Solid Waste Treatment Lecture PDF

Lecture 4-SOLID WASTE TREATMENT I hope everybody is SAFE and SOUND  INTRODUCTION Solid waste is a term usually used to describe non-liquid materials arising from domestic, trade, commercial, agricultural and industrial activities, and from public services....

Lecture 4-SOLID WASTE TREATMENT I hope everybody is SAFE and SOUND  INTRODUCTION Solid waste is a term usually used to describe non-liquid materials arising from domestic, trade, commercial, agricultural and industrial activities, and from public services. Increasing of the amount of solid waste and the pressure what it has on the environment, impose the need to introduce advanced approach to effectively managing of solid waste.  INTRODUCTION Food waste (FW) can be defined as the “end products of various food processing industries that have not been recycled or used for other purposes. They are the non-product flows whose economic value is less than the cost of collection and recovery for reuse; therefore discarded as waste” Solid Waste Management Hierarchy  Solid Waste Management Hierarchy WASTE MINIMIZATION is the process of reducing the amount of waste produced by a person or a society. RE-USE, it means use an item more than once. This includes conventional reuse where the item is used again for the same function and new-life reuse where it is used for a new function. Recycling and composting are processes of material waste recovery. Recycling means obtaining substances from waste (secondary raw materials) and their utilization as a substitution of the primary raw materials. COMPOSTING is biochemical decomposition of organic substances found in the waste. ENERGY RECOVERY technologies allow to obtained volume reduction and energy recovery. Waste disposal is proper disposition of a discarded or discharged material in accordance with local environmental guidelines or laws. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES COMPOSTING Composting is nature's process of recycling decomposed organic materials into a rich soil known as compost.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting With composting process organic materials are reduced. This reduction occurs because of СО2, H2O and other gases are release into the atmosphere. The product of the end, compost, is composed of microorganisms, products of decomposition and organic matter that these organisms could not decompose. Compost is an excellent fertilizer for gardening and horticultural plants. At the end of the process, the amount of composting pile is reduced for 20-60%, moisture content is smaller than 40% and weight is reduced for 50%. pH value of compost is 7 and the ratio carbon/nitrogen should be smaller than 80:1. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting : windrow MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting : Static Pile MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting : Closed Reactor  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting The following factors are important: -The size of the particles of the organic material -Aeration/Temperature -Porosity -Moisture content -pH value of the material -the ratio of carbon and nitrogen C/N.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting -The size of the particles of the organic material Microbiological activity takes place on the surface of the particles of the composting material. With cutting on smaller parts, the surface of organic material can be enhanced. The increased surface allows microorganisms to decompose material faster and generate more heat. A good particle size would be 1.25-4 cm.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - Aeration Aeration is achieved by enriching the compost pile with fresh air, where oxygen is missing. Quick aerobic decomposition occurs only if there is sufficient amount of oxygen. Therefore, at the beginning of the process, the composting pile should be regularly mixed to satisfy quantity of fresh air. In the first weeks of composting, the needs of oxygen are greatest.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - Porosity Porosity refers to the space between particles in the compost. If the material is not saturated with water, these spaces are partly filled with air which supplies the microorganisms with oxygen. Otherwise, saturated composting pile with water reducing air space, and it comes to slowing down the process of composting.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - Moisture Content The moisture content of 40-60% provides adequate moisture without aeration inhibiting. If the moisture content is below 40%, bacterial activity will be slowed down, and completely broken if it falls below 15-20%. On the other hand, if the moisture content is above 60%, the volume of air is reduced creating an unpleasant smell and the process of decomposition slows down.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - Temperature Heat is developed as a result of the activities of microorganisms for decomposition of organic material. There is a relationship between temperature and oxygen consumption. Higher temperature means greater consumption of oxygen, thus faster decomposition of the material is possible. The temperature of the pile between 32 and 60°C, indicate a rapid process of composting. Temperatures above 60°C reduces the activity of many microorganisms. Thus, the optimal range for composting is 32 and 60 °C. The temperature of composting pile, increase to 55-60°C, gradually, and remains so weeks, then, the temperature falls to 38°C or to temperature of surrounding air.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - pH The optimal pH value for microbial activity is between 6.5 and 7.5. The release of organic acids may temporarily or locally to reduce the pH, thus the acidity of material increase. On the other side, the production of ammonia from nitrogen compounds can increase the pH, thus the alkalinity of the material increase. But regardless, the pH measurement of the organic material at the beginning of the process, the pH value of the compost at the end of the process will be 7, neutral.