The use of local stone can avoid exploitation of workers and damage to the environment elsewhere in the world.

CONCLUSIONS

26. Suitable building and roofing stone is essential for the repair and maintenance of historic structures and for building in local styles, as well as enhancing other new buildings. But many types of English building and roofing stone are scarce and need to be safeguarded and the best use must be made of these materials. Planning permissions are needed for new sites. Most building and roofing stone operations are of small to modest sizes, and consequently with limited impacts on the local environment and communities, but these still require good standards of management.

24. Building and roofing stone appear to perform fairly well in terms of carbon emissions during the life cycle compared with other building materials but more research on this is needed. Restoration of sites offers good opportunities for contributing to biodiversity, geodiversity and preservations of the industrial archaeology heritage as well as cultural uses. Building stone and roofing stone can be reused and recycled but care must be taken to avoid demolition of structures for reuse elsewhere. A realistic view of operations is needed. Few sites can exist on repair and maintenance contracts alone. Most need contracts for stone in new structures to survive in an internationally competitive market. In some cases the use of local stone can avoid excessive exploitation of workers and damage to the environment elsewhere in the world. Overall building and roofing stone from England performs a crucial function for our national heritage and, if extracted from well managed sites and distributed and used responsibly is a relatively sustainable source of construction materials.

REFERENCES

Cooper, B J 2004 Sustainable development: an opportunity for dimension stone Roc Maquina 54, 12-17

Hammond, G and Jones, C [Ed. F Lowrie and P. Tse 2011 Embodied carbon: The inventory of carbon and energy (ICE) Department of Mechanical Engineering, University of Bath (Bath) 128pp www.bath.ac.uk/mech-eng/sert/embodied

Heriot Watt University 2010  Embodied carbon in natural building stone in Scotland – final project report. Project HSC/C/45168/3624. v+42pp

Simpson, T P; Cooper, B J and Pullen, S  2008 The embodied energy of dimension stone use in buildings: its value in promoting sustainability  9pp

3. A recent report from the University of Bath compares materials in terms of embodied energy and embodied carbon (i.e. the carbon emissions resulting from use of the materials) based on a very extensive review of published literature. These results are rather perplexing because stone. seems to be less well placed than aggregates and concrete. However it should be noted that, for stone, they omit transport from the cutting shed to the place where the materials are used and factors relating to the materials once in use (e.g. the influence of thermal mass and longevity of the structure on the overall levels of emissions). It is generally acknowledged that a high proportion of the emissions associated with aggregates come from transport. The high figure for granite, compared with other natural stone, is also puzzling but all of these figures come from a survey of sites in the USA. Some consideration is needed of how sites there compare with sites in the UK.

EXTRACTION AND USE OF BUILDING AND ROOFING STONE - SUSTAINABILITY ISSUES

INTRODUCTION

Before the industrial revolution building and roofing stone was generally worked and used locally

1. Materials from England that are used as building and roofing stone formed in the geological past and are not renewable. Some occur fairly widely and could potentially be worked for many years, but others are localised and might become worked out in the foreseeable future. A strict view of sustainability might suggest that we should avoid, as far as possible, using non-renewable materials particularly if these are scarce. But that is too simplistic. We must have suitable building materials to repair historic structures and for new buildings that fit with local styles and traditions. 

2. Therefore we need to obtain and use natural resources wisely. That means examining the economic, social and environmental costs and benefits of doing so, for now and for the future, to identify courses of action that meet all of these factors well. A useful context is the concept of thinking globally but acting locally, not least because suitable building and roofing stone are important to the local “sense of place”.

3. Before the industrial revolution building and roofing stone was generally worked and used locally although there were instances of imports. The development of canals and railways led to wider or national use of some types of stone, and international trade increased. In recent years, stone worked in England has been competing increasingly with stone from Asia, Africa and South America. Supply from local sources minimises the environmental effects of transportation so, intuitively, it is less sustainable to secure supplies from further away. But imports from developing countries, despite the costs of transport, are generally cheaper than local supplies. Unit prices may also be lower from European countries, such as Italy, where natural stone is worked from large quarries giving economies of scale.

To suggest that we should avoid using non-renewable materials is too simplistic. We must have suitable building materials to repair historic structures and for new buildings that fit with local styles and traditions.

ENVIRONMENTAL ISSUES

Safeguarding resources

4. Building and roofing stones are characterised by rather precise physical and chemical properties and, therefore, have limited geographical distributions. Sources of specific types of stone are sometimes fairly widespread. But some types may occur only in restricted geographical areas, or as thin layers between other less suitable rocks, and the known quantities in the ground may be limited so it is important that, as far as possible, these should be kept available for suitable use by preventing other development that might sterilise them. This requires knowledge of the locations and extent of resources and the adoption of suitable policies in local planning documents.

