Going underground with greenhouse gas

Industrial plants like this steel-making factory account for a large share of global greenhouse gases.

With the turn of a pipe valve, three researchers began silently pumping carbon dioxide (CO2) captured from a German refinery more than 700 metres (almost 2,300 feet) into the earth beneath a former natural gas storage reservoir. For the assembled onlookers at the site outside the town of Ketzin near Berlin last month, there was little to actually see. So after the formalities, local residents, the mayor and other officials at the ceremony discussed the significance of the day over beer and goulash and posed for photographs, while journalists conducted interviews with the research team.

Despite the lack of drama, the event was an important milestone for this study -- known as CO2SINK -- into the feasibility of storing CO2 underground as a way to reduce greenhouse gas emissions that cause climate change. It is the first of its kind onshore in Europe. Geologists and scientists from 18 European power producers, universities, government agencies and energy companies -- including Shell – participating in the small-scale project will spend the next several years steadily injecting the gas and monitoring its movement over time.

The hope for carbon capture and storage (CCS) technology is huge. If proved to work on a commercial scale, it could be used at big industrial facilities like power plants, cement factories, refineries, chemical plants, and iron and steel works that account for a large share of global greenhouse gases. A recent report by the United Nations Intergovernmental Panel on Climate Change (IPCC), says that capturing CO2 may one day contribute up to 55% of the emission reductions that scientists believe necessary to address global warming. That – along with energy efficiency measures – would help allow modern societies to keep burning fossil fuels while renewable energy matures and expands, providing a bridge to a low-carbon energy future.

But it will likely take years before the technology sees widespread use. Technical questions still remain, like how best to inject large volumes of CO2 and how to ensure that it stays underground. The main obstacle however, is not technology, but economics. The dozens of large-scale demonstration projects that experts believe are necessary to fine-tune the technology will cost hundreds of millions of dollars each. And at present companies have no way to recoup their investment in the equipment to capture and store CO2 – a major obstacle to the widespread adoption of the technology by industry.

Overcoming these hurdles will take time and means that even if it works, CCS is unlikely to make much impact on CO2 emissions before perhaps 2020.  “CCS is not a silver bullet,” says Leo Meyer, a senior author of the IPCC report. “Theoretically its potential is enormous, but there’s a long way to go.”

No time to waste

CO2 is an ingredient in products such as fertilizer and chemicals.

And time is short. As global demand for electricity accelerates, particularly in Asia, so do CO2 emissions. Although renewable energies like solar and wind are growing fast, they can’t keep up with demand, prompting the use of more fossil fuels, especially coal. According to Xinhua press agency, in 2007 China added 91 gigawatts of capacity in the power sector, more than the total existing capacity of the UK. More than three-quarters was coal-fired. Yet burning coal for power accounts for about a quarter of the world’s total emissions of CO2. To tackle climate change seriously, 90% of power plants in the developed world and half of those in the developing world will need to capture and store their CO2 emissions by 2050, estimates Shell’s energy scenarios team.

New use for old skills

Many of the building blocks of storage and capture technology are well known. A number of industrial processes already capture CO2. Some chemical plants that produce methanol, for example, use liquid chemicals to absorb CO2 from gas. Once captured, CO2 is used for a range of purposes. It is an ingredient in products such as fertiliser and chemicals. Some of the carbon dioxide from Shell’s Pernis refinery in the Netherlands puts the fizz into soft drinks and is pumped into local greenhouses to help grow tomatoes. Transporting large amounts of CO2 via pipeline and injecting it underground is also common. For decades oil companies have done so to extract more oil from ageing fields.

But the final step in CCS – permanently storing CO2 underground – is less common and now the focus of more research. One of the largest storage operations is the Sleipner project operated by StatoilHydro off the coast of Norway. Each year StatoilHydro separates one million tonnes of CO2 from natural gas produced at an offshore field and stores it in a deep layer of permeable rock containing salt water. That helps StatoilHydro comply with Norway’s regulations on CO2 levels in the national gas system. CO2 is non-combustible and so must be removed before gas is sold into the grid.

Demonstration plants are key

Storing CO2 this way uses the same geological trapping mechanisms that have contained large reservoirs of oil, gas and CO2 underground naturally for millions of years. The technique involves injecting CO2 into permeable rock. The CO2 displaces salty water and is held securely by tightly-spaced pores in the rock, invisible to the human eye, while a layer of impermeable rock above prevents it from rising to the surface and escaping into the atmosphere.

But researchers need to learn more about what happens to the CO2 once underground. At depth and under pressure, CO2 behaves like a fluid. So researchers in Ketzin are using a range of techniques, such as time-lapse seismic analysis and sensors, to track its movement, study how it dissolves in salty water and reacts with minerals, and test for leakage.

“We already know a lot about these reservoir rocks and the fluids in them but CCS requires long-term storage of thousands of years,” says Wolf Heidug, Shell’s General Manager for CO2 Policy and senior co-author of the IPCC report. “CO2SINK’s extensive monitoring and simulation -- both during injection and after it has stopped -- will help us better understand the long-term fate of the injected CO2.”

The CO2SINK project will be the first of its kind onshore in Europe to study underground storage of CO2.

