Municipal solid waste in Mostaganem city (Western Algeria)

Municipal solid waste in Mostaganem city (Western Algeria)

Waste Management 29 (2009) 896–902 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman Muni...

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Waste Management 29 (2009) 896–902

Contents lists available at ScienceDirect

Waste Management journal homepage: www.elsevier.com/locate/wasman

Municipal solid waste in Mostaganem city (Western Algeria) N. Guermoud, F. Ouadjnia, F. Abdelmalek, F. Taleb, A. addou * Laboratoire des Sciences et Techniques de l’Environnement et de la Valorisation (STEVA), Departement de Genies des Procedes, Director of STEVA Laboratory, University of Mostaganem, 27000 Mostaganem, Algeria

a r t i c l e

i n f o

Article history: Accepted 24 March 2008 Available online 21 July 2008

a b s t r a c t The management of municipal solid waste (MSW) and valorisation is based on the understanding of MSW composition by its categories and physicochemical characteristics. In this study, we characterize and determine physicochemical parameters (density, fire loss, electric conductivity, average pH, moisture level, lower calorific value (LCV), total and organic carbon, and nitrogen) in order to establish MSW valorisation models for Mostaganem city (located in Western Algeria). The results show that organic matter represents 64.6% of waste, followed by paper-cardboard 15.9%, plastic 10.5%, glass 2.8%, textile 2.3%, metals 1.9%, and diverse materials 2%. These statistics are similar to results from developing countries, especially if organic matter, paper and plastic are taken into account, but differ from developed countries. This reflects the difference in lifestyle and consumption behaviour between the two communities. The parameters used to determine the possible valorisation model had the following average values: fire loss (63%); ash (37%); pH (6.1); electric conductivity (2.39 ms cm1); total carbon (29.5%); nitrogen (1.5%); LCV (1028.6 kcal/kg), density (0.36), C/N (19.7) and moisture level (58.9%). The study shows that 31.1% of paper-cardboard, plastic, glass and metal wastes are recyclable. Incinerating MSW, with energy recovery, was a poor option because of the weak LCV (1028.6 kcal/kg). However, MSW produced a good methane yield of up to 1852.4 equivalent tons of oil per year. The agricultural benefits, C/N ratio values, levels of moisture and pH and the Tanner diagram all supported compost production. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Economic development contributes to improvements in life standards. However, it also induces environment degradation with long-term consequences for both people and nature. Eradicating poverty and reaching desirable levels of economic and industrial development seem to conflict with environmental considerations. The real problem, however, is the lack or inadequate level of environment management at a town level. The industrialization of Algeria improved socio-economic conditions but triggered a massive urban drift towards towns. This phenomenon led to urban anarchy and an increase in MSW production. It is known that waste is not a threat to the environment if carefully collected and treated. However, it is clear that poor MSW disposal and management systems are direct threats to nature and health (Mayster and Duflon, 1994; Dotreppe and Grisaron, 1986). In industrialized countries, MSW management is an important and competitive economic activity. However, in Algeria (31.5 million inhabitants in 2002 with annual growth rate of 2%), the problem is far from resolved if compared to other developing countries. The present difficulties are mainly due to a lack of organization, methodology, education and information (MATE, 2003; Girod * Corresponding author. Tel./fax: +213 45 20 21 06. E-mail address: [email protected] (A. addou). 0956-053X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2008.03.027

et al., 1982). The absence of MSW treatment infrastructure and experts make it difficult to manage an increasing amount of industrial and municipal waste. In the last three decades, the economic and social development of Algeria did not take into account the protection of the citizen and the environment. Nearly 325,100 tons of special industrial wastes (asbestos, pesticides, mercury, cyanide, expired pharmaceutical products) are produced in Algeria each year. Special industrial wastes are generated by four sectors: hydrocarbons (34%), chemistry, rubber and plastic (23%), metallurgy (16%) and mines (13%). Packaging represents a major portion of waste up to 200,000 tons per year. Almost all (95%) packaging is made from plastic, with 5% made from metal, while only 0.02% is recycled. Healthcare wastes reach 125,000 tons per year, of which 53.6% is general waste, 17.6% is infectious waste, 23.2% is toxic waste and 5.6% is special waste. Each year, Algeria produces 8.5 million tons of MSW, a rate of 0.9 kg/inhabitant/day for urban zones and 0.6 kg/inhabitant/day for rural zones. Waste disposal reaches 92% in urban zones and 65% in rural zones. It should be noted that 96.8% of Algerian MSW is dumped openly. Only 2% of waste is recycled, 1% is used as compost and 0.2% is disposed in landfills. There are 3000 open dumpsites in Algeria. There are 350 sites located near big cities, which represent a surface area of 150,000 ha. Usually, these sites are close to agricultural facilities or rivers (MATE and PROGDEM, 2003; METAP, 2002). With the current MSW

