STONE- PAVING
Stone is an important material globally with different countries being famous for specific types. Like India which is known for its strong and durable sandstone or the UK which has its recognizable slate. Because of modern shipping and trade, we have more choice than ever before, so it’s important than people can make informed decisions on what stone is right for them and the potential effects on the environment are.
Effects of the quarrying industry:
–Large scale industry operating across the globe so often goes unchecked.
–Biodiversity is severely negatively impacted by open mining as habitats are destroyed. The use of heavy metals which are industry pollutants, are toxic to wildlife and accumulate in the food chain causing further harm (1).
–Water pollution happens when there is contamination of local water sources from quarry waste which can be sediment debris or other industry pollutants. Increased sediment in freshwater environments can increase the turbidity harming plant and aquatic life causing the ecosystem to be imbalanced (2).
–Land degradation: as a result of quarrying activities the landscape is stripped, without vegetation to secure the top soil its often eroded away severely decreasing soil fertility and effecting local agriculture (1, 2).
–Socio- economic impacts: often low-income communities are the most effects with either being displaced for quarrying operations or low wage labour which can be dangerous along with significant health risks like dust and pollutants causing respiratory problems (3).
Regulations:
Due to the global scale of quarrying countries have different regulations on the industry and the environmental effects they produce. The sheer diversity of quarries around the world makes it hard to advise on the sustainability or environmental impact of specific stones, be that marble, sandstone, granite, limestone etc.
Despite this, there are some ways to ensure stone has been harvested in an environmentally and ethically sustainable manner. This is through third-party certification. Organisations such as ISO, Fair Stone, and the Natural Stone Institute all offer certifications allowing a consumer to know the standards by which the stone was harvested.
UK stone:
In the UK the state does not own the stone on British shores, the stone is owned by the landowner. A licence is not required to extract stone, however, planning permission is required to harvest stone, and this permission will take into account safety and the environment (4). Locally sourced stone is likely to be the most sustainable option due to tighter regulations along with a reduction in shipping emissions as it hasn’t had to be transported across the globe.
BRICK
A versatile building material, the most common type of brick is made from clay. Depending on the composition of the clay used and other processes, bricks can come in a variety of colours. Bricks are durable and versatile, however, clay itself is not renewable, and eventually will run out, meaning clay will always be a limited resource. Kiln-drying clay can also be costly for the environment as this can emit a lot of carbon emissions depending on the fuel type.
Bricks can be sourced far more locally than other types of stone paving. With factories in both the UK and across Europe, often being close to clay formations to reduce the amount of travel needed between sites. Although we have the resources and infrastructure to produce brocks in the UK, they are often still imported in with around 800,000 tonnes being imported in 2020 (5). With the potential for imported bricks along with the extra process of kiln drying, these may make natural stones like local Granite or Sandstone more favourable.
Pros:
– Clay bricks are incredibly durable and can withstand harsh weather conditions, including extreme heat and cold. They are resistant to fire, pests, and moisture (6, 8).
– Once installed, clay bricks require minimal maintenance. They do not need to be painted or treated, unlike other materials and don’t need to be replaced after a certain number of years (8).
– Clay manufacturing plants tend to be near the source, reducing emissions and making it more eco-friendly as less transport is needed, as well as supporting the local community (6).
– Waste bricks are being developed that use waste clays and chalk along with other by products. These waste bricks also can be fired at a lower temperature in the kilns due to the added materials as well as some bricks that absorb carbon dioxide after firing, further reducing the carbon emission from production (7).
Cons:
– Even though clay is a natural resource it is a non-renewable material as it takes millions of years for deposits to form , so will never truly be sustainable (9).
– Bricks are dried in a kiln, which can harm the environment through the power needed to do this as they kilns operate at 1000-1,200°C. depending on the fuel used the carbon emissions can be significant (10).
–Harvesting of the clay can cause large scale environmental disruption through land clearing and using heavy machinery. This can cause land degradation and habitat destruction particularly in the vulnerable river/ floodplain ecosystems that clay is found in.
