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recycling municipal solid waste
1 Submitted to the 28 th conference of the Federation of Engineering Organizations RECYCLING MUNICIPAL SOLID WASTE FOR CONSTRUCTIONAL MATERIALS Nguyen Xuan Hoan and Vo Dinh Long Nguyen Xuan Hoan is with the Vice-president of Ho Chi Minh University of Industry Email: ngxuanhoan@hui.edu.vn. Vo Dinh Long is with the Director of the Center for Environmental Resources Research, Ho Chi Minh University of Industry Email: vodinhlong@hui.edu.vn. Abstract: In this research, we concentrate to study how to make of constructional materials from mixture of organic waste collected from municipal solid waste (MSW) and clay. Using of MSW to produce constructional materials will help reduce clay, recycle organic wastes and protect the environment. Besides, the new bricks (bricks are made from mixture of MSW and clay) have high quality as bricks made from traditional methods. Keywords: Constructional materials, Organic waste, Fixed carbon, Ash, Municipal Solid Waste. 1. INTRODUCTION Municipal Solid Waste (MSW) increases its weigh and changes its characteristics within the increase in population and modernization. Present, most of MSW in Vietnam is collected and transported to dumping sites, especially in the rural areas. These dumping sites located in the suburb of urban areas and generated lots of environmental problems, and therefore new processing and recycling techniques should be put forward in order to save land area, recover or conserve energy as well as lower the emission of greenhouse gases. The first method is reduction of MSW at sources of generation; secondary, composting, recycling of MSW and dumping the leftover or dumping of ash from incinerators. When burning of organic waste, large amounts of moisture and volatile combustible matter (VCM) released into the environment in the form of steam and air mixture, leaving only about 6-9% of fixed carbon (ash from combustion). It is wasted if we buried this ash into landfills because most of ash from combustion of organic waste is fixed carbon, characterized by smooth, light and heat-resistance so it is better to mix it with clay to create constructional materials. There are numerous studies on the utilization of ash from the incinerators to produce constructional materials. However, most of these studies concentrate on utilizing fly ash from thermal power plants. Therefore, the utilization of ash from combustion of organic waste to produce constructional materials is still relatively new. 2 2. MATERIALS AND METHODS 2.1. Materials Materials used for experiments including clay and organic solid wastes. Fixed carbon was obtained from the combustion the dried organic solid wastes at 950 0 C in 60 minutes. Above systematical flow chart showed that ash received from furnace can mix with clay to produce constructional materials. Composition and ratio of the mixture are presented in the following table. Figure 1. Systematical flow chart of recycling MSW for constructional materials Flue gas after treating Generator Constructional materials Air waste Thermal Ash Other gases Activated sludge Sludge Wastewater treatment system Hazardous waste MSW Industrial waste Food and other biomass organics Paper and other recyclable materials Brick and concrete Organics and in- decomposable materials Brick and concrete Paper and other recyclable materials Topography improvement Composting Recycling Furnace Methane Leachate Compost Gas Clay 3 Table 1. Components and materials included in the experiments Components Clay (%) Ash (%) Sand Limonite Clay Fixed carbon Sample 1 9 12 9 70 Sample 2 12 16 12 60 Sample 3 15 20 15 50 Sample 4 18 24 18 40 Sample 5 21 28 21 30 2.2. Methods a/ Withdrawal of fixed carbon from organic wastes Organic wastes and in-decomposable materials obtained from MSW and industrial waste combined with hazardous substances and sludge from wastewater treatment plants are combusted in the furnace at 950 0 C in 60 minutes to obtain ash as the flow chart. - Step 1: Collect organic waste and in-decomposable materials including food scraps, waste products from plants, carton, paper, rags, wood, rubber . - Step 2: Remove moisture from these wastes by drying them in oven at 105 0 C in 60 minutes. - Step 3: Combust these waste in furnace at 950 0 C in 60 minutes to obtain fixed carbon. Moisture and volatile combustible matter (VCM) released into the environment in the form of steam and air mixture. b/ Preliminary experiments - Step 1: Create the frame block sized 5cm x 5cm x 5cm and place this frame block into the stainless steel tray. - Step 2: Mix fixed carbon with dried clay, the ratio we choose are 3/7; 4/6; 5/5; 6/4; 7/3 and the zero fixed carbon sample for comparison. After mixing, we added water for combining materials and creating brick form. - Step 3: Continue to dry all the bricks in the oven at the room temperature, after that increase the temperature to 120 0 C in 60 minutes to obtain dried bricks. - Step 4: All bricks were heated in furnace in 6 hours. Heating details for our experiments were done as followed: Table 2. Temperature control and time apply for heating bricks Temperature Time for heating Temperature Time for heating 200 0 C 60 minutes 600 0 C 120 minutes 400 0 C 60 minutes 850 0 C 120 minutes - Step 5: Remove moisture and keep all bricks in the room temperature and conduct preliminary test on water absorption and their durability after absorption of water. - Step 6: Do brick tag with the mixture of clay and ash which receiving the most durable products to check the compressive strength, bending strength, water absorption and weigh. - Do experiments with three replications. 