Sustainable System Implementation for Natural Stone Production and Use

Technical Handbook

December 2012

LIFE Project Number

LIFE08/ENV/E/126

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Index

I. Introduction .................................................................................................................................................. 2

II. Environmental Evaluation of the Nowadays Production Chain. ......................................................... 7

III. Eco-efficiency of the natural stone production chain. Best available techniques. Demonstration activities. Feasibility of the new technologies and products. ................................................................ 21

III.1. Quarrying and processing factors affecting embodied energy of natural stone products ...... 21

III.2. Energy Analysis in the Natural Stone Manufacturing Process ..................................................... 35

III.3. New Cutting Disc for Natural Stone .................................................................................................. 41

III.4. Thermal Energy Storage in Natural Stone ........................................................................................ 50

III.5. LCA - Study on traditional marble chain production ...................................................................... 61

IV Potential for Implementation of Environmental Management Systems & the EU Ecolabel in the Marble Sector ................................................................................................................................................ 72

V. Conclusions .............................................................................................................................................. 80

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I. Introduction

1. This Book

This manual is a particular deliverable of the

project Ecostone. Considering the strong

component for dissemination that involves the

project this manual was designed to, with the

other tools developed, be the preferred vehicle

for the dissemination of the technical work

developed during the three years of the project.

It is intended for an easy and wide dissemination

of the results with the key stakeholders, related to

Natural Stone sector and not only.

Under the concept of sustainable development

the project encompass a significant diversity of

activities, including aspects related to the life

cycle of natural stone, with special emphasis on

the development of new materials and more

efficient equipment, waste reduction and

optimisation of resources.

With an organization by chapters that

corresponds to technical articles or reports, the

main intention is to highlight the different issues

observed in the project and submit the technical

results achieved in each of them.

The texts refer their authors which form part of

the project partnership and of the teams that

were responsible for the development of the

technical work.

2. Ecostone Project.

The main objective of the project is the

implementation, dissemination and promotion of

a sustainable system in order to enhance the

production and use of natural stone, by using the

best available techniques and products to

produce an ECO-STONE (or sustainable stone).

The project is focused on three main aspects:

1) Optimization of use of natural sources and raw

materials.

2) Optimization of energy consumption in the

production chain.

3) Use of new multifunctional natural stone based

materials with energy and environmental

efficiency in architectural use.

In the overall objective of the project is included

the dissemination and promotion of a sustainable

system of the new developed technology to

increase the energy efficiency in production of

stone, with reduction of the wastes and with the

substantial improvement in the use of the raw

materials. These objectives will be achieved

through a new High-Tech Production system,

having a Traditional but low energy cost Stone

and new High-Tech Stone products in benefits of

the energy efficiency in Buildings and able for

New Application for Construction.

The benefits are addressed to the stone sector

with the new systems and products, and also to

the construction sector with the new applications

of multifunctional stone.

More defined objectives are:

-Scientific-technological objective:

Implementation of the new technologies and

innovative materials: i) fast systems for natural

stone cutting, consolidation techniques to reduce

stone wastes; ii) innovative materials based on

natural stone with multifunctional properties

(thermal energy storage capacity, self-cleaning

properties); iii) products based on natural stone

wastes (slurries).

-Environmental objective: The new system

proposed will reduce the number of wastes to the

environment. New stone materials with thermal

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energy storage capacity will reduce the use of the

heating/cooling systems in buildings and thus

energy demands, contributing to the reduction of

CO2 emissions.

-Social objective: Improvement of life quality and

human comfort in buildings due to the reduction

of temperature fluctuations between day and

night using natural materials.

Reduction of energy consumption in buildings

implies the reduction of energy costs.

-Industrial objective: To increase the

competitiveness of the natural stone sector due

to the development of new technologies and

materials. This will bring the traditional natural

stone sector into a higher position in the market,

with products with higher added value.

-Economical objective: Energy costs during the

stone production will be reduced with the new

technologies (cutting, consolidation techniques)

and new materials with energy storage

properties. The project is not oriented to the

market. The market is not applicable in any case

in the actions proposed in this project, what is

being promoted in the ECO-STONE project is the

sustainable development of the natural stone

market.

2.1. Optimization of use of natural sources and raw materials.

The use of diamonds and cutting discs during the

natural stone production reduces the raw material

needed to obtain the same yield production as

with conventional cutting techniques. Moreover,

the use of consolidation techniques to reinforce

natural stone during processing will also reduce

breakages and thus stone wastes will be

decreased. This means natural sources savings.

The stone blocks being part of the original natural

stone deposit continue to present different kinds

of defects, such as fractures, hairline long micro

fractures, cracks, fissures, big pores and cavities,

many of which lie in the inner part of the block

and therefore cannot be detected simply by

visual inspection. These defects are the origin

and the reason for the breakage of stone blocks

and consequently of all the stone products at any

stage of the stone production chain. These

breakages can be avoided if they can be

promptly detected and repaired before or during

the block/slab processing.

The consolidation of defected blocks and slabs

can be achieved by impregnation of materials in

the fractures, cracks and fissures of damaged

stone material. The main function of the

consolidating material will be to fill the stone

defects and re-establish cohesion between the

partly separated areas of the defected stone. The

impregnation consolidation procedure to be

applied significantly depends both on the

dimension of the existing defects and the size of

the stone product under treatment block, slab,

strip or tile.

Consolidating materials traditionally used in

dimension stones are organic polymers with

organic solvent based on polyesters, acrylates,

epoxies, or even polyurethanes, xylanes, and

ethyl silicates (tetraethyl silicates). However, the

toxicity of these agents can cause health

problems to the working personnel during the

resin application procedure, and is strongly

suspected to seriously pollute the indoor

environment due to the release of harmful

substances in the long run after flooring or

cladding. From a technical point of view, the

application of these polymers results in higher

energy consumption in certain processing stages

(cutting with water).

For a feasible and environmentally friendly

reinforcement system it is necessary to identify

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and use environmentally friendly organic and

inorganic consolidating materials and develop

automated impregnation techniques. The

consolidated stone should generally be as

durable as the unweathered stone. Durability of a

consolidated stone depends on several factors,

including the consolidant durability, the

compatibility of the consolidant with the

weathered stone, the properties of the

consolidated stone and the environment. The

properties of the consolidating materials affecting

their ability to penetrate a specific stone at a

given temperature are viscosity, surface tension,

and the rate at which gel or precipitate is formed

and the rate of solvent evaporation. Moreover,

consolidating materials should be compatible

with stone, which means that they must have

similar thermal properties, not severely disrupt

the stone microstructure and not to form harmful

to stone by-products.

