A waste management planning based on substance flow analysis

Transcription

1 A waste management planning based on substance flow analysis Umberto ARENA and Fabrizio Di GREGORIO Department of Environmental, Biological and Pharmaceutical Sciences and Technologies Second University of Naples

2 A SUSTAINABLE WM PLANNING The decision making process over WM policy is a complex issue, which has to evaluate the environmental impacts, the technical aspects, the implementation and operating costs of each specific treatment and disposal option as well as the social implications. The process often involves accurate as well as missing data, expert evaluations as well as ill-defined and changing public opinions, and sometimes it is guided by preconceptions for or against a specific WM solution. The complexity of this framework greatly raised in the last two or three decades, as a consequence of increasing generation and complexity of solid wastes and of the deep and extensive changes that consequently occurred in their management.

3 INCREASING DIFFICULTY of an ECO-SUSTAINABLE MATERIAL RECYCLING Growing complexity of goods (and waste) composition (e.g. information products) 15 Elements 60 Elements 11 Elements Source: T. McManus, Intel Corp., 2006 (Courtesy T. Graedel)

4 A SUSTAINABLE WM PLANNING A comprehensive and systemic, goal-oriented approach is needed to design an integrated and sustainable WM system. There is a general accordance about the final goals: i) protection of human health and the environment; ii) conservation of resources, such as materials, energy, and land; iii) after-care-free waste management, meaning that neither landfills nor WtE, recycling or other treatments leave problems to be solved by future generations; iv) economic sustainability of the whole cycle of MSW management, also in a welfare economy perspective.

5 A SUSTAINABLE WM PLANNING Since these goals are substantially all substanceoriented, the assessment tools cannot refer just to bulk flow of wastes and residues: the flows of individual substances have also to be investigated, controlled, and directed to appropriate treatments and sinks. In other words, given that individual substances are responsible for environmental loadings and resource potentials, it is necessary to observe the system even at the substance level.

6 A SUBSTANCE ORIENTED APPROACH In this framework of increasing generation and complexity of solid waste composition, the combination of two valuable tools, the MFA and the SFA, together with an environmental assessment method such as LCA, can efficiently support waste management decisions on both strategic and operating levels. In particular, it is greatly attractive the SFA ability to connect sources, pathways, and intermediate and final sinks of each chemical species in a specific process, as demonstrated by its utilization in the assessment of thermal treatments, recycling options and waste management scenarios.

7 THE WM PLANNING TOOL BOX On site data and waste process data (waste amount and composition, air and water emissions, co-products, etc.) System definition Technical tools (material balances, energy balance, allocation models, etc.) Material Flow Analysis Analytical tools Life Cycle Analysis Life Cycle Costing Substance Flow Analysis Health RA Environmental RA WM Planning

8 AIM of the WM PLANNING PROCEDURE to quantify mass flow rates of wastes and of their main chemical elements in order to provide a scientific support to the decision making process. LCA approach is utilized to define the overall WM scheme and to individuate the specific technical solutions to be included in this scheme. MFA and SFA are then developed on the basis of the transfer coefficients of all the waste treatment processes included in the WM scheme. The procedure has been recently applied to three areas of the Middle and South of Italy characterized by very different densities of population (from 72.2 to inh/km 2 ) and waste generation rates (from 420 to 470 kg/inh. y).

9 INPUT DATA and WASTE MANAGEMENT SCENARIOS

10 THE ASSUMED MSW COMPOSITION MSW composition % C, % Cl, % F, % H, % O, % N, % S, % Cd, mg/kg Cr, mg/kg Hg, mg/kg Pb, mg/kg ash, % moisture, % Organic fraction Paper Glass Plastics Metals Aluminum Wood and textiles Bulky waste and WEEE LHV, MJ/kg TOTAL

11 THE THREE MSW WM SCENARIOS Waste fractions Organic fraction Paper Glass Plastics Metals Aluminum Wood + Textiles Bulky waste and WEEE Total in MSW, % SCENARIO SSL 35% Interception Efficiency, % % Separate Collection Waste, t/d Unsorted Residual Waste, t/d SCENARIO SSL 50% Interception Efficiency, % % Separate Collection Waste, t/d Unsorted Residual Waste, t/d SCENARIO SSL 65% Interception Efficiency, % % Separate Collection Waste, t/d Unsorted Residual Waste, t/d

12 THE COMPOSITION of SEPARATELY COLLECTED and UNSORTED RESIDUAL WASTES

13 Phase 1: Definition of WM scheme on the basis of LCA studies

14 A SCENARIO ANALYSIS The waste management system is defined and developed according to the following hierarchy: 1. to minimize use of landfill and ensure that no waste that is biologically active or that contains mobilizable hazardous substances is landfilled 2. to minimize operations entailing excessive consumption of raw materials and energy without yielding a real environmental advantage 3. to maximize recovery of materials 4. to maximize energy recovery, given that, in a LCA approach, energy recovery from waste allows decreasing consumption of fossil fuels and of overall emissions with respect to all energy conversion systems.