The Ketzin project will store approximately 30,000 tonnes of the gas over the next two years. That’s a small amount compared to the approximately eight million tonnes of CO2 produced by a conventional 1,000-megawatt coal-fired plant each year. Teams at other projects around the world are already working on the challenges of storing far greater quantities. One of the largest is the Weyburn-Midale project in Saskatchewan, Canada. Led by the International Energy Agency and co-sponsored by Shell, it is monitoring the storage of well over one million tonnes annually of CO2 piped from a coal-gasification plant in North Dakota, USA.

In Queensland, Australia, Shell engineers are providing the technical assistance on another demonstration project known as ZeroGen that will test CCS technology at a coal-fired power plant. Research is now focused on finding the most efficient method to inject the CO2. Although tightly-spaced pores in permeable rock help store CO2 securely, they can also make pumping it in more difficult. To overcome this problem, a team of engineers from Shell and ZeroGen has been trying a new technique called “punch and go”. A drill mounted on a mobile truck bores down to the layer of permeable rock. Small explosive charges then punch multiple injection arms into the surrounding rock, increasing the amount of CO2 that can be pumped in. When one well is complete, the mobile unit moves to the next site.

As well as answering technical questions and establishing the safety of the process, such demonstration projects provide the information necessary to set rules for CO2 storage. “The data collected at Ketzin and other demonstration projects is important to help politicians and policy makers as they design a regulatory framework for CCS,” says Heidug. For example, companies and governments still need to agree the ownership and liability for buried CO2  before industry will deploy the technology commercially.

As safe as Mother Nature?

Carbon dioxide occurs naturally in small concentrations in the atmosphere, is exhaled by people and animals as they breathe and is essential to plant growth. It is not dangerous in low concentrations. The IPCC says it is likely that 99% of CO2 stored underground using CCS would remain there for over a thousand years.

The report also states that with appropriate systems in place, the local health, safety and environmental risks of storing CO2 would be comparable to storing natural gas – a  practice that is common already. Indeed, the Olympic stadium in Berlin (pictured) that hosted the football World Cup in 2006 sits on a large gas store.

Nevertheless, using CCS at industrial facilities and power stations may mean pipelines pass through communities, and storage sites may be located close to populated areas – hence the importance of more demonstration projects to show the practice is safe.

“Public perception is perhaps the biggest potential hurdle for CCS,” says Meyer, who believes people may worry that there are unknown safety risks associated with storing CO2. “Unless these issues are handled right, CCS will likely not live up to its potential.” 

Making CCS a commercial reality

Tightly-spaces pores, invisible to the human eye, in rock such as sandstone can securely store carbon dioxide.

Finding the money to build demonstration projects has so far proven difficult. That’s partly because environmental concerns are behind the drive to store CO2 underground, rather than the technology’s commercial potential. CO2 has little value as a commodity and few consumers have so far been willing to pay a premium for “green” energy.

Moreover, power plants equipped with CCS produce 10-15% less power than those without because of the energy necessary to capture and store CO2. And the additional equipment can add hundreds of millions of dollars to a power plant’s price tag. Together, this would push up the cost of producing electricity. Although the cost is likely to fall as the technology becomes more widespread, it will remain more expensive than current technology.

With no obvious way to recoup their investment, companies and shareholders view CCS as an added cost. That often translates into a go-slow approach to storage projects. To stimulate investment and encourage large-scale carbon dioxide storage, some executives and experts argue that companies need strong government-mandated incentives, such as carbon taxes or credits for stored CO2 that can be traded in emission trading schemes.

“An important prerequisite is that there is a significant price for CO2 in the international business environment,” says Meyer. Making industries pay for the CO2 they put into the air should encourage them to find cheaper ways to reduce emissions, he says.  But governments could take years to agree on a cost for CO2 and a payment mechanism, delaying the technology’s adoption.

To accelerate it, some governments are helping to finance demonstration projects. The European Union, for example, has contributed €8.7 million ($13.6 million) to CO2Sink while the German government has provided €6 million ($9.3 million). Shell, meanwhile, is providing some of the finance and significant technical assistance to the project. And in July, the government of Alberta, Canada announced a fund of 2 billion Canadian dollars to accelerate CCS projects in the province. Shell plans to apply for funds to help finance a project that would capture and store about one million tonnes of CO2 from Shell’s Scotford Upgrader, which processes oil from oil sands in the province.

Storing CO2 is similar to storing natural gas - a common practice. The Olympic stadium in Berlin sits on a large gas store.

“The costs of CCS at the moment are prohibitive and the financial risks are high,” says Paal Frisvold, Chair of Bellona Europa, a Brussels-based international environmental organisation that is encouraging the EU to finance construction of up to 12 CCS-equipped power plants by 2015. “It’s unfair to ask companies to make the first move without incentives. We need to encourage them to dare to be first and to make the leap.”  Frisvold stresses that public funds should only be used to kick-start CCS and should be limited to the earliest projects.

This autumn, the researchers from CO2SINK will invite politicians and officials from the EU to Ketzin to see the project for themselves – a useful opportunity as they decide whether to support the large-scale flagship programme. In the meantime, the scientists at Ketzin will continue to study the carbon dioxide slowly filling the ground beneath the natural gas reservoir – a small but important part of global efforts to develop a technology that could help build that bridge to a low-emission energy future.

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