In order to re-establish the physical and

mechanical properties of the defected stone

products and therefore significantly reduce the

amount of stone products that cannot be

processed, it is necessary to develop a new

generation of environmental friendly organic and

inorganic consolidants with chemical

characteristics similar to that of the stone, which

will efficiently consolidate and prevent them from

breaking during processing. Moreover, it is

necessary to develop an automated block

reinforcement process appropriate for the big

block sizes and a flexible slab consolidation

process that can be efficiently applied in various

production lines.

These developments are expected to increase

the efficiency of the sawing and further

processing stages by 118%. The development of

an easily applicable fault detection system will

enable both the discrimination of the defected

blocks/slabs and also verify the effectiveness of

the reinforcement/consolidation process.

2.2. Optimization of energy consumption in the production chain.

LOWER ENERGY CONSUMPTION. The reduction

of energy consumption can be obtained with the

use of fast and thin cutting systems with lower

energy consumption.

Stone blocks are cut into slabs and strips. Slabs

are at about 2.5 m (marble) or 3 m (granite) x 1.5

m x 2 cm in size; that is, the length and width of

the block but reduced thickness. Slabs are

obtained by block sawing with gang sawing

machines (granite), diamond wire sawing

machines (granite), linear diamond blades sawing

machines (marble), or sometimes with block

cutters with a single diamond disc having big size

(3-5 m).

Strips size is about 2.5 m (marble) or 3 m (granite)

x 30-60 cm x 10-30 mm. Strips have the

approximate width and thickness of a tile but the

length of the block. Strips are usually a semi

finished product, to be further processed in order

to obtain tiles or other final products. They are

obtained by block sawing with block cutting

machines, usually equipped with many vertical

diamond discs (for granite sawing up to 100 discs

are currently used) with a diameter of 1.000 mm

or more (1.700-1.800 mm are also reported).

These vertical cutting disks have about 5 mm

thickness and segment width about 6.8 mm. One

or more horizontal discs detach each strip from

the block. Usually, block cutters are equipped

with automatic strip unloaders. Strips are also

obtained by sawing (trimming) slabs by means of

trimming machines equipped with vertical

diamond discs having small sizes (300-400 mm);

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this process gives low yield and it is no longer

applied.

Drilling and cutting operations are two time

consuming and therefore low productivity stages

in the stone production chain associated with

increased losses of valuable stone material and

environmental impacts. Drilling operations are

applied during quarrying, at the beginning of the

production chain, while cutting processes are

mainly used for the production of tiles and slabs

at a later stage of the chain.

Drilling is predominantly used as an independent

technique, while it can be also used as an

auxiliary technique, preparatory to other cutting

method (e.g. making holes for diamond wire).

Drilling equipment is either pneumatic or

hydraulic. A series of holes are drilled along the

line required to split the stone mass. Drilling, as it

is currently applied, is a time consuming process

as with the drilling speed of the existing

equipment (10 m/hour for pneumatic 70 m/hour

for hydraulic) the time needed to prepare the drills

for the extraction of one stone block varies

between 1 and 7 hours. Moreover, the current

drilling process presents serious environmental

impacts such as high vibration (up to 25 m/s2),

noise (80-120 dB), depending on the equipment)

and dust generation. With the currently used

drilling equipment, it is not possible to safeguard

the straightness of the drilled holes due to the

hammering movement of the tool. Deviations of

0.1 m over 3 m are usual, resulting in stone

losses of about 0.5 m3 per block during the

squaring process. Therefore, the development of

new high speed drilling tools without hammering

will increase productivity, efficiency, precision

and reduce the environmental impact.

Cutting operations are used for the production of

slabs and strips from stone blocks. With the

available cutting equipment peripheral speeds

between 25 and 32 m/s and removal rates of

about 150 cm2/min can be achieved in the case

of granite, while during marble cutting peripheral

speeds of more than 70 m/s and specific removal

rates of 5.000 cm2/min are possible.

Big machines equipped with up to 100 discs in

parallel cut the block into strips and slabs. A

major disadvantage of this technology is the big

amount of stone waste produced due to the

thickness of the cutting tool. This proportion

leads to high losses of stone material, which can

be up to 40%, depending on the ratio of tool

thickness to the thickness of the stone product.

Economical and ecological disadvantages are the

consequence. Besides this disadvantage, a

second problem arises from the cobalt content of

the existing bonding material used in the

diamond cutting segment. Due to the wear of the

metal-diamond bonds during cutting, cobalt is

introduced in the stone waste and therefore,

stone wastes produced by the current cutting

equipment are characterised as toxic. The

development of heavy metal free metal-diamond

bonds is a feasible solution for this problem.

The loss of valuable stone material can be

decreased by reducing the thickness of the

diamond discs. However, the reduction of tool

thickness leads to lower stiffness of the cutting

disk and increased deviations of the disc during

the cutting operation, resulting in lower slab/strip

quality. Technically, this problem of the thin tools

can be solved with the application of high

peripheral speeds, which are able to increase the

dynamic stiffness and stabilize the steel centre of

the tool. The increase of peripheral speeds will

result in increased productivity. However, high

cutting speeds result in severe mechanical and

thermal stresses to the tool, and especially to the

diamonds, and increased diamond losses, as

existing diamonds and metal-diamond bonds are

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not efficient under such conditions. The currently

available industrial diamonds are characterised

by micron dimensions, not perfect structure, low

physicochemical properties and low thermal

stability. The development of mono-crystalline,

nano-structured diamonds with perfect crystals

(Ultra Fine Dispersed diamonds) and heat and

mechanical shock resistant to withstand the high

temperatures and mechanical stresses induced

during these processes is essential.

Therefore, the progress required at this stage is

to improve productivity and reduce the amount

and the environmental toxicity of the stone waste

produced. This can be achieved with the

development and application of new high-speed

drilling and cutting tools and extra thin cutting

disks with Ultra Fine Dispersed Diamonds and

heavy metal free metal-diamond bonds.

2.3. Use of new multifunctional natural stone based materials with energy and environmental efficiency in architectural use.

New materials will be based on natural stones

and natural stone residues. Sustainable stone

materials:

a) Natural stone materials with thermal properties

allow the energy storage/release, contributing to

reduce the use of heating/cooling systems in

buildings and increasing human comfort indoors.

Some studies from IDEA (Instituto para la

Diversificacin y Ahorro de la Energa, Ministerio

de Industria y Energa, Spain), indicate that a flat

consumes approximately 4000 kWh/year and

64% of this energy is due to heating and cooling.

The energy demand in buildings rises every year

due to the increased population and the higher

number of heating/cooling systems.

b) Natural stone materials with self-cleaning

properties. Main effects of these properties are

the durability increase of natural stone,

environment and human health improvement.

