CHEM, INC. HYDRO GEO EVALUATING AEROBIC LANDFILL BIOREACTIONS USING A NUMERICAL MODEL By G.R. Walter, S.J. Smith, L. Major, and J. Tang

CHEM, INC. HYDRO GEOBACKGROUND SPACE FOR MUNICIPAL SOLID WASTE (MSW) LANDFILLS IS AT A PREMIUMSPACE FOR MUNICIPAL SOLID WASTE (MSW) LANDFILLS IS AT A PREMIUM DEGRADATION OF ORGANIC WASTE IN LANDFILLS IS SLOW DUE TO ANAEROBIC CONDITIONSDEGRADATION OF ORGANIC WASTE IN LANDFILLS IS SLOW DUE TO ANAEROBIC CONDITIONS CLOSED MSW LANDFILLS CAN GENERATE METHANE AND UNDERGO SUBSIDENCE FOR DECADESCLOSED MSW LANDFILLS CAN GENERATE METHANE AND UNDERGO SUBSIDENCE FOR DECADES METHANE RECOVERY FOR ENERGY FROM SMALL LANDFILLS IS UNECONOMICALMETHANE RECOVERY FOR ENERGY FROM SMALL LANDFILLS IS UNECONOMICAL

CHEM, INC. HYDRO GEO CONCEPT OF A SUSTAINABLE LANDFILL (SWITZERLAND, 1986) EACH GENERATION SHOULD MANAGE ITS WASTE TO FINAL STORAGE QUALITY (30 YEARS)EACH GENERATION SHOULD MANAGE ITS WASTE TO FINAL STORAGE QUALITY (30 YEARS) FINAL STORAGE QUALITY: Any emissions to the environment are acceptable without further treatment or controlFINAL STORAGE QUALITY: Any emissions to the environment are acceptable without further treatment or control UK FINAL STORAGE QUALITY CRITERIAUK FINAL STORAGE QUALITY CRITERIA –Reduce landfill gas generation by 99.9 % (200 cubic meters/metric ton to 0.1 cubic meters/metric ton) –Leachate quality determined by local environmental conditions

CHEM, INC. HYDRO GEO CONCEPT OF THE AEROBIC BIOCELL PURPOSE:PURPOSE: –Speed the degradation of organic waste by creating aerobic conditions ADVANTAGES:ADVANTAGES: –Preserve disposal space in active landfills and extend their life –Limit or eliminate methane production in closed landfills –Promote consolidation of refuse to improve future land use OPERATING PRINCIPLES:OPERATING PRINCIPLES: –Derived from composting science and experience

CHEM, INC. HYDRO GEO CONCEPTUAL MODEL OF AEROBIC BIOCELL + O 2 + ORGANIC WASTE + CO 2 + H 2 O + HEAT

CHEM, INC. HYDRO GEO OPERATING FACTORS WATER APPLICATIONWATER APPLICATION –Maintain Desired Moisture Content to Support Microbial Population –Replace Water Removed by Evaporation TEMPERATURE CONTROLTEMPERATURE CONTROL –Aerobic Biodegradation Releases Approximately 3600 cal/gm substrate oxidized –Optimal Biodegradation: 40 to 60 o C (100 to 140 o F) –Prevent Hot Spots that May Result in Spontaneous Combustion > 80 o C (180 o F)> 80 o C (180 o F)

CHEM, INC. HYDRO GEO BIODEGRADATION RATE AS A FUNCTION OF TEMPERATURE

CHEM, INC. HYDRO GEO PRIMARY HEAT REMOVAL PROCESSES VAPORIZATION OF WATERVAPORIZATION OF WATER ADVECTIVE TRANSPORT OF HEAT IN AIR FLOWADVECTIVE TRANSPORT OF HEAT IN AIR FLOW

