Sustainable Development Practice in China. Niu Dongjie

Transcription

1 Sustainable Development Practice in China Niu Dongjie

2 Table of Contents What are wastes and ISWMS? Landfilling Incineration Composting Anaerobic digestion

3 What are Wastes? Comprises all the wastes arising from human and animal activities that are normally solid and that are discarded as useless or unwanted. Basel Convention Definition of Wastes substances or objects which are disposed of or are intended to be disposed of or are required to be disposed of by the provisions of the law Disposal means any operation which may lead to resource recovery, recycling, reclamation, direct re use or alternative uses (Annex IVB of the Basel convention) 3

4 Some important features Waste contains the same materials as are found in useful products Only differs from useful materials by its lack of value The lack of value can be related with mixed and unknown composition of the waste.

5 Classification of waste by physical state By original use (Packaging, food, etc) Physical property (combustible, compostable, recyclable) Origin Safety level

6 Kinds of Wastes Solid wastes: domestic, commercial and industrial wastes especially common as co disposal of wastes Examples: plastics, styrofoam containers, bottles, cans, papers, scrap iron, and other trash Liquid Wastes: wastes in liquid form Examples: domestic washings, chemicals, oils, waste water from ponds, manufacturing industries and other sources 6

7 Quality of waste Combustible or not MC

8 Physical properties of MSW

9 Physical properties of MSW Specific weight Weight of unit volume of a substance, it is not its density. It is normally reported as loose, as found in containers, uncompacted, compacted Typical MSW without compaction is about 0.1~0.6t /m 3, after compacton, it is about 1 t/m 3.

10 Particle size and size distribution L W H

11 Classification of Wastes according to their Properties Bio degradable can be degraded (paper, wood, fruits and others) Non biodegradable cannot be degraded (plastics, bottles, old machines, cans, styrofoam containers and others) 11

12 Classification of Wastes according to their Effects on Human Health and the Environment Hazardous wastes Substances unsafe to use commercially, industrially, agriculturally, or economically that are shipped, transported to or brought from the country of origin for dumping or disposal in, or in transit through Non hazardous Substances safe to use commercially, industrially, agriculturally, or economically that are shipped, transported to or brought from the country of origin for dumping or disposal in, or in transit through 12

13 What is Municipal Solid Waste? Municipal Solid Waste (MSW) Generally known as trash or garbage consists of items such as: Product packaging Grass clippings Furniture Clothing Bottles Food scraps Newspapers Appliances Paints Batteries

14 Defining ISWM Integrated solid waste management refers to the strategic approach to sustainable management of solid wastes covering all sources and all aspects, covering generation, segregation, transfer, sorting, treatment, recovery and disposal in an integrated manner, with an emphasis on maximizing resource use efficiency United Nations Environment Programme Division of Technology, Industry and Economics International Environmental 14

15 How to Implement ISWM Develop an ISWM Plan Implementation and Monitoring of ISWM Plan 15

16 ISWM Plan An ISWM Plan per se is a package consisting of a Management System including: Policies (regulatory, fiscal, etc.), Technologies (basic equipment and operational aspects) & Voluntary measures (awareness raising, self regulations) A management System covers all aspects of waste management; from waste generation through collection, transfer, transportation, sorting, treatment and disposal. Data and information on waste characterization and quantification (including future trends), and assessment of current solid waste management system for operational stages provide the basis for developing a concrete and locality-specific management system. 16

17 Data/Information Required Waste Characterization & Quantification with future trends Assessment of Prevailing Management System(s) including institutions, policies, financing, technologies and stakeholders role Stakeholders Concerns and suggestions Targets & Constraints 17

18 What is Landfilling?

19 Definitions of Terms Landfill: facility disposal of waste in to soils. Sanitary landfill: Engineered facility for the disposal of MSW designed and operated to minimize public health and environmental impacts. secure landfill hazardous waste Landfilling The process: monitoring of the stream, placement and compaction, installation of landfill environmental monitoring and control facility

