Co-incineration of Municipal Solid Waste in Cement Industry

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					Proceedings of the International Conference on Sustainable Solid Waste Management,
5 - 7 September 2007, Chennai, India. pp.348-355

     Co-incineration of Municipal Solid Waste in Cement Industry
                                             Axel Seemann

                         Centre for Sustainable Development, Bangalore, India


   The aim of the paper is to introduce the use of high calorific waste components as secondary
   fuel in cement plants. For this purpose the basic ideas and requirements of co-incineration will
   be explained. This includes physical properties of the secondary fuel to be produced from solid
   waste as well as technical requirements of the required pre treatment of the waste. The highly
   water containing organic part of municipal solid waste has to be separated from the high calo-
   rific fraction, which can be used as secondary fuel. The remaining organic components can be
   used for composting or for the generation of bio gas.

   Based on experiences in Europe as well as on studies on waste generation in the City of Ban-
   galore and Karnataka, possibilities for the use of municipal solid waste as secondary fuel in
   India will be discussed in the paper.

   Keywords: Municipal Solid Waste, Mechanical Biological Waste Treatment, Recycling, Reuse,
   Anaerobic, Composting


The Indian gross domestic product (GDP) increased 2.5 times over past 2 decades. As a consequence
of increasing industrial activity and a continuous rise of incomes, there has been as well a significant
increase in waste generation in India. The present system of solid waste management in India, like any
other fast growing countries has to be adapted to these changes. Illegal dumping is a major problem
that raises significant concerns with regard to safety, property values, and quality of life in our com-

The Centre for Sustainable Development (CSD) in Bangalore has carried out studies on waste genera-
tion and the composition wastes. Based on information generated, approaches for the recycling of
municipal solid waste have been developed and adapted to Indian conditions. Especially a combina-
tion of anaerobic composting of organic parts of waste combined with the use of high caloric waste as
secondary fuel in cement plants is a very promising recycling option.


The waste from residential, commercial and institutional activities in a municipality is commonly
termed as Municipal Solid Waste (MSW). As defined in the Municipal Solid Waste Rules, 2000 mu-
nicipal solid waste includes commercial and residential wastes generated in a municipal or notified
area in either solid or semi solid form, excluding industrial hazardous wastes but including treated

                                                              Sustainable Solid Waste Management

bio-medical waste.

The quantity and the content of municipal solid waste (MSW) varies according to the socio-economic
status and cultural habits, prevailing climate, location, urban structure, density of population and ex-
tent of non-residential activities. The Centre for Sustainable Development (CSD) in Bangalore has
carried out studies on generation and composition municipal and industrial wastes. To assure repre-
sentative results, the study covered main areas of urban waste generation. From focus areas waste
samples were taken and analysed. The segregated wastes were weighed to ascertain the percentage
composition of individual waste constituents. The waste composition is shown in Figure 1.
                                                Percentage wise constituents of Municipal Solid Waste in Residential Area

                                                             Plastics               Paper       Cloth      Metals
                                                             10,75%                 6,00%       0,25%                        Paper
                                                                                                                1,25%        Metals
                                                                                                         E - waste
                                                Organic matter                                                               E - waste
                                                   81,00%                                                                    Organic

  Percentage wise constituents of Municipal Solid Waste in Commercial Area – Sample 1           Percentage wise constituents of Municipal Solid Waste in Slum area

                                                                         Plastics                                                     Plastics               Cloth
                                            Paper                                                                                                  Paper
                            Plastics                                                                                                  9,25%                  3,50%
                                                                                                                                                  12,25%             Plastics
                            12,00%          8,00%
                                                        1,00%                                                                                                        Paper
                                                           5,00%         Cloth                                                                                       Cloth

                                                                         Coconut shell
                                                Coconut shell                                       Organic matter                                                   Organic
                Organic matter                     5,00%                                               75,00%                                                        matter
                                                                         Organic matter

                              Figure 1 Composition of Municipal Solid Waste in India [Seemann 06]


In waste management there is a worldwide push towards implementing a 3R strategy: Reduce, Reuse
and Recycle. This policy puts an emphasis on energy recovery over the disposal of waste in landfills,
encouraging technologies such as mechanical biological treatment (MBT) providing a high calorific
fraction which can be used as secondary fuel.

