HERC Waste Summit

Waste Conversion Technologies101: 

Waste Conversion Technologies 101 James Liao and Vasilios Manousiouthakis UCLA Chemical & Biomolecular Engineering Department & Hydrogen Engineering Research Consortium

Slide2: 

Hercules cleaning up the stables of Augeas, following Athena’s suggestion on where to dig, so as to let the water clean the accumulated dirt UCLA Hydrogen Engineering Research Consortium (HERC)

Slide3: 

Solid Waste Generation and Management Trends in municipal solid-waste generation and management in the United States, 1960-2010 (Source: NAE 2000).

Slide4: 

Material Classes in the Waste Stream *1999 California Statewide http://www.ciwmb.ca.gov/WasteChar/Study1999

Municipal Solid-Waste composition by weight: 

Municipal Solid-Waste composition by weight *Source: NAE 2000

Slide6: 

*R. B. Williams et al. 2003

Cellulosic Waste : 

Cellulosic Waste Biomass components of MSW: Paper/Cardboards 30.2% Food 15.7% Leaves and Grass 7.9% Other Organics 7.0% C&D Lumber 4.9% Prunings, Trimmings 2.4% 68.1% Estimated Cellulosic Components: 40-50% MSW: 40 M tons. Cellulosic components: 15-20 M tons.

Conversion Technologies: 

Biochemical: Anaerobic Digestion Aerobic conversion Fermentation Thermochemical: Pyrolysis Gasification Conversion Technologies

Biochemical - Anaerobic digestion: 

A fermentation technique typically employed in waste water treatment facilities but also the principal process occurring in landfills. Produces fuel gas called biogas containing mostly methane and carbon dioxide but frequently carrying impurities such as moisture, H2S, siloxane. Anaerobic digestion requires attention to the nutritional demands of methanogenic bacteria degrading the waste substrates (C/N ratio is important.) Biogas can be used as fuel for engines, gas turbines, fuel cells, boilers, industrial heaters, other processes, and the manufacturing of chemicals. Biochemical - Anaerobic digestion

Slide10: 

Aerobic conversion uses air or oxygen to support the metabolism of the aerobic microorganisms degrading the substrate. Nutritional considerations are also important to the proper functioning of aerobic processes. Aerobic processes operate at much higher rates than anaerobic processes, but generally do not produce useful fuel gases. Biochemical - Aerobic Conversion

Slide11: 

Fermentation generally used industrially to produce fuel liquids such as ethanol and other chemicals. Also operates without oxygen. Cellulosic feedstocks including the majority of the organic fraction of MSW, need pretreatment (acid, enzymatic, or hydrothermal hydrolysis) to depolymerize cellulose and hemicellulose to monomers used by the yeast and bacteria employed in the process. Lignin in biomass is refractory to fermentation and as a byproduct is typically considered for use as boiler fuel or as a feedstock for thermochemical conversion to other fuels and products. Biochemical - Fermentation

Converting Cellulose to Ethanol: 

Converting Cellulose to Ethanol Currently, the cost of producing ethanol from cellulose is estimated to be between $1.15 and $1.43 per gallon in 1998 dollars. The cost of producing ethanol could be reduced by as much as 60 cents per gallon by 2015. 20 M tons of cellulosic wastes (in CA)  1-2 Billion gal Ethanol. ~ 300 billion gal gasoline/yr used in US.

Slide13: 

Industrial Process For Fuel Ethanol

Cellulosic Material Pre-treatment: 

Cellulosic Material Pre-treatment 40–50% cellulose, a glucose polymer 25–35% hemicellulose, a sugar heteropolymer 15–20% lignin, a non-fermentable phenyl-propene unit; desirable Remove, destruct

Methods of Pretreatment: 

Methods of Pretreatment Dilute Acid, Ammonia, or Lime Wyman, et al, Bioresource Technology (2005) 1959–1966

Conceptual Process for Cellulosic Ethanol Production: 

Conceptual Process for Cellulosic Ethanol Production Pretreatment to remove or destruct hemicellulose and lignin Size reduction Enzyme digestion to Release glucose Yeast Fermentation Ethanol distillation Cellulosic Waste

Current Bio-Ethanol : 

