Improving Cold Region Biogas Digestor Efficiency Cordova Electric - - PowerPoint PPT Presentation

Improving Cold Region Biogas Digestor Efficiency

Denali Commission Emerging Energy Technology Grant Cordova Electric Cooperative - Institute of Northern Engineering UAF - Cordova Schools

Climate limitation of conventional biogas production

(59°F)

Project Summary

• Experiment with cold-loving microbes (psychrophiles) to

improve efficiency in biogas digestors for generating cooking and heating gas for Alaskan households.

• Phase 1: Compare efficiencies of warm-loving, conventional digestor microbes

(mesophiles) and psychrophiles on common Alaskan feedstock at various temperatures.

• Phase 2: Application of digestors in practical household scale projects to
• perate appliances and an electrical generator to evaluate feasibility and

sustainability for widespread use in Alaska.

Clay Koplin Project Manager Cordova Electric Cooperative Executive

Project Partners

• Dr. Katey Walter Anthony

Principal Investigator INE UAF Laurel McFadden Peter Anthony Technical Assistants INE UAF T H Culhane Expert Consultant Solar Cities Adam Low Director of Operations Cordova Schools High School Students Research Technicians Cordova Schools Dennis Rose, Mgr. Feedstock Donor AC Value Center Engineers INE UAF

Collaborators: Autumn Bryson, Native Village of Eyak Bernie Karl, Chena Hot Springs Erika Behrends, Cordova Schools

Biogas

Biogas is a flammable gas created by bacterial degradation of an

• rganic food source, roughly:

~60% methane (CH4) ~35% carbon dioxide (CO2) ~5% other gases Biogas can be used as a fuel source in gas- burning technologies, such as

• stoves
• heaters
• lights
• electrical generators

Methanogens

ARE: bacteria that produce methane (CH4, biogas) HOW: anaerobic process, consortium of hydrolytic and fermentative bacteria WHERE: anywhere with the right environmental conditions and food source Biogas production is highly dependent on: Temperature, pH, nutrient availability, and carbon/nitrogen ratios

NASA and STScI

Organic Material Monomers

C-1 Compounds, H2

Acetate

Fatty acids, alcohols CH4, CO2

1 1 1 1 2 3 4 4

How can we use methanogens to produce a low-cost, sustainable supply of biogas as an alternative energy source?

Mimic their natural optimal environment and methanogens will naturally supply a continual source of biogas. The beginnings of digestor technology: Ruminant digestion systems

Conventional Digestor Technology

Collect ruminant manure:

• warm-loving microbial source
• feedstock source

Mix with water and seal in primary tank

• microbes consume O2 naturally  anaerobic conditions
• biogas production starts
• 2 to 4 weeks later (temperature dependent), biogas burns

Utilization:

• Direct methane to a biogas-burning technology

http://enviro-toons.com/page2.html

PROBLEM #1: manure is a nutrient-poor resource SOLUTION:

supply high-quality feedstock (rich in sugar and starch) for optimal biogas production – such as household organic waste

Problems with traditional digestors

PROBLEM #2: temperature limitation

The bacterial populations in ruminant digestion tracks are warm-loving microbes (mesophiles).

• Optimal methane production at 37°C
• Shuts down at 15°C
• Standard digestor technology only works if
• the equipment is built in warm climates
• the equipment is kept heated, at fuel costs

SOLUTION:

Improve biogas production for people who live in cold climates by inoculating digestors with cold-loving, Arctic methanogens (psychrophiles).

Where do we find cold-loving methanogens?

• Methane production at 0-1°C to 21°C
• Recently discovered (Zimov et al. Science 1997; Walter et al. Nature 2006)
• 4x more efficient than European psychrophiles that live at 5°C

Alaskan thermokarst-lake sediments

Cordova Experimental Digestor Set-up

Cold Room: 15C Warm Room: 25C

Psychrophiles Mixed Psychrophiles and Mesophiles Mesophiles Psychrophiles Mixed Psychrophiles and Mesophiles Mesophiles

Phase 1 Test Design

Collecting the Methanogens

Picking up manure at the Northern Lights Dairy farm in Delta Junction (mesophile collection) Coring for mud in Fairbanks (psychrophile collection)

Implement closed-tank system with water-pressure technology in tandem

New Pressurizing Design

Construction

Working at the Cordova High School

Data Monitoring: Gas Flow

Biogas Flame Test

Digestor First Biogas Produced 1 1/31/2010 2 NA 3 1/22/2010 4 2/1/2010 5 1/21/2010 6 1/26/2010

Digestors sealed on January 19, 2010

Data Monitoring: Chemistry

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 Temperautre (C) Date (mm/dd/yyyy)

Digestor #3: Interior Tank Temperature Trend

• 160
• 140
• 120
• 100
• 80
• 60
• 40
• 20

20 40 1/27/2010 1/28/2010 1/29/2010 1/30/2010 1/31/2010 2/1/2010 2/2/2010 2/3/2010 Oxidation/Reduction Potential (mV) Date (mm/dd/yyyy)

Digestor #1: ORP Trend

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Dissolved Oxygen Date (mm/dd/yyyy)

Digestor #5: Dissolved Oxygen Trend

Challenges Experienced

Freezing

• Water pressure system risks freezing and

breaking pipes at temperatures below 32F Maintaining optimal slurry temperature

• Energy expenditure in keeping microbes

comfortable Time costs

• Designing feasible feeding regimen for students
• Balancing scientific rigor with enthusiasm for

immediate application Availability of construction materials

• Limited local resources, extensive time required

to gather necessary start-up equipment Determining economic feasibility

• Need more flow data and progress to Phase 2

Solutions and Progress

Include antifreeze or water-bucket heater to prevent freezing in water pressure system Extensive insulation of tanks to maintain temperature Utilize recycling opportunities and work within local resources

Solutions and Progress

Student-designed ideas for easier feeding procedures Beginning construction manual

Phase 2: Deploy digestors to fuel appliances and an electrical generator to evaluate feasibility and sustainability for widespread use in Alaska

125