The Paris climate summit proposed some stringent targets for global warming and emissions. These can only be reached if we manage to engineer a reduction in greenhouse gas output and currently the main means of achieving this are switching to gas away from coal and deploying renewable energy and increased nuclear sourced energy.
BGS was asked by Friends of the Earth how we were responding to the Paris decisions and the BGS Director of Science and Technology has produced a reply which is copied below.
BGS provides scientific evidence on subsurface processes that are relevant to the economy of the UK, and may be used by government in support of policy.
Response to Friends of the Earth
BGS is an internationally recognised centre in several sciences that contribute to lower emissions, including carbon capture and storage, geothermal and the siting of offshore wind farms.
Carbon capture and storage
Predictions like those of the International Energy Agency’s (IEA) New Policies Scenario suggest that coal will continue to be used heavily in the future, and will probably remain the backbone of global electricity generation for many years to come. This underlines the need for a switch away from coal, and for the coal that is to be burnt to be used in power stations that are fitted with carbon capture and storage facilities. A look at three large countries with big coal resources, China, India and South Africa, illustrates the problem. China is by far the largest coal consumer in the world, accounting for almost half of global coal use in 2010. In the IEA New Policies Scenario, China’s coal demand will increase to over 2850 million tonnes per year by 2020, and stabilise above 2800 million tonnes until 2035. Coal will continue to provide more than half of China’s electricity until 2035. Similarly in the New Policies Scenario, South African coal production, which is mainly for electricity, will peak around 2020 but continue to be high into the future. India is struggling to electrify its rural economy and it is likely that much of this electricity will come from coal.
In Europe for 2020, the EU has committed to cutting its greenhouse gas emissions to 20% below 1990 levels, and further cuts are being decided for 2050. This commitment is one of the headline targets of the Europe 2020 growth strategy and is being implemented through binding legislation. Power generation will have to take a particularly large part in emissions reductions, mainly by focussing on increasing surface renewables (wind, tidal and solar), nuclear and geothermal power, but it is likely that carbon capture and storage on fossil fuel power plants will be important.
Carbon capture and storage may be particularly important for the 2°C limit set at COP 21, in Paris in December. Most of the Intergovernmental Panel on Climate Change’s (IPCC) scenarios limiting global temperature increases to 2 °C include some form of ‘negative emissions’ or permanent removal of greenhouse gas (GHG) emissions from the atmosphere. Of the 400 IPCC climate scenarios that have a 50% or better chance of less than 2 °C warming, more than 300 assume the successful and large-scale uptake of negative-emission technologies. The most popular of these is Bioenergy with Carbon Capture and Storage (BECCS). BECCS involves growing energy crops for power stations for electricity and scrubbing out the CO2 in the flue gas for permanent sequestration in the subsurface.
The main constraints on BECCS are how much land and resource can be devoted to biofuel crops, and how much subsurface storage space for carbon dioxide there is. The first is a difficult problem and not within BGS’ remit. Given the weight that the IPCC gives to BECCS there is an urgent need to explore the potential ecological limits to, and environmental impacts of, implementation of BECCS at a scale relevant to climate change mitigation.
BGS main research in CCS involves questions over the feasibility of large scale geological storage of carbon dioxide. Though in Norway two deep subsurface sites 20 million tonnes of carbon dioxide have been safely stored, other geological environments must be tested and it is vital that more demonstration and full scale schemes are started, like the Aquistore scheme in south-eastern Saskatchewan where 40000 tonnes of carbon dioxide has been safely stored, and where 1100 tonnes of CO2 are injected per day.
BGS is researching the feasibility of geothermal heat for residential and civic use including the use of disused mine workings as a geothermal resource in urban areas, geothermal from deep sedimentary rocks, and ground source heat pumps. Geothermal could be an important way for the UK to achieve its goals in emissions reduction.
Although the UK is not actively volcanic, there is still a substantial resource of geothermal energy at shallow depths but it is exploited in different ways. The upper 10–15 m of the ground is heated by solar radiation and acts a heat store. This heat can be utilised by ground source heat pumps that can substantially reduce heating bills and reduce emissions. The heat from the sun is conducted downwards into the ground. At a depth of about 15 metres, ground temperatures are not influenced by seasonal air temperature changes and tend to remain stable all year around at about the mean annual air temperature (9–13°C in the UK). Hence, the ground at this depth is cooler than the air in summer and warmer than the air in winter. This temperature difference is exploited by ground source heat pumps that are used for heating and/or cooling of homes and office buildings. There are different types of systems which can be broadly grouped into closed-loop systems and open-loop systems.
With increasing depth, the ground temperatures are also affected by the heat conducted upwards from the Earth's core and mantle, known as the geothermal heat flow. When combined with the thermal conductivities of the rocks this allows the prediction of subsurface temperatures. The UK's geothermal gradient, the rate at which the Earth's temperature increases with depth, has an average value of 26°C per km. Some rocks contain free flowing water (groundwater) and so at depth this water will be warm and can be extracted for use in district heating schemes or for industrial uses such as heating green houses.
There are also regions in the UK where the rocks at depth are hotter than expected. This occurs in granite areas because some granite generates internal heat through the radioactive decay of the naturally occurring elements potassium, uranium and thorium. Granites have very little free flowing water, but it is possible to engineer the fracture system such that water can be made to flow from one borehole to another through the granite. The extracted hot water is at a sufficiently high temperature to drive an electricity generating turbine. Parts of Cornwall have geothermal gradients that are significantly higher than the UK average due to the presence of granite and have potential for geothermal power generation.
Offshore wind turbines
The Marine Environmental Mapping Programme (MAREMAP) and the Strategic Environmental Assessment (SEA), both of which BGS is a part, are coordinated efforts to improve seafloor and shallow geological mapping to establish the ground and geotechnical conditions for many offshore wind turbines. The shallow geology can produce impacts and constraints on design, installation and operation of seabed structures and sub-seabed foundations. Some of these constraints relate to the variability in the composition and distribution of Quaternary sediments (at the seabed and in the subsurface) and bedrock within the first 50 m below the seafloor. Additionally, other constraints relate to the geological processes that have occurred in the past or are active today.
As well as these sciences aimed at direct emissions reduction, BGS is working intensively on the effects of coming climate change, including on groundwater levels (in the UK and in Africa), landscape and erosion, and sea level. We are working with a whole range of partners on how these changes can be forecasted and planned for so that society is more resilient to change.
BGS is, of course, interested in all other areas of research into emissions reduction and climate change science and welcomes discussions on its science strategy.
Prof Mike Stephenson
Director of Science and Technology, BGS