Mechanical-biological Waste Treatment (MBT) is a technique to pre treat solid waste prior to dis-
posal. The facilities required can be operated with relatively simple equipment, i.e. with a low degree
of automation and modest expenditures on process technology and structures. However, depending on
the anticipated results of treatment and on financial and other conditions it is also possible to imple-
ment highly sophisticated and enclosed facilities with optimised process technology.

The use of MBT in conjunction of using the high calorific fraction as secondary fuel could present a
number of environmental advantages. In the field of recycling, there would be a reduction of odours
and emissions arising from waste handling and treatment [Senkpiel/Ohgke 98], as well as an improved
recycling of materials such as metals and finally the possibility of converting the organic fraction into
soil conditioners (or compost). The energy recovery through production and use of secondary fuel in

                            Co-Incineration of Municipal Solid Waste in Cement Industry

cement kilns is a major advantage saving natural resources and reducing green house gas emissions.

MBT consist of the two main technical elements the den mechanical treatment ant the biological
treatment. The configuration of MBT plants as well as the chosen equipment can differ extremely.
MBT plants can incorporate a number of different processes in a variety of combinations. The "me-
chanical" element is usually an automated mechanical sorting stage. This either removes recyclable
elements from a mixed waste stream, such as metals, plastics and glass or processes them. It typically
involves factory style conveyors, industrial magnets, eddy current separators, drum sieves, shredders
and other tailor made systems.

The "biological" element refers to either:
   Anaerobic digestion,
   Aerobic composting or to
   a combination of both techniques

In general it can be said that processing biodegradable waste either by anaerobic digestion or by
composting, MBT technologies help to reduce the contribution of greenhouse gases to global warm-
ing. But in anaerobic digestion being the more efficient option.

Figure 2 shows flow sheeting diagrams for main MBT configurations. The simplified dry stabilisation
technique on the right hand side can be an option to introduce the MBT technique in emerging

    Conventional MBA Technique                 Dry Stabilisation Technique       Simplified Dry Stabilisation

          Municipal Solid Waste                     Municipal Solid Waste              Municipal Solid Waste

           Mecanical Treatment                       Mecanical Treatment

       Low                  High                     Biological Treatment                 Biological Treatment
     Calorific             Calorific
     Fraction              Fraction

                                                   Mecanical PostTreatment            Mecanical PostTreatment

    Biological            Secondary
    Treatment               Fuel

                                                   Low               High             Low                 High
                                                 Calorific          Calorific       Calorific            Calorific
    Mecanical                 Co-                Fraction           Fraction        Fraction             Fraction
      Post-               Incineration

     Landfill              Landfill             Recycling/         Secondary       Recycling/           Secondary
                            (Ash)                Landfill            Fuel           Landfill              Fuel

     Figure 2 Flow Sheeting Diagrams for Main MBT Configurations [Nelles Et Al 07], [SWMPP 06]

                                  Sustainable Solid Waste Management

countries, having a high amount of organics in their municipal solid waste. This technique is currently
in a trial stage in Thailand by the Thai-German Solid Waste Management Project (TWMP), Bangkok
a cooperation of the Ministry of Natural Resources and Environment (MoNRE) in Thailand and the
German Technical Cooperation (GTZ)


The waste composition as well as the climatic conditions in India differ very much from European
countries were MBT-Techniques are commonly applied. First experiences with the introduction of
MBA-techniques under Asian conditions have been made in Thailand by the Thai-German Solid
Waste Management Project (TWMP) in Bangkok a cooperation of the Ministry of Natural Resources
and Environment (MoNRE) in Thailand and the German Technical Cooperation (GTZ).

To use the municipal solid waste maintained in the MBT for other applications the material was seg-
regated into three fractions by sieving drums: diameter less than 10 mm, between 10 and 40 mm and
diameter more than 40 mm. The sieved products have been investigated for composition, physical-
chemical characteristics as well as for its heating value.

The results of the analysis of the physical and chemical composition of the municipal solid waste after
MBT are shown in the figures below. Figure 3 compares the composition of the high calorific fraction
after MBT of 5 and 9 months. In respect of the main components the composition is very similar after
5 month and 9 month treatment. The content of plastic, which has a high calorific value is 72 % after 5
months and 80 % after 9 months treatment.

