The rock that burns
The first genuine historical record of the unusual properties of the mineral that would be named kukersite was made about 1725 - a report about local shepherds using the shale to build the nighttime fires by which to watch their flocks. Another reference appeared in 1777, in a report by August Hupel, (1737-1819), Lutheran minister, savant and man of letters in the city of Põltsamaa.
<Fig 1 Location of shale deposits in the Baltic Oil Shale Basin (Heikki Bauert) >
Kukersite occurs in two main units in Estonia. In the North East part of the republic is the "Estonian" deposit, which comes from the base of the Viivikonna Formation (Kukruse Stage) of Upper Ordovician age (actually the precise stratigraphic position of the oil shale is still uncertain. Conodonts indicate Upper Ordovician (in the recent global timescale), while graptolites, which are very rare in limestones, support a topmost Middle Ordovician age.) The Estonia Deposit forms the western part of the Baltic Oil Shale Basin, covering an area about 5000km2. Easternward extension of the Baltic Oil Shale Basin into Russian territory is called the Leningrad deposit. The Tapa deposit in central Estonia which is slightly younger in age, lies at a depth of 60 to 170 metres. It is not well explored.
Kukersite is a light brown rock flecked with abundant fossil remains. Unlike in monotonous black shales as well as in microlaminated Green River oil shales, specific cell structures can be observed in kukersite microscope studies, particularly well distinguished under SEM. The kukersite organic matter derives from a colonial microorganism called Gloeocapsomorpha prisca – thought either to be an alga or cyanobacterium. G. prisca also shows many morphological similarities to the modern cyanobacterium Entophysalis major, which forms intertidal and subtidal mats in places like Shark Bay, Australia. The calorific value of the kukersite deteriorates to the south, falling from 10 Megajoules per kilogram in the north to about half that in the south and southwest. The thickness of the commercial horizon also decreases in that direction.
Because of the chemical and isotopic characteristics of the organic fraction, the accumulations are thought to have originated in shallow subtidal marine lagoons of the Baltic epicontinental sea. More than 300 different species of fossil have been recorded from them, and they tend to have a rather low pyrite content – all indicative of good oxygenation. Palaeomagnetic data suggest a palaeolatitude of 30 to 50 degrees south, suggesting a temperate environment.
Since 1916-18, when commercial oil shale mining began in Estonia, it has had an enormous influence on the country's economy, particularly when it was part of the Soviet Union, and subsequently in the modern Estonian Republic. By 1955 annual output had reached seven million tonnes and was mainly used a power station/chemical plant feed, and in the production of cement (using the ash). The opening of the 1400 MW Baltic Thermal Power Station (1965), followed in 1973 by the 1600 MW Estonian Thermal Power Station, again boosted production, and annual output peaked in 1980 at 31 million tonnes.
The decline in oil shale production started in 1981, when the fourth reactor was launched at the Leningrad Nuclear Power Plant located in Sosnovy Bor and it became clear that no additional thermal power plant will be built in Estonia. By 1999 annual oil shale production had fallen to 10 million tonnes. Most was used for electricity and heat generation, and 1.3 million tonnes were distilled to produce 151,000 tonnes of shale oil. Estonian oil shale resources are currently put at 5 billion tonnes, including 1.5 billion tonnes of active (mineable) reserves. Since the turn of the century, each subsequent year has seen small recoveries in production, reflecting the rising power demand in Estonia as its economic recovery has gathered pace.
Future trends
As the consumption of oil globally begins to outstrip the discovery of new fields, oil-poor countries like Estonia can be forgiven for looking upon their oil shale as a blessing. But the shale has, as well as its actual overburden, an invisible one – namely, opposition from environmentalists.
It is not hard to see why environmentalists instinctively oppose the industry. First, like most industries dating mainly from the Soviet era, it has had a dubious environmental past. The shale (mostly) needs to be strip-mined; typically, Estonian opencast oil shale mines have to take out 20-30 metres of overburden to excavate a mere 3-4 metres of kukersite. Although new Wirtgen milling machines have improved the efficiency of this mining process (picture), relieving the need for further enrichment of the product before burning, all overburden must be replaced and the landscape restored and re-vegetated.