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management system in Mostaganem city, all of the collected MSW is disposed of in open dumpsites in the nearest available low lying areas and wastelands of the city’s outskirts. Selection of these disposal sites solely depends on availability, and not on scientific or socio-environmental landfill criteria. MSW is disposed of in an uncontrolled manner and daily cover material is not applied regularly. The consequences of such mismanagement cost up to 0.32% of the PIB, with 0.19% of the PIB as health costs and 0.13% of the PIB as economic losses (recycling and valorisation potentials not achieved) (MATE and PROGDEM, 2003; METAP, 2002). Recently, the Algerian government decided to create 65 sanitary landfill sites, resulting in the reorganisation and update of the waste disposal system (including compost and methane production from organic waste and incineration). In this study, our objective is to characterize the physical composition of the MSW in Mostaganem city, located in Western Algeria. This will help us understand the physical and chemical parameters of the city’s waste. The results will allow us to propose the best method of MSW valorisation in Mostaganem city. Fig. 1. Algeria map.

2. Composition of waste in Mostaganem city MSW is a heterogeneous mixture of products with very different physicochemical properties. Its composition is variable and depends on the nature of the products, customs of the population, the relative level of quality of life and the type of city. Knowledge of MSW composition is essential for the determination of valorisation options such as compost production, recycling, and incineration. Such knowledge also allows for environmental protection. 2.1. The average composition of MSW The composition of MSW in Mostaganem city was obtained from waste generated during the study period and was classified into six categories. The average composition is given in Table 3 and Fig. 2. Six major categories of waste were identified: organic matter, paper-cardboard, plastics, glass, metals, textiles and diverse. Organic matter was the predominant category and represented 64.6% of waste collected. The other categories were represented as follows: paper-cardboard (15.9%), plastic (10.5%), glass (2.8%), metals (1.9%), textiles (2.3%) and diverse (2%). Demolition and construction waste were not taken into account because they are disposed of in uncontrolled open-air sites. The high consumption of fruits and vegetables by the city’s inhabitants (a common characteristic of developing countries), could explain the preponderance of organic matter in Mostaganem’s waste. The study of waste composition by zone (Table 3) shows that the level of paper-cardboard is higher in zones 1 and 6, with 17% and 22.3%, respectively. This is explained by the high concentration of shops, administrative buildings, and schools in these zones. The large numbers of restaurants, hotels and cafes explain the high proportion of plastic in the city centre (zone 1). Zones 2 (the old city) and 3 (the new city) are characterized by a high level of glass (3.5% and 4%), which could be explained by the frequent use of packages and bottled drinks. 2.2. Comparative study The composition of MSW can vary from one country to another, from one region to another, and from one zone to another inside a city. This is true for Algerian cities as well as cities around the world (Aloueimine, 2006; Mbuligwe, 2002; Mohee, 2002). In order to understand MSW in Mostaganem city, we did a comparative

Diverse 2% Textiles 2.3 %

Metals 1.9 %

Glass 2.8 % Plastic 10.5 % Paper, cardboard 15.9%

Organic matter 64.6%

Fig. 2. Average composition of MSW in Mostaganem city.

