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Global Warming: Solving The CO2 Puzzle

Carbon Dioxide - CO2 - is the villian of the piece in the global warming debate. But without it, life on earth would not exist as we know it. CO2 absorbs infrared radiation, or heat, from the earth's surface, the atmosphere and clouds, thus trapping it and keeping us warm.

We breathe it out. Plants take it in. Every tree, every plant, every flower, eevry piece of wood, the fruits and vegetables we eat, every grain of rice, are all made from CO2. Plants have the wonderful ability to convert CO2 into "bio-mass", using energy from sunlight in a process known as photosynthesis. Incidentally, plants are green because of the chemicals they use in the conversion.

However - and this is where climate change experts agree - it is possible to have too much of a good thing.

That, simply put, is the problem with CO2? In this recent report. the Intergovernmental Panel on Climate Change (IPCC) delivered the clear message: It is virtually certain that CO2 levels and global warming are far above the range of natural variability over the past 650,000 years.

In other words, the problem is caused by man, by us.

The basic structure of CO2 is one atom of carbon bonded to two atoms of oxygen. It makes up around 380 ppmv (parts per million by volume) of the earth's atmosphere, or about 0.04 per cent. In the last 150 years, this level has risen dramatically. Yet for over a thousand years before that, it was almost constant.

The reason for this dramatic rise is mostly because of our burning of fossil fuels; coal, crude oil and natural gas. These are derived from ancient vegetable matter over hundreds of millions of years. They are all hydrogen and carbon atoms.

When hydrocarbons are burnt, say in a power station or a car engine, they react with oxygen from the air to produce CO2 and water, plus a lot of energy. Globally, we produce 65 million tonnes of CO2 every day this way. This is quite apart form the additional CO2 we produce by deforestation through burning trees. We are basically taking all of that carbon locked away in the ground for million of years, and releasing it into the atmosphere.

Controlling CO2
So the level of CO2 in the atmosphere is rising, causing the earth's temperature to rise, at an estimated two to four degrees Celsius this century. It is now looking like an ecological nightmare. And it is our fault, so what can we do about it?

The best and most obvious starting point is to reduce the amount of fuel we burn. Simply turning up the temperature of the air-conditioner by a couple of degrees, using smaller and more fuel-efficient cars, or better still, using buses and the MRT, buying more energy-efficient household appliances, switching off lights and computers when not in use - all this could make a difference.

Flying less and video-conferencing more, and designing more energy-efficient buildings, can help to reduce the CO2 load. As well as saving power, we can also use alternatives to fossil fuels. Solar energy can be used for water heating and, to a limited extent, to generate electricity. The equipment is currently expensive, but the price is falling and it does reduce CO2 emisions.

We can also look for ways to convert CO2 back to fuels and chemicals. Plants already do this. Biofuels are a potentially good way of recycling carbon, by using plants and sunlight to convert CO2 into oils, biomass or carbohydrate, which can be processed into fuels and chemicals.

However, biofuels alone will not solve the problem. The rate at which plants can convert CO2 is very slow compared to the rate at which we generate it, and the amount of land required to replace fossil fuels is impossibly large.

One interesting technology involves using algae which can convert CO2 to biomass. There is even a strain that can convert CO2 directly to hydrocarbons. Again, however, the current problem is that a huge pond area would be required to capture large amounts of CO2 and a lot of R&D is needed to develop a viable system.

There are currently some industrial uses of CO2, for example to manufacture polycarbonates, but these are small compared to the huge volume emitted. We could always consider trying to convert CO2 to fuels via synthesis gas, a mixture of carbon monoxide and hydrogen, chemically, by a process known as "dry reforming" with natural gas, or even to the very useful basic chemical methanol.

Syn gas and methanol can be converted to fuels and useful chemical products. However, the problem with this approach is that CO2 is extremely stable and requires a lot of energy to break apart and ironically, more CO2 can be generated in the process than is actually converted back.

Alternative Solutions
This is why Life Cycle Assessment, or LCA, is emerging as an important analytical tool; to understand the environmental impact of the total process from "cradle to grve".

Even after harnessing energy-saving measures and using renewable sources and biomass, we will still continue to burn fossil fuels for decades, so people are developing systems to capture and store the CO2 produced. But this is only feasible for large "point" sources of CO2 such as power stations, natural gas producers and large energy users. The CO2 can be captured by a range of techniques such as reacting it with a liquid solvent. It can be released by reversing the reaction.

Once captured, the CO2 could, for example, be used to enhance oil recovery, and then stored underground. As an oil well appraoches the end of its productive life, the oil pressure falls and it becomes difficult to recover. Injecting CO2 under pressure can "force out" the remaininig oil. Similarly it has been proposed that CO2 can be used to displace and recover methane from coal seams, or it can simply be stored in depleted oil and gas reservoirs and favourable geological formations.

The injection of CO2 into these geological storage systems involves a lot of the same technology as drilling, and Singapore is well placed to develop the technology, building on our world-leading position in ocean drilling rig development and construction.

