케냐의 Carbon Valley

WHY KENYA COULD TAKE THE LEAD IN CARBON REMOVAL

 

The Economist - 2023.06.17

 

 

East Africa’s Rift Valley, which runs for thousands of kilometres from the Red Sea to Mozambique, provides a unique window into the evolutionary history of humanity. The shifting of tectonic plates that formed its deep lakes and sheltered canyons created conditions that first nurtured the ancestors of modern humans and then preserved their bones. Those geological forces may also push open a door to the future by making it possible to capture and store global-warming carbon dioxide cheaply from the air.

 

That, at least, is the hope of James Irungu Mwangi, a Kenyan environmentalist and development expert, who talks of the opportunity that could be afforded by what he calls “the Great Carbon Valley”. The rift, he argues, has the key attributes that make it attractive for “direct air capture” (DAC) stations to suck carbon dioxide from the air: renewable-energy potential and the right geology for storing carbon.

 

 

DAC

 

DAC의 작동 방식

 

 

이산화탄소를 모아서 현무암 속으로 쏙~

 

 

DAC plants need huge amounts of energy. Some of this is in the form of electricity, which is used to run fans blowing air through or over chemicals that absorb carbon dioxide. Much more energy is then needed in the form of heat to make these chemicals belch the gas, which is then compressed for use or storage.

 

Because the earth’s crust is thinner than usual along the rift, it has vast geothermal potential. The American government reckons Kenya alone could generate 10,000MW of geothermal power, more than ten times the amount it currently produces. A by-product of such power stations is plenty of waste steam, which can then be used to heat DAC machines. Moreover, since close to 90% of Kenya’s power is renewable, the electricity these machines consume does not contribute to more global warming.

 

Capturing carbon dioxide is just part of the process. Next it has to be safely locked away. The rift’s geology is particularly good for this, too. It has bands of porous basalt (a volcanic rock) that stretch across thousands of square kilometres. This makes the region “ideal” for carbon capture and storage, according to a paper published in 2021 by George Otieno Okoko and Lydia Olaka, both of the University of Nairobi. After carbon dioxide has been sucked from the air it is dissolved in water (in the same way one would make sparkling water). This slightly acidic and bubbly liquid is then injected into the rock. There it reacts with the basalt to form carbon-rich minerals—in essence, rocks—which means the gas will not leak back into the atmosphere.

 

A similar combination of geothermal energy and volcanic rock has already attracted companies elsewhere. Climeworks, a Swiss firm, opened the world’s biggest DAC plant in Iceland in 2021. It can remove some 4,000 tonnes of carbon dioxide a year from the atmosphere at a cost of $600-800 a tonne.

 

Martin Freimüller, the founder of Octavia Carbon, a Kenyan startup, is working to build the world’s second-biggest DAC plant in the Rift Valley. He hopes it will be able to sequester carbon dioxide far more cheaply than Climeworks can, in part thanks to cheap renewable electricity and geothermal steam, and in part because hiring skilled engineers and chemists costs less in Kenya than in the rich world.

 

Octavia’s pilot plant, scheduled for completion next year, is forecast to have costs of well below $500 a tonne. Mr Freimüller aims to cut this to below $100 within five years. That is far cheaper than industry-wide forecasts of $300-400 by BCG, a consulting firm. As this new market matures, nascent firms and technologies will have to evolve quickly, or die out. ■

 

 

Der Spiegel - 2023.05.13

 

 

케냐가 탄소 제거에 앞장설 수 있는 이유

홍해에서 모잠비크까지 수천 킬로미터에 이르는 동아프리카의 리프트 밸리는 인류의 진화 역사를 들여다볼 수 있는 독특한 창을 제공합니다. 깊은 호수와 보호 협곡을 형성한 지각판의 이동은 현생 인류의 조상을 키우고 뼈를 보존할 수 있는 조건을 만들었습니다. 이러한 지질학적 힘은 또한 지구 온난화를 일으키는 이산화탄소를 공기 중에서 저렴하게 포집하고 저장할 수 있게 함으로써 미래의 문을 열어줄 수도 있습니다.