study between Algerian cities and between developed and developing countries (ANAT, 2001). 2.2.1. Comparison of Algerian cities The results from the comparison of Algerian cities are shown in Table 4 (ANAT, 2001). In all Algerian cities, organic matter is the most predominant waste category. In littoral cities (Mostaganem, Bejaia and Annaba), the level of organic matter varied between 64.6% and 69.4%. However, this level increased in cities far from the sea, such as Tlemcen (71%) and Djelfa (83.5%). Mostaganem, a northern city, is characterized by a high level of paper (15.9%) due to the existence of a paper factory in the area. However Djelfa, a southern town, produces a much smaller amount of paper-cardboard (7.9%). This is because life styles in the north and the south of the country are different and southern people use less packaging and newspaper. Bejaia is characterized by a high level of plastics (12.3%), due to the existence of a plastic factory in the region. Similar to the results for paper waste, Djelfa has a low level of plastic (2.4%) for the same reasons mentioned above. Metals, glass and textiles vary from 3% to 1% without major differences among cities. 2.2.2. Cities in developing and industrialized countries The composition of MSW varies from one country to another without a clear correlation with wealth. Nevertheless, there is a difference in the nature of MSW between developing and industrialized countries. The main difference is the high level of organic matter in developing countries, sometimes reaching 60% (except Istanbul (36.1%) and Nouakchott (4.8%)). In Mauritania, organic matter is used as animal food (Aloueimine, 2006). In comparison,

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Table 1 Quantity of waste generated by day and study zone Zone

Zone 1

Zone 2 Zone 3 Zone 4 Zone 5 Zone 6

Sector

1 2 3 4 5 6 7 8 9 Total

Designation

Table 4 Waste composition of some Algerian cities (%)

Surface (ha)

Population 2003–2004

City centre BeymoutBelvedere Saint Jules Tigditt

81 130

11,197 13,015

6.83 7.94

74 80

11,326 15,588

6.91 9.51

0.61

CIASalamandre Chemouma5 Juillet El Houria Raisin ville ALNKharouba

278

11,691

7.13

0.61

120

12,131

7.40

0.61

85 180 280

14,594 22,770 22,078

8.90 13.89 13.47

0.61

1308

134,390

81.98

0.61

Mostaganem city

Quantity of waste generated (T/d)

Ratio (kg/ inh/d) 0.61

0.61

Table 2 Waste production in some cities Country

Town

Waste production (kg/inh/d)

References

Algeria

0.62 1 0.89

This study Kehila (2005) ONEM (2001)

Tunisia Jordan

Mostaganem Algiers Grand Casablanca Rabat Tunis Amman

0.60 0.8 0.85

Turkey Mauritania Brazil Mexico

Istanbul Nouakchott Uberlândia Guadalajara

0.95 0.21 0.51 0.51

Cameroon

0.85 0.37 0.62 0.55

France Spain Greece

Yaounde Bafousam Ouagadougou Bobo Dioulasso Paris Madrid Athens

ONEM (2001) METAP (2002) Abu-Qudais and AbuQudais (2000) Metine et al. (2003) Aloueimine (2006) Fehr et al. (2000) Bernache-Perez et al. (2001) Ngnikame (2000) Ngnikame (2000) Tezanou et al. (2001) Desseau (1999)

USA

New York

2

Marocco

Burkina Faso

1.51 1.59 1.21

Aina (2006) Moldes et al. (2007) Mastro and Mistretta (2004) Aina (2006)

Table 3 Waste composition by zone (%) Category Organic matter Cardboard Plastics Metals Glass Textiles Diverse Total

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

Zone 6

54.9

55.0

65.5

70.9

72.3

69.0

64.6

17.0 20.5 1.0 2.9 2.9 0.8

15.3 13.1 4.1 3.5 4.0 5.0

13.0 7.0 3.5 4.0 3.0 4.0

15.2 8.2 1.4 2.0 1.6 0.7

12.8 9.5 1.4 2.0 1.0 0.8

22.3 4.5 0.3 2.4 1.0 0.5

15.9 10.5 1.9 2.8 2.3 2.0

100

100

100

100

100

100

Average

100

the level of organic matter is around 30% in industrialized countries (Table 5). Generally, the level of paper-cardboard represents differences in socio-cultural lifestyles. In industrialized countries, packaging,