  Figure 3 Composition of the High Calorific Fraction after 5 Months (Left) and 9 Months (Right) MBT
                                             [ERC/GTZ 07]

The physical and chemical characteristics of the solid waste treated by a 5 and 9 months MBT process
is shown in Table 2. It is obvious that the characteristics of 5 months MBT are about the same as that
for a 9 months treatment. The fine fraction below 10 mm is mainly compost, while the fraction bigger
than 40mm contains the high calorific materials, which is indicated by the parameters density and
volatile solids. While the density is approx 132 to 143 kg/m3 compared to 590 to 816 kg/m3 for the
fraction less than 10mm, the content of volatile solids is much higher in the high calorific fraction
(790 to 842 mg/g) to 215/175 mg/g in the fraction less than 10mm.

                        Co-Incineration of Municipal Solid Waste in Cement Industry

For most of the parameters the concentration of heavy metals in the treated solid waste is lower than
the limiting values for secondary fuels in Europe (see Table 3). Arsenic is the only exception exceed-
ing the limits. The high concentration of aluminium and iron in the materials is even useful for cement
production, which needs these metals as additives for the clinker. The most critical heavy metal, mer-
cury, is within the limits for secondary fuels. Therefore, the use of the high calorific fraction as fuel in
cement production seems to be feasible. The is fortified by the high calorific value of the material with
a diameter greater than 40 mm which is much higher than for the other fractions and approximately at
the same level as the heating value of diesel fuel.

    Table 2. Physical and Chemical Characteristics After 5 and 9 Months MBT Process [ERC/GTZ 07]
                                     5 months MBT                            9 months MBT
        Parameter                       10 mm -   > 120                         10 mm -   > 120
                             < 10 mm                                 < 10 mm
                                         40 mm     mm                            40 mm     mm
 Phisical & chemical
 Density (kg/m3)               590          589             132        816            673         143
 Moisture content (%)           29           37              16         27             25          13
 Total solids (mg/g)           712          720             843         31            748         879
 Volatile Solids (mg/g)        215          244             790        175            336         841
 Ash Content (mg/g)            784          756             210        825            664         159
 Organic Carbon (mg/g)         371          268             110        300            195         114
 Hydrogen (mg/g)                14           16              53         12             22          56
 Nitrogen (mg/g)                21           16               5         13              9           5
 pH                              7.9          7.6             8.1        8              8.3         7.7
 Chloride (mg/g)                 8           10               9          6              7           7
 Sulfate (mg/g)                 10           11               1          6             10           4
 Heavy metals
 As (mg/kg)                    223          132              49        172          138           30
 Cr (mg/kg)                     24           35            1932         63           31           13
 Fe (mg/kg)                   2058         2140            1678       2127         1820         1615
 Al (mg/kg)                  15153        40479            4248      18268        50228         5092
 Hg (mg/kg)                      1.1          0.31          ND           0.56         0.37         0.46
 Cu (mg/kg)                    143          121              33        196           96           96
 Mn (mg/kg)                    221          136             109        310          202           68
 Ni (mg/kg)                    ND           ND              ND         ND           ND           ND
 Cd (mg/kg)                      1.7          0.9           ND         ND           ND           ND
 Pb (mg/kg)                     90          141.4            13.3      130.7         64.9         36.1
 Calorific value
 As collected (J/g)           6050        14603            33168      5132        18196         36867
 Moisture free (J/g)          6122        15234            33801      5680        18810         38230

                                  Sustainable Solid Waste Management

         Table 3. Maximal Content of Heavy Metals in Secondary Fuels in Europe [MUNLV 05]
               Parameter                                  Content of Heavy Metals
              in mg/kg TS                          Average                      Maximal
 Cadmium                       Cd                     4                            9
 Thallium                      Tl                     1                            2
 Mercury                       Hg                    0,6                          1,2
 Antimony                      Sb                    50                           120
 Arsenic                       As                     5                           13
 Lead                          Pb                 70 – 190                     200 – 400
 Chromium                      Cr                 40 – 125                     120 – 250
 Cobalt                        Co                     6                           12
 Copper                        Cu                120 – 350**                  300 – 700**
 Manganese                     Mn                 50 – 250                     100 – 500
 Nickel                        Ni                    50                           100
 Vanadium                      V                     10                           25
 Tin                           Sn                    30                           70