GRANITE
Granite stone is a strong material which comes in a variety of colours including white, pink and grey. It can be found all over the world from Europe to China, but it can also be mined locally in the UK in particularly in the northeast of Scotland. Its durability and attractive colour range make it a great resource is garden design, especially for things such as paving.
Although the cost of granite which is sourced from within the UK is often more expensive than if it’s imported from abroad. This can lead to a whole range of environmental issues as granite quarrying in places like India and Sierra Leone have been liked to illegal mining and have contributed to the destruction of the surrounding environment (24). Along with the severe damage that can be caused in the quarrying process, importing granite will further contribute to environmental damage due to it having a high carbon footprint.
However, stone can be third party certified, which helps ensure how it was sourced was in a sustainable and environmentally friendly way (25). There are alternatives to granite like Sandstone or Marble which are also very durable and aesthetically pleasing option.
Pros:
– Granite is a very durable stone, which can withstand heavy loads and has a natural slip resistant quality making it great to patios and driveways. Because of its hardwearing nature this means it will not have to be replaced for a long time (26).
– Due to granites natural low porosity this can make it resistant to stains and scratches, meaning there is little to no maintenance to keep granite looking clean and new (27).
– Granite can be sourced locally with large quarries near Aberdeen, although it can be more expensive it reduces the distance stone has to travel bringing down the carbon emissions accumulated from the transport of the material. It also means the stone adheres to the UK’s regulations for mining and labour standards.
– The durability of granite means it can be repurposed and recycled instead of going to waste, as it has a long lifespan (28).
Cons:
– The mining and extraction of granite can be extremely damaging to the environment. For example, the Western Peninsula National Park in Sierra Leone has lost 22% of forest cover in less than two years due to illegal mining. Along with surrounding villages water sources being contaminated causing people to be hospitalized (24).
– Installation of granite can be very labour intensive and costly. Because it’s a very strong and heavy material it’s hard to shape and install often need professional labour, the cost of transporting granite to site can be high (29).
– Granite sourced from the UK can be significantly more expensive due to higher labour costs are more extensive regulation, drive up the demand for imports (13).
– Imports of granite in 2022 totalled $96.3 million making the UK the 3rd largest imported in the word. The largest share of the UKs imports came from India which supplied $50.3 million worth of granite (30). Working conditions of these mines can be questionable with some found to have at least 10% of their workforce to be children (31).
SANDSTONE
A popular paving material, sandstone can be found across the globe in places with high sand accumulation like riverbeds, deserts and coastal areas. Indian sandstone is a popular choice although not the most sustainable option compared to a local Yorkstone found here in the UK. There are many variations in colours from reds and yellows to golden browns as well as it being highly durable making it an attractive stone to use for landscaping.
Whilst Sandstone sourced locally may have a relatively small environmental impact, sources from further afield, such as India are problematic. Both people and the environment are negatively affected by the sandstone manufacturing process from its extraction in quarries to its shipping and transportation. There are some third-party certifiers that are meant to ensure the stone was sourced in an environmentally conscious way however, due to complex production processes its often hard to track and guarantee the sandstone was sourced sustainably. Alternative stone can be used in garden design such as Granite, Bricks, or Porcelain, although each has other impacts that should be taken into consideration.
Pros:
– Sandstone is a strong durable material but is also easier to work with (cutting to shape and size) than other stones like granite for example, meaning less energy is used in its production (13).
– The natural texture of the stone provides grip and visual depth so as a paver its slip resistant even when wet (15).
–Due to its high strength sandstone blocks and paving can be reused, lowering the demand for new materials as well as reducing how much waste is generated therefore saving resources (16).
– Sandstone is also able to be recycled, as the demand for sand is so high in the construction industry, especially in concrete production, turning unused sandstone into high quality aggregate is a great way to prevent further waste (17).