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Composting - C/N ratio Carbon and nitrogen are constituents of organic waste, which can easily disrupt the process of composting if that are in insufficient or excessive quantities or if the ratio C/N is inappropriate. Microorganisms use carbon as an energy source, and nitrogen for the synthesis of proteins. The ratio of these two elements should be approximately 30 parts carbon, 1 part nitrogen, depending by the weight. C/N ratio in a range of 25:1 to 40:1 results in efficient process MATERIAL AND ENERGY RECOVERY TECHNOLOGIES GASIFICATION MATERIAL AND ENERGY RECOVERY TECHNOLOGIES GASIFICATION  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Gasification Gasification is defined as a thermal reaction with insufficient oxygen present for reaction of all hydrocarbons (compounds of carbon, hydrogen and oxygen molecules) to CO2 and H2O. This is a partial oxidation process which produces a composite gas comprised primarily of hydrogen (H2) and carbon monoxide (CO). The oxidant may be air, pure oxygen and/or steam. The gasification conditions are between 1000-1600°C. Steam is injected into gasification reactor to promote CO and H2. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Gasification MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Gasification The main reactions taking place during gasification are: THERMAL TREATMENT -GASIFICATION Combined cycle  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Gasification The raw syngas exits the reactor and is cleaned up of carry-over particulate matter from the reactor, sulfur, chlorides/acid gases. Syngas is sent to the power generation plant to produce energy, such steam and electricity for use in the process and energy. Heating values of syngas are generally around 4-10 MJ/m3 (butane 128MJ/m3) MATERIAL AND ENERGY RECOVERY TECHNOLOGIES PYROLYSIS  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Pyrolysis Pyrolysis is the thermal degradation of carbon-based materials through the use of an indirect, external source of heat, typically at temperatures of 450 to 750°C, in the absence or almost complete absence of free oxygen to produce a carbonaceous char, oils and combustible gases. This process drives off the volatile portions of the organic materials, resulting in a syngas composed primarily of H2, CO, CO2, CH4 and complex hydrocarbons  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Pyrolysis The reactions taking place initially are decomposition ones, where organic components of low volatility are converted into other more volatile ones Moreover, at the early stages of pyrolysis process, reactions occurring include condensation, hydrogen removal and ring formation reactions that lead to the formation of solid residue from organic substances of low volatility  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Pyrolysis The products obtained from the pyrolysis process are solid residues and synthetic gas "syngas". The majority of the organic substances in waste are subjected to pyrolysis by 75 – 90 % into volatile substances and by 10–25% to solid residue (coke). Syngas is used in the power generation plant to produce energy, such as steam and electricity, for use in the process and export energy. The export energy is typically converted into electricity and supplied/sold to the grid. Synthetic gas typically has energy value between 10 and 20 MJ/Nm3. The bottoms from the reactor are ash, carbon char, and metals. The carbon char and metals have use as recyclables in industry. However, the ash from the pyrolysis process is usually disposed of in a landfill. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES INCINERATION  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Incineration The incineration is process of combustion of solid waste chemical elements (carbon, hydrogen, sulfur) in an oxygen-rich environment, at temperature higher than 850°C and producing combustion gases, especially CO, CO2, NOx, H2O, SO2, ash, and heat. The inorganic content of the waste is converted to ash. High-pressure steam produced in the fluid bed boiler is sent to the power plant for energy generation. Hot exhaust gases from the fluid bed boiler are sent for gas cleanup and heat recovery sent to the power plant for generation of energy. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Incineration The main elementary reactions of solid wastes in the combustion process at the incinerator are the following ones  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Incineration The object of this thermal treatment method is the reduction of the volume of the treated waste with simultaneous utilization of the contained energy. The recovered energy could be used for: heating, steam production, electric energy production. The net energy that can be produced per ton of solid waste is about 0.7 MW/h of electricity and 2 MW/h of district heating. Note: Incineration is a process that can be used to treat different types of waste including municipal solid waste and industrial solid waste. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES COMPARISON OF HEAT TREATMENT METHODS MATERIAL AND ENERGY RECOVERY TECHNOLOGIES BIOMETHANATION (Biogas) MATERIAL AND ENERGY RECOVERY TECHNOLOGIES BIOMETHANATION)biogas) BAALBECK BIOGAS PLANT BIOLOGICAL TREATMENT -BIOMETHANATION COMPOSTING BIOMETHANATION AEROBIC PROCESS: FULL O2 ANAEROBIC PROCESS: NO O2  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas) Biomethanation is a process based on anaerobic digestion of organic matter in which microorganisms break down biodegradable material in the absence of oxygen. The process is widely used to treat wastewater sludge (wet biogas technology) and solid organic wastes (either wet or dry biogas technologies) because it provides volume and mass reduction of the input material. BIOLOGICAL TREATMENT -BIOMETHANATION BIOLOGICAL TREATMENT -BIOMETHANATION MATERIAL AND ENERGY RECOVERY TECHNOLOGIES BIOMETHANATION )biogas) MATERIAL AND ENERGY RECOVERY TECHNOLOGIES  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas) It produces methane and carbon dioxide rich biogas suitable for energy production and hence, is a renewable energy source. The nutrient-rich solids left after digestion can be used as a fertilizer. It generally treats Sorted organic fraction only (highly putrescible) for better gas yield.  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas) This slide is NOT required. MATERIAL AND ENERGY RECOVERY TECHNOLOGIES BIOMETHANATION )biogas)  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas)  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas)  MATERIAL AND ENERGY RECOVERY TECHNOLOGIES Biomethanation (Biogas) MATERIAL AND ENERGY RECOVERY TECHNOLOGIES