New technology offers hope for storing carbon dioxide underground


Dom Wolff-Boenisch, Curtin University

To halt climate change and prevent dangerous warming, we ultimately have to stop pumping greenhouse gases into the atmosphere. While the world is making slow progress on reducing emissions, there are more radical options, such as removing greenhouse gases from the atmosphere and storing them underground.

In a paper published today in Science my colleagues and I report on a successful trial converting carbon dioxide (CO₂) to rock and storing it underground in Iceland. Although we trialled only a small amount of CO₂, this method has enormous potential.

Here’s how it works.

Turning CO₂ to rock

Our paper is the culmination of a decade of scientific field and laboratory work known as CarbFix in Iceland, working with a group of international scientists, among them Wallace Broecker who coined the expression “global warming” in the 1970s. We also worked with the Icelandic geothermal energy company Reykjavik Energy.

The idea itself to convert CO₂ into carbonate minerals, the basis of limestone, is not new. In fact, Earth itself has been using this conversion technique for aeons to control atmospheric CO₂ levels.

However, scientific opinion had it up to now that converting CO₂ from a gas to a solid (known as mineralisation) would take thousands (or tens of thousands) of years, and would be too slow to be used on an industrial scale.

To settle this question, we prepared a field trial using Reykjavik Energy’s injection and monitoring wells. In 2012, after many years of preparation, we injected 248 tonnes of CO₂ in two separate phases into basalt rocks around 550m underground.

Most CO₂ sequestration projects inject and store “supercritical CO₂”, which is CO₂ gas that has been compressed under pressure to considerably decrease its volume*. However, supercritical CO₂ is buoyant, like a gas, and this approach has thus proved controversial due to the possibility of leaks from the storage reservoir upwards into groundwater and eventually back to the atmosphere.

In fact, some European countries such as the Netherlands have stopped their efforts to store supercritical CO₂ on land because of lack of public acceptance, driven by the fear of possible leaks in the unforeseeable future. Austria went even so far as to ban underground storage of carbon dioxide outright.

The injection well with monitoring station in the background.
Dom Wolff-Boenisch, Author provided

Our Icelandic trial worked in a different way. We first dissolved CO₂ in water to create sparkling water. This carbonated water has two advantages over supercritical CO₂ gas.

First, it is acidic, and attacks basalt which is prone to dissolve under acidic conditions.

Second, the CO₂ cannot escape because it is dissolved and will not rise to the surface. As long as it remains under pressure it will not rise to the surface (you can see the same effect when you crack open a soda can; only then is the dissolved CO₂ released back into the air).

Dissolving basalt means elements such as calcium, magnesium, and iron are released into pore water. Basaltic rocks are rich in these metals that team up with the dissolved CO₂ and form solid carbonate minerals.

Through observations and tracer studies at the monitoring well, we found that over 95% of the injected CO₂ (around 235 tonnes) was converted to carbonate minerals in less than two years. While the initial amount of injected CO₂ was small, the Icelandic field trial clearly shows that mineralisation of CO₂ is feasible and more importantly, fast.

Storing CO₂ under the oceans

The good news is this technology need not be exclusive to Iceland. Mineralisation of CO₂ requires basaltic or peridotitic rocks because these types of rocks are rich in the metals required to form carbonates and bind the CO₂.

As it turns out the entire vast ocean floor is made up of kilometre-thick oceanic basaltic crust, as are large areas on the continental margins. There are also vast land areas covered with basalt (so-called igneous provinces) or peridotite (so-called “ophiolitic complexes”).

The overall potential storage capacity for CO₂ is much larger than the global CO₂ emissions of many centuries. The mineralisation process removes the crucial problem of buoyancy and the need for permanent monitoring of the injected CO₂ to stop and remedy potential leakage to the surface, an issue that supercritical CO₂ injection sites will face for centuries or even millennia to come.

On the downside, CO₂ mineralisation with carbonated water requires substantial amounts of water, meaning that this mineralisation technique can only succeed where vast supplies of water are available.

However, there is no shortage of seawater on the ocean floor or continental margins. Rather, the costs involved present a major hurdle to this kind of permanent storage option, for the time being at least.

In the case of our trial, a tonne of mineralised CO₂ via carbonated water cost about US$17, roughly twice that of using supercritical CO₂ for storage.

It means that as long as there are no financial incentives such as a carbon tax or higher price on carbon emissions, there is no real driving force for carbon storage, irrespective of the technique we use.

*Correction: The sentence has been corrected to note that gas volume rather than density decreases when it is compressed. Thankyou to the readers who pointed out the error.

