UC Davis Biogas Energy Project
Ruihong Zhang, Professor
Biological and Agricultural Engineering
University of California, Davis
Email: rhzhang@ucdavis.edu
AWWEE Workshop: Major Drivers to Transformation in
California Energy and Water Markets
May 22, 2012, Sacramento
Presentation Outline
• Status of anaerobic digestion technologies and
opportunities for further development
• UC Davis Biogas Energy Project for new
technology development, demonstration and
commercialization
$$$
Value Positioning of
Biogas Energy Systems
Biogas Energy
Biogas
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Organic Waste
 Food
 Collected Green
 Agricultural
CH4, CO2
H2 , CO2
Organic acids
Sugars,
Amino acids,
Fatty acids
Anaerobic Digester
 Electricity and heat
 Natural gas
 Compressed natural gas
 Liquefied natural gas
Gasoline
Chemicals
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Digester
Effluent
 Nutrients
Fibers
 Water
$$$ Carbon Credit
Wastewater Digestion Technologies
• Current status
– Well established for treatment of sewage, animal manure
(swine and dairy), and some food processing wastewater
– Common technologies: covered lagoon, completed mixed
digester, plug flow digester, upflow sludge blanket reactor
(UASB)
• Opportunities for new technology development
– Creative digester design and integration of unit operations to
provide higher energy efficiencies and more capabilities to
handle variable influent
– Co-digestion of different wastes (e.g. food waste with sewage
or manure)
Solid Waste Digestion Technologies
• Current status
– Europe has several technologies in commercial use
for more established markets.
– US has the first commercial technologies for
emerging markets
• Opportunities
– Digester technology implementation and
integration of digestion with waste preprocessing
and composting operations
– US project and business models
Organic Resource Recovery with
Solid
Organic
Residuals:
Advanced
Anaerobic
Digestion
Food Processing and Agricultural Residues, Animal Manures,
Municipal Solid Waste,
6
A Real Problem with Solid Waste
• Millions of tons of organic waste dumped in landfills every year
result in harmful greenhouse gas (GHG) emissions
• Mandates require businesses producing high volumes of
organic waste to seek more sustainable waste disposal
solutions
• Businesses have committed to sustainability and are now
scrambling to follow through
– Wal-Mart: Zero waste by 2014; all suppliers must report
waste and greenhouse gases
http://walmartstores.com/sustainability/9292.aspx
– Campbell: new sustainability policy
http://www.campbellsoupcompany.com/csr/planet.asp
• Anaerobic digestion (AD) of organic solid waste has not been
successfully implemented in the US to date in commercial scale
Food Scraps in the US (EPA)
• Amount of food scraps
– 44 million tons per year
– 25% food prepared
• Cost of disposal
– $1 billion per year
– $20 per ton
• Current method of management
– 97% disposed in landfill
– 3% recovered for composting
or combustion
Needs For Efficient Solid Waste Digester
Technologies
• Capable of handling multiple and variable
biomass feedstock from different supply
sources
• Can be easily scaled up and down
• Easy to operate and maintain (automation)
• High conversion efficiencies and smaller foot
prints
• Affordable cost
Biogas Energy Project at UC Davis
• Research and demonstration of new anaerobic digestion
and biogas energy technologies for converting various
organic residuals into biogas energy and biobased
products
• Public education on waste to energy conversion and
environmental management
UC Davis Biogas Project Sponsors
UC Davis Technology
Anaerobic Phased Solids (APS) Digester
• Two-stage digestion system that has first stage sequential
batch loaded digester and continuous second stage digesters
• Allows for high system stability regardless of fluctuations in
loading and waste composition
• Provides even gas production and rapid waste digestion
• Mesophilic and thermophilic temperature options
• Can be configured for sustained hydrogen and methane
production
