Two doctoral theses look at carbon capture and storage options

Two Dutch researchers recently defended their doctoral thesis on the subject of carbon capture and storage (CCS) (for a typical set-up, see image, click to enlarge). Dr Kay Damen (Copernicus Institute for Sustainable Development and Innovation, Utrecht University), analysed the potential for CO2 storage in the Netherlands, the costs involved and the need for a coordinated international planning effort. His thesis, entitled ‘System analyses of transition routes to advanced fossil fuel utilisation with CO2 capture and storage’ was part of the programme ‘Transition to sustainable use of fossil fuels’ that was funded by the Netherlands organisation for Scientific Research (NWO) and the €5.45 million SenterNovem Stimulation Programme Energy Research. This programme aims to develop knowledge in the natural and social sciences for the transition to a sustainable energy supply.

As part of the same program, Dr Saikat Mazumder defended his thesis at the Delft University of Technology on how to better predict routes of the 'underground highways' along which gasses like carbon dioxide (CO2) and methane (CH4) will move during storage operations. He found coal to be highly suitable for filtering carbon dioxide out of waste gasses and storing it.

Both works are highly interesting additions to the growing body of research into CCS, which we track because the technology promises the creation of carbon netgative energy systems based on the utilisation of biomass (socalled 'Bio-Energy with Carbon Storage').

'Major potential'
According to Dr Damen, CO2 capture and storage can make a major contribution to CO2 reduction in the Netherlands. By the mid-21st century 80 to 110 million tonnes of CO2 per year could be avoided in the sectors energy, industry and transport. This is half of the current CO2 emission. Moreover, this can be realised against acceptable costs, the researcher concluded.

To realise such reductions in CO2 emission, a clear and internationally-oriented vision and bridging strategy is necessary, so that the storage capacity that is released over the next few decennia can actually be used for CO2 storage says Damen. He investigated the technical possibilities, costs and risks of CO2 capture, transport and underground storage:
bioenergy :: biofuels :: energy :: sustainability :: climate change :: carbon capture and storage :: fossil fuels :: biomass :: carbon negative ::

Electricity greatest potential
In 2020 15 million tonnes of CO2 per year could be avoided by capturing CO2 in the new coal-fired power stations yet to be constructed. Moreover, existing pulverised coal-fired power stations may also be equipped with CO2 capture installations, although the costs of this are relatively high. In 2050 the reduction potential is estimated to be 60 to 84 million tonnes of CO2 per year, for a scenario in which the electricity production is doubled.

By capturing CO2 in industrial processes a further 16 million tonnes of CO2 per year can be avoided. Further if cars are run on hydrogen or synthetic diesel produced from fossil fuels combined with CO2 capture then this could eventually lead to a difference of more than 10 million tonnes of CO2 emission per year. For the production of hydrogen in the transport sector, Damen investigated the thermodynamic performance and costs of decentralised membrane reformers. This new technology makes it possible to capture CO2 against relatively low costs.
CO2 transport and storage

Damen calculated the costs of the pipelines necessary to transport the captured CO2 to underground storage reservoirs. Gas fields are, in addition to deep saline aquifers and coal seams, the most suitable reservoirs for CO2 storage in the Netherlands. The capacity that becomes available for CO2 storage can, however, be limited by a series of geological factors, including the risk of CO2 leakage via wells and faults. Although the mechanisms of CO2 leakage are known, quantifying the risks is still a challenge. Additionally CO2 storage could compete with the underground storage of natural gas, especially if the Netherlands develops into an international gas 'roundabout'. If the Netherlands has to maximise its efforts on CO2 capture and storage then eventually one of the 'mega storage reservoirs’ will have to be released, for example, the Groningen gas field or large structures in the British or Norwegian part of the North Sea.

CO2 storage in coal can be predicted better
Saikat Mazumder for his part made it possible to better predict routes of the 'underground highways' along which gasses like carbon dioxide (CO2) and methane (CH4) will move. Moreover, he found that coal might be highly suitable for filtering carbon dioxide out of waste gasses and storing it.

The ‘Enhanced Coalbed Methane process’ kills two birds with one stone: carbon dioxide (CO2) is stored in coal seams in the ground and at the same time methane (CH4) is obtained from the process. To optimise this process it is important to know how coal retains and stores some fluids and gasses whilst allowing others through. The network of cracks is essential for this. Mazumder developed a measuring technique using CT scans that led to an improved understanding of the patterns of cracks. He also did experiments with waste gas and pure CO2 to determine the uptake capacity of single and multi-component gasses. In both wet and dry experiments, CO2 was strongly absorbed and CH4 was released. This methane production in a coal seam can vary over the course of time. Mazumder developed two estimating methods to gain a better understanding of this. When used together these could generate good predictions.

Problems due to swelling
The research revealed that a considerable quantity of CO2 could be removed from waste gas by allowing it to be adsorbed onto coal under high-pressure. According to Mazumder this means that the injection of waste gas into coal seams can be applied to filter out CO2 on an industrial scale and to retain it. Mazumder also carried out a preliminary study into the decrease in porosity and permeability as a consequence of coal swelling due to the injection of CO2. The decrease in the permeability can give rise to serious injection problems in the area of the well into which CO2 is injected.

More information:
NWO: CO2 storage in coal can be predicted better - April 10, 2007.
NWO: Prepare CO2 capture and storage now for greater environmental benefit later - April 10, 2007.