Thermal storage capacity of the new stone

products will be achieved by the incorporation of

Phase Changing Materials (PCMs). These are

materials able to absorb, store and release heat

when they change state, such as from a solid to a

liquid. The melting point of PCMs is near the

standard room temperature (18-22C). Using

PCM on indoor walls serves as an

environmentally friendly climate control and

functions as follows: when indoor temperature

rises above 22C, the PCM begins to melt and

absorbs the heat from the room, without

becoming warmer itself. At night, the heat stored

is discharged for indoor heating and the cycle

can be continuously repeated. In such cases the

use of conventional air-conditioning may become

unnecessary, saving energy and protecting the

environment. Common PCMs include inorganic

salt hydrates and paraffin. They can be used

encapsulated in stable structures of about 20m

diameter or as they are.

Moreover, self-cleaning properties and photo-

catalytic properties will be introduced in the new

products with the addition of photo-catalytic

agents. The most promising agents with photo

catalytic properties are TiO2 (anatase) and ZnO.

In combination with UV sun light these agents

degrade biological fouling into CO2 and water

and transform harmful NOx into less harmful

NO2.

This a highly innovative aspect of the project, as

these materials (PCM, TiO2/ZnO) have never

been applied in the production of construction

materials made of stone.

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II. Environmental Evaluation of the

Nowadays Production Chain.

N. Bonito1, N. Cristo1

1. CEVALOR - Technological Centre for the Utilization and Exploitation

of Ornamental and Industrial Stones

nuno.bonito@cevalor.pt; nelson.cristo@cevalor.pt

A Sustainable Development is the one that meets the

present needs without compromising the ability of

future generations to meet their own needs.

World Commission on Environment and Development (Bruntland Commission), 1987.

1. Abstract

The dimension stone industry even though is a

traditional activity, with a rather significant

influence on the economy of the country, has

environmental and social constraints that

compromise their relationship with the

surroundings.

The ornamental rock companies should be

managed trough a sustainable perspective with

the integration of economic, environmental and

social aspects as key factor towards a better

efficiency of the current process and for

continuing this industry for future generations.

The ornamental Stone industry is:

Usually related with a bad image in

what concerns to the environmental

questions.

An important activity that provides

significant employment and strongly

develops the regions where it is

located.

2. Brief Description of the Sector

The use of Natural Stone has followed the history

of man almost from its origins, creating a

relationship of coexistence that can be

considered somewhat timeless.

From the beginning it was the perception of the

importance of the stone as a tool, building

material, or as a mere decorative object. A close

relationship was developed that immediately led

to the recognition of the physical, mechanical and

visual characteristics of the stone as ideal for

human use, assigning this material with a value

that is not only economic and influences the

market of dimensional stone with subjective and

not merely technical aspects, like fashions.

What is certain is that the ornamental rock is an

endogenous resource for a given region, finite

and irrecoverable on a human scale and that for

this reason deserves to be valued over the

materials that currently compete in the same

market but that does not follow necessarily the

same "rules" since they can be mass-produced in

the desired quantities or incorporate specific

properties according to a predetermined usage.

The production chain of ornamental rock consists

in three main phases, including the Extraction,

Processing and Application/Maintenance (Figure

1).

Figure 1. Dimensional Stone Production Chain

(ISTONE, Deliverable 1.1. Assessment of Production

Chain, 2007).

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- Extraction: is the first stage in the production of

stone. It is intended at this stage to extract

blocks of regular shape and size of the mineral

mass. This is a series of operations, each one

requiring one or more types of machinery and

equipment and personnel.

- Processing: corresponds to the processing of

the rock, where the blocks are transformed into

finished products.

- Implementation and Maintenance: the

construction sector is the main consumer of

stone products, widely used on pavements and

other interior applications, facades, patios,

sidewalks, plazas, sculptures and many other

items for setup and equipment of the most

different spaces.

The different existing rocks, after the extraction,

will lead to a diversity of products related to the

degree of transformation in the processing, which

determines the various markets in the sector of

ornamental stone. Table 1 shows the different

products for each degree of transformation.

Table 1. Dimensional stone products ornamental stone

sector, depending on the processing degree (adapted

from CEVALOR 2004).

The following diagram will illustrate in a synthetic

manner the flow of products in the processing

subsector (Figure 2):

Figure 2. Overall flow of products in the processing of

dimensional rocks (adapted from CEVALOR, 2004).

3. Sustainability in the Dimensional Stone Industry

"How can we apply the concept of

sustainability to the sector of ornamental

rock?

... meet the present needs without compromising

the ability of future generations to meet their own

needs.

The need of exploit a natural

resource.

The capacity of the natural system to

fulfil the human demands.

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The guaranty of the continuity of the

process.

In order to be sustainable a particular human

venture must necessarily follow four basic

principles that are presented without hierarchy:

be economically viable, environmentally

sound, socially just and culturally acceptable.

These four principles contain the main pillars of sustainability.

Figure 3. Schematic representation of the structure that

supports the concept of sustainability.

The case of the dimensional rock industry has

special features that distinguish it from other

industries, first for processing a raw material that

is natural, finite and not renewable on a human

scale.

So how it is then possible to consider

sustainability in the processing of a material

that is not renewable at the scale of operation

and when we know in advance that when

removing a geological resource of the quarry,

it will not recover and we cannot guarantee

the continuity of the existing reserves?

In fact the concept of sustainability is perfectly

applicable to this industry, however inherent to a

temporal and spatial basis, which is related to the

type and amount of exploitable reserves of the

mineral mass.

The quarries or processing plants can obtain a

sustainable performance with the adoption of an

organization and daily procedures toward a

greater efficiency, the increase of the value of

the raw materials and the extension in time of

the exploitation.

To assess the sustainability of a specific project

we can use indicators aiming not only to analyse

the present situation but also to make

comparisons with similar situations.

The use of indicators appears in order to assist

the presentation of technical and scientific

information, providing a better and more direct

understanding of its meaning.

The sustainability indicators, in order to

characterise the performance of enterprises in the

sector of dimensional stone, should answer

certain technical and scientific criteria:

Be representative;

Be simple and easy to interpret;

Show trends over time;

Be sensitive to changes in the aspect to

which they refer;

Be based on existing information or

possible to obtain a reasonable cost;

Be based on information properly

documented and recognised quality;

Be able to update one at regular

intervals;

Have a standard with which to be

compared (laws, rules, etc.)...

There should be considered four categories of

sustainability indicators in general:

Environmental Indicators.

Economic Indicators.

Social Indicators.

Institutional Indicators.

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The list of indicators below is neither definitive

nor exhaustive, but illustrates one way of getting

the industry to evaluate the mining and

processing of the dimensional rock, using

information that can be achieved with reliability in

the current management of the enterprises.

Table 2. Possible list of sustainability indicators

applicable to the sector of dimensional stone (ISTONE,

2007)

4. Dimensional Stone Production Chain Analysis

The definition of a profile related to sustainability

in the dimensional stone industry is not an easy

task mainly due to the diversity of the existing

layouts for the quarries and processing plants.

The variables are many and therefore each case

will have different frameworks regarding the

environmental performance of the enterprises.