It is also widely asserted by environmental campaigners that the sludgy material left behind by retorting and burning, because of a so-called "popcorning effect" unique to oil shale, occupies 30% more volume than the original unburned material. The hole it came out of being too small to receive all this waste, the result has been large mountains of ash that are a familiar feature of the NE Estonian landscape. Moreover, environmentalists say, this residue contains phenol-rich organic molecules that then leach into groundwater.
However, Heikki Bauert, an expert on Estonian oil shales, but who no longer works in the industry says: "the popcorning effect…exists only in fantasy. The actual mass balance for kukersite oil shale and retorted waste are similar. Kukersite…is really a lightweight rock… and during retorting at least 10% of mass is removed as raw oil."
The main reason for not dumping the sludge back into mines was not because it wouldn't fit, but to avoid contaminating groundwater. And as for those toxic phenols, the environmentalists' argument is also misleading and deceptive, according to Bauert. "During the Soviet time, all kinds of oil processing industry waste was dumped together into the same hills. Today, retorting waste may even be free of phenol compounds” he says.
But the biggest single charge levelled by environmental campaigners against oil shale is that because burning it also decomposes carbonates as well as hydrocarbons, it creates more than four times as much greenhouse gas as conventional hydrocarbon fuel. This assertion again, industry supporters say, is highly misleading because the central assertion (that burning oil shale decomposes carbonates) is outdated. The German cold milling engines are highly selective and have much improved the quality of the power-plants' feedstock. Also those plants now employ much more advanced combusting technology.
Bauert says: "We are not "burning carbonates" in power plants any more". The companies who have developed the circulating bed combustors now employed in Estonian power plants say that while during conventional burning, as during the Soviet era, 30% extra CO2 emissions could result from decomposing the carbonate gangue, in modern circulating bed combustors roughly 25% of the included carbonate stays intact." Also, the nitrogen content in kukersite is very low, Bauert says. These improvements have made it possible to consider expanding oil shale mining within emissions guidelines imposed by the EU.
Since 2001 the Estonian government has phased in liberalizing measures in its electricity sector. However, the government was chary of wholesale adoption of EU energy policy for the simple domestic reason that opening Estonia's energy market to competition from abroad would likely put mines, quarries and two huge power stations out of business – precipitating an economic and social crisis in the NE of the country. Estonia therefore pushed for the EU to recognise that most of its power would continue to come from oil shales until 2015 at least. In this they were largely successful.
Although a recent Estonian Economic Development Plan stated that oil shale's share in the country's national primary energy balance must fall to 52-54% by 2005 and to 47-50% by 2010, thanks to technological improvements in mining and combustion, the country's most recent governmental projection is able to project a marked increase in mining in the near future, with output rising to 31 million tonnes by 2015. Mining permits for this amount have already been issued.
Interestingly, regulatory hurdles have not only afflicted the power generation side of the oil shale industry. In May 2006, the European Parliament approved the Registration, Evaluation and Authorisation of Chemicals Directive (REACH). By June, the Estonian chemical industry was already complaining that it was now put at a competitive disadvantage because its unconventional feedstock meant that it had to re-test all its products to ensure compliance - even if the molecule in question was already on the EU approved list.
But while the country's major chemical producer Viru Keemia Grupp (VKG) has struggled with gaining certification for its chemical products, Estonia as a whole is finding that improved technology has saved it from a very uncomfortable situation, despite the continuing opposition of green lobbies. Where once it seemed that Estonia's main mineral product and energy source had either to be reformed beyond the efficiency of any proven technology, or abandoned in favour of imports, the industry is now looking at a renaissance.
Shale renaissance
Estonia's response to its very singular energy problems is being watched intently by others with strategic concerns of their own. Outside Estonia, oil shales are exploited only sporadically – notably the Permian Irati Formation (Brazil), and Tertiary lake sediments at Fushun, Liaoning Province, China. However the energy potential of oil shale globally is truly vast. According to the BP Statistical Review of World Energy, the world's remaining oil and gas reserves total 2.1 trillion barrels. The total estimated global resources of oil shale are thought to be well over 2.6 trillion barrels. The total energy resource represented by the Tertiary Green River Formation is said to exceed the total oil and gas reserves of Saudi Arabia.
The amazing fact is that oil shales in Australia, Brazil, Canada, China, Estonia, France, Russia, Scotland, South Africa, Spain, Sweden and the USA have an energy potential exceeding all known conventional oil reserves. So how can all the valuable organic material contained in them be converted into energy at a market price, and without environmental damage?