• Well suited for treating high-solids (10 - 50% total solids)
lignocellulosic waste streams, such as:
– Municipal solid wastes
– Green and food wastes
– Agricultural residues
APS Digester Technology
Biogas
Day 10-12
Biogasification Reactor
Hydrolysis Reactors
Digesting Organic Acids and Converting Solids into Organic Acids and Producing
Producing Methane Gas
Hydrogen Gas
Residual Material & Water
Drained & Separated
Separated Water Returned to
Tank; Excess Discharged for
Treatment & Recycling
Separated Solids
Post treatment for Soil Amendment
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UC Davis Technology
High Rate Digester (HRD)
• Three stage anaerobic digestion
• Well suited for treating highly degradable
solids waste streams and mixed solid/liquid
waste streams, such as:
– Municipal food waste
– Food processing waste
– Biosolids
– Meat product waste
slide 14
HRD: High Rate Digester
Biogas
Out
Liquid Feed
Solids Feed
Hydrolysis
Reactor (HR)
Biogasification
Reactor (BGR)
Separator
Biostabilization
Reactor (BSR)
Grinder
Solids
Wet Grind
Water Recycle
INPUTS
PRESSURE, TEMPERATURE,
MASS FLOW, pH, LEVEL,
OTHER INPUTS
OUTPUTS
CONTROLS AND
DATA ACQUISITION
PROPRIETARY MIXING, CONTROL & MEDIA
VALVES, PUMP BOILER
MIX, PUMP OVER, TRANSFER
PERF., PERFORMANCE & DATA
TREND
Liquid
Effluent
UC Davis Biogas Project
APS Digester Demonstration System
Digester capacity – 3-5 tons per day,
Digestion temperature – 125-135 F , Digester volume – 50,000 gal
Expected biogas yield –350-583 m3/day,
Electricity output – 600- 1200 kWh/day
16
Food Processing Residuals from
Campbell Soup Plant in Sacramento
Food Waste (Average):
Moisture – 80%
Total Solids – 20%
Volatile Solids – 19%
APS-Digester Performance
• Digester testing with 200 tons of food processing
residuals from June 2008 to April, 2009
• Digester Performance Summary:
– Solids reduction in food waste:
89.5% for total solids, 90% for volatile solids
– Biogas production: average 4,600 ft3/ton (wet)
– Methane production: average 2760 ft3/ton (wet) (7 ft3/lb
VS)
– Energy content in biogas: 27 therm/ton (wet)
– Biogas composition: 55-60% methane, 2-5% hydrogen
– Digester pH: 5-7 for hydrolysis reactor and 7-8 for
biogasification reactor.
Clean World Partners Commercial Projects
• American River Packaging – 8-10 ton per day
mixed organics (papers and food waste)
• City of Sacramento – 25 ton per day organic
waste with a potential to expand to 300 ton
per day capacity
• UC Davis Renewal Energy Anaerobic Digestion
Project - 22-35 ton per day mixed campus
waste (animal manure, food scraps, papers,
yard waste, etc.)
Clean World Partners Built the First Commercial
Digesters for Food and Paper Waste at American River
Packaging, Sacramento
www.cleanworldpartners.com
Clean World Partners Projects
American River Packaging (ARP): Packaging
manufacturer with corrugated waste
• 8 tons per day (0.5 cardboard and 7.5 tons food
waste)
• System size 10 tpd (accounting for paper
absorption)
• Producing 1300 kWh per day of electricity with
micro-turbines for use on site
• Food waste coming from local food processors
• System continuously operating since March 16,
2012
slide
24
ARP Organic Waste Recycling Center
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Clean World Partners Current Projects
UC Davis: Moving towards zero waste and showcasing
conversion of closed landfill into valuable resource
• Phase I - 25 tons per day manures from campus and
food waste from campus dining facilities
• Phase II – 35 to 50 tpd separated organics from MSW
• Allow other surrounding communities to use digester
system
• Combining landfill collection and digester gas streams
• Producing electricity to feed its net zero community
• Sophisticated preprocessing system
• Opening December 2012
slide
26
UC Davis CWP Project
slide 28
Successful Technology Development and
Commercialization
• Research innovation and technology
development
• Public and private investment and partnership
• Competent and effective technical,
management, and business development
• Favorable market environment