Following the different scenarios that can exist

associated with each layout a common point to

consider is that in every operation there are

certain inputs and outputs which generally are the

same only varying essentially in quantitative

terms.

As an example we can present a typical layout for

a quarry (Figure 4) and processing plant (Figure

5).

Figure 4. Extractive Process Layout, indicating the

inputs and outputs.

Figure 5. Manufacturing process Layout, indicating the inputs and outputs.

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Inputs Outputs

Raw Material Final Product Energy Noise Water Dust Ancillary materials Gases Liquid effluents Wastes

5. Cost Analysis

In terms of the cost breakdown is possible to find

different scenarios, depending on each company,

either for quarries (Figure 6) or for processing

(Figure 7), these scenarios will vary according to

the company's strategy and the type of

exploitation.

The analysed costs are divided by the most

significant parameters in terms of the enterprise

management, including those related to water,

the auxiliary materials necessary for the

development of activity, energy, the human

resources, the machines (cost of the use

equipment, excluding energy and considering the

equipment depreciation), the management of

emissions (noise and dust) and the waste.

Regarding the quarries we can see that the

largest share of the costs break down is divided

between the human resources and the machines.

The different scenarios presented allow in one

hand to understand the diversity of situations that

may occur, and simultaneously a slight pattern in

terms of costs distribution.

It is interesting to note that the costs associated

with the water, energy and also waste and

emissions management, have very low

proportions in the general costs, which is

probably related to the accounting systems and

to the poor quantification of these issues. These

costs are diluted in other respects, particularly in

the manpower and the costs with the use of

equipment (e.g. pumping and disposal of water in

a quarry).

Figure 6. Cost Breakdown in three marble quarries

(CEVALOR-INETI, 2008).

Figure 7. Cost Breakdown in three processing plants

(CEVALOR-INETI, 2008).

6. Inputs

Raw Material

When considering the raw material as an input

into the system we refer more clearly to the

transforming process, since the extraction as a

primary sector of activity directly exploits a

natural resource without processing, where the

raw material is the mineral mass itself.

So the blocks of marble, limestone or granite, or

shale and slate, are the end product of the

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extraction process and the main raw material for

processing factories.

If we compare the mass balance of the three

processing plants we can observe the following

(Table 3):

Table 3. Mass Balance for three marble processing

plants (CEVALOR, INETI, 2008).

It appears that regardless of the quantities that

vary depending on the size of the factory and its

labour market, the efficiency of the process

among the 73% and 57% is framed within the

average values assumed for this industry.

Energy

The energy appears in the extraction process and

manufacturing in several forms, electricity, diesel

and other "secondary" which will be dependent

on the first two, compressed air, which can be

produced by a diesel or electric compressor.

Energy is an input at all stages of the process,

whether extractive or manufacturing.

While in the processing the electricity is the most

consumed in the quarries where diverse mobile

machinery, or even the use of compressors

exists, diesel is the most used energy.

In order to standardise the analysis of the energy

efficiency and to frame the enterprises in a

consumption profile is used usually one unit that

can correlate the different forms of energy and

then categorise the consumers. This unit is the

tone of oil equivalent, or toe, and the conversion

will be done according to the following table:

Table 4. Conversion to Tone of Oil Equivalent (TOE).

On this basis and taking into account the existing

information for three quarries and processing

plants we can present the following table:

Table 5. Energy consumption for three marble

processing plants and quarries (CEVALOR-INETI,2008).

Water

Water is an essential element both in the

quarrying and in the processing of dimensional

rock. Its function is to cool the drilling and cutting

diamond tools and clean the cuts.

Simultaneously this use complies with

environmental functions also allowing the

reduction of dust emissions into the atmosphere.

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The water used, either in quarries or factories

may come from three origins:

Caption:

Surface Waters.

Underground Waters.

Public Distribution.

Reuse.

Its normal to reuse about 80% of the water both

for quarries and processing plants, since the

treatment systems are increasingly effective.

In order to replace the normal losses, especially

through the sludge, it is usually necessary to have

an external supply.

Tables 6 and 7 present values of consumption

and reuse of water measured over a year in three

plants and three marble quarries.

Table 6. Water Consumption in three marble quarries

and processing plants (CEVALOR-INETI, 2008).

Table 7. Recycled Water in three marble quarries and

processing plants (CEVALOR-INETI, 2008).

7. Outputs

Final Products

The attainment of the final product is the principal

object of the extraction and processing of

dimensional stones, varying that same product

from a rough block, result of the extraction of

the mineral mass to a variety of products

associated with the processing process (Table 9).

The rates of recovery are quite different for the

quarrying and for the processing, being in the

case of the ornamental rock quarries, directly

related to the conditions of the mineral mass and

in the case of the processing plants with the

quality of the raw materials purchased and the

type of product required.

The products resulting from the processing

process, and which are being addressed

throughout this work are distinguished primarily

according to their size, ranging from the sawn or

finished plates sawn to the modular tiled.

In addition to these products usually considered

standard there are some others that are not

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related to the dimensions, since these are

variable, and even those related to works by

measuring or special assignments.

Table 9 lists some of the products resulting from

the processing of the dimensional stone.

Table 8. Typical products in the processing of the

dimensional stones (OSNET vol. 1, 2003).

Noise

The issue of noise as output of the production

systems can be viewed from two standpoints:

Occupational Noise - the noise to which

workers are exposed, usually considered

in the context of Occupational Safety and

Health at Work;

Environmental Noise - the noise that

goes beyond the facilities.

The main sources of environmental noise can be

divided, according to the type of noise they

produce, in the following groups:

Operation of drilling and cutting;

Use of explosives;

Load and transport.

Table 9. Workplaces (%) with noise levels above the

limits established by law, for three processing plants

and three marble quarries (CEVALOR-INETI, 2008).

In situations where the emission of noise goes

beyond the legislated values it is important to

maintain a constant monitoring to prevent

possible impacts. In this sense, the processing

plants carry out every year new measurements to

assess the preventive measures applied. The

specific prevention measures for workers' health,

usually includes the provision and use of

appropriate personal protective equipment (PPE).

Dust

On open-air quarries the main air pollutant is

made of airborne dust particles, whose size

varies between 1 m and 1000 m (Jimeno, C. et

al 1989).

These dusts may be detrimental to the

environment and consequently for human health,

depending on some parameters such as chemical

composition, particle size and volume in the

atmosphere. The most damaging to human

health are of smaller diameter (

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Gases

Vehicles used on natural stone quarries, other

combustion diesel engines, and the use of

explosives, are activities that emit gases into the

atmosphere.

Usually these are open-air quarries these gases

accumulation does not pose health problems for

the workers or the public in general, since that

the dust spread is rather quickly.

In underground quarries will have to consider the

problem in a different way, since it can become

more relevant in terms of working conditions. For

that, as mentioned above, should be planned and

designed specific ventilation systems.