The Conversation

Dom Wolff-Boenisch, Senior Lecturer, Western Australian School of Mines, Curtin University

This article was originally published on The Conversation. Read the original article.

Rising carbon dioxide is greening the Earth – but it’s not all good news


Pep Canadell, CSIRO and Yingping Wang, CSIRO

Dried lake beds, failed crops, flattened trees: when we think of global warming we often think of the impacts of droughts and extreme weather. While there is truth in this image, a rather different picture is emerging.

In a paper published in Nature Climate Change, we show that the Earth has been getting greener over the past 30 years. As much as half of all vegetated land is greener today, and remarkably, only 4% of land has become browner.

Our research shows this change has been driven by human activities, particularly the rising concentration of carbon dioxide (CO₂) in the atmosphere. This is perhaps the strongest evidence yet of how people have become a major force in the Earth’s functioning.

We are indeed in a new age, the Anthropocene.

How do you measure green?

Plants play a vital role in maintaining Earth as a habitable place, not least through absorbing CO₂. We wanted to know how people are affecting this ability.

To do this, we needed to know how much plants are growing. We couldn’t possibly measure all the plants on Earth so we used satellites observations to measure light reflected and absorbed from the Earth’s surface. This is a good indicator of leaf area, and therefore how plants are growing.

We found consistent trends in greening across Australia, central Africa, the Amazon Basin, southeast United States, and Europe. We found browning trends in northwest North America and central South America.

Updated figure to 2015. Source: http://sites.bu.edu/cliveg/files/2016/04/LAI-Change.png

We then used models to figure out what was driving the trends in different regions.

A CO₂-richer world

Plants need CO₂ to grow through photosynthesis. We found that the biggest factor in driving the global greening trend is the fertilisation effect of rising atmospheric CO₂ due to human activity (atmospheric concentration grew by 46 parts per million during the period studied).

This effect is well known and has been used in agricultural production for decades to achieve larger and faster yields in greenhouses.

In the tropics, the CO₂ fertilisation effect led to faster growth in leaf area than in most other vegetation types, and made this effect the overwhelming driver of greening there.

A warmer world

Climate change is also playing a part in driving the overall greening trend, although not as much as CO₂ fertilisation.

But at a regional scale, climate change, and particularly increasing temperature, is a dominant factor in northern high latitudes and the Tibetan Plateau, driving increased photosynthesis and lengthening the growing season.

Greening of the Sahel and South Africa is primarily driven by increased rainfall, while Australia shows consistent greening across the north of the continent, with some areas of browning in interior arid regions and the Southeast. The central part of South America also shows consistent browning.

A nitrogen-richer world

We know that heavy use of chemical nitrogen fertilisers leads to pollution of waterways and excess nitrogen which leads to declining plant growth. In fact, our analysis attributes small browning trends in North America and Europe to a long-term cumulative excess nitrogen in soils.

But, by and large, nitrogen is a driver of greening. For most plants, particularly in the temperate and boreal regions of the Northern Hemisphere, there is not enough nitrogen in soils. Overall, increasing nitrogen in soils has a positive effect on greening, similar to that of climate change.

A more intensively managed world

The final set of drivers of the global greening trend relates to changes in land cover and land management. Land management includes forestry, grazing, and the way cropland is becoming more intensively managed with multiple crops per year, increasing use of fertilisers and irrigation.

All of this affects the intensity and time the land surface is green.

Perhaps surprisingly, felled forests don’t show as getting browner, because they are typically replaced by pastures and crops, although this change has profound effects on ecosystems.

The greening trends in southeast China and the southeastern United States are clearly dominated by land cover and management changes, both regions having intensive cropping areas and also reforestation.

Although this management effect has the smallest impact on the greening trend presented in this study, the models we used are not suitable enough to assess the influence of human management globally.

The fact that people are making parts of the world greener and browner, and the world greener overall, constitutes some of the most compelling evidence of human domination of planet Earth. And it could be good news: a greening world is associated with more positive outcomes for society than a browning one.

For instance, a greener world is consistent with, although it does not fully explain, the fact that land plants have been removing more CO₂ from the atmosphere, therefore slowing down the pace of global warming.

But don’t get your hopes up. We don’t know how far into the future the greening trend will continue as the CO₂ concentration ultimately peaks while delayed global warming continues for decades after. Regardless, it is clear that the benefits of a greening Earth fall well short compared to the estimated negative impacts of extreme weather events (such as droughts, heat waves, and floods), sea level rise, and ocean acidification.

Humans have shown their capacity to (inadvertently) affect the word’s entire biosphere, it is now time to (advertently) use this knowledge to mitigate climate change and ameliorate its impacts.

The Conversation

Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO and Yingping Wang, Chief research scientist, CSIRO

This article was originally published on The Conversation. Read the original article.