Current EtOH Production = 3.4 billion gal/year (1.3% of gasoline energy) Incentives for Bio-ethanol production $0.51 tax credit per gal Energy Policy Act (EPACT) mandate: up to 7.5 billion gallons of Bio renewable fuel to be used in gasoline by 2012. Current agriculture waste stockpile (corn stover) will give 7-12 b gallons of EtOH. Current Bio-Ethanol

Corn Ethanol: 

Corn Ethanol $0.04/gal Production cost: $1.18/gal, Selling price: $1.35-2.6/gal From G. Chotani,

Cellulosic Ethanol: 

Current enzyme cost: $0.45/gal Potential enzyme cost: $0.10/gal Cellulosic Ethanol Currently, the cost of producing ethanol from cellulose is estimated to be between $1.15 and $1.43 per gallon in 1998 dollars. The cost of producing ethanol could be reduced by as much as 60 cents per gallon by 2015.

Slide20: 

Similar to gasification except generally optimized for the production of fuel liquids (pyrolysis oils). Usually, processes that thermally degrade material without the addition of any air or oxygen are considered pyrolysis. Direct pyrolysis liquids may be toxic, corrosive, oxidatively unstable, and difficult to handle. Catalytic cracking employs catalysts in the reaction to accelerate the breakdown of high molecular weight compounds into smaller products. Thermochemical - Pyrolysis

Thermochemical - Gasification: 

Conversion via partial oxidation using substoichiometric air or oxygen or by indirect heating Produce fuel gases (synthesis gas), principally CO, H2, methane, and lighter hydrocarbons in association with CO2 and N2. Gasification products can be used to produce methanol, Fischer-Tropsch (FT) liquids11, and other liquid and gaseous fuels and chemicals. Thermochemical - Gasification

Slide22: 

Gasifier Types Reactant contacting patterns Operating temperatures Moving bed (nonslagging, countercurrent) Fluidized bed C) Entrained flow D) Molten bath

Waste Gasification Technologies: 

Advantages of moving-bed gasifiers (1) The technology is mature with many commercial designs available. (2) A large variety fuels can be used. (3) The gasifier may be operated for long periods. (4) The carbon conversion efficiency is high. (5) The thermal efficiency is high because of countercurrent flow. Disadvantages of moving-bed gasifiers (1) Internal moving parts with some mechanical complexity are employed (2) Gasifier capacity is limited by gas flow rates (3) Feedstock fines must be handled separately (e.g., via agglomeration) (4) Excess steam for temperature control leads to thermal losses Waste Gasification Technologies

Waste Gasification Technologies: 

Waste Gasification Technologies Advantages of fluidized-bed gasifiers (1) Commercial designs are available (2) The technology does not involve moving parts (3) The large fuel inventory provides safety, reliability, and stability (4) A large variety of fuels can be handled (5) The amount of tar and phenol formation is low (6) Product composition is steady due to uniform conditions in the bed (7) Moderate gasification temperatures can be used Disadvantages of fluidized bed-gasifiers (1) Capacity flexibility is limited by entrainment at high gas velocities (2) Caking wastes may require pretreatment (4) Difficult to handle feeds with conflicting temperature requirements (5) Loss of carbon in ash occurs due to uniform solids composition of the bed

Waste Gasification Technologies: 

Advantages of Entrained-Flow Gasifiers (1) Commercial designs are available (2) The gasifier has no moving parts and a simpler geometry than a fluidized bed (3) The gasifier has the highest capacity per unit volume (4) Any type of waste may be used without pretreatment (5) No fines are rejected (6) The product gas is free of tar and phenols (6) The slagged ash produced is inert and has a low carbon content Disadvantages of entrained-flow gasifiers (1) Nozzles and heat recovery in the presence of molten slag are critical design areas (2) Advanced control techniques required to ensure safe, reliable operation (3) Pulverizing and drying of surface moisture are required (4) The high gasification temperatures causes thermal losses Waste Gasification Technologies

Waste Gasification Technologies: 

Advantages of molten-bath gasifiers (1) The large heat inventory provides safety, reliability, and stability (2) The high-temperature bath ensures safe gasification (3) Wide variety of feedstocks can be used without pretreatment (4) Products contains no sulfur, halogens, tar, phenols (retained in molten bath) Disadvantages of molten-bath gasifiers (1) Cleanup of molten media is complicated (2) Capacity is limited by melt entrainment at high flow rates (3) Ash is removed as liquid slag, leading to loss of sensible heat (4) The melt is highly corrosive to refractory at the gasifier temperatures Waste Gasification Technologies

