Prof. Dr. H. Yılmaz ARUNTAŞ
Gazi University, Faculty of Technology, Department of Civil Engineering
1. INTRODUCTION
Places built underground and aboveground are generally called “structures.” As a matter of course these structures can damage the environment during their construction. It is a known fact that the construction sector is not at peace with nature and negatively affects the ecological balance. We can analyze the negative effects of the construction sector on nature under two groups: 1) Effects during the construction of structures 2) Effects by the raw materials used during the factory production of building materials.
Before constructing any structures, first an excavation work is carried out at places where buildings, airports, highways, bridges, dams and suchlike structures to be built and this process damage the natural environment and scenery. Then, following the completion of the construction a landscaping work is carried out in the building site so as to enhance the environment. This is the very method that has been used during constructions from past to present in order to meet the needs of people. Today many efforts towards improving this situation are made and these efforts yield successful results. On the other hand, raw materials used in the production of building materials such as brick, cement, lime, plaster, adhesive mortar, concrete, reinforced concrete steel, autoclaved aerated concrete, ceramic, glass, and rockwool etc. are obtained from nature. The fact that these raw materials are obtained from nature causes agricultural lands damage. Naturally the increase in the production of building materials is in parallel with the increase in the population of the world and our country. In connection with all of these, people have long been using various industrial waste as raw materials in the production of building materials in order to reduce the environmental damage and costs. The use of waste materials as raw materials reduces the amount of CO2 emissions released to the atmosphere and causing a greenhouse effect during the production of building materials. The decrease in the amount of CO emissions released to the atmosphere 2 helps reduce the global warming or the average world temperature and protect the ecological balance.
This study offers brief information on cement production, as well as fuels and alternative fuels used in cement production. A detailed analysis of this subject is reserved for another article.
2. CEMENT PRODUCTION
The word cement is derived from the Latin word caementum, which means hewn stone particles and which later began to be used to mean binder. The world’s first cement factory was built in 1848 in the UK (1). In 1824, English engineer Joseph Aspdin produced and patented a cement he called Portland cement. In the early 1850s, the first factories to produce Portland cement were established in France, Belgium, and Germany (2).
Our country, on the other hand, began to produce cement about 100 years ago, coinciding with the last years of the Ottoman Empire. Turkey’s first cement factory began its operations with the capacity of 20,000 metric ton/year in Darıca, Istanbul in 1911 at the beginning of the 20th Century. 13 new cement factories entered into service from 1950 – 1960 and the current cement factories also increased their capacities during the same period. The year 1957 saw the establishment of the Turkish Cement Manufacturers’ Association (TÇMB), which gathered all cement factories under one roof. In 1965 Turkey’s cement production reached 2 million metric tons and in 1970 cement started to be exported on a regular basis (3).
It was the 1980s when Turkey started to discuss privatization. The privatization efforts in the Turkish cement sector started in 1987 when public shares in ten cement factories – of which half of them are affiliates of Turkish Cement and Earth Industry Trade A.Ş. (ÇİTOSAN) and the remaining factories are subsidiaries of the same entity – were included in the privatization plan. Of the shares included in the privatization plan in the same year, the entire public shares in Ankara, Balıkesir, Pınarhisar, and Söke Cement, as well as the 51 percent of the public shares in Afyon Cement were sold as a block. These were followed by some other privatization efforts, and in 1998 the privatization process in the cement sector was completed with the privatization of Kurtalan Cement (4).
When we take a look at Turkey’s annual cement production we see that the production increased from an annual amount of 30 million metric tons in 2001 to 49.3 million metric tons in 2007. The annual cement production further increased in 2010 to 62.7 million metric tons, then again in 2015 to 72.8 million metric tons (Table 1). Turkey, together with Brazil, ranks in the top five among the top cement producing countries, according to 2015 world cement production data (5).