Categories

Mostaganem

Bejaia

Annaba

Tlemcen

Djelfa

Organic matter Cardboard Plastics Metals Glass Textiles Diverse

64.6 15.9 10.5 1.9 2.8 2.3 2.0

69.4 11.1 12.3 2.7 0.7 3.3 0.5

68.2 12.6 11.2 3.7 1.1 2.1 1.1

71.0 11.0 11.0 3.0 1.0 2.0 13.0

83.5 7.9 2.4 1.7 1.2 1.4 1.9

newspapers, magazines, and leaflets are used frequently. In Nouakchott, paper-cardboard is used as animal food. Plastic is variable in developing countries and seems stable in industrialized countries. Only Toronto (Canada) produces a large quantity (20.3%) of plastic, and no large differences are observed in other cities. People in developing countries try to reach the level of plastic use found in industrialized countries. Metals, being potential pollutants, are scarce in all countries. Interestingly, industrialized countries generate more glass than developing countries. This is due to nutritional practices and the tendency towards a unification of the quantity rejected. Only France produces a large quantity of glass (13.1%), understandable given that country’s levels of wine production. The composition of MSW varies according to cultural habits, economic status, urban structure, density of population, and extent of commercial and industrial activity. This comparative study confirms the numerous results obtained on lifestyle differences of the two population types, the role of weather (higher production of fruits and vegetables in summer), food processing activities and socio-cultural status. 3. Materials and methods 3.1. Study area Mostaganem city is located about 350 km west of Algiers. It is limited by the Mediterranean Sea from the north and by Oran (Algeria’s second city) (Fig. 1). It has a surface area of 2269 km2 with 717,054 inhabitants, of which 147,022 inhabitants live in Mostaganem city itself (2006). It is a littoral town with 120 km of coastline. The climate is semi arid, mild in winter and slightly humid at more than 500 m. Rainfall is irregular and varies between 250 and 500 mm/year. The average temperature is 18 °C near the coast and 24 °C inland (TAD, 2004). Mostaganem city is an important tourist attraction in Western Algeria. There are 32 beaches along the coast, 19 of which are authorized for swimming. As far as tourist infrastructures are concerned, Mostaganem has 7 urban hotels with 394 beds, 5 seaside resort hotels with 128 beds, 3 tourist residences with 387 beds, 13 family centres with 2550 beds and 19 holiday colony centres with 8442 beds, totalling 11,900 beds. 3.2. Source generation of the MSW Open dumpsites in Mostaganem are not equipped for the direct determination of waste quantities. The calculation of quantities is undertaken by the cleaning and environment protection department of Mostaganem. The activities and services generating MSW in Mostaganem are (ANAT, 2001):  73 economic units.  6228 trade centres.

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N. Guermoud et al. / Waste Management 29 (2009) 896–902 Table 5 Composition (%) of MSW in some world cities Country

City

Organic matter

Cardboard

Plastics

Metals

Glass

References

Algeria Morocco Jordan Turkey Tunisia Mauritania Guinea France Portugal Greece Canada

Mostaganem Agadir Amman Istanbul Tunis Nouakchott Labe Paris

64.6 65–70 63 36.1 68 4.8 69 28.8 35.5 31.7 30.2

15.9 18 11 11.2 11 6.3 4.1 25.3 25.9 23.1 29.6

10.5 2–3 16 3.1 7 20 22.8 (+textile) 11.1 11.5 11.8 20.3

1 .9 5.6 2 4.6 4 4.2 1.4 4.1 2.6 2.7 2.1

2.8 0.5–1 2 1.2 2 4 0.3 13.1 5.4 8.3 2

This study ONEM (2001) Abu-Qudais and Abu-Qudais (2000) Manassero et al. (1997) Hafid et al. (2002) METAP (2002) Matejka et al. (2001) Aina (2006) Magrinho et al. (2006) Mastro and Mistretta (2004) Vogt et al. (2002)

Palermo Toronto

 3 covered markets, 1 weekly market, 3 daily markets of fruits and vegetables and 5 shopping centres.  1 hospital, 2 polyclinics, 4 health centres and 3 private clinics with a global capacity of 1200 beds.  1 professional centre (CFPA) with 900 students.  4 university residences with a global capacity of 7500 beds.  8 secondary schools serving up to 700 meals/day.  1 university with 22,000 students.