From the perspective gas emissions that

contribute to the greenhouse effect is possible by

converting the values associated with energy

consumption, conclude about the CO2 values

emitted by a particular enterprise, in this sense

and as an example we can cite the following

data, resulting from values considered for the

year 2007 (Table 10).

Table 10. CO2-eq Emissions in 2007 for two quarries

and a marble processing plant (Eco-efficiency Project

in Quarrying Industry, 2008).

Enterprise CO2-eq Emissions/m3 of Commercial Block

Quarry A 297 Kg

Quarry B 80 Kg

Plant C 100 Kg

Wastewater

In the ornamental stone the production of liquid

effluents has particular importance since that,

generally, the processes take place in wet

conditions, either in quarries or in the processing

plants.

On the other hand most of the wastewater, water

and suspended solids (stone dust), require a

strict management and have relatively high costs.

Most companies, whether processing plants or

quarries, usually use a system for wastewater

treatment which allows the recovery of water for

the production system on average values that

may be around 80%, which represents a very

significant efficiency in relation this feature.

The effluent circuit is different in quarries and

processing units.

In quarries usually the procedure is a pumping

system that takes the water from the bottom of

the quarry for specific deposits that are

strategically placed according to the capacity of

the pumps and the depth of the excavation. The

treated water will be used for primary processing

surface of blocks or reintroduced, by gravity, the

quarry (Figure 8).

Figure 8. Schematic representation of typical system of

treatment and recirculation of water in a quarry.

In the case of processing plants the effluent is

collected in gutters, and in the equipment in each

operation and is subsequently referred for

treatment in tanks for brewing, or for a more

complete treatment plant constituted not only by

settling ponds but also by a pumping station, a

unit for flocculants, a clarifier, a press filter and a

tank of clean water (Figure 9).

Technical Handbook

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The sludge, after filter-pressed, have a moisture

content ranging between 20% -30% or higher,

and are subsequently deposited in landfills.

Figure 9. Schematic representation of typical treatment

system and recycling water in manufacturing.

Waste

A waste is any substance or superfluous object

without economic interest from an activity and

whose holder discards, intends to do it, or is

required to.

The natural stone industry, either in quarrying or

in the processing plant, produces waste similar to

urban waste, but which stand out primarily by the

quantities produced is the waste rock debris

without commercial value.

These are not hazardous wastes and are

considered inert. Given the volume they occupy

is stored in the form of landfill or tailings, within

the licensee area of the enterprise, see Figure 10.

Figure 10. Waste heaps of natural stone.

The origin of the various types of waste provided

from the quarrying or processing is summarised

in Figure 11.

Figure 11. Types of waste from quarrying and

processing of natural stone (ISTONE, 2007, D5.11).

In terms of possible final destinations for the

waste is accepted and even indicated by

legislation a preferential hierarchy (Figure 12)

reflecting, in order, the prevention, recovery and

disposal:

Technical Handbook

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Prevention - prevent or reduce, preferably

at the source, as far as possible the

production or harmfulness of the waste;

Recovery - recycling of waste operations,

such as: reuse, recycling or energy

recovery.

Disposal - designed operations to give a

final destination to the waste, such as its

treatment, recovery or landfilling.

In situ management immediately contributes to

waste production prevention, its important to

highlight some actions that are now common on

quarrying and processing of dimension stone.

The following pictures give some good practice

examples for waste management in quarries and

processing plants:

Figure 12. Waste Management.

8. Environmental Impacts

Within the principles of sustainability of the

natural stone industry, in both quarrying and

processing, its important to carry out an impact

analysis of the activity on the environment,

because lot of the balance and continuity of the

sector depends on the implementation of specific

measures.

The compatibility of this industrial activity goes

through the adoption of good environmental

practices, which should allow the mitigation and

prevent the major impacts, reducing their

magnitude and providing the recovery of the

affected area, once quarrying activity ends or a

better harmony with the environment for the

processing plants.

Preparation stages and the exploitation of a

quarry usually are characterised by the major

destructive activities of the production process.

9. Conclusions

The concept of sustainability applied to the

natural stone industry will have to be seen in the

perspective of management of the premises

where the exploitation takes place, the industry in

the broadest sense will not be sustainable since it

is not possible to guarantee a continued

indefinitely, for dealing with a finite resource at a

human scale.

It appears that the costs of the environmental

component, including water management,

emissions and waste, there are very limited

distribution in general, which essentially

correspond to the way they are accounted for,

possibly diluted in the emerging costs of hand

work or in energy costs, which have a significant

size.

In the ornamental stone industry profitability of

raw material is closely related to waste

management, consisting mostly representative

for more remains of stone with no ornamental

value.

The management from the perspective of

sustainability requires the integrated

consideration of all aspects related to resource

Technical Handbook

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exploitation, with the primary objective of an

increased efficiency of industrial facilities in the

tight balance between consumption, production

and relationship with its surroundings.

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III. Eco-efficiency of the natural stone

production chain. Best available techniques.

Demonstration activities. Feasibility of the

new technologies and products.

III.1. Quarrying and processing factors

affecting embodied energy of natural stone

products

A. Gazi, G. Skevis, M.A. Founti

Laboratory of Heterogeneous Mixtures and

Combustion Systems, Thermal Engineering

Section, School of Mechanical Engineering,

National Technical University of Athens,

1. Introduction

Marble is a financially important and highly

versatile material used extensively both in the

construction, decoration and art. Marble

production is concentrated in specific areas (e.g.

Mediterranean basin, Central and East Asia etc.)

with more than 90% of total natural stone

production coming from China, Italy, India, Iran,

Spain, Turkey, Brazil, Egypt, Greece and

Portugal. Each of the above countries which

produces more than 2 million tonnes of natural

ornamental stones per annum (Napoli, 2010). The

European Union (EU) accounts for approximately

30% of world stone production, of which 90% is

concentrated in Mediterranean countries

(EUROSTAT, 2008). In the EU, stone quarrying

activities are carried out by almost 60,000

companies employing approximately 500,000

people with an annual turnover of more than 20

billion (Bruno and Paspaliaris, 2004).

The majority of quarrying and stone processing

activities worldwide are performed by Small-to-

Medium Enterprises (SMEs). In the EU, SMEs

constitute 99.2% of the total stone quarrying

companies and employ more than 80% of the

relevant workforce (EUROSTAT, 2008). These are

necessarily located close to the natural stone

producing areas, very often in remote,

mountainous areas, may not connected to the

electricity supply grid. They are usually vertically

organized companies with limited access to

financial resources and difficulties with

incorporating new technologies, implementing

modern organization schemes and fully adopting

national and supranational regulations. A lack of

skilled labour trained in contemporary

technologies may also be a problem.