Cement production has very high energy requirements, which typically account for 30-40% of the
production costs (excluding capital costs) [Coprocem 06]. Traditionally, the primary fuel has been
coal, but a wide range of other fuels is also used, including petroleum coke, natural gas and oil. In
addition to these fuels, various types of waste can be used as fuel. Co-processing refers to the use of
waste materials in industrial processes, such as cement production. The co-processing of selected
waste materials in the cement industry is a proved alternative and possible solution for treatment of
high caloric wastes. Co-processing has the following characteristics during the production process:
   The alkaline conditions and the intensive mixing favour the absorption of volatile components
   from the gas phase. This internal gas cleaning results in low emissions of components such as SO2,
   HCl and, with the exception of mercury and thallium, this is also true for most of the heavy metals.
   The clinker reactions at 1450°C allow incorporation of ashes and in particular the chemical bind-
   ing of metals to the clinker.

Figure 4 shows the feeding points and the temperature profile of a rotary kiln for clinker production.
The Primary firing system can be used by macerated materials as lignite, treated fractions of waste,
scrap wood as well liquid waste as used oil, solvents and heavy fuel oil. The secondary firing can be
used for tyres, paper and sewage sludge. Beside the physical requirements on the fuel the temperatures
in the kiln limit the used of secondary fuels. While some plastics, tyres and some kind of sludges can
be fired at the secondary firing, Fuels containing hazardous substances have to be fired at the main
burner. Only the use in the main burner ensures that hazardous substances are destroyed due to the
high temperatures above 1450° C combined with a residence time of over 2 seconds.

A major restriction for the use of secondary fuels is the content of chlorine. High chlorine contents
lead to corrosion problems in the cement plant but also to problems at the connection of the pre-heater

                        Co-Incineration of Municipal Solid Waste in Cement Industry

to the cement kiln. Chlorine containing plastics as PVC are melting at low temperatures. The melted
plastic can hamper or even block the material flow form the pre heater into the cement kiln. Due to
this problem cement industry in Europe is limiting the content of chlorine in secondary fuel to 0.3 to
0.5 mass-%, depending on the company and cement kiln. These limits are even stricter than the limit-
ing values set by the authorities, which are allowing a chlorine content of 1 mass-%.

                               Figure 4 High Calorific Fraction after BMT

                                        1                              Primary firing system
                                             raw meal dosage           o Macerated material

                                                                        - lignite
                                                                        - treated fractions of
                                                                          industrial waste
                                                                        - scrap wood
       evaporation                 1
                                                 Monitoring            o Liquids
       cooler          VDK                       firing temperatur       - waste oil, used solvents
                                                                         - heavy fuel oil
            150°C                            850°C
                                                                                      Main Burner
   Secondary firing system                                       3
                                                                                  2             1
   - old Exhaust gas to electro-
   - paper sludge
         static precipitator                      1000°C
   - sewage sludge

 Figure 5 Feeding Points and Temperature Profile of a Rotary Kiln with Cyclone Preheater [Ebertsch 07]


The high calorific fraction of municipal solid waste can be used as secondary fuel in cement industry
according to its physical composition. Concerning the chemical properties of the material there are
still some open points. The major concern is the content of chlorine arising from PVC in the waste. As

                                   Sustainable Solid Waste Management

a next step towards the use of high calorific fraction of municipal solid waste in cement industry, the
PVC content has to be analysed. This analysis is carried out by CSD but till now the results are not
available. PVC is a limiting material in secondary fuels due to its low melting point and especially
because chlorine can react to dioxin and furan, which are extremely poisonous substances.

In order to obtain the high calorific fraction of municipal solid waste a pre treatment of the waste is
absolutely required. Biological mechanical treatment BMT is a very good option combining aerobic or
anaerobic composting with mechanical cutting and segregation. BMT generates a high calorific frac-
tion that can be used as secondary fuel. The application of BMT with Asian waste composition and
climatic conditions in Thailand showed promising results. On the one hand BMT converts the organic
fraction into a stable and non reactive material, which can be land filed without risk. In some cases the
organic can even have the quality to be used as manure. The use as mature requires a very strict moni-
toring and management of the waste input stream into the BMT process.

A broad application of BMT combined with the use of the high calorific fraction as fuel in cement
kilns could solve more than one problem of infrastructure in India. There is the general problem of
proper management of municipal solid waste including avoidance of wild dumping and other negative
effects for the environment like ground water contamination by leaking pump sides and landfills. But
the concept is also a solution for another problem. Secondary fuel can be used by the high energy
demanding Indian cement industry saving the natural coal resources in India.


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