Blasting is largely avoided in modern quarries. Sometimes excavators simply lift the stones from a weak bedding plane (above) or diamond wire saws are used to cut block from the face (below)

Impacts of extraction, processing and transportation

5. Extraction, processing and transport of stone inevitably lead to some environmental impacts but many building and roofing stone sites produce comparatively small amounts of materials sporadically compared with other types of mineral working. The scale of operations can vary between: isolated quarries producing only tens of tonnes of stone per year; to groups of sites that individually have modest production but, together, have significant impacts; and fairly major dimension stone sites which may produce thousands of tonnes per year although these are still modestly sized compared with many aggregates quarries.

6. Noise is associated with extraction, processing and transport. Extraction is undertaken carefully to avoid damaging the rock. This may be done by hammering in wedges, buy use of water pressure to prise apart cracks in the rock or sometimes just large excavators simply lifting the stones from a bedding plane. Building and roofing stone are extracted whenever possible without sometimes just large excavators simply lifting the stones from a weak bedding plane. Any unavoidable blasting is undertaken using black powder to lift the beds of rock relatively gently and is unlikely to be at the scale and intensity of major aggregate quarries that produce hundreds of thousands to millions of tonnes of stone annually.  More modern stone quarries and mines now use chain and wires saws.  These operations are very quiet and involve least disruption to the stone before extraction so tend to lead to increased yields.

Rock extraction is usually undertaken on a modest scale

7.  and using fairly gentle methods the amounts of dust generated during extraction are relatively small. Dust from transportation within the site is minimised by spraying water on haul roads. Dust from cutting of rock is limited because of water used in cooling saws and because these operations are contained within sheds either at the quarry or at the place where material is to be used.  The water is invariably continuously re-cycled through specialist plant.

8. The amount of traffic depends on the amount of stone being produced. Building stone quarries rarely have daily vehicle movements in double figures. Even so they are required to use routes agreed with the planning authority to reduce adverse impacts. 

9. Quarrying can have impacts on surface and underground water. Because building stone operations are generally modest in size these normally have fewer impacts than most other types of quarrying. Nevertheless fine residues washed from the site by rainfall and fine debris from sawing and/or polishing of rock within processing works may cause residues that could cause potential loss of water quality. However there are strict controls imposed by the Environment Agency on quantity and quality of water discharges.  Some companies sell limestone fines as agricultural lime.

10. It is necessary for sites to be well managed if impacts are to be minimised. Much of the energy use in this sector arises during processing (e.g. cutting) and transport and, in line with emissions reduction through industry as a whole, needs to be minimised to improve the sustainability of operations.

Reinstatement of quarries is usually continuous so that the impact is only temporary. The quarry shown above was opened and reinstated within one year (below).

Stone suitable for building and roofing has very specific properties and usually very limited occurrence.

Re-instatement of sites

11. Because , with limited work, be readily used for improving local biodiversity and geodiversity if suitable arrangements for subsequent site management can be secured. Problems may arise if material is required intermittently since interesting wildlife and flora develop leading to subsequent opposition to further extraction. On the other hand, periodic disturbance of the ground at intervals can increase overall biodiversity. Sites may also have industrial archaeological evidence that is worthy of preservation in an integrated restoration scheme.

12. However a few areas have been worked extensively in the past and have given rise to major quarries or groups of quarries.  A few have been worked for considerable periods and have become large and deep and are therefore difficult to reinstate without landfill but others, such as the Portland Stone Quarries are extensive, but because they have been worked over many hundreds of years, and are of moderate depth they can be, and are, restored to a variety of uses including wildlife conservation or cultural facilities such as the Portland Sculpture and Quarry Trust. 

Recovery, reuse and recycling

13. Much emphasis is now placed on reducing waste in all sectors through reduction, reuse and recycling. Much stone can be re-used either in the original structure as a retained facade or recovered for use in another structure built of compatible material.  This process of re-use is widely evident in ancient and medieval buildings.  If stone cannot be reused and is segregated from other types of waste it can be crushed for use as aggregate. In most cases this requires, less embodied energy compared with construction materials such as bricks, metals and plastics. However it is important to prevent damage to heritage structures (e.g. demolition of disused barns) either commercially or through theft to provide building materials elsewhere.

ECONOMIC ISSUES

Making the best use of quarried materials

14. Stone suitable for building and roofing has very specific properties. Some material extracted at the quarry is unsuitable for these uses but may be suitable for other purposes, such as crushing as aggregate of for use in site landscaping when working is completed. The sale of excess materials may make the difference between economic viability and closure of an operation. It makes sense in sustainability terms to put extracted materials to good use but this is sometimes prevented by the imposition of strict end-use controls on sites for the understandable reason of preventing workings permitted primarily for building and roofing stone becoming aggregates quarries. In such cases excess rock may be left as tips in the quarry although some may be incorporated into plans for restoration of the site. A suitable degree of flexibility in policies may avoid that situation. 