Marble production requires an advanced level of

technology, which results at higher costs but at

the same time presents significant profit-making

opportunities. Major problems of the marble

sector relate to its conservative nature, its low

productivity coupled with low penetration of new

technologies in production and processing

operations, traditional manufacturing of end-

products, significant quantities of waste material

generated in all production stages, as well as

high production costs and a lack of sustainable

management of resources. The latter, together

with the current fragmented nature of commercial

activities and the small size of production

companies poses serious barriers to the

modernization of the sector (Gazi et al., 2012).

To change the picture, it is necessary to adopt

measures that lead to a marked increase in

production efficiency coupled with substantial

reductions in material waste. Energy efficiency of

a vertically-organized enterprise (quarry and

processing plant) is a function of raw material

properties (uniformity, density, rigidness,

existence of cracks etc.), type of end products

and size of production. In order to be able to

estimate energy saving potentials, it is necessary

Technical Handbook

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to adopt a methodology capable of identifying,

defining, estimating and assessing energy flows

in natural stone quarries and processing plants,

accounting for details and peculiarities of the

examined processes (Gazi et al., 2012).

This article targets engineers, production

managers and stone producers in need of

knowledge of the energy details of specific lines

in order to take up specific measures. It assesses

the energy flows and the environmental impact

related to the production stages (quarrying and

processing) of typical marble products by

implementing an energy audit approach. The

implemented methodology is based on the

identification of energy demanding processes

related to marble production in a specific plant,

definition of appropriate operation/installation

parameters that control the above processes,

and evaluation of the effect of such parameters

on the energy consumption per final product.

2. Marble quarrying and processing plants: An inventory

A detailed inventory, including machinery

technical specifications and operational

characteristics, of the examined typical medium-

sized marble quarry and processing plant in

Greece has been presented elsewhere (Gazi et

al., 2012). The selected plant is a typical SME in

the marble production sector (Laskaridis Marble

S.A., 2012) with typical quarrying and processing

activities, as far as equipment, quarrying and

processing methods and economic size are

concerned. The main activities of Laskaridis

Marble S.A. are extraction from privately owned

quarries in the Limenas and Theologos areas of

Thassos, Northern Greece, and processing and

elaboration of white dolomite and crystalline

marble.

3. Marble quarrying

The Limenas quarry is located on the island of

Thassos, at an altitude of 440-530m covering a

total area of about 47,800 m2. It is an open pit

quarry with several fronts and seven beds, each

6m high. The annual productivity is ca. 2,900 m3

in rough blocks, of 2 m3 up to 8 m3 according to

customers' orders, and ca. 4,000m3 of irregular

small sized blocks with a market value ranging

from 280 to 600/m3. The quarry has 20

employees and can operate for about 10 months

per year (Gazi et al., 2012).

Quarrying operations involve isolating blocks

from the parent ledge by cutting them free on all

sides perpendicular to each other. The basic

quarrying sequence includes: pre-production

operations; primary cuts; secondary cuts and

finishing of blocks and removal and haulage of

blocks. The isolated stone block has dimensions

suitable for sale and processing or it may be

further subdivided into smaller blocks. The block

maximum width is constrained by weight limits

that are given by safety factors in handling and

transportation of the blocks, as well as the

dimensions of the gang-saw frame, where blocks

are placed and cut to produce slabs. Quarrying

and processing practices demonstrate that the

larger the block dimensions the lower their

production costs and the higher their processing

yields (Gazi et al., 2012).

The electric power requirements of the quarry are

covered by two power generators of nominal

power 250kVA each. These are used to power

two air-compressors, seven diamond wire saws,

two drill machines, two pneumatic top-hammers

and one water drill pump. Auxiliary drilling

equipment includes short plugs, hydraulic jacks

and air pillows. In addition, the quarry uses

Technical Handbook

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various vehicles such as excavators and loaders,

truck/dumpers, cars and jeeps.

Water consumption, required for cooling and

cleaning the diamond wire saws and for the

drilling procedures, is of the order of 80 m3 per

day. The water comes either from dams located

on the mountain at a higher altitude than the

quarry, or from a water-drill, especially during the

summer months. The water is stored in three

40m3 overflow-tanks, from where water is

supplied to the quarry under free-fall flow.

4. Processing Plant

The processing plant is located approximately

30km from the quarrying area. The basic

processing sequence includes cutting and

finishing operations (polishing, curing, edge

profiling), packaging of products and storage or

distribution to customers. The total installed

power is 625kW and the processing plant electric

power demand is covered by grid electricity. The

installed power and make/model for selected

processing plant machinery are shown in Table 1.

The processing plant operates 12 months per

year, 8 hours per day and employs 15 persons

either on a full or part time basis (Gazi et al.,

2012). An outline of the processing plant is

depicted in Figure. 1.

Processing plant employs both cutting and

finishing equipment. Cutting equipment includes

monowire and monoblade machines, a multiblade

gang-saw and bridge cutters. A monowire (using

a diamond wire) or a monoblade (using a

diamond blade) machine, is used to give

rectangular shape to irregular blocks. The

monowire has a higher feed rate while the

monoblade has a lower level of productivity but a

narrower cut (better yield) and a longer lifetime.

Both machines are also used for the production

of slabs of varying thicknesses, not limited to the

2mm or 3mm thickness obtained from the

multiblade gang saw. Passing the raw block

through a monowire or a monoblade machine

(block-squaring for fitting into the gang-saw)

improves the productivity of the cutting process

significantly, achieving better efficiency in block

cutting and reducing material waste (Carosio and

Paspaliaris, 2003).

A multiblade gang saw is used for cutting blocks

into slabs (flat surface semi- finished product with

unfinished edges obtained by sawing or splitting

from a rough block minimum dimensions of a

slab: 2m x 1m x 0.02m (EN 1468, 2003)). In the

multiblade gang saw, up to 81 slabs are

simultaneously cut by 80 blades. The slabs can

be further cut into smaller products such as

strips, stairs, tiles, etc. of different dimensions, by

using bridge cutters.

The finishing equipment includes two polishing

machines, used to adjust the product thickness

to a prescribed tolerance and to give light

reflecting properties to the marble surface. The

first polishing machine is on line with curing

treatment, resin application, UV and IR furnaces.

Both polishing machines offer the possibility of

alternative use of bush hammering tools and

other ribbing heads, instead of polishing heads, in

order to give a rough surface to the products and

make them suitable for anti-slipping applications

(e.g. pavements), or acquire a special visual

effect (e.g. for wall cladding). An edge profiling

machine is used to give the four upper edges of

each product the desired inclination.

