Outreach & Policy

Response #189

Submitted: 23 September 2008

The Geological Society of London welcomes the opportunity to respond to the Consultation. In addition to the ‘traditional’ role of geologists in fossil fuel energy production, the profession increasingly addresses geological aspects of renewable sources of energy, particularly heat energy and carbon capture and storage.

We respond specifically to Questions 14 and 27.

Q14. Are our assessments of the potential of renewable heat deployment correct?

We believe that you may have underestimated the potential for a spectrum of ground source/geothermal sources and sinks of heat. Ground source heat pumps are gaining in popularity (particularly in rural areas where heat is provided by oil brought in by road), and geologists have as much of a role to play in their development as in any near-surface engineering operation. Similarly, the use of thermal piles that act as heat sources and sinks for buildings is becoming increasingly common.

You mention the Southampton district heating scheme, and should recall that this has at its heart a deep geothermal source. Although the geothermal contribution to the heating scheme is now rather small (5% or less), the Southampton Geothermal Heating Company has commented that the visual presence of a borehole headgear in a shopping centre car-park has raised awareness of renewable energy and has helped win the public over to a range of schemes to reduce CO₂ emissions. The potential of renewable heat deployment, therefore, extends further than direct energy contributions alone.

It is also important to note that exploration for geothermal resources has taken place at Eastgate in County Durham, where a remarkably high yield of water at approx 40°C was encountered in granite at 1 km depth. This resource (potentially greater than that at Southampton in terms of water yield ) is integrated within the redevelopment plan for the Eastgate site, where it is intended to supply a spa and to contribute to a CHP scheme. Additional exploration is expected to follow, using geological principles to identify promising structures elsewhere in the north-east of England, especially urban Tyneside.

Importantly, ground source heat pump systems and thermal piles can play a very important role in reducing electricity consumption for air conditioning and cooling systems. The ‘Merton Rule’ requires new developments to obtain a proportion of their energy requirements from on-site renewable sources . To achieve this, many developers include borehole-based schemes or thermal piles when planning integrated heating/cooling systems for large buildings or complexes of buildings. In some cases a 10% reduction in CO₂ emissions is achieved using renewable energy from ground sources.

Finally, exploitation of groundwater as an energy source (i.e. abstraction followed by discharge, in contrast to a closed loop system) does occur in some schemes (e.g. Southampton), and needs to be regulated to prevent compromising groundwater resources. Licensing shallow ground source heat pumps individually, on a house by house basis, would not be appropriate. However, larger scale use of geothermal energy by water abstraction clearly requires appropriate licensing from the Environment Agency or SEPA. This action currently takes place. In due course we expect that it will be necessary to develop a licensing scheme to cover indirect abstraction of heat energy, to protect the interests of all concerned. The Geological Society would be keen to play an advisory role in the development of such a scheme.

Q27. How can we best ensure that our use of biomass is sustainable?

As geologists, we are concerned with the protection of soil resources and with carbon sequestration, particularly in the context of the International Year of Planet Earth. Ultimately, key mineral nutrients have a geological origin.

For truly sustainable production of biomass, especially to produce second-generation biofuels, we need to ensure that the soil’s stocks of nutrients and organic matter are not depleted. Any analysis of the environmental impact of biomass production should consider nutrient offtake and the long-term sustainability of the soil resource.

The rise in atmospheric CO₂ levels caused by the combustion of fossil fuels must be corrected. The approach taken throughout the Consultation Document emphasizes the reduction of emissions. As geologists we have a role to play in reducing absolute amounts of CO₂ in the atmosphere. With current technology, there are two routes for doing this with low energy input:

1. by encouraging calcium carbonate precipitation in soils, which is known to occur widely in urban soils.
2. to add char (‘biochar’) to soils. Biochar is produced when biomass is partially combusted through pyrolysis rather than gasification. As well as capturing atmospheric CO₂ through biomass growth, when added to soils biochar improves fertility, reduces greenhouse gas emissions, and improves water retention. This approach has tremendous potential, if developed in a sustainable way, for remediation of contaminated land in the UK, and for bringing poor quality land back into crop production in the developing world.

It is essential that the vital role of soil as a component of the entire biomass production cycle is considered, in order for sustainable production of biomass to be achieved.

Professor Edward Derbyshire
Secretary, Foreign & External Affairs
For and on behalf of
The Geological Society of London