– Sandstone can be sourced locally, notable Yorkstone which is a very traditional stone and because it is quarried and manufactured in the UK the carbon emissions from its manufacturing and transportation are much smaller compared to Indian sandstone that has to be shipped over.
Cons:
–Colour and quality can hugely vary, particularly with more cost-effective imported stone like Indian sandstone (18).
–Without regular care sandstone can become stained and discoloured due to it being a porous stone, preventative measures can be used like sealing the stone to reduce the effects of weathering (15, 19).
Indian Sandstone:
Impacts on the Environment:
Habitat destruction – Mining is extremely damaging to local environment as habitats can be destroyed from clearing of the land and heavy machinery. This destruction of the existing environment would reduce the biodiversity of the area (20, 21).
Air pollution – due to the nature of sandstone dust is a significant byproduct of quarrying and cutting processes. It can lead to air pollution which can severely affect the surrounding area; Such as dust being deposited on agricultural land affecting soil fertility as well as causing plants to asphyxiate due to oxygen deprivation (20).
Water contamination – Large volumes of water are used for cutting sandstone, due to limited water resources often groundwater reserves are used creating an even higher demand. In rainy season large amounts of run off will transport water containing suspended soils, industrial chemicals and other waste products into the surrounding area. Contaminated water can affect animal, plant and human health (55).
Transportation of sandstone is a major contributor to its unsustainability, with around 2.1 million shipments of sandstone are exported from India (23).
Rehabilitation – Indian mining laws require holders of prospecting licences or mining leases to undertake phased restoration, reclamation, and rehabilitation of affected lands before concluding mining operations. However, little to no active rehabilitation of the environment ever occurs after a mine is closed (59).
Impacts on people:
Child labour – child labour is a significant problem with the mining industry in India, with dangerous working condition and pay as little as 10 Rupee’s a day (>£1). It is predicted that In the sandstone mining sector Bundi in the district of Rajasthan, of 100,000 quarry workers roughly 15,000- 20,000 are children (56, 22).
Indebtedness – often mine owners will extend loans to their workers, creating dependency and binding the workers to the mines as they struggle to pay debts. Loans are usually impossible to pay back with annual rates of over 200% it is common for loan obligations to be passed down generations (57).
Health problems are severe due to poor working conditions , the nature of sandstone mining and the lack of Personal Protective Equipment (PPE), with more than 11 million people living in India have been exposed to silicosis causing dust (22). Additionally, secondary exposure is also of concern as an 11 year old boy developed a case of Silicotuberculosis from living in close proximity to the mines and having family members working in them (58).
Certification – there is no centralized system in place to regulate sandstone and if it was produced sustainably and ethically and usually retailers purchase their stone from third parties not directly the quarries so it’s hard to trace the supply chains. Some stone companies like Marshalls are member of the Ethical Trading initiative (ETI) which means they agree to follow the base code and are subject to audits on if the standards are being upheld (60).
MARBLE
Marble is a durable stone that is known for its colouring and distinct patterns. As it is so strong it can last a lifetime so doesn’t need to be replaced frequently, reducing the demand for materials and other stone to replace it. Since it is so durable, it can be recycled making it a great option for sustainable landscaping. Like all stone, quarrying is required to extract marble, and this has a negative for the environment in many ways, be that through water contamination or destroyed environments, third-party certifications ensure that the impact of these activities is limited. Other hard stones, such as Granite or Sandstone offer an alternative to marble, however, sourcing is a key factor to consider.
Pros:
– Marble has a long lifespan due to its durability; it can withstand heavy loads without cracking. This is a massive benefit as the material will not need to be replaced for a very long time and this will reduce the amount of stone used in the long run (32).
– Heat resistant, due to its high density it can conduct heat well making it feel cool to the touch. In gardens as paving tiles this is highly beneficial as the sun’s rays can either be reflected (if a light colour is chosen) and absorbed by the stone making it cool underfoot (33).
– Requires little maintenance, can be cleaned like any other types of stone paving. However, is recommended to apply a surface sealer to prevent any staining and discolouration (34).