The processing plant also includes auxiliary

equipment, such as two bridge cranes with a

lifting capacity of 5,000kg and 25,000kg

respectively, a rotary crane, several trolleys and

forklifts. The processing plant utilizes a

wastewater treatment facility. The latter is

Technical Handbook

-24-

necessary since the water used in all cutting and

finishing processes contains substantial

quantities of marble splint and dust that need to

be filtered before reuse. Plant wastewater

(0.005m3/sec) is fed into a conical shaped

settling tank, with a volume in the order of

120m3, where a chemical agent is added to

increase the rate of coagulation and to facilitate

faster sedimentation. The sediment formed at the

bottom is led through a pneumatic diaphragm

pump to a filter press which retains marble

sludge containing relative small amounts of

humidity (approx. 10%). The filtered water is

subsequently led to a 6700lt storage tank for

further use. The efficiency of the water recycling

process is about 70% (Gazi et al., 2012).

5. Energy Assessment

5.1. Outline

The present article proposes a methodology that

can be used to estimate the energy saving

potential of a typical medium sized marble plant

based on the calculation of energy inputs per

product, taking into account the details of

quarrying and processing activities, as well as

details of machinery required for the production

of each product. Such an approach is markedly

different from holistic approaches, such as Life

Cycle Assessment (LCA) being able to account

for the peculiarities of a particular plant (Gazi et

al., 2012). The first step in such methodology

includes product specification (e.g. slab, tile).

Depending on the particular product, a different

combination of plant machinery is required, as

shown in Table 2. The next step is to calculate

the energy consumption of each individual

operation of the production line in order to define

the total energy requirement (energy input) for

every specific product and processing scenario.

This approach gives the possibility to compare

the total energy requirement of similar products

and processes. The calculation of the energy

consumption of each operation was based on

efficiency values defined as a percentage of

nominal machine power and derived from

literature for similar cutting and machining

processes. Reductions in efficiency originating

from normal wear and tear have not been taken

into account; as such the calculated energy

values constitute an upper limit. Common to all

processing scenarios are extraction in the marble

quarry and transportation of blocks from the

quarry to the processing plant. The proposed

methodology can be easily extended and applied

to any similar SME.

5.2. Calculation of Energy Inputs for Typical Final Products

Several operating sequences are possible in a

typical marble plant as described in detail in (Gazi

et al., 2012) and shown in Table 2. In such a

typical scenario (Scenario 6) a block extracted

from the quarry (average dimensions

2.15x2.10x3.10m) is shaped and squared-off in

the diamond monoblade (squared block

dimensions 2x2x3m), and cut into large slabs

(2x2x0.02m) in the multiblade gang-saw.

Subsequently, the slabs are transferred to the

bridge cutter and are further cut to the required

finished product dimensions (0.4x0.4x0.02m). The

finishing process includes passing through the

polishing machine where surface roughness is

reduced. At this stage, products are given the

light reflecting properties of the marble surface

and finally the tiles pass through the edge

profiling machine to create the desired inclination

for its two upper edges. An outline of this

scenario is shown in Figure . 2.

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Calculations for operating scenario 6 are

presented in Tables 3-8. Tables 3 and 4 present

the calculated energy consumption for quarrying

and transportation from the quarry to the

processing plant. Table 5 presents energy

calculations for block squaring in the diamond

monoblade and Table 6 calculates energy

consumption for block cutting into slabs in the

multiblade gang saw. Energy consumption for the

polishing and edge profiling finishing processes is

shown in Tables 7 and 8, respectively. In Table 7,

the total power of the polishing machine is

calculated, assuming that there are 12 polishing

heads having a power of 4.1kW each, 3 diamond

heads of 18.6kW each and 3 cold air blowers of

3kW each.

Based on the above calculations, it is possible to

define the total energy consumption for the

production of a typical product (Table 9) and the

(energy) contribution of every stage of the quarry-

to-final product process (Fig. 3). It becomes clear

that cutting (in the processing plant) is by far the

most energy demanding process in the

production of a polished tile.

5.3. Extension of Energy Assessment Methodology and Sensitivity Analysis

The methodology outlined in the previous section

is here applied to possible operating scenarios in

order to assess the effect of alternative plant

processes in the total energy consumption for

selected final products. Figure 5 summarizes total

energy consumption for all ten operating

scenarios. A breakdown of the total consumption

into individual processes is presented in Fig. 6 for

scenarios 1-3 and in Fig. 7 for scenarios 4-10.

Clearly, scenarios 1-2 have significantly lower

energy consumption than the other cases since

they only involve primary cutting processes.

The major energy cost (more than 85%) is related

to the multiblade gang-saw operation, while using

a monowire or a monoblade cutter makes no

appreciable difference to the total energy

consumption. Note, however, that the monoblade

energy consumption is by a factor of two higher

than that of the monowire machine. Polishing, on

the other hand, introduces significant energy

costs as shown both in Figs. 6 and 7. For

example, slab cutting and polishing (scenario 3) is

almost a factor of 2 more energy demanding than

simple slab cutting (scenario 2). Similar

arguments can also be made in the case of tiles

production (cf. compare scenario 4 with

scenarios 5-7). When curing treatment is also

required, energy consumption increases

enormously, as clearly indicated by simple

inspection of the energy consumptions

associated with scenarios 7 and 10. The edge

profiling machine generally has a moderate

contribution, of about 20-50%.

A comparison of the energy consumption of the

processing plant machinery is shown in Fig. 8.

Clearly, the most energy demanding machines

are the multiblade gang-saw (as far as the cutting

process is concerned) and the polishing and

curing machines (as far as finishing processing is

concerned). A detailed description of these

calculations can be found in Table 10. For useful

comparisons, all results are given in kWh/m3. In

the case of tile production, where the final

product has a specified thickness (2cm), results

are also presented in kWh/m2.

A sensitivity analysis has also been performed in

order to quantitatively assess the impact of

operating parameters for each process on the

overall energy consumption. Values of pertinent

parameters (e.g. the time spent by a tile in the

curing oven) have been varied within a pre-

defined range (e.g. up to 100% of the current

production value) and the energy consumption

Technical Handbook

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per product has been evaluated for each case. It

should be noted that the specific parameter

values implemented in the sensitivity analysis are

not optimized solutions but are used herein order

to highlight the effect of each specific parameter

on energy consumption.

The energy consumption in cutting processes is

simply related to block and final product

dimensions. As a result, no significant energy

improvements can be made without the

modification or replacement of the existing

machinery. The edge profiling machine

contributes 40% of the total energy consumption

in operating scenario 6. Significant improvements

in total energy consumption could be achieved by

moderately increasing the belt advancing speed.

For example, a 50% increase of belt advancing

speed results to almost 20% less total energy

consumption, but no further gain is achieved by

further speed increase. This is due to the fact

that, in order to attain higher belt advancing

speeds, the belt motor would need to operate

beyond its maximum rated efficiency. The above

calculations are performed by assuming a certain

distance (13 cm) between products in the belt.

Increasing tile stacking (i.e. decreasing the

distance between successive tiles) is also

beneficial in terms of energy consumption. For

example, a 10cm distance between successive

tiles results in 5% less total energy consumption

per product.