3.3. Collection of samples The study was completed in zones subdivided into 6 areas of 9 sectors. Collection was performed by the municipal cleaning department of Mostaganem, from whom the waste was obtained for analysis. The classification of waste into categories was done manually. Categories selected were: organic waste (able to ferment), plastic, paper-cardboard, glass, metals, textiles and diverse. The study was conducted from November 2003 to July 2004. Six, 400-kg samples were collected from each sector. Waste samples were obtained randomly from municipal waste collection vehicles. 3.4. Physical composition of MSW in Mostaganem The average composition of waste was calculated according to the results collected from each sector sample. After sampling, sorting was performed in order to classify waste into the categories mentioned above. First, removed large objects such as bottles, paper-cardboard, containers, and packaging were removed. Then the smaller objects were separated. During this operation, plastic bags were used to separate objects and each category was weighed after sorting was complete. In order to prepare laboratory samples, safety was a priority (masks, gloves, glasses); scissors and knives were used in order to reduce waste material size without affecting the material moisture. Laboratory sampling was conducted according to the quarter method (sorting out, drying, grinding) (Gillet, 1985). 3.5. Chemical analysis – The determination of moisture level (%M), ash level (%A), and volatile matter level (%VM) was conducted according to ASTM E790, E830 and E897 standards. – The determination of carbon (%C), hydrogen (%H) and nitrogen (%N) was conducted according to ASTM E777 and E778 standards. – Higher calorific value (HCV) was measured experimentally by a calorimetric bomb (IKA C 4000 A) according to ASTM E-711 standards.

– The level of moisture (% M) was determined after baking the sample for 24 h at 105 °C (Memmert type). – Fire loss (volatile matter) was determined after burning at 550 °C for 2 h in a Nabertherm (L3/C6 model) oven. – The level of ash was calculated according to this equation: (% Ce = 100  % VM). – Organic carbon was determined by the most current method (Scmacher, 2002). – Total nitrogen was determined by the modified Kjeldhal method (Aubert, 1978). – Heavy metals (lead, cadmium) were determined by ICP-AES (Jobin Yvon Ultima C). – Mercury level was determined by the Perkin–Elmer 50B Mercury Analyzer System.

4. Results and discussion 4.1. Quantity of waste generated A clear understanding of MSW production is important to achieve adequate levels of disposal, collection, treatment and valorisation. In order to obtain this understanding, the quantity of MSW was estimated by sector by the cleaning municipal department of Mostaganem. The quantity of MSW by sector and by day is given in Table 1. The estimation takes into account the sector surface and human population. The municipal department collects 62% of MSW, with the remainder being managed by five private operators. From 1983 to 2006, the MSW production of Mostaganem increased from 65 tons to 91 tons per day with a population growth rate of 2%, an increase of nearly 50%. During our study period in 2003–2004, the quantity of waste generated by Mostaganem city was 81.98 tons per day, a rate of 0.61 kg/inhabitant/day. In 2006, for a population of 147,022, the production of waste increased to 91 tons per day, a rate of 0.62 kg/inhabitant/day (TAD, 2004; ANAT, 2001). The average quantity of generated waste is 0.9 kg/inhabitant/ day in large Algerian towns and 0.6 kg/inhabitant/day in middle size towns (METAP, 2002). The results found for Mostaganem MSW confirms the small size of the city as well as its agricultural character. A comparison of the MSW differences between towns is presented in Table 2. The quantity and nature of waste generated is a socio-economical indicator and a function of the degree of a nation’s development. The big difference in waste production between cities in developed countries (1.5 and 2 kg/inhabitant/day) and cities in developing countries (generally less than 1 kg/inhabitant/day) is noteworthy. This is due to consumption modes. Industrialized countries consume more products and use more packaging. There