CHEM, INC. HYDRO GEO VAPORIZATION OF WATER HEAT OF VAPORIZATION

CHEM, INC. HYDRO GEO THERMAL PROPERTIES OF WET AIR

CHEM, INC. HYDRO GEO TYPICAL ENERGY BALANCE (% of total energy) Heat in Applied Water (2%) Heat In Injected Air (7%) Heat in Extracted Air (24%) Heat Associated with Water Vaporization (75%) Heat Released during Aerobic Degradation (90%) Initial Heat of Refuse (1%) Final Heat of Refuse (1%)

CHEM, INC. HYDRO GEO PROCESSES SIMULATED AIR FLOWAIR FLOW –DARCY’S LAW APPLIED TO COMPRESSIBLE FLUID –LINEARIZED HEAT TRANSPORTHEAT TRANSPORT –ADVECTION IN AIR FLOW –CONDUCTION THROUGH SOIL –HEAT CAPACITY OF AIR FUNCTION OF TEMPERATURE AND WATER CONTENT (ABSOLUTE HUMIDITY) OXYGEN TRANSPORTOXYGEN TRANSPORT –ADVECTION AND DISPERSION IN AIR FLOW BIOGENIC HEAT PRODUCTIONBIOGENIC HEAT PRODUCTION –IMMOBILE SUBSTRATE (REFUSE) –HEAT GENERATION FUNCTION OF: TemperatureTemperature Oxygen (Monod Rate Equation)Oxygen (Monod Rate Equation)

CHEM, INC. HYDRO GEO COUPLED, NON-LINEAR PROCESSES HEAT FLOW, HEAT GENERATION, AND OXYGEN TRANSPORT ARE COUPLED SIMPLIFICATIONS IN MODEL –AIR FLOW PROPERTIES NOT DEPENDENT ON TEMPERATURE –TRANSPORT EQUATIONS DECOUPLED (LINEARIZED) –ACCURACY CONTROLLED THROUGH TIME STEP –AIR ASSUMED TO APPROACH 100% HUMIDITY RAPIDLY IN REFUSE

CHEM, INC. HYDRO GEO COMPLEXITIES ASSOCIATED WITH USING WELLS AIR FLOW RATE DECREASES RADIALLY FROM WELLAIR FLOW RATE DECREASES RADIALLY FROM WELL ASSUMING ADEQUATE OXYGEN AND EQUAL TEMPERATURE, BIODEGRADATION RATE IS CONSTANTASSUMING ADEQUATE OXYGEN AND EQUAL TEMPERATURE, BIODEGRADATION RATE IS CONSTANT RATE

CHEM, INC. HYDRO GEO RELATIVE REACTION RATE VS GAS OXYGEN CONTENT

CHEM, INC. HYDRO GEO 1 day OXYGEN TEMPERATURE SCALE Gas Oxygen

CHEM, INC. HYDRO GEO 5 days 10 days 15 days20 days 25 days 30 days 35 days 40 days 45 days50days55days60 days

CHEM, INC. HYDRO GEO BIODEGRADATION RATE T O2O2 TEMPERATURE AND OXYGEN VS DISTANCE

CHEM, INC. HYDRO GEO SUMMARY AEROBIC BIODEGRADATION REACTIONS ARE GOVERNED BY COMPLEX INTERACTION BETWEEN AIR CIRCULATION RATES AND TEMPERATUREAEROBIC BIODEGRADATION REACTIONS ARE GOVERNED BY COMPLEX INTERACTION BETWEEN AIR CIRCULATION RATES AND TEMPERATURE THESE INTERACTIONS CAN LEAD TO INTERESTING AND SOMETIMES SURPRISING BEHAVIOR (AT LEAST IN NUMERICAL MODELS)THESE INTERACTIONS CAN LEAD TO INTERESTING AND SOMETIMES SURPRISING BEHAVIOR (AT LEAST IN NUMERICAL MODELS) THE MODELS DISPLAY SELF-LIMITING BEHAVIOR IN TERMS OF TEMPERATURE REGIMETHE MODELS DISPLAY SELF-LIMITING BEHAVIOR IN TERMS OF TEMPERATURE REGIME

CHEM, INC. HYDRO GEO BIORATE T, O 2, and BIORATE AFTER 20 DAYS 100 cfm O cfm O 2