Alternative Sewage Sludge Management Routes in Cyprus CYPRUS 2016 4th International Conference on Sustainable Solid Waste Management, Limassol, 23–25 June 2016 Angeliki Kylili, MSc, Frederick University, Cyprus Paris Fokaides, PhD, Frederick University, Cyprus Demetris Nicolaides , PhD, Frederick University, Cyprus Polycarpos Polycarpou, PhD, Agricultural Research Institute, Cyprus Panayiotis Dalias, PhD, Agricultural Research Institute, Cyprus
Presentation Content 1. Study Motivation 2. Theoretical Background 3. Methodology 4. Results and Discussion 5. Conclusions
1. S tudy Motivation • Sewage sludge: by-product of the treatment process of wastewater • One of the most challenging problems of environmental control • Existing practices for the disposal of sewage sludge are seen as insufficient and/ or harmful for the natural environment • Alternative practices, which are environmentally viable and perform better in terms of sustainability
1. S tudy Motivation Key objectives • Demonstrate the environmental performance of treating sewage sludge for biogas and agricultural use for the case of Cyprus • Implement Life Cycle Assessment (LCA) for evaluating the potential environmental benefits of the defined sewage sludge treatment system
2. Theoretical Background – S ewage sludge • Available routes and process systems for the treatment of sewage sludge permit the recovery of valuable minerals and energy from a hazardous waste Figure 1 S ewage sludge treatm ent scenarios (Xu et al., 20 14)
2. Theoretical Background - LCA Compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product/ system throughout its life cycle Assists in identify opportunities inform decision-makers select relevant indicators of environmental performance marketing
2. Theoretical Background - LCA
3. Methodology – S cope Definition • Management route (system) under investigation: Treatment of sewage sludge for biogas and agricultural use for the case of Cyprus • Scope: Definition of the environmental performance of the defined sewage sludge treatment system (gate-to-gate) • Functional unit: 1 tonne of sewage sludge dry solids • System boundaries: Product manufacturing (Gravity thickening, Anaerobic Digestion, Drying)
3. Methodology – S cope Definition Figure 2 S ystem boundaries of sewage sludge treatm ent for biogas and agricultural use for the case of Cyprus (Xu et al., 20 14)
3. Methodology – S cope Definition Figure 2 Process and system boundaries of sewage sludge treatm ent for biogas and agricultural use system (GaBi software)
3. Methodology - LCI System Processes Inputs Am ount Units Outputs Am ount Units 01. Gravity Sewage sludge 1000 kg Sewage sludge 1000 kg Thickening m 3 PAM 4 kg Wastewater 3,56 Electricity 39,5 kWh 02. Anaerobic Sewage sludge 1000 kg Sewage sludge 600 kg Digestion m 3 Electricity 153,85 kWh Wastewater 3,56 Electricity 615,38 kWh Regeneration Energy Regeneration 12500 MJ 3. Drying Sewage sludge 600 kg Sewage sludge 600 kg (treated, dry) Electricity 39 kWh Energy 1530 MJ Table 1 Life Cycle Inventory (LCI) of sewage sludge treatm ent for biogas and agricultural use system (Xu et al., 20 14)
4. Results and Discussion Environmental impact categories - CML 2001 methodology: • Global Warming Potential (GWP 100 years), • Acidification Potential (AP), • Eutrophication Potential (EP), • Ozone layer Depletion Potential (ODP, steady state), • Resource Depletion, Mineral, Fossil, and Renewable (ADP elements & fossil), • Photochemical Ozone Creation Potential (POCP)
4. Results and Discussion - LCIA System Processes Environm ental Im pact Categories GWP [kg AP [kg ODP [kg ADP Elements ADP POCP [kg CO2- SO2- R11- [kg Sb-Equiv.] Fossils Ethene- Equiv.] Equiv.] Equiv.] [MJ] Equiv.] 0 1. Gravity Thickening (Electricity 34,31 0,29 0,04 0,15 435,87 0,02 Consum ption) 0 1. Gravity Thickening 133,65 1,13 0,14 0,58 1697,70 0,06 (PAM Manufacturing) 0 2. Anaerobic Digestion 21,45 0,06 3,11 0,50 448,97 0,01 (Electricity Consum ption) TOTAL 189,42 1,48 3,29 1,23 2582,54 0,08 Table 2 Life Cycle Im pact Assessm ent (LCIA) results of sewage sludge treatm ent for biogas and agricultural use system
4. Results and Discussion - Interpretation 1. GWP: Total of 190 kg of CO 2 - equivalent, of which the 70% is attributed to the polymer production, followed by electricity consumption in the GT and AD stages respectively 2. AP and POCP: Polymer production represents the 75% of the total impact. Energy demand for gravity thickening is responsible for the 20% of the total impact for the AP and the 25% for the POCP categories 3. ODP: Required electricity for the AD stage is the main contributor of the impact with 3.11 kg of R-11 equivalent, ie. 95% contribution 4. ADP: Polymer production represents the 47% of the total for the ADP elements and 65% for the ADP fossils categories. Significant contribution of the AD stage in the ADP elements category, ie. 40% contribution
4. Results and Discussion - Interpretation 5. Drying stage: Utilises electricity and energy generated by the biogas in the previous stages, thus appears to have no contribution. Drying does not always require an additional supply of energy and therefore carries no extra costs in sewage sludge treatment management (Cieslik et al., 2015) 6. Non- renewable energy consumption: The treatment of 1 tonne of sewage sludge dry solids consumes a total of 2890 MJ, of which 80MJ are sourced from renewable energy resources 7. Carbon dioxide emissions: The treatment of 1 tonne of sewage sludge dry solids emits 183 kg of CO2. Environmentally superior than conventional fuels, given that the combustion of 1 tonne of conventional fuels emits 3.1 tonnes of CO2.
5. Conclusions The treatment of sewage sludge for energy generation and agricultural use is an environmentally viable and sustainable solution for the final disposal of a toxic and difficult to handle waste material The LCA revealed indicative figures of the potential of sewage sludge treatment, and significant influential factors of the system’s environmental impact, ie. use of coagulation agents This work provides a drive for further research in sewage sludge environmental management and treatment in Cyprus for both the local scientific community and the relevant decision- makers
Alternative Sewage Sludge Management Routes in Cyprus CYPRUS 2016 4th International Conference on Sustainable Solid Waste Management, Limassol, 23–25 June 2016 Angeliki Kylili, MSc, Frederick University, Cyprus Paris Fokaides, PhD, Frederick University, Cyprus Demetris Nicolaides , PhD, Frederick University, Cyprus Polycarpos Polycarpou, PhD, Agricultural Research Institute, Cyprus Panayiotis Dalias, PhD, Agricultural Research Institute, Cyprus
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