Maintenance and repair orders alone are too small to sustain a quarry.  To keep the staff in employment and to support investment in plant and equipment new build orders are essential.

Economics of extraction

15. In some cases communities have been willing to accept stone quarrying to undertake repair of historic structures but have opposed the use of material for new buildings. That is sometimes possible but usually is not. Orders for maintenance and repair tend to be for modest quantities of stone and are placed sporadically. To be economic, a site needs a reasonably steady cash flow to keep the staff in employment and to support investment in plant and equipment. Therefore other, more regular, orders are needed to smooth out production at reasonable levels and those are generally for new building. It is important, if we are to maintain and repair our cultural heritage, to make sure that sites are allowed to operate viably by selling stone for other purposes.

Quarries have to be economically viable. If stone is to be available for the repair of old buildings they must be allowed to supply the market for new buildings

 Road traffic at building stone quarries is small - daily vehicle movements are rarely in double figures.

SOCIAL ISSUES

Contributions to cultural heritage

16. Building and roofing stone contribute significantly to preservation of cultural heritage providing suitable materials for repair and conservation of historic structures and through compatibility with traditionally used local materials. Thus, stone is aesthetically pleasing and can help to preserve local character. It can also provide good external and internal finishes to prestige contemporary buildings. 

Employment and skills

17. Extraction, processing and transport of stone all create jobs. However the use of these materials also supports a wide skills base in, for instance, roofing and stone masonry, and stone walling; skills that would otherwise disappear making it impossible to properly maintain our cultural heritage which is, itself, a major source of work and revenue through tourism.  Most quarries have unique geology and the local knowledge of the properties and behaviour of the stone during extraction and preparation can be lost through a break in the extraction cycle that extends beyond a generation.  The loss of this local knowledge will further hamper any attempts to re-open old sites

Competition and ethical trading

18. Overall policies for free trade within and beyond the European Union promote competition between sources of supply. But a crucial issue is whether there is a level playing field for the competing companies. Material sourced at some sites in certain developing countries is cheap because of: lower standards of environmental protection and health and safety provisions than in the UK; low wages; and, sometimes, use of child labour. This raises the issue of ethical trading: whether importers and consumers should buy material from suspect sources, even though it is cheaper. Some importers now check to make sure material is supplied with due social responsibility. A check list should be used to assess whether a supplier meets ethical standards. 

Stone is strong, durable and has good thermal characteristics that stabalise the conditions within a building; keeping it cool in Summer and warm in Winter reducing operational costs,

Sustainability compared with other building materials

19. An important issue is how well natural stone compares, in sustainability terms, with other construction materials. Natural stone is strong and has good thermal characteristics that tend to stabilise the conditions within the structure: keeping it cool in summer and warm in winter thus helping to reduce operational costs. Also, if selected and placed properly, it is durable for many years. 

20 It has been estimated that at least 40% of the world’s materials and energy are used in buildings and, although much of this relates to the occupancy and use of buildings, the materials that go into them make a significant contribution. The reduction of energy inputs could make a significant contribution to improving the sustainability of building construction. There are a number of ways in which energy implications of materials use can be considered.

21. The “embodied energy” is consumed in the production of the materials, “operational energy” in the use of the building, and energy is also used in delivery of the products to the place in which these are used. This involves identification of the energy consuming operations in the quarry (mostly fuel), determination of the total production per annum for each operation, and determination of the total amount of primary energy used to produce the stone products. Indirect use of energy such as that needed for ancillary functions, supplies and equipment must also be taken into account. Transport energy for delivery of products is estimated separately. All energy estimates have to be converted to uniform units. For most building materials, the “embodied energy coefficient” is expressed as the amount of energy (in megajoules) per unit of material (kilogrammes) (see Table 1 column 2, which is based on work undertaken in Australia)

22. An alternative approach is to consider the “material intensity” of the product when used in walling. This takes account of the density of the material. Thus one square metre of stone walling constitutes a greater mass of material than, say, autoclaved aerated concrete blocks. The material intensity has been calculated for some materials using the equation:

           Material density = Density (kg/m3) X wall width (Metres)

Results are shown in Table 1 column 3 which suggests that natural stone has relatively low embodied energy but high density (which relates to good thermal capacity.

Building and roofing stone from England performs a crucial function for our national heritage and, if extracted from well managed sites and distributed and used responsibly is a sustainable source of construction materials.