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are also differences in waste production between cities and suburbs in developing countries. Within the same city, there are differences from one sector to another, according to the quality of life of the population (Ojeda-Benitz et al., 2003). Other factors (weather, tourism, migration) could also affect MSW production (Aloueimine, 2006; Ngnikame, 2000; De Vries et al., 2001). 4.2. Evolution of MSW composition in Mostaganem city The composition of MSW in Mostaganem city has evolved during the last two decades (Table 6) (ANAT, 2001). Between 1983 and 2004, the fraction of organic matter decreased 17%, from 78% to 64.6%. Paper-cardboard and plastic increased to 26% and 29%, respectively. Metals did not vary and glass increased slightly from 1.1% in 1983 to 2.8% in 2004. This is due to international free trade and the massive use of disposable glass bottles. The evolution of the nature and type of MSW (decrease in organic matter, increases in paper-cardboard, plastic, glass, and stabilization of metals) is the consequence of the Algerian citizen’s desire to reach the lifestyle of industrialized countries. 5. Valorisation of MSW Knowledge of the physicochemical parameters of MSW allows the evaluation of the potentially harmful risks of pollution on the environment and human health. Also, it allows determination of the best ways for the valorisation of waste. The most important conditioning parameters for valorisation are: (i) the level of moisture, (ii) the LCV, (iii) the amount of ash, (iv) the volatile matter content, (v) the C/N ratio (vi) and the pH. The results given in Table 7 show that the level of moisture and volatile matter (representing the actual quantity of organic matter) of paper-cardboard, plastic and organic matter in Mostaganem is very high, confirming the high level of carbon in these compounds. Organic matter contains up to 29.5% of carbon. The amount of ash (26.9–37%) suggests a good level of mineral matter. Total nitrogen, in the form of nitrates, nitrites and ammonium, represents 1.5% of dry matter. In order to establish a proper, and long lasting, plan for landfill sites, waste density was taken into account. Waste density varies according to its nature and the country disposing of it. For developing countries, density varies from 0.35 to 0.5 tons/m3. The density (tons/m3) of Mostaganem city’s waste is around 0.36; Burkina-Faso is 0.63; 0.35 for Morocco; 0.3 for Tunisia (Tezanou et al., 2001; Aina, 2006). Waste density is higher in developing countries than in industrialized countries (Aina, 2006). 5.1. Potentially recyclable waste The recyclable matter (paper-cardboard, plastic, glass, metals) contained in Mostaganem’s MSW was determined from generated quantities per study zone and represented 31.1% of MSW. This value is close to that found in other developing countries: (i) Amman (Jordan) 31% (Abu-Qudais and Abu-Qudais, 2000) and (ii) Istanbul (Turkey) 34% (Metine et al., 2003). However, it remains negligible Table 6 Evolution of MSW composition in Mostaganem city (%) Categories

1983

2001

2004

Organic matter Cardboard Plastics Metals Glass Textiles Diverse

78.0 12.6 2.7 2.2 1.1 3.4 –

77.5 13 7.5 1.5 0.5 – –

64.6 15.9 10.5 1.9 2.8 2.3 2.0

Table 7 Physicochemical analysis of Mostaganem MSW Parameter

Organic matter

Cardboard

Plastic

pH % Moisture % Volatile matter % Ashes % Carbon % Nitrogen % Hydrogen HCV (kcal/kg) C/N Pb ppm Cd ppm Hg ppm

6.1 58.9 63 37 29.5 1.5 2 1490 19.7 0.07 0.06 0.02

– 9.5 73.2 26.9 – – – – – – – –

– 3.7 64.9 35.1 – – – – – – – –

when compared to industrialized countries: (iii) Palermo (Italy) 45.9% (Mastro and Mistretta, 2004); (iv) Paris (France) 53.6% (Aina, 2006); (v) Toronto (Canada) 54% (Vogt et al., 2002). This difference comes from the fact that, in industrialized countries, the amount of organic matter is low (35–40%) and is replaced by other easily recyclable matter (paper-cardboard, cans, plastic, glass). Recycling is a common occurence in industrialized countries but is negligible in Algeria (0.1%). 5.2. Energy content of MSW The higher calorific value (HCV) of waste samples was determined by calorimetric measurement. The value found is 1490 kcal/ kg. In order to calculate the LCV, we used Eq. (1) (Khan et al., 1991)

LCV ¼ HCV  6ðM þ 9HÞ ðkcal=kgÞ

ð1Þ

where M is the total waste moisture and H is the total hydrogen contained in MSW. Using Eq. (1), we obtain

LCV ¼ 1490  6½58:9 þ 9ð2Þ ¼ 1028:6 kcal=kg The low heat value, necessary to evaluate the amount of MSW to be incinerated with energy recovery, has a lower value than predicted (1700 kcal/kg) for energy valorisation. The value obtained for Mostaganem’s MSW indicates that incineration with energy recovery is not possible. However, the introduction of paper and plastic into the HCV calculation from Eq. (2) allows us to increase this value. Thus, the new higher heating value would be

HCV ¼ 0:051½OMW þ 3:6PWÞ þ 0:352ðPLWÞ ðMJ=kgÞ

ð2Þ

where OMW = weight in % of organic matter; PW = weight in % of paper; and PLW = weight in % of plastic. Using Eq. (2)

HCV ¼ 0:051½64:6 þ 3:6ð15:9Þ þ 0:352ð10:5Þ ¼ 9:906 MJ=kg This is equivalent to 2370.8 kcal/kg The application of Eq. (1) allows for the calculation of the new LCV

