Waste and Biomass Processing as a Contribution to Sustainable Development

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1 Waste and Biomass Processing as a Contribution to Sustainable Development Petr Stehlik Brno University of Technology Institute of Process and Environmental Engineering (VUT UPEI) 1

2 Background and Societal Impact Renewable energy Waste to Energy systems (WTE) = waste disposal + energy utilization Biomass processing (combustion, gasification, biogas generation, ) Air Exhaust gas Society Water Raw materials Energy Waste water WTE Waste 2

3 Growing World Energy Consumption ( ) Recent history of total world energy consumption (in MtOE/yr) exhibits steady growth (International Energy Agency, Key World Energy Statistics, 2006) ** negligible (wind, solar etc.) ** 3

4 Current and Expected Share of Renewable Energy in World Consumption Prediction uses mean growth rate of consumption Present share of combustible renewable and wastes is ca 11 % Expected share of renewables in 2050 is ca 22 to 39 % (World Energy Council, 2000 and International Energy Agency, 2004) 4

5 Ever-Present (if not Renewable) Waste The average municipal waste production in the EU countries per capita 600 kg per capita In EU, amount of municipal waste increases by ca 2.3 % yearly (average from 2000 to 2004) EU-25 total MSW amount in 2004 was 250 Mt/yr Average amount of MSW per capita USA: 700 to 800 kg/yr EU: 540 kg/yr

6 Options for Dealing with Waste Recycling the priority Land filling totally un-sustainable and thus undesirable Thermal treatment enables waste utilization (waste-to-energy) and therefore it is better than land filling, provided that auxiliary fuel consumption is low and emissions are well controlled. Non-thermal treatment may be a good option, but only for a fraction of MSW (bio-degradable part of MSW), requires waste sorting Note: sewage sludge = potential for energy utilization 6

7 Biomass thermal processing Significant recent developments in biomass-based heat and power production Small boilers for individual houses are becoming commonplace Sophisticated systems for large-scale heat and power generation from biomass are operated modelling (CFD) optimization 7

8 Technical Principles Energy Potential of MSW Estimated average calorific walue of MSW is 10 MJ/kg (locationspecific) Total calorific value of MSW in EU per year is ca 2500 PJ/yr = 59 MtOE/yr Assuming 30 % efficiency of electric power production from waste incineration The calorific value of waste in EU is approx. 10 % of total EU electric energy consumption Fraction of incinerated MSW in EU is approx. 22 % 8

9 Municipal Solid Waste (MSW) Incineration Typically one-stage incineration process (combustion chamber of a boiler) Auxiliary fuel energy consumption is usualy small Large energy production Emissions control technologies are successful in making MSW incineration a clean energy source Power Internal power demand G Q prod Steam SCC Steam I circ ESP HRSG Ew Waste Ef DENOX I circ Supplementary fuel SCRUBBER Combustion air Condensate I imp STACK Natural gas 9

10 Typical Waste Water Treatment Plant (WWTP) Sludge Incinerator For self-sustained combustion of sludge, drying is necessary (minimum 60 to 70 % of dry matter) Steam, Steam 14 t/hr Combustion air Fluegas 900 C 200 C HRSG 170 C Air-Preheater Stack Off-gas cleaning 10 MW 200 C Natural gas 600 to 800 mn3/hr Sludge 7,5 t/hr Sludge, 10

11 State-of-the-Art Selection of Technology Database of best available technologies (BAT) exists Combustors Waste heat boilers for steam generation and electricity production Gas cleaning processes Applicability of technologies to the treatment of any specific waste must be carefully considered Factors influencing selection of incineration technology include: Waste-to-energy is a priority Environmental legislation Locality 11

12 Economical Factors in Municipal Thermal Waste Treatment Typically low auxiliary noble-fuel consumption (only during startup and shutdown) Heat utilization is critical for plant profitability Low on-site energy consumption in incinerator implies the necessity to export heat or electricity Prices of heat and electricity determine plant profitability Design of heat recovery system is tightly connected with integration of waste-to-energy plant into surrounding networks 12