– Marble can also be reused due to its durability; large slabs can be reworked into small ones or other pieces. Reducing the demand for it from quarries and helping limit the extraction of a finite source (35).
– Studies have found that waste marble from the quarrying process can be recycled into a cement and aggregate replacement for in concrete. The marble mixtures also showed higher strength (36).
Cons:
– Marble is relatively soft so can get scratched and chipped under heavy use, its particularly noticeable if it is polished marble (34).
– Due to marbles porous and alkaline nature, it can easily stain and discolour from acidic substances such as foods, drinks and some cleaning products, often meaning it has to be sealed. This can negatively impact the stone when eventually discarded as it will be harder to break down (34, 37).
– Quarrying of marble often results in 30-70% of the raw material turning into waste and refuse from the extraction and the cutting of slabs. As well, these processes consume high amounts of water and energy in the production and transportation of marble as certain types are only found in specific locations (35).
– All stone that is mined will leave behind a negative impact on the environment as habitats will be destroyed through deforestation, land degradation and contamination of water sources (38). Marble mining uses heavy machinery and often explosives which can pollute the area with industrial waste (39).
LIMESTONE
Limestone is a great strong stone that is popular for garden paving as it comes in colours ranging from blue and black to grey and yellow. Its strength and durability also mean it can be reused and recycled. This generates environmental benefits as the stone will not be replaced for a long time, reducing the need for new, materials, and using a recycled stone will have the same effect.
However, there are downsides to limestone, one of the most notable being its vulnerability to acid rain causing it to be degraded over time if not cared for properly. Along with this, mining of limestone can cause a range of environmental issues, such as biodiversity reduction, groundwater pollution, and air pollution in the form of dust that can be a severe health risk. Due to this, alternates such as local Sandstone or Granite may be worth consideration.
Pros:
– Limestone has a more limited colour range compared to granite for example but its fine grain is a highly desirable finish as well as making it easy to cut and shape (13).
– The durability of limestone is a big benefit meaning it will not have to be replaced frequently and can be reused. Meaning demand for new limestone should be lower as the stone has a good longevity (40).
– Calcium carbonate within limestone can react with the rainwater to form a protective layer over its surface making it naturally weather resistant. As a result, the stone only absorbs a small volume of water (41).
– Limestone can be recycled and can be repurposed in a range of different ways. Cement mixes commonly use waste limestone, as the ground up stone acts as aggregate in concrete production. Limestone is also useful for restoring the Ph balance is soils to help improve their fertility after high concentrations of acid rain (40, 42).
Cons:
– Limestone can be damaged by acid rain which can cause pitting on the stone and makes damaging it through wear more likely (13).
– As the stone is porous its susceptible to discoloration and staining often meaning sealant is used to maintain the look and colour of the limestone. Some solvent based impregnators can be harmful to the environment as they produce volatile organic compounds (40, 43).
– Groundwater contamination is common with limestone quarrying as aquifers are often present. Increases in sediment as well as industrial pollutants (oil) will lower the water quality, even after quarrying ends the contamination can last for a ling time (44, 45).
– Subsidence is another risk involved with limestone quarrying. In humid climates limestone often dissolves forming large underground caverns, heavy machinery brough in for quarrying can cause the ground to collapse and sink wholes to form. This can have knock on detrimental effects to surrounding communities but also local wildlife (44).
Environmental destruction occurs as with all quarrying projects. The consequences are severe for the local ecosystem, including habitat destruction, land degradation, soil fertility reduction and loss of biodiversity (46).
– Dust from the quarries and transportation of limestone can become an issue for the environment as well as local communities. There are multiple associated health risks with the inhalation of dust, specifically long term exposure to limestone dust has been identified as a carcinogen (45).