There are many experimental CO2 storage programmes around the world, and there are systems already operating commercially although not yet applied to power stations. Natural gas produced at the Sleipner West field under the North Sea contains about 9.5 per cent CO2, which has to be removed before the gas can be used. The Co2 used to be vented into the atmosphere. But since 1996, Statoil, the operators of the field, have been injecting the CO2 down a 3km-long well and storing it in the porous and permeable rock. About a million tonnes of CO2 per year is prevented from entering the atmosphere in this way.

In Weyburn, Canada, the gas producer, EnCana, injects CO2 into an oilfield in order to boost production. It is anticipated that 20 million tonnes of CO2 will be permanently stored there in the first phase of the demonstration. The CO2 actually comes from a power plant in North Dakota in the United States.

In Algeria, the In-Salah Gas project is a joint venture between Sonatrach, BP and Statoil. It is the largest natural gas development project in Algeria. The gas contains up to 10 per cent CO2 which is separated and re-injected back 1,800m deep under water layer at a lower level of the reservoir.

Injection into the deep ocean is also being researched. Theoretical predictions show that at depths of greater than 1,000m it would become isolated from the atmosphere for centuries.

Another possible storage technique is to convert the CO2 to mineral carbonates, such as magnesium carbonate or calcium carbonate (limestone). CO2 is slightly acidic and will react with basic mineral oxides, such as lime (calcium oxide) to form the carbonate, which is like rock and can be used in construction.

This could be aprticularly attractive if the raw materials are also waste streams. Ironically all of these techniques use energy to capture and store the CO2, so although they reduce CO2 emissions they also increase the rate of use of fossil fuels.

Clearly no single technique will be the answer to global warming. A whole range of measures is required, and urgently.

Keith Carpenter
01 Mar 2007

Keith Carpemter is the executive director of the Institute of Chemical and Engineering Sciences, an Institute of the Agency for Science, Technology and Research.

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Carbon Emission Trading

This article deals with carbon emissions trading between nations. For carbon trading schemes for individuals.

Carbon emissions trading involves the trading of permits to emit carbon dioxide (and other greenhouse gases, calculated in tonnes of carbon dioxide equivalent, tCO2e). It is one of the ways countries can meet their obligations under the Kyoto Protocol to reduce carbon emissions and thereby mitigate global warming.

Carbon emissions trading has been steadily increasing in recent years. According to the World Bank's Carbon Finance Unit, 374 million metric tonnes of carbon dioxide equivalent (tCO2e) were exchanged through projects in 2005, a 240% increase relative to 2004 (110 mtCO2e) which was itself a 41% increase relative to 2003 (78 mtCO2e).

The world's only mandatory carbon trading program is the European Union Emissions Trading Scheme (or EUETS). Created in conjunction with the Kyoto Protocol, a 1997 international treaty that took effect in 2005, it caps the amount of carbon dioxide that can be emitted from large installations, such as power plants and factories, in the EU's 25 member countries.

A country (or group of countries) caps its carbon emissions at a certain level (this is known as cap and trade) and then issues permits to firms and industries that grant the firm the right to emit a stated amount of carbon dioxide over a time period. Firms are then free to trade these credits in a free market. Firms whose emissions exceed the amount of credits they possess will be heavily penalised. The idea behind carbon trading is that firms that can reduce their emissions at a low cost will do so and then sell their credits on to firms that are unable to easily reduce emissions. A shortage of credits will drive up the price of credits and make it more profitable for firms to engage in carbon reduction. In this way the desired carbon reductions are met at the lowest cost possible to society.

Business opinion
With the creation of a market for trading carbon dioxide emissions within the Kyoto Protocol, it is likely that London financial markets will be the centre for this potentially highly lucrative business; the New York and Chicago stock markets would like a share (which is unlikely as long as the US rejects Kyoto). The European Union Greenhouse Gas Emission Trading Scheme (EU ETS) began operations on 1 January 2005.

23 multinational corporations have come together in the G8 Climate Change Roundtable, a business group formed at the January 2005 World Economic Forum . The group includes Ford, Toyota, British Airways and BP. On 9 June 2005 the Group published a statement stating that there was a need to act on climate change and stressing the importance of market-based solutions. It called on governments to establish "clear, transparent, and consistent price signals" through "creation of a long-term policy framework" that would include all major producers of greenhouse gases.

There are critics of the schemes, mainly environmental justice NGOs and movements who see carbon trading as a proliferation of the free market into public spaces and environmental policy-making. They point to failures in accounting, dubious science and destructive impacts of projects upon local peoples and environments as reasons why trading pollution rights should be avoided. Instead they advocate making reductions at the source of pollution and energy policies that are justice-based and community-driven.

The National Allocation Plans by member governments of the European Union Emission Trading Scheme have been criticised due to some governments issuing more carbon credits than emissions during Phase I of the scheme. They have also been criticised for the widespread practice of grandfathering, where polluters are given carbon credits by governments, instead of being made to pay for them.

Many environmental activists and foundations consider Al Gore's strong proponency of carbon trading to be a denial of the imminence of climate change and a formalized failure of international policy to address the gravity of the carbon increase. Critics of carbon trading, such as Carbon Trade Watch argue that offsets place disproportionate emphasis on individual lifestyles and carbon footprints, distracting attention from the wider, systemic changes and collective political action that needs to be taken to tackle climate change.
The Free Encyclopedia
05 Apr 2007