Carbon capture and storage (CCS) is one way of mitigating carbon dioxide emission in to the atmosphere. What it means to a layman is, carbon dioxide gas, especially from coal fired power plants, will be captured (with out being emitted in to the atmosphere) and stored in a container. This container could be a natural geological formation i.e. say a sedimentary rock like sandstone, saline aquifer (aquifer that contains water with salinity > 10,000 mg/L, a coal seam or the ocean. The oceans are in fact natural sinks for the CO2 that is being ejected in to the atmosphere either from power plants or from other sources.
According to the estimates reported by the Intergovernmental Panel for Climate Change (1966), the amount of carbon in the oceans, in the atmosphere and the biosphere is 40,000, 750 and 2200 billion tonnes of carbon respectively. Thus oceans are the main CO2 sink.
The process sounds very simple and exciting. This process i.e. CCS, is also known as carbon dioxide sequestration. This idea started a decade ago when countries are debating on methods to control carbon dioxide emissions into the atmosphere to contain global climate change by not increasing the global temperature. This idea emerged from oil and gas industry as early as 1970s where CO2 was injected into the reservoirs to enhance the oil recovery. This process was economical as long as the oil prices was at its peak. When the oil price dropped in mid 1980s, oil recovery through CO2 injection became expensive and hence was kept in abeyance.
In this case the CO2 injected escapes to the atmosphere while the present concept of CCS is to retain it in the reservoirs. CO2 by itself will escape from the reservoirs since it is in gas form but if the phase is changed in to a carbon compound, then it can be stored for a long period of time. In fact this process is not new. Oil industry using this process for enhanced oil recovery from the reservoirs by pumping carbon dioxide and forcing oil to be expelled from the aquifer.
Why the world is analysing CCS to mitigate global climate change? In a recent news item by IEA titled “CCS is a necessity for a world hooked on fossil fuels” IEA feel that only 1/5 of world energy supply is from renewable sources thus making fossil fuels as the primary source of energy and will continue be so for a long time. Then CCS is going to be the future technology to mitigate carbon dioxide emissions and mitigate global climate change scene. IEA in its “Blue Map” indicted that cost incurred in CCS technology from 2010 to 2050 will be of the order of 2 to 3 trillion US$ distributed over as many as 3400 CCS projects. These projects envisages about 62 Giga tonnes of CO2 capture from coal based power plants, 9 Gt from gas based power plants and 7 Gt from biomass based power plants. The big question is, will the technology to contain such large volume of CO2 in geological formations will be in place by 2050? One has to wait and see. Perhaps some other CCS technology may emerge by then!! One thing for sure is, carbon capture and transport technology may mature by then but storage in geological formations may not. Geological formations do not behave the way we wish!
CCS is not a new technology. In 1996 the first CCS facility started by Statoil in Norway where CO2 was stored in a sandstone aquifer in the North Sea at the rate of about 20000 tonnes in a week. The CO2 was captured from a 140 MWe coal based power plant. The Govt. gave an incentive of US$ 50 per tonne of CO2 stored.
Capturing CO2 from fossil based power plants is expensive as the process of capture reduces the net out put of electricity by about 20% thus attracting penalty. But, the current concern on global climate change and the deliberations of IPCC may reduce the penalty in future. This is not an incentive for the coal based power plant to go in for CCS but reduces the burden on consumers.
Although it is claimed that CCS is an established technology, there are several issues related to site selection, capturing and purification, environmental issues and cost. Not all geological formations are suitable for carbon sequestration. Similarly CO2 capturing may be relatively easy but purifying CO2 is a cost intensive. The cost, ,in all cases, can not be thrust on the consumer, even though industry is given incentives by the governments. The most critical aspect is the fate of CO2 injected into the formation. In the past attempts have been made to inject CO2 in to sandstone formation sandwiched between two shale beds. Initial runs gave encouraging results but subsequently CO2 started leaking through microfractures in the shale. Phase transformation through rock-water interaction process, in the geological formation, however, may captures the CO2 permanently. Not one, but several methods needs to be employed on case to case basis, geological strata wise depending on the existing physico-chemical environment of the geological strata, to evolve economically sustainable and feasible CCS methodology.
The CCS based sustainable development is being implemented by several countries along with the development of all available renewable energy sources like solar, wind and geothermal. Under the business as usual situation IEA estimates that India and China projected to capture 29 Mt CO2/year by 2020. China is developing all it renewable sources on war footing to reduce CO2 emissions. China is emerging as the forerunner in utilizing GSHP for space heating and cooling, green house cultivation etc. Very soon China may emerge as the leader in accumulating carbon credits to its advantage and out beat Europe. Hence IEA’s prediction may be true with China but not India. India’s renewable energy development, especially geothermal resources, is limping for no reason. Even if investors are ready to fund geothermal projects, govts are not ready to pick up the opportunities in implementing sustainable development. This is true with solar PV projects as well. If countries are dreaming of energy source mix with solar PV to mitigate carbon foot prints, it is a day dream. Countries have a long way to go to make solar PV affordable to common man. “ National solar mission may get derailed as banks hesitate to give loans for its high risk projects’ states a special report in the recent edition of Down to Earth ( March 1-15, 2011). A mission without financial support is created. Newspapers, weekly magazines and all other print media talk about availability of large funds for solar power. The numbers run into crores!! Where are these funds? If funds are not available within the country under the solar mission scheme, how can entrepreneurs expect grants/loans from foreign financial institutions or investors? The solar PV needs a break-though. Until then the unit cost of solar PV will stay high. The ground reality is different. The type of data required for the financial institutions to release funds are not available. Solar PV is not just to keep a solar panel and generate electric power. There is science behind it and handful of entrepreneurs know about it!! The rest go with the tide and jump into the bandwagon.
Solar PV and wind are very popular in Sub-Sahara countries, although the unit cost is much higher compared to thermal. For example, the levelized grid supplied cost of solar PV is about 16 to 50 US cents in areas with good net work connectivity while the cost escalates to one dollar per unit in remote areas in Ethiopia. Diesel generated power costs little over 70 US cents per unit. Thus diesel and solar PV are on par with each other as for as cost is concerned. The only difference is diesel has to be transported from the nearest sea port Djibouti, which is several hundreds of kilometres away from Ethiopia.
Compared to solar PV, geothermal power in Ethiopia is very competitive to all the renewable and with an estimated resources of 60000 MWe spread over the entire East African Rift valley. The Aluto Lungano geothermal field alone is capable of generating 500 MWe. Unit cost of geothermal power is about seven US cents. The advantage here is to have local grid systems that can supply power to clusters of rural areas. Small geothermal power plants that can generate 5 to 10 MWe are most suitable and cost effective in the entire rift valley. A 5 MWe geothermal power plant may need only one acre of land (1 acre is equal to 4047 sq. m or 43200 sq. ft). This is far less compared to the land requirement of solar. In future, with the hot dry rock technology taking shape, power can be generated in everyone’s back yard! Let’s hope that this will happen before the next young generation retires! We should work on what is possible immediately to reduce carbon foot prints rather than dreaming of methods that are not cost effective to the country in the near future ..that too with a large socio-economically population depending on lost cost energy source.