LCV ¼ 2370:8  6½58:9 þ 9ð2Þ ¼ 1909:4 kcal=kg This value is superior to 1700 kcal/kg. Consequently, with a level of moisture equalling 58.9%, the LCV calculated with plastic and paper allows for incineration with energy recovery. In order to use this valorisation, Mostaganem city should have centres for waste sorting. At the present time, Mostaganem city does not have such facilities. 5.3. Organic matter valorisation 5.3.1. Methane production (biogas formation) Methane production is the degradation of organic matter by microbial flora in the absence of oxygen. It produces a mixture of

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methane and carbonic gas, called biogas. This process depends on some optimised parameters: (i) moisture (60%), (ii) C/N ratio (20–35), (iii) temperature (30–35 °C) and (iv) pH (5.5–8). In addition to the values of these parameters, methane production is linked to the level of biodegradable waste (BW) calculated from Eq. (3) (Gillet, 1985)

BW ¼ OM þ CP

A 0 10

ð4:1Þ

Then Q ¼ 80:5%ðOM  dM  375Þ

ð4:2Þ

70 60

40

Ashes %

50

Moisture %

50

60

40

Zone 1

70

Q ¼ BWðOM  dM  375Þ

80

30

BW ¼ 64:6% þ 15:9% ¼ 80:5% Thus, 80.5% of Mostaganem’s waste produces methane. Assuming that 1 kg of dry biodegradable matter potentially contains 350– 400 l of biogas. Mostaganem city’s MSW contains 64.6% organic matter, 37% dry matter from which 80.5% is biodegradable. The reserve (in m3 per ton of biogas) is given by Eq. (4.1) (Gillet, 1985)

90

20

ð3Þ

where BW = the amount of biodegradable waste; OM = level in % of organic matter = 64.6 (Table 3); and CP = level in % of cardboard paper (15.9) (Table 3). Using Eq. (3), the amount of biodegradable waste of Mostaganem city is equal to

100

30 20

80

Zone 2

90

10

100

B 0

10

20

30

40

50

60

70

80

90

0 100

C

Volatile Matter % Zone 1 : incineration, Zone 2 : compost production

where Q is the reserve of biogas in m3; OM is the level in % of organic matter; dM is the level in % of dry matter; 375 l is the average reserve value. Using Eq. (4.2)

Q ¼ 80:5%ð64:6%  37%  375Þ ¼ 72:15 m3 Assuming that production is 81.98 tons per day, the yearly biogas reserve is

72:15  81:98  365 ¼ 21:6  105 m3 which is 778.9  105 MJ or 1852.4 tons of equivalent oil (Robert and Jean, 2002). 5.3.2. Composting Compost production is the biological aerobic process of organic matter fermentation. It is rich in humus (principally humic acids), stable and contains nutritive species (N, P, K). Generally, in order to produce compost from MSW the following physical and chemical parameters should be respected: (i) a moisture level of 50–60%, (ii) a C/N ratio of 20–35, (iii) a pH of 5.5–8 and (iv) a minimal oxygen level of 5%. The values determined in our study match these values with a moisture level of 58.9%, a C/N ratio of 20 and a pH of 6.1. These values are suitable for composting. In addition to these results, we were able to confirm this valorisation by using the Tanner graphic method (Gillet, 1985); taking three parameters into account: % M, % Ce, % VM. The application of this method to Mostaganem city’s MSW (Fig. 3) shows that this mode of valorisation is very suitable for zone 2 where the levels of moisture and volatile matter are high (% M: 58.9%, VM: 63.00%, Ce: 37.00). An analysis of the diagram shows that a large quantity of Mostaganem’s MSW is suitable for compost production. Nevertheless, additional studies on the nature and the quality of the compost that would be produced are necessary. In addition to recuperation for recycling, Mostaganem’s mode of MSW valorisation could be incineration with energy recovery (taking paper and plastics into account), or production of biogas and compost. Because of the agricultural orientation of the Mostaganem region, compost production is preferred as a means of MSW valorisation in order to produce a soil amendment. This study is the first investigation in this field. The pilot tests found here were suitable in order to evaluate: (i) the incineration

Fig. 3. Tanner ternary diagram.

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