Monday, September 13, 2010

Carbon Capture and Storage (CCS) - Yay or Nay?

A new paper (1) published in the prestigious American Chemical Society journal, Environmental Science and Technology, has put the cat among the pigeons over carbon capture and storage (CCS). It argues that the colossal amount of money that CCS would entail globally would be better spent on "virtual CCS", meaning per se that instead of actual CCS, the emission of carbon be avoided in the first place by a wholesale implementation of non-fossil energy sources, specifically wind and nuclear power. As a statistic to prove the point, it is estimated that one wedge (billion tonnes) of carbon in the form of CO2 sequestered by CCS would cost $5.1 trillion over 50 years, while the same amount of money used to build wind-turbines would save 1.91 "wedges" worth of CO2 over the lifetime of the windmills. A strong rebuttal to this case is presented in the September Chemistry World (2), which calls for a parallel development of CCS and non-fossil energy rather than the exclusion of the former.

Since 100 million tonnes per DAY of CO2 would need to be so sequestered by CCS the engineering required to bring it to fruition is phenomenal. There are essentially two methods to remove carbon from fuel: post-combustion and pre-combustion. Post-combustion, CO2 is removed from flue gas by passing it through a liquid amine which dissolves the CO2. Pre-combustion, the fuel (coal, gas, biomass) is processed into a mixture of CO2 + H2 and the CO2 is removed. Either way, the CO2 must be put somewhere, for which strategies include pumping it into rocky formations (such as depleted oil and gas wells) at a pressure of 100 atmospheres, or even piping it in liquid form under pressure onto the sea-floor where it is cold enough and the pressure high enough that it is hoped the material will stay there, assisted by the formation of CO2-hydrate.

(1) C Tsouris, D S Aaron and K A Williams, 2010, Environ. Sci. Technol., 44, 4042

Tuesday, September 07, 2010

So, What Did Happen After the Chinese Oil-Spill?

On the 16th of July, China experienced its first major oil-spill. The Chinese incident was also caused by an explosion (this time during the transfer of oil from a tanker to a reserve owned by the China National Petroleum Corp), but is nothing like the size of the BP spillage in the Gulf of Mexico. The amount of public information released in any level of detail has so far been scant, but in this month's Chemistry World, the British Royal Society of Chemistry has published an article which provides some update of the state of play in the aftermath of the event.

Around 1,500 tonnes of crude-oil ended-up in the Dalian Bay, which is a popular resort for tourism and conferences, located in the far east of China. The initial clean-up was pretty much over in two weeks, but residual problems in safety management are highlighted. As usual, there are various estimates of the size of the resulting oil-slick, of between 150 - 450 square kilometers of ocean covered, but the main concern is that the oil might contain toxic organic contaminants that could invade the food-chain, threatening the health of humans, animals and that of the wider environment for decades to come.

It is argued that a lack of technical expertise and equipment in China made the clean-up process more complicated and protracted than it need have been. Many thousands of workers were garnered in Dalian and simply sent-out in fishing-boats to collect the oil in buckets, which was then poured into storage-tanks. Since they had little or no protective equipment or were untrained in how to use what they did have, the long-term effects of their exposure to a mixture of chemical substances remains to be seen. It appears that the Dalian municipal government had only enough capacity to cope with 200 tonnes of oil, and less than the 1,500 actually spilt.

While this is nothing compared to the 750,000 tonnes of oil that poured into the gulf of Mexico, for which BP are taking part of the blame along with their subcontractors, the point is made that China needs to advance its capability to provide long-term solutions to environmental problems of this kind. There is currently a great lack of environmental and geochemical research into oil-spills in China. The Dalian oil-spill is likely to be a microcosm of greater future catastrophes for a highly populous country that is expected to expand its oil-based personal transportation by a factor of ten to 200 million by 2020.

Related Reading.
"China tackles its first major oil spill," Chemistry World, September 2010, p10.