20 The Dump

21 Terms Cell: volume of materials, Daily cover: soil or materials, working face, at the end of each working period. Lift, Final cover layer, Leachate Landfill gas, Liner, Environmental monitoring

22 Sanitary Landfills Engineering principles used to: confine waste to smallest practical area reduce waste to smallest practical volume cover waste with layer of compacted soil (or tarps) each day (finishing cover is ~50 cm or more of compacted clay-rich soil) NOTE: Compaction and subsidence will continue after site is closed; any further development must be able to accommodate these potential problems. S. Hughes 2000

23 USEFUL DEFINITIONS LEACHATE - Leachate is a combination of infiltrated precipitation and any liquids squeezed from the waste as it naturally compacts. Leachate will percolate to the base of land disposal sites due to the influence of gravity. Leachate can carry particulate matter, pollutants, biological contaminants and other constituents with it. Leachate will travel through the subsurface following the same flow direction as groundwater. All land based disposal facilities must incorporate a leachate collection and disposal system into their designs. Liners and covers must be added so as to minimize infiltration into the waste site thereby minimizing leachate production or escape. LINER - Generally there are several layers of liners at the base of a land disposal site. Layers consist of compacted clay alternating with plastic. The purpose of the liner is to prevent leachate from escaping into the subsurface. CAP/COVER - Caps and covers are constructed (starting at the waste and working outward) of compacted, low permeability clay. This is followed by a flexible plastic liner (theoretically impermeable). Next comes a drainage layer designed to transport surface water away from the waste disposal site. Finally, this is followed by a layer of earth and then some type of vegetative cover.

24 Structure of landfill Liner system Drainage system (leachate collection, underground water protection system) Cover(Daily cover, intermidit cover) Gas collection system

25 Municipal Solid Waste Incineration

26 Fundamentals of thermal processing Stoichiometric combustion Excess-air combustion(incineration) Gasification is partial combustion under substoichiometric conditions to generate a combustible gas(co, H 2, etc) Pyrolysis is thermal processing of waste in complete absence of oxygen.

27 Definition Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. [1] "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas, and heat. The ash is mostly formed by the inorganic constituents of the waste, and may take the form of solid lumps or particulates carried by the flue gas.

28 Heating value The heating value or calorific value of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. a characteristic for each substance. units : kcal/kg, kj/kg, J/mol,

29 Heating value Heating value is commonly determined by use of a bomb calorimeter. The heat of combustion for fuels is expressed as the HHV, LHV, or GHV.

30 Higher heating value determined by bringing all the products of combustion back to the original pre-combustion temperature, and in particular condensing any vapor produced. 25 C. HHV assumes all the water component is in liquid state at the end of combustion (in product of combustion).

31 Lower heating value determined by subtracting the heat of vaporization of the water vapor from the higher heating value. This treats any H 2 O formed as a vapor. The energy required to vaporize the water therefore is not realized as heat.

32 Heating value LHV HHV 2420 H 2O 9 H 式中 LHV lower heating value 低位热值,kJ/kg; HHV higher heating value 高位热值,kJ/kg; H 2 O mass percent of water in product 焚烧产物中水的质量百分率, %; H Cl F mass percent of H, Cl, F in waste % Cl F

33 Combustion Systems Incineration (energy recovery) Mass burn RDF

34 Mass burn incineration of unsorted municipal waste in a Municipal Waste Combustor (MWC) or other incinerator designated to burn only waste from municipalities. This waste management method avoids the expensive and unpleasant task of sorting through the garbage for unburnable materials.

35 RDF Refuse Derived Fuel: a fuel produced by shredding and dehydrating solid waste (MSW) with a Waste converter technology. RDF consists largely of organic components of municipal waste such as plastics and biodegradable waste. RDF processing facilities are normally located near a source of MSW and, while an optional combustion facility is normally close to the processing facility, it may also be located at a remote location. SRF can be distinguished from RDF in the fact that it is produced to reach a standard such as CEN/343 ANAS.