2.1. Fuels Used in the Cement Production
According to the annual report prepared by the Energy Department of the U.S. Energy Information Administration (EIA), the construction sector, with a rate as high as 39 percent, is deemed as the sector causing the most CO2 emissions among all sectors (6). The entire cement sector in the world is one of the leading sectors with a CO2 emission rate of 5 percent, according to data from 2003 (7). However when we look at the Turkish cement sector we see that the share of the cement sector in total CO2 emission is about 10 percent (8).
In general, fossil fuels are the most frequently used fuels in cement factories. These fuels are as follows:
• Coal
• Petroleum Coke
• Bituminous Schist
• Fuel Oil
• Natural Gas
• Lignite Coal
Fossil fuels used in cement production are seen as primary fuels. The main ash constituents of these fuels are silica and alumina components. These combine with raw materials to form a clinker part. This should be taken into consideration when calculating the rate of raw materials and, thus, fuels with a fixed ash content should be used however the ash content of the fuel should not necessarily be low (9).
On the other hand, cement production comes at a high energy cost resulting from the grinding process carried out particularly with clinker obtained from rotary kilns at 1400-1500°C. The reason behind this is the high amount of fuel used in order to achieve the stated high temperature. Table 2 shows the costs of the items used in the cement production. We can see from the table that the fuel and energy items constitute about 60 percent of the total cement cost. This is why the term “energy-intense process” is used for cement production.
3. ALTERNATIVE FUEL USAGE IN CEMENT PRODUCTION
Many kinds of industrial waste have long been used as raw materials or additives in the production of cement and concrete. The use of various kinds of waste as alternative fuel in the industry is, on the other hand, deemed a new approach. These kinds of industrial waste are grouped into two categories: hazardous and non-hazardous waste. Recently, solid waste called secondary, in other words, auxiliary fuels has been used as fuel in cement factories. These fuels are in the non-hazardous waste group and listed as follows:
1. Used/Waste Tires
2. Wooden Waste
3. Textile Waste
4. Plastic Waste
5. Paper/Cardboard Waste
6. Waste Oils
7. Used Solvents
8. Bleaching Earth
9. Bilge Waste
10. Contaminated Waste
11. Solvents
12. Sewage Sludge (11, 12, 13)
Medical waste, nuclear waste, batteries, and unprocessed municipal waste are banned from being used as alternative fuel. The European Court of Justice classified the use of waste as alternative fuel in cement kilns as “recovery” instead of “incineration” (14).
Advantages of using these alternative fuels:
a) Reducing the cement costs.
b) Utilizing the waste that does not dispose of in nature for thousands of years.
c) Bringing waste in the economy.
d) Preventing environmental pollution thanks to the decrease in waste landfill sites.
e) Not causing ashes/fly ashes after waste incineration in cement kilns.
f) Saving on natural raw material sources.
g) Reducing the amount of CO2 emissions, which cause a greenhouse effect, as the use of fossil fuel decreases.
h) Causing no emission in water or soil as a result of waste incineration.
Of Turkey’s 49 cement factories, 35 recycle industrial and domestic waste into alternative fuel and alternative raw material under the permissions obtained from the Ministry of Environment and Urbanization (14). The alternative solid waste used as fuel in 2009 in Turkey’s cement factories is shown in Table 3.
Data regarding the use of waste tires in cement production refers to the importance of the subject. Waste tires have been incinerated in cement kilns in Europe and particularly in Germany for over 25 years (12). In Turkey 500,000 metric tons of waste materials were used as alternative fuel sources in the cement sector in 2013. 30% of the cement factories in the EU use alternative fuel at a rate of 100% whereas 3% of the Turkish cement factories use alternative fuel at a rate of 25% (15). As you can see there is a huge difference between Turkey and the EU on this subject.
4. CONCLUSION
The use of waste is increasing more and more in developed countries, and advanced implementations are being developed regarding this subject. For instance, the level of alternative fuel usage in the cement sector of developed countries varies between 40-60%. This level is about 25-35% in developing countries. Encouraging the use of alternative fuels in the cement factories of our country will definitely do well for our country.