15 A SCENARIO ANALYSIS WM systems that are operating successfully worldwide demonstrated that: no one process is suitable for all waste streams no single waste management practice can handle the full array of waste types. The WM scheme should then utilize the fundamental options (selected on the basis of a series of LCA investigations) for the extent that is adequate to the specific catchment area characteristics and compatible with the technical, economic and environmental performance of the specific option. They should include only technologies that are state-ofthe-art and have already proven high reliability and sustainability, with known total costs for treatment and aftercare.

16 THE MSW WM SCHEME: the crucial role of Source Separation and Collection

17 Phase 2: Substance Flow Analysis of WM options

18 RECYCLING CHAIN sorting and recycling residues MSW fractions SSL 35% SSL 50% SSL 65% SR, % RR, % SR+RR, % SR, % RR, % SR +RR, % SR, % RR, % SR +RR, % Organic fraction Paper Glass Plastics Metals Aluminum Wood and textiles Bulky waste and WEEE TOTAL

19 MFA/SFA for recycling chain of plastics and metals

20 MFA/SFA for recycling chain of paper and cardboard

21 MFA/SFA for Integrated Anaerobic Digestion

22 MFA for Thermal Treatment

23 SFA (C layer) for Thermal Treatment

24 SFA (Cl layer) for Thermal Treatment

25 Phase 3: MFA and SFA of alternative WM scenarios

26 MFA of WM SCENARIOS

27 MFA of WM SCENARIOS Scenario SSL 35% SSL 50% SSL 65% Mass of Waste to Landfill, % entering MSW from sorting&recycling chain from biological treatment from thermal treatment Total Volume of Waste to Landfill, m 3 /d (% entering MSW (a) ) from sorting&recycling chain from biological treatment from thermal treatment Total (8.7) (10.6) (12.2) Energy Net Production, GWh/y Electric energy Thermal energy (in cogeneration) Total Lost and Available Feedstock Energy, GWh/y (% entering waste energy) converted in electric and thermal energy (78.0) (70.0) (62.0) lost in landfill 51.3 (5.2) 78.5 (8.0) 99.0 (10.0) Recovered Materials, t/d (% entering MSW ) Glass Plastics Metals Aluminum Paper Textiles Wood Compost Total (18.4) (22.9) (29.8) (a) assuming a bulk density of collected MSW of 0.48 t/m 3

28 SFA of WM SCENARIOS feedstock energy 70.0% 8.0% 22.0%

29 SFA of WM SCENARIOS Carbon layer 68.4% 22.1% 9.5%

30 SFA of WM SCENARIOS layers of C Scenario SSL 35% SSL 50% SSL 65% Carbon to Landfill, t/d (% input C ) from sorting&recycling chain 2.5 (1.0) 3.9 (1.5) 5.8 (2.2) from biological treatment 11.0 (4.2) 18.3 (7.0) 23.0 (8.7) from bottom ash 2.0 (0.8) 1.7 (0.6) 1.5 (0.6) from APC residues 0.9 (0.3) 0.8 (0.3) 0.7 (0.3) Total 16.4 (6.2) 24.7 (9.4) 31.0 (11.8)