 케냐의 환경운동가이자 개발 전문가인 제임스 이룽구 므왕기는 "그레이트 카본 밸리"라고 불리는 이 기회가 가져올 기회에 대해 이야기합니다. 그는 이 균열이 재생 에너지 잠재력과 탄소 저장에 적합한 지질학적 특성 등 대기에서 이산화탄소를 빨아들이는 '직접 공기 포집'(DAC) 스테이션에 매력적으로 작용하는 핵심 특성을 가지고 있다고 주장합니다.

 DAC 플랜트에는 막대한 양의 에너지가 필요합니다. 이 중 일부는 전기의 형태로, 이산화탄소를 흡수하는 화학 물질을 통과하거나 그 위로 공기를 불어넣는 팬을 작동하는 데 사용됩니다. 그런 다음 이러한 화학 물질이 가스를 내뿜게 하고 사용 또는 저장을 위해 압축하기 위해 열의 형태로 훨씬 더 많은 에너지가 필요합니다.

 지각이 균열을 따라 평소보다 얇기 때문에 지열 잠재력이 방대합니다. 미국 정부는 케냐에서만 현재 생산량의 10배가 넘는 10,000MW의 지열 전력을 생산할 수 있다고 추정합니다. 이러한 발전소의 부산물은 많은 양의 폐증기이며, 이 폐증기는 DAC 기계를 가열하는 데 사용될 수 있습니다. 게다가 케냐 전력의 90% 가까이가 재생 가능 에너지이기 때문에 이 기계가 소비하는 전기는 지구 온난화에 더 이상 기여하지 않습니다.

 이산화탄소를 포집하는 것은 과정의 일부일 뿐입니다. 다음 단계는 이산화탄소를 안전하게 가두는 것입니다. 균열의 지질학은 특히 이 작업에 적합합니다. 다공성 현무암(화산암) 띠가 수천 평방킬로미터에 걸쳐 뻗어 있습니다. 나이로비 대학의 조지 오티에노 오코코와 리디아 올라카가 2021년에 발표한 논문에 따르면, 이 지역은 탄소 포집 및 저장에 "이상적인" 지역입니다. 이산화탄소를 공기 중에서 빨아들인 후 탄산수를 만드는 것과 같은 방식으로 물에 녹입니다. 이 약산성이며 거품이 있는 액체를 암석에 주입합니다. 현무암과 반응하여 탄소가 풍부한 광물, 즉 암석을 형성하므로 가스가 대기 중으로 다시 누출되지 않습니다.

 지열 에너지와 화산암의 유사한 조합은 이미 다른 곳에서도 기업들의 관심을 끌고 있습니다. 스위스 회사인 Climeworks는 2021년에 아이슬란드에 세계 최대 규모의 DAC 공장을 열었습니다. 이 공장은 톤당 600~800달러의 비용으로 연간 약 4,000톤의 이산화탄소를 대기에서 제거할 수 있습니다.

 케냐의 스타트업인 옥타비아 카본의 설립자 마틴 프라이뮬러는 리프트 밸리에 세계에서 두 번째로 큰 DAC 공장을 건설하기 위해 노력하고 있습니다. 그는 부분적으로는 저렴한 재생 전기와 지열 증기 덕분에, 그리고 부분적으로는 케냐에서 숙련된 엔지니어와 화학자를 고용하는 데 드는 비용이 부유한 세계보다 저렴하기 때문에 이 공장이 Climeworks보다 훨씬 더 저렴하게 이산화탄소를 격리할 수 있기를 희망합니다.

 내년에 완공 예정인 옥타비아의 파일럿 플랜트는 톤당 500달러 미만의 비용이 소요될 것으로 예상됩니다. 프라이뮬러는 5년 내에 이 비용을 100달러 이하로 낮추는 것을 목표로 하고 있습니다. 이는 컨설팅 회사인 BCG가 예측한 업계 전반의 예상치인 300~400달러보다 훨씬 저렴한 수준입니다. 이 새로운 시장이 성숙해짐에 따라 초기 기업과 기술은 빠르게 진화하지 않으면 도태될 것입니다. ■

 

 

 

https://geowiki.tistory.com/234

동아프리카 열곡 (East Africa's Great Rift Valley)

 

https://geowiki.tistory.com/3282