River flows drop as carbon dioxide creates thirstier plants


Anna Ukkola, UNSW Australia and Albert Van Dijk, Australian National University

Rising carbon dioxide concentrations are causing vegetation across large parts of Australia to grow more quickly, in turn consuming more water and reducing flows into river basins.

Our research, published today in Nature Climate Change, shows that river flows have decreased by 24-28% in a large part of Australia due to increasing CO₂ levels, which have risen by 14% since the early 1980s.

This could exacerbate water scarcity in several populated and agriculturally important regions.

Contrasting effects

It was previously unclear whether the increasing CO₂ in the atmosphere has led to detectable changes in streamflow in Australian rivers. This is partly because increasing CO₂ can have two opposing effects on water resources.

CO₂ is the key ingredient for photosynthesis, and higher concentrations allow plants to grow more vigorously. This fertilisation effect could be expected to lead to denser vegetation that needs more water to grow, in turn reducing the amount of rainwater that can run off into rivers.

Acting directly against this is the fact that increased CO₂ concentrations allow plants to use water more sparingly. Small pores called stomata on the surface of leaves allow plants to regulate their uptake of CO₂ for photosynthesis and water loss to the atmosphere. At higher CO₂ concentrations, plants can partially close these pores, maintaining the same influx of CO₂ while also reducing water loss through transpiration. This could be expected to leave more rainwater available to become river runoff.

The net effect of these two counteracting processes has so far been highly uncertain. In our study, we used a new method that combines satellite measurements of vegetation cover with river flow data collected for over 30 years. Using statistical methods we factored out other influences that affect river flows, such as variations in rainfall.

Our results suggest that the net effect of increased CO₂ has been declining runoff across the subhumid and semi-arid parts of Australia, and that this can be attributed to the increased vegetation.

Reduced streamflow due to CO2-induced vegetation greening was observed in subhumid and semi-arid climates.
Anna Ukkola, Author provided

The good news is that increasing CO₂ might also make plants better able to survive in these drying landscapes. By using water more efficiently, plants can grow more vigorously in arid regions and should better withstand droughts, such as those commonly associated with El Niño events. In areas with an average annual rainfall below about 700 mm, we found that the amount of vegetation cover that can be sustained has increased by about 35% since the early 1980s. This is good news for dryland cropping and grazing which are likely to enjoy increased yields as a consequence.

Despite these positive effects, in less dry parts of Australia, the reduction of river flow adds yet more pressure to water resources. As natural vegetation is greening and consuming more water, local rivers and dams are receiving less. At the same time, rainfall patterns are changing. With the exception of northern Australia, many of the affected areas are already experiencing declining rainfall and this trend is projected to continue into the future with increasing global temperature.

Elsewhere around the world, vegetation increases have also been observed in other dry regions such as southern and western Africa and the Mediterranean. It is certainly possible that these regions are also facing declining streamflow as a result.

The increase in vegetation helps to draw CO₂ from the atmosphere, but the effect is not enough to significantly slow the rise in atmospheric CO₂ and the resulting long-term climate change. Despite the observed greening, most of Australia’s vegetation continues to be very sensitive to rainfall changes. If rainfall continues to decline as projected, the greening trend may end or even be reversed, releasing the stored carbon back into the atmosphere.

The Conversation

Anna Ukkola, Research Associate, Climate Change Research Centre, UNSW Australia and Albert Van Dijk, Professor of Water Science and Management, Fenner School of Environment & Society, Australian National University

This article was originally published on The Conversation. Read the original article.

Australia: Native Trees and Climate Change


The link below is to an article reporting on research into the capability of native Australian trees to cope with increased carbon dioxide as climate change accelerates.

For more, visit:
http://www.smh.com.au/environment/conservation/native-trees-put-to-the-carbon-test-20120404-1wdeg.html

Earth Hour 2012: Tonight


The link below is to an article on Earth Hour 2012, which is being held tonight. The article below includes a history of the event, which is now a global movement for ‘change.’ However, just how much change is brought about by Earth Hour is still a matter of debate. There seems to be more of an emphasis on going beyond the hour this time round, which is a far better way of drawing awareness to the need of green energy for the future and the major issue of climate change that is facing the planet. If the event is to is bring lasting change, we need to move beyond the hour as just a fun thing to do and actually bring about change to the way we live our lives the world over. There is a long way to go, as can be seen with the great difficulty of reaching any useful agreements on CO2 emission reductions and the like. Hopefully awareness can bring about real change through this event.

For more visit:
http://www.kleenexmums.com.au/sustainability/earth-hour/the-hour-of-no-power/