BioDigestion and Biogas Energy

Ruihong Zhang, PhD, ProfessorBiological and Agricultural Engineering Department

University of California, Davis Email: rhzhang@ucdavis.edu

November 20, 2014

BioDigestion- Anaerobic Digestion

Biogas

Sugars,

Amino acids,

Fatty acids

CH4, CO2

Anaerobic Digester

H2 , CO2

Organic acids

Biogas Energy Electricity and heat

Renewable natural gas

Digestate for

Water and

Fertilizer• Fibers

• Nutrients

• Water

Organic Waste Food

Green

Agricultural

Organic Resource Recovery with Advanced Anaerobic Digestion

3

Feedstock for Anaerobic Digesters: Food Processing and Agricultural Residues, Animal Manures,

Municipal Solid Waste,

• Diverts organic waste – food , green and agricultural – from landfills;

• Produces bioelectricity, heat & renewable Natural Gas to power homes and vehicles;

• Converts byproducts to valuable organic soil amendments for farming; and

• Captures greenhouse gases & other harmful emissions.

BioDigestion - Anaerobic Digestion

• Theromophilic digestion (three stage)

• Capable of treating a variety of organic solid waste

• Fast digestion rate and short retention time

• High biogas energy output

• Destruction of pathogens in waste, producing safe biofertilizers

High Solids Anaerobic Digestion (HSAD) Technology Developed at UC Davis

5

Water Recycle

Solids

Compost

Solid

Waste

Wet Grind

Hydrolysis Biogasification

Liquid

Effluent

Biogas

Biostablization

Grinder1st

Stage

2nd

Stage 3rd

Stage

High Solids Anaerobic Digester

(HSAD) System

Concept

development

laboratory

testing

Engineering design

Equipment selection

Construction,

Operation,Monitoring,

Process scale-up

Pilot testing

0.5-6 Gallons

50,000 Gallons>300,000 Gallons

Commercialization

By CleanWorld

20112000 2004 20122005 20102008

Pilot DesignPilot

Construction

Pilot Testing

Economic and

Environmental

Analyses

2007

Design

commercial

plants

Concept to Commercialization for High Solids Anaerobic Digestion (HSAD) Technology

CleanWorld’s Commercial Digester Projects

• American River Packaging – 10 ton per day organic wastes (papers and food waste)

• City of Sacramento – 100 ton per day organic waste (food, yard and paper waste) (25 ton per day in first phase and 75 ton per day in second phase)

• UC Davis Renewal Energy Anaerobic Digestion Project – 50 ton per day mixed waste (food waste, animal waste, etc.)

• Treats 20,000 tons per year of mixed organic wastes

• Combines biogas and landfill gas to generate 5.6 GWhelectricity per year

• Jointly developed by CleanWorld and UC Davis, with funding support from US Department of Energy, and the California Energy Commission and private investors

UC Davis Renewable Energy Anaerobic Digester

Completed in January 2014

UC Davis Renewable Energy Anaerobic Digester

Digester Feedstock: Food Waste Food Processing Waste

• Increase renewable energy supplies

– 5.6 million kWh per year

• Reduce greenhouse gas emissions

– Electricity ≈ 4,000 metric tons CO2e /year

– Feedstock emissions ≈ 6,000 metric tons CO2e/year

• Reduce waste sent to municipal landfills

– 50 tons/day from UC Davis campus and the region

(20,000 tons/year)

UC Davis Renewable Energy Anaerobic Digestion (READ) Project Benefits

• 6 Percent of Greenhouse Gases

come from the production of

fertilizers, more than cement

production, aviation and iron and

steel production

• A typical BioDigester will produce

enough liquid and solid fertilizer

product to provide nitrogen for 290

acres of California farmland,

every day

• CleanWorld Organics specializes in

creating high value fertilizer

products from digester effluent

• Custom design soil products

according to the feedstock

characteristics and market needs

Fertilizer and Soil Products from Digestate

Digestate Processing and BiofertilizerProduction

• Characterization and analysis of digestate • Solids, fibers, nutrients and salt • Particle size

• Digestate Processing for separation, • concentration, and odor reduction

• Filtration • Membrane Separation • Aeration

• Solid and liquid fertilizer production • Pelletized fertilizer • Liquid Fertilizer

Fertilizer Production from Digestate

Testing Digestate As Organic Fertilizer Products

Testing Variables • Digestate dilution • Application rate • Application schedule

Measurement • Plant size • Plant biomass • Chlorophyl in leaves • Nutrients uptake• Soil properties

RAD (50%) RAD (25%)

RAD (12.5%)

RAD (6.25%)

Determining optimum application method and rate of raw anaerobic digestate (RAD)

Field Testing of Digestate

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