36 Incinerators type Moving grate incinerators Rotary kiln incinerator Static heart incinerator Fluidized bed incinerator Amunition destruction incinerator Plazma incinerator

37 Incinerators Waste Medical/hazardous/industrial waste Domestic / household waste Liquid/gas/fluid waste Homogenous waste (ex.wwtp sludge) Ammunition destruction Unburnable waste (ex. Asbestos 石棉 ) Technology Rotary kiln Moving grate static hearth Fluidized bed Ammunition Plazma

38 Incinerator

39 Process Horizontal: the conversion of the waste (a heterogeneous mixture of all kinds of solids and liquids) to gases. Vertical: de oxidation of these gases resulting in complete combustion.

40 Horizontal process Drying: this is the evaporation of the water present in the waste; Outgassing: here volatile compounds in the waste escape as a result of heating up the waste; Degassing/pyrolysis: in this sub-process certain compounds in the waste are transformed to combustible gases; Burnout: what is left from the previous processes contains mainly combustible solids (fixed carbon) that are now burned in the presence of oxygen and transformed to gases. Cooling of the ashes: the solid non-combustible material (inert) present in the waste have been heated up in the previous processes and are now cooled as much as possible in order to recuperate this heat.

41 Vertical Process Gas production: at the lowest level the series of horizontal sub-processes takes place Gas combustion: by adding air (or rather: by adding the oxygen in the air) the gases are fully burned Gas burnout: in this zone the combustion is completed to ensure that the legal requirements are met: for a minimum of two seconds the gases remain at a temperature of at least 850 C in the presence of at least 6% (by volume) oxygen after the last addition of oxygen.

42 Principles of Composting What Is Compost? The product resulting from the controlled biological decomposition of organic materials Sanitized through the generation of heat Stabilized to the point where it is beneficial to plant growth Provides humus, nutrients, and trace elements to soils Organic Materials Landfilled wastes (food, wood, textiles, sludges, etc.) Agricultural wastes (plant or animal) Industrial manufacturing byproducts Yard trimmings Seafood processing wastes In short, anything that can be biodegraded

43 The Composting Process Biological decomposition in aerobic environment Decomposition & mineralization by microbes Bacteria, actinomycetes, fungi, protozoans, nematodes Food source Nitrogen (biodegradable organic matter) Energy source Carbon (bulking agent) Outputs Heat Water Vapor Carbon Dioxide Nutrients and minerals (compost) Process occurs naturally, but can be accelerated by controlling essential elements

44 Composting Essential Elements Nutrients Carbon/Nitrogen (C/N) 20:1 to 35:1 Carbon/Phosphorus (C/P) 100:1 to 150:1 Moisture Content 50% to 60% (wet basis) Particle Size 12~60 mm optimum Porosity 35% to 50% ph 6.5 to 8.0 Oxygen concentration - >5% Temperature 50 to 60. Time one to four months

45 When is compost finished? Compost is mature when The color is dark brown It is crumbly, loose, and humus like It has an earthy smell It contains no readily recognizable feedstock The pile has shrunk to about 1/3 of its original volume

46 Anaerobic Digestion

47 A new look at the cow The Biogas Plant Outlet Inlet Biogas digester

48 Anaerobic Digestion in Waste Management Definition: Anaerobic Digestion is a biological process carried out in the absence of O 2 for the stabilization of organic materials by conversion to CH 4 and inorganic end-products such as CO 2 and NH 3. Anaerobic microorganisms Organic materials + Nutrients CH 4 + CO 2 +NH 3 + Biomass

49 Organics Conversion in Anaerobic System COMPLEX ORGANIC MATTERS acidogenesis hydrolysis Proteins Carbohydrates Lipids Amino Acids, Sugars Fatty Acids, Alcohols acetogenesis INTERMEDIARY PRODUCTS (C>2; Propionate, Butyrate etc) methanogenesis Acetate Methane Carbon dioxide Hydrogen, Carbon dioxide 72 28

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