3. DISCUSSION OF RESEARCH RESULTS 3.1. Results of research Bricks are made from the mixed materials with the ratio of 3/7; 4/6; 6/4 and 7/3 have some characteristics: - Bricks made from mixture of small percentage of standard clay having high water absorption. 4 - Bricks made from mixture of high percentage of standard clay being cracked and broken during incineration. Through preliminary experiments, we determined the optimal ratio of mixing between clay and fixed carbon is 5/5. With this ratio, materials meet the heat-resistance and low water absorption. Using materials with the optimal ratio for a number of experiments related to the compressive strength, bending strength, water absorption and weigh of materials, we obtained following results: Table 3. Experiments on the compressive strength, bending strength, water absorption of bricks made from a mixture of organic waste and clay Indexes Compressive strength (N/mm 2 ) Bending strength (N/mm 2 ) Water absorption (%) Weigh (kg) Value Ave. for 5 samples Min value Aver. for 5 samples Min value Ave. for 5 samples Min value 8,38 7,65 0,17 0,16 18,18 1,1 TCVN 1451:1986 5 3,5 1,6 0,8 8-18 TCVN 1451-1986: Vietnamese standard for solid brick M50 3.2. Comment Optimal ratio for ash and clay is 5/5. With this ratio, we can explain that the fixed carbon contenting in ash increase the heat-resistance for bricks. Moreover, fixed carbon has its fine- grained combining with fine-grained clay increasing their structure and leading to the increasing in durability of the products. On the other hand, fixed carbon contents in the bricks make it light and decrease in water absorption capacity comparing to the other ratio. Figure 2. The bricks samples after drying We also received good results from testing bricks made from mixture of organic waste and clay. Compressive strength of bricks ranges from 1.5 to 2 times higher than the standard and water absorption is not over the standard. It needs to say compressive strength and water absorption are two indicators for assessing the quality of constructional materials. 1 2 3 4 5 0 5 Figure 3. Bricks products Each brick sized 5cmx5cmx5cm, the ratio for mixture is 50% clay and 50% is fixed carbon. It means, to produce a brick, we need 1 kg of clay and 0.5 kg of dried ash. In the case of receiving fixed carbon from combustion is 7 to 10 percent of total MSW, we need the ratio of 1 kg of clay and 5 to 7 kg of MSW to produce a brick. In other words, each ton of organic waste generating will produce 170 to 200 bricks and save about 170 to 200 kg of clay. Moreover, bricks made from mixture of clay and organic waste is lighter than usual. If we do not consider the economic aspects, constructional materials made from organic waste would have some significant meanings: - Solving a large amount of organic waste to landfills. - Saving resources (clay) to produce constructional materials. 4. CONCLUSION Recycling municipal solid waste for constructional materials has number advantages: - In the terms of natural resources and environment: Recycling MSW for constructional materials will reduce amount of clay to use and save land area for burry of organic waste or ash from incinerators. - In the terms of government management: Recycling MSW for constructional materials will reduce the pressure of solid waste on landfills and saving the budget for treatment of solid waste and environmental pollution. - In the terms of construction: constructional materials (bricks) made from mixture of organic waste and clay ensures the compressive strength, water absorption and lightweight, it makes the lighter structure for building. Moreover, in this study, we used the composition of sand/limonite/clay being of 30/40/30 and the ratio of clay and ash is 5: 5 for optimal results. In the case using higher percentage of clay in the composition the ratio of ash and clay would be lower and the bricks would be made from high amount of organic waste. 5. REFERENCES [1] Nguyen Van Phuoc, Management and treatment of solid waste, Vietnam National University, Ho Chi Minh City Publishing house, 2007. [2] Vo Dinh Long, Treatment of Municipal Solid Waste (MSW) and Hazardous Waste, Ho Chi Minh University of Industry Publishing house, 2010. 6 THE 28 TH CONFERENCE OF THE FEDERATION OF ENGINEERING ORGANIZATIONS CAFEO 28 HANOI VIETNAM, 30 TH NOV. - 2 ND DEC., 2010 TITLE: Recycling Municipal Solid Waste for constructional materials YOUR PHOTO (or you can attach a separate file for photo) AUTHOR(S)’ NAME(S): Nguyen Xuan Hoan and Vo Dinh Long ORGANIZATION & DESIGNATION Ho Chi Minh University of Industry ADDRESS: 12 Nguyen Van Bao St., Ward 4, Go Vap Dist., Ho Chi Minh City, Vietnam TEL: 08. 22167376 - 0983163788 (Mr. Vo Dinh Long) FAX: 08.3.9893452 EMAIL: vodinhlong@hui.edu.vn