项目中，大约 95% 的二氧化碳在两年内被矿化。这速度快得令人难以置信。至少在地质时间尺度上是这样。”
Capable of removing 36,000 tonnes of CO2 a year, an amount similar to taking 8,000 petrol cars off the road, Mammoth is almost 10 times larger than Climeworks’ first commercial plant called Orca. It costs Climeworks almost $1,000 (£774) to capture and store a tonne of CO2. To make money it sells carbon offsets to clients. “Mammoth has already sold close to a third of its lifetime capacity,” states Mr Chan, who believes technological improvements and scaling up, will drive down future costs. “By the end of the decade, we want to be at a cost of capture of between $300 and $400.” Among its customers are Microsoft, H&M, JP Morgan Chase, Shopify and Lego; as well as over 20,000 individuals who subscribe on Climeworks’ website. “We're following the science,” Microsoft’s senior director of energy and carbon removal, Brian Marrs, previously told the BBC. “Carbon removal has to be part of the equation. You can't reduce emissions that are already in the atmosphere, you have to remove them.” Eventually Mammoth will be dwarfed by US-based Project Cypress, which breaks ground in 2026, and which Climeworks hopes will remove up to a million tonnes of CO2 annually, using new technology which it claims will be cheaper and more energy efficient.
Mammoth 每年能够去除 36,000 吨二氧化碳，相当于减少道路上 8,000 辆汽油车的排放量，Mammoth 的体积几乎是 Climeworks 首个名为 Orca 的商业工厂的 10 倍。 Climeworks 捕获和储存一吨二氧化碳的成本接近 1,000 美元（774 英镑）。为了赚钱，它向客户出售碳补偿。 “猛犸象已经售出了其生命周期产能的近三分之一，”陈先生表示，他相信技术改进和扩大规模将降低未来的成本。 “到本世纪末，我们希望捕获成本在 300 至 400 美元之间。”其客户包括微软、H&M、摩根大通、Shopify 和乐高；以及超过 20,000 名在 Climeworks 网站上订阅的个人。 “我们遵循科学，”微软能源和碳清除高级总监布莱恩·马尔斯此前告诉英国广播公司。 “碳去除必须成为方程式的一部分。你无法减少大气中已经存在的排放物，你必须将它们消除。”最终，与美国的 Cypress 项目相比，Mammoth 项目将相形见绌，该项目将于 2026 年破土动工，Climeworks 希望该项目能够使用新技术，每年消除多达 100 万吨二氧化碳，据称该技术将更便宜、更节能。
DAC technology is, however, not without critics who think its over-hyped, pointing to high costs, high energy consumption and limited scale. Those critics would argue that capturing CO2 where it is emitted would be far more efficient. “It's much easier to remove the carbon dioxide directly from smokestacks,” says Dr Edvard Júlíus Sólnes, a professor at the University of Iceland and former Icelandic Environment Minister.
然而，DAC 技术并非没有批评者认为其被过度炒作，指出其成本高、能耗高且规模有限。这些批评者认为，在二氧化碳排放的地方捕获二氧化碳会更加有效。 “直接从烟囱中去除二氧化碳要容易得多，”冰岛大学教授、冰岛前环境部长爱德华博士说。
Despite repeated calls to curb emissions, a record amount of planet-heating CO2 was churned out last year. The UN's Intergovernmental Panel on Climate Change has warned that emissions must be urgently slashed, but that still won’t be enough to prevent harmful global warming. Many climate scientists agree that carbon removal will also be necessary but this also divides opinion. Multiple methods have emerged, and some caution against reliance on so-called techno-fixes, which might discourage polluters from changing their ways. Currently, no carbon removal is taking place at anywhere near the scale that would be needed. “We release about 40 billion tonnes of carbon dioxide into the atmosphere every year, so this [DAC] won't make a dent in the big problem,” says Dr Sólnes. “We need to divest from fossil fuels and find other sources of energy,” he asserts. “But I think we should use all methods to fight this problem.” More DAC projects are getting off the ground. According to the International Energy Agency, 27 plants have been commissioned worldwide, but only four of them capture more than 1,000 tonnes of CO2 annually. Plans for further 130 facilities are also on the drawing board, and around $3.5bn has also been earmarked by the US government to kickstart three large-scale hubs aimed at eventually removing a mega-tonne of CO2, per year. However, Doug Chan is convinced that DAC can help battle global warming. “I really do believe direct air capture and other engineered solutions are going to get us to the point that we need to help fight climate change.”
尽管人们一再呼吁遏制排放，但去年导致地球供暖的二氧化碳排放量仍创历史新高。联合国政府间气候变化专门委员会警告说，必须紧急削减排放量，但这仍然不足以防止有害的全球变暖。许多气候科学家一致认为，碳去除也是必要的，但这也存在分歧。已经出现了多种方法，一些人警告不要依赖所谓的技术修复，这可能会阻止污染者改变他们的方式。目前，任何地方都没有进行任何接近所需规模的碳去除。 “我们每年向大气中排放约 400 亿吨二氧化碳，因此 [DAC] 无法解决这个大问题，”Sólnes 博士说。 “我们需要放弃化石燃料并寻找其他能源，”他断言。 “但我认为我们应该使用一切方法来解决这个问题。”更多 DAC 项目正在启动。据国际能源署称，全球已有 27 座工厂投入运行，但只有 4 座工厂每年的二氧化碳捕集量超过 1,000 吨。进一步建设 130 个设施的计划也正在酝酿之中，美国政府还指定了约 35 亿美元用于启动三个大型中心，旨在最终每年消除 100 万吨二氧化碳。然而，Doug Chan 坚信 DAC 可以帮助应对全球变暖。 “我确实相信直接空气捕获和其他工程解决方案将使我们达到我们需要帮助应对气候变化的地步。”
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