Although the polishing machine makes large

contributions to the total energy consumption

(e.g. 20% in scenario 6), altering polishing

process parameters (i.e. belt advancing speed

and/or tile stacking) does not appreciably alter

energy consumption. For example, a 50%

increase of belt advancing speed has only 7%

positive effect on energy consumption. Also,

increasing tile stacking by 3cm results in less

than 1% reduction in the total energy

requirement. On the other hand, significant gains

could be achieved by optimizing polishing and

curing machine operation, which constitute

almost 67% of the total energy consumption in

operating scenario 7. This can be done by, for

example, using only one IR oven instead of two.

In this case, it would be advisable to increase the

time of the curing in the single IR oven, so as to

have the same curing efficiency. Thus, assuming

a 25% increase of the time of the curing in the

single IR oven, the energy consumed for the

production of the final product would be reduced

by 8%. Similarly, the possibility of reducing the

number of UV or IR lamps was also considered.

Using 18 instead of 24 UVA lamps makes no

significant difference in the total energy

requirements, whereas the use of 15 IR lamps in

each IR oven reduces by 5% the total energy

consumption in operating scenario 7. In this case,

it would be also advisable to increase the belt

advancing time in order to attain similar

efficiencies. Sensitivity analysis shows that the

reduction of UVA lamps has an almost

insignificant effect on the final energy

consumption (only 1% for a 25% reduction in the

number of UVA lamps). The effect of IR lamps

reduction is tenfold due to the significantly higher

power rating of the latter (0.45 kW/UVA lamp

compared to 6 kW/IR lamp). Increasing the

processing time, using 18 instead of 24 UVA

lamps and a single IR oven with 18 IR lamps,

results in a 9% reduction of the total energy

consumption. However, in order to fully assess

the impact of the above, a complete thermal

analysis of the curing processing in the ovens

needs to be performed.

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5.4. Embodied Energy

Embodied Energy is the sum of all the energy

required to produce goods or services,

considered as if that energy was incorporated or

'embodied' in the product itself. Embodied

energy is an accounting methodology which aims

to find the sum total of the energy necessary for

an entire product life-cycle. Determining what

constitutes this life-cycle includes assessing the

relevance and extent of energy into raw material

extraction, transport, manufacture, assembly,

installation, dis-assembly, deconstruction and/or

decomposition as well as human and secondary

resources. Different methodologies produce

different understandings of the scale and scope

of application and the type of energy embodied.

Until recently, it was thought that the total

embodied energy content of a building was

negligible compared to the operating energy

spent throughout life cycle of the building. As a

result, efforts were focused on reducing

operating energy and improving the energy

efficiency of the building envelope. Research has

shown that this is not always the case. Embodied

energy can be the equivalent of many years of

operational energy. The most important factor in

reducing the impact of embodied energy is to

design long life, durable and adaptable buildings.

In this section, the energy efficiency of the

examined quarry and processing plant is

compared to the energy efficiency of two Italian

marble plants, through comparing the embodied

energy of similar marble products. The calculated

energy input of scenario 6 for a typical Greek

marble tile is compared in Table 10 with literature

on embodied energy data for Italian marble

products (Traverso et al., (2010) and Nicoletti et

al., (2002)), based on LCA. Traverso et al. (2010)

presents embodied energy per volume of marble

product (functional unit). Similarly, Nicoletti et al.

(2002) presents primary energy consumption data

for the production of one m2 tile (functional unit).

The above data were adjusted to the functional

unit used in this work, which is a typical

commercial tile of dimensions 0.4x0.4x0.02m,

corresponding to 0.16m2. The current choice of

functional unit has been based on the practical

requirements of selected target groups (e.g.

architects, energy engineers). Traverso et al.

(2010) follow a production sequence similar to

that of scenario 6 that includes extraction in the

quarry, transportation of products, and

processing in a monoblade, a block-cutting

machine (sawmill 1) and a tile polishing machine

(SIMEC LM 600, sawmill 2). Nicoletti et al. (2002)

include pre-production and marble extraction,

transportation and processing. Calculated energy

values are graphically presented in Figure. 4. It is

apparent that the calculated energy consumption

per product in the processing plant is similar for

all three cases. The increased overall energy

consumption for the case of Nicoletti et al. (2002)

is due to the very high transportation costs inside

the quarry and from the quarry to the processing

plant.

Another useful comparison between Greek and

Italian typical marble products can be made on

the basis of embodied energy. The term is

loosely used here, since in its strict definition it

should include the sum of all energy inputs

(fuels/power, materials, human resources etc.)

from extraction, and processing to bringing it to

the market, and disposal/re use. Traverso et al.

(2010) state that the embodied energy for the

examined Italian marble is 324.4kWh/m3 for slabs

and 492.2kWh/m3 for polished tiles. The currently

estimated embodied energy for the Greek marble

varies depending on the particular production

scenario. The calculated embodied energy for

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slabs is 100-160 kWh/m3, whereas for polished

tiles lies between 300-700 kWh/m3. The

significantly lower embodied energy of the typical

Greek slab can be attributed to the high quality of

the raw material, which precludes the need for

slab strengthening with nets or fault repair (e.g.

crack or hole filling) using resins. Both such

processes require intermediate drying of the

material that significantly impacts the energy

consumption.

6. Environmental Assessment

The quarrying and processing of natural stones in

general, and marble in particular, raise important

issues that relate not only to process efficiency

but also environmental impact. There are three

aspects relevant to the marble industry: energy

consumption, material waste management and

environmental pollution (gaseous and particulate

emissions, dust, noise, disturbance of natural

habitats).

The energy efficiency of the current quarrying and

processing practices has been discussed in

Section 3. However, any improvements in energy

consumption will naturally have a direct beneficial

impact to greenhouse gases emissions and as

such will improve the sustainability of the plant.

The quantification of CO2-eq emissions

associated with all stages of the marble

production process (quarry extraction,

transportation, processing) is presented in this

section.

The energy consumption of operating scenario 6,

as outlined in Table 9, was considered as a basis

for CO2-eq emissions calculations. In the case of

quarry extraction and transportation phases, the

primary energy source is diesel fuel, used to

power the quarry machinery and the trucks,

respectively, and the CO2-eq emission per final

product (kg/tile) is calculated by equation (1). The

contribution of other Greenhouse Gases, besides

CO2, in the environmental impact of diesel fuel is

negligible and amounts to less than 1% of the

total.

(kg CO2/tile) (1)

In Eq. (1), Ec is the energy consumption per tile in

kWh, obtained from Table 9, th is the thermal

efficiency of the quarry machinery and/or diesel

truck engine, assumed here to have a value of

0.4, LHV is the lower heating value of a typical

diesel fuel in kJ/kg and is the diesel fuel density

in kg/m3. Eq. (1) has been formulated on the

basis of dimensional analysis and takes into

account the crucial process para