13 Example: WWTP Sludge production and Treatment EU production of WWTP sludge is ca Mt/yr Sewage sludge treatment options in some EU countries: [%] m lgiu Be ark nm De Agriculture e nc Fra y an rm Ge Landfill s nd rla the e N Combustion ain Sp dk ite Un c m bli do pu ing Re h ec Cz Deposition in see Other 13

14 Barriers Waste Disposal or Utilisation? Recent focus on incineration highlighted environmental impacts, not performance Legislative definition of the status of thermal waste treatment is the subject of Europe-wide discussions (unified definition and methodology is currently nonexistent) Advanced technologies for off-gas cleaning are available, that can accommodate very strict emission standards Further tightening of emission limits represents more economical than technical issue 14

15 Limitations of biomass utilization Biomass is a local source of energy (long distance transport increases fuel costs and reduces positive environmental impact) Presently available biomass combustion units are not universal, they are always highly specialised for a specific type of biomass Emissions from small applications are difficult to abate (the pollutants produced include polychlorinated dioxins/furans concentration up to 7 ng TEQ/mN3, polyaromatic compounds, etc.) 15

16 Options for Sewage-Sludge Disposal Barriers Land filling neither material nor energy utilisation Agriculture (land spreading, composting) Material utilization (replacement of a part of mineral fertilizers) Strict legal limits for sludge qualities (content of heavy metals, pathogens etc.) Thermal treatment - energy utilization, reduction of biodegradable material, Co-firing in cement works Calorific value of de-watered sludge is too low for incineration without auxiliary fuel 16

17 Recommendations How about applying process integration (synergy) to MSW and WWTP sludge incineration? WTEC WTEC (Waste to Energy Center) Waste heat WWTP WWTP MSW Incinerator MSW Incinerator Power Power Biogas Utilization Biogas Utilization Sludge Incinerator Steam Digested Sludge CHP CHP Natural Gas? Digested Sludge Transport Sludge Incinerator Steam Heat Power and Heat Additional Emissions Heat and Power 17

18 Example: Integrating MSWI and sludge incinerator Steam Potential effects: City of approx. 1 mil. inhabitants CHP Steam Stack Combustion air Waste Heat MSW Incinerator HRSG Dryer Natural Gas Air Preheater Off-gas cleaning MSW production..400,000 t/yr WWTP sludge prod...50,000 t/yr Fuel saving.3,000 toe/yr Increasing efficiency Sludge Sludge Incinerator of energy utilization by 3 to 4 % 18

19 Applying Synergy Effects Municipal solid waste Waste-to-Energy Centers (WTEC) Founding a WTEC brings WTEC Long-term environmental benefit Saving natural resources Generating profit General principles Waste sorting Recycling and special attention to bio-degradable waste Steady development in environmental legislation Respecting local conditions Small towns/villages vs. big cities Hazardous and industrial waste Waste gas Sludge from sewage plant up-to-date technology Energy Alternative fuels 19

20 Future Role of Biomass as an Energy Source The role of waste biomass as an energy source will increase. The growth will depend on governments policies and environmental regulations. Meeting the requirements concerning exhaust gases including toxic compounds concentration is easier with increasing capacity of units for biomass combustion. Processes for biomass gasification for consequent syngas/energy gas production for obtaining chemicals or biofuels will be further developed. 20

21 Respecting Local Conditions for founding WTECs 21

22 References 1. Sjaak L., Koppejan J., Handbook of Biomass Combustion and Co-Firing, Twente University Press, (2002) 1. Stehlík P., Puchýř R. and Oral J., Simulation of Processes for Thermal Treatment of Wastes, Waste Management, vol. 20, pp , (2000) 1. Liuzzo G., Verdone N. and Bravi M., The benefits of flue gas recirculation in waste incineration, Waste Management 27, pp (2007) 1. Pavlas M., Stehlik P., Oral J. and Sikula J., Integrating Renewable Sources of Energy into an Existing Combined Heat and Power System, Energy 31, pp (2006) 1. European IPPC Bureau, Reference Document on the Best Available Techniques for Waste Incineration, Brussles, available on (2005) 1. Niessen W. R., Combustion and Incineration Processes, Marcel Dekker Inc., USA, (1995) 1. Klass D. L., Biomass for Renewable Energy, Fuels, and Chemicals, Academic Press, San Diego, (1998) 22