31 SFA of WM SCENARIOS layers of Pb Lead to Landfill, g/d (% input Pb ) from sorting&recycling chain 13,712 (7.5) 23,162 (12.6) 36,923 (20.1) from biological treatment 1,210 (0.7) 1,980 (1.1) 2,454 (1.3) partial total 14,922 (8.2) 25,142 (13.7) 39,377 (21.4) from bottom ash 66,173 (36.0) 53,197 (28.9) 28,650 (15.6) from APC residues 54,069 (29.4) 43,467 (23.6) 23,410 (12.7) Total 135,164 (73.5) 121,806 (66.2) 9,437 (49.7) Lead in recycled product, g/d (% input Pb ) Glass 13,339 (7.2) 14,422 (7.8) 19,505 (10.6) Plastics 3,241 (1.8) 5,298 (2.9) 6,814 (3.7) Metals 24,594 (13.4) 32,799 (17.8) 51,967 (28.2) Aluminum 5,595 (3.0) 6,947 (3.8) 10,954 (6.0) Paper 1,023 (0.6) 1,144 (0.6) 1,464 (0.8) Textiles 34 (0.02) 45 (0.02) 56 (0.03) Wood 608 (0.3) 859 (0.5) 1,145 (0.6) Compost 287 (0.2) 454 (0.2) 544 (0.3) Total 48,721 (26.5) 61,968 (33.6) 92,449 (50.2)

32 SFA of WM SCENARIOS layers of Cd Cadmium to Landfill, g/d (% input Cd ) from sorting&recycling chain 920 (9.1) 1,614 (16.0) 2,589(25.6) from biological treatment 249 (2.5) 405 (4.0) 499 (4.9) partial total 1,169 (11.6) 2,019 (20.0) 3,088(30.6) from bottom ash 831 (8.2) 721 (7.1) 588 (5.8) from APC residues 7,477 (74.0) 6,487 (64.2) 5,292(52.4) Total 9,477 (93.8) 9,227 (91.3) 8,968 (88.8) Cadmium in recycled product, g/d (% input Cd) Glass 81 (0.8) 87 (0.9) 118 (1.17) Plastics 305 (3.0) 508 (5.0) 641 (6.3) Metals 47 (0.5) 63 (0.6) 99 (1.0) Aluminum 2 (0.02) 3 (0.03) 5 (0.05) Paper 177 (1.8) 198 (2.0) 253 (2.5) Textiles 1 (0.01) 1 (0.01) 1 (0.01) Wood 3 (0.03) 4 (0.04) 5 (0.05) Compost 2 (0.02) 4 (0.04) 5 (0.05) Total 618 (6.1) 868 (8.6) 1127 (11.1)

33 WM SCENARIOS comparison 35,0 Recovered Materials, % treated MSW 30,0 25,0 20,0 15,0 10,0 5,0 0,0 scenario SSL 35% scenario SSL 50% scenario SSL 65%

34 WM SCENARIOS comparison Required Volume of landfill, m3/y scenario SSL 35% scenario SSL 50% scenario SSL 65% from sorting and recycling chain from biological treatment from thermal treatment total

35 WM SCENARIOS comparison 50,0 Recovered Energy, % MSW energy 45,0 40,0 35,0 30,0 25,0 20,0 15,0 10,0 power production in cogeneration 5,0 0,0 scenario SSL 35% scenario SSL 50% scenario SSL 65%

36 CONCLUSIONS A procedure for goal-oriented WM planning has been proposed to provide a knowledge basis for MSW management decision makers. It is based on the extensive utilization of MFA and SFA, in the framework of a LCA approach and together with a scenario analysis. The procedure appears as an attractive tool-box to compare alternative waste management technologies and scenarios, even though the obtainable results are just a part of the input data to the decision making process, which should further take into account a variety of economic and social aspects.

37 CONCLUSIONS The study shows the benefits of high quality household source separation and collection, biological treatment of the organic fraction coming from this separate collection and thermal treatment of unsorted residual waste: landfill mass and volume are drastically reduced, greenhouse gas emissions are reduced, toxic organic materials are mineralized, heavy metals are concentrated in a small fraction of the total former MSW volume, and the accumulation of atmophilic metals in the APC residue allows new recycling schemes to be designed for metals. A significant reduction in the requirement of landfill volume can only be achieved if the URW is sent to WtE process. The scenarios with high energy recovery provide that energy produced by carbon oxidation is full utilized; inorganic materials are mainly concentrated in the residues of WtE plants; hazardous organic compounds are completely destroyed.

38 CONCLUSIONS The results suggest that the optimal source separation level should be lower than 65%, on the basis of: the high amounts of toxic substances that can be found in the recycled products the large quantities of sorting and recycling residues the difficulty of obtaining very high interception levels the remarkable operating costs. High levels of separate collection could ensure the desired environmental sustainability only with considerable improvements in sorting and recycling technologies, which should become able to separate toxic additives from materials of value, thereby preventing their accumulation in recycled products.

39 THANK YOU for your kind attention