Gasification Process Flow Diagram: 

Gasification Process Flow Diagram Source: Orr D., Maxwell D., “A Comparison of Gasification and Incineration of Hazardous Wastes”, Radian International LLC Report for DOE, 2000

Slide28: 

Toxic Contaminants in Gasifier gas

Slide29: 

Toxic Metals in Gasifier ash

HERC Vision for MSW Management: 

HERC Vision for MSW Management Embrace Zero Waste Principles Develop Source Reduction/Recycling strategies Develop Material Substitution strategies based on sustainability concepts Convert material that reaches “waste” status to hydrogen, electricity, and usable/recyclable products, in facilities featuring only oxygen and nitrogen air emissions, and carbon sequestration

Slide31: 

Energy and Possible Water Flows Among Subsystems Not Shown Waste Recyclable Light Metals Gasification Subsystem Volatile Metal Separation Subsystem Chemical Manufacturing Subsystem Shift Subsystem Carbon Sequestration Subsystem Hydrogen Purification Subsystem Oxygen Production Subsystem Air Recyclable Heavy Metals Chemicals (HCL,HF,S,..) Nitrogen Oxygen Nitrogen, Oxygen Hydrogen Carbon (Dioxide or other chemical form) Oxygen Impurities A Zero-Waste Conversion Plant

Elements by Boiling Point: 

Elements by Boiling Point

Slide33: 

Dioxin Vapor Pressure Data taken from Rordorf et al., Chemosphere Vol. 15, #9 – 12; p. 2073 – 2076 (1986)

Natural Gas to Hydrogen: Steam reforming and CO2 sequestration: 

Natural Gas to Hydrogen: Steam reforming and CO2 sequestration Source: Posada A, Manousiouthakis V. “Hydrogen and dry ice production through phase equilibrium separation and methane reforming”, J. Power Sources (2005)

Natural Gas to Hydrogen: Steam reforming: 

Natural Gas to Hydrogen: Steam reforming CH4 + 2H2O = CO2 + 4H2 ΔHo: 164.9 kJ/mol CH4 H2O feed Cooling CH4 feed electricity heat Source: Posada A, Manousiouthakis V. “Hydrogen and dry ice production through phase equilibrium separation and methane reforming”, J. Power Sources (2005) Natural gas cost: 0.33 $/kg (Jul 2005) CO2 sequest. cost: 13 $/ton CO2

Biomass to Hydrogen: 

Biomass to Hydrogen Source: Spath PL, Mann MK, Amos WA. “Update of Hydrogen from Biomass-Determination of the Delivered Cost of Hydrogen”, NREL (2003)

Slide37: 

DaimlerChrysler-UCLA H2 Vehicle

Hydrogen Vehicle: 

Hydrogen Vehicle Source: “F-Cell Quick Reference Card”, Daimler Chrysler

PEM Fuel Cell Mechanism: 

PEM Fuel Cell Mechanism

Well-to-Wheels (WTW) Analysis: 

Well-to-Wheels (WTW) Analysis * Source: “Well-to-Wheels analysis of future automotive fuels and powertrains in the European context” (2004). Vehicle comparable to a Volkswagen Golf (33.8 mi/gal gasoline)

Hydrogen Safety: 

Hydrogen Safety *Source: “The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs”, National Research Council and National Academy of Engineering - © 2004 National Academies Press (page 240) †Source: “Hydrogen Fuel Cell Engines and Related Technologies Course Manual”, College of the Desert Energy Technology Training Center - © 2001 National Academies Press (module 1, pages 25 and 26)

Hydrogen v. Gasoline Vehicles: 

Hydrogen v. Gasoline Vehicles *Source: Dr. Michael R. Swain, University of Miami, Coral Gables Gasoline Leak: 1/16 in diameter hole in fuel line; 70,000 BTU energy released; one failure needed; flame visible Hydrogen Leak: Tank Pressure Release Device; 175,000 BTU energy released; four failures needed; flame visibility due to Na containing particulate matter

Hydrogen v. Gasoline Vehicles: 

Hydrogen v. Gasoline Vehicles

Hydrogen v. Gasoline Vehicles: 

Hydrogen v. Gasoline Vehicles

Hydrogen v. Gasoline Vehicles: 

Hydrogen v. Gasoline Vehicles