PORCELAIN
This material is man-made, usually using kaolin (China clay), but it can also be made from ball clay. Other materials include glass, felspar etc. It is known for its low permeability, high strength and white colour. The process of extracting kaolin is very resource intensive with large amounts of water and energy being used. Its typically extracted from its host rock using high pressure water jets creating a slurry that then has to be refined. This industry produces on average 9 tonnes of waste for every 1 tonnes of kaolin causing severe negative effects on the environment (47). The UK is the seconded largest exporter of kaolin globally with around $285 million being exported annually (48). As production is strong in the UK it means that the total distance the materials have to travel is less reducing their carbon footprint, compared to importing them. However, depending on the fuel source, the energy required for Porcelain can pollute massively as it needs to be fired at over 1000°C. Alternates to man-made Porcelain can be seen from natural rocks, Granite, Sandstone, or Marble, for a similar colour and look.
Pros:
– Porcelain is durable with some tiles lasting up to 50 years. This is because it’s not as porous as other rocks, reducing the amount of water that will go through it. Meaning that is resistant to extreme weather conditions such as frost (49).
– Easy to maintain as low porosity means it doesn’t require sealing along with a lack of algae and mould build up reducing the amount of chemicals needed to clean the tiles (50, 51).
– Kaolin can be mined in the UK, particularly in the southwest, in areas such as Cornwall and Devon (47). This means that the kaolin does not need to travel far if it is manufactured and purchased in the UK significantly reducing its carbon footprint compared to kaolin which has from the USA (largest exporter of the material).
– In the UK, the environment agency works with kaolin-producing companies to ensure their environmental impact is lessened, and that the companies have the correct licensing for the volume of water they are using in the production process (52).
–Kaolin waste has been research and found to be able to replace coarse gravel and fine sand aggregates in concrete mixtures (53).
Cons:
– A lot of waste can be made from the extraction of kaolin. For every tone of kaolin, nine tonnes of waste rock and mica are left behind (47).
– Hydraulic pressure is usually used in the extraction; this uses a lot of water. The company called Imerys Minerals Ltd (IML) abstracts around 430,000 cubic meters of water a year, although having infrastructure to recycle the used water its estimated that only 40% actually is recycled (52).
– The mining process removes topsoil but also uses explosives to access the mineral, which would cause large scale environmental disruption.
– Porcelain tiles can be imported from abroad from places like India, China and Italy. As they are imports, they will have a higher associated carbon footprint, so it is best to source porcelain from the UK where possible.
– To make the clay, it needs to be heated in a kiln, these can get to temperatures in the thousands of degrees Celsius and some glazing requires porcelain to go into a kiln multiple times (54). To heat large industrial kilns to the high temperatures that are required lots of energy is consumed.
SLATE
A dark coloured stone, slate is a fairly durable commonly used for tiles in roofing, but slate can also be used for paving. It can be sourced within the UK, with Wales being particularly well known for the material. If slate is sourced locally, it will have much less of a carbon footprint as it hasn’t travelled as far, making it a more sustainable option.
A downside to Slate can be seen in its durability, whilst fairly durable, heavy rain and frost can chip it, and considering that the UK gets both of these, it may be worth looking at alternates and hardened materials such as Bricks or Granite.
Pros:
–Slate quarries in Wales used to be some of the largest in the world, however now with cheaper labour abroad they don’t produce as much anymore. However, Penrhyn and Elterwater in Cumbria, still quarry slate and are great for sourcing local slate with minimal extra transport emissions, compared to importing from the China for example (11).
–Slate can last for decades, it is a naturally strong material which absorbs little water as well as being very fire resistant (12). Because of this slate can lats for decades and can even be reused.
–Aesthetically pleasing, due to the range of colours slate comes in it can support a variety of designs along with being a more traditional material.
Cons:
– Whilst durable slat is not the strongest when it comes to direct impacts, these can cause a slate slab to chip or shatter creating uneven surfaces (13).
–In the global slate industry 90% of Europe’s exports originate from Spain. Recent figures show that Spain, China and Brazil are the biggest exports of slate globally, with Spain exporting around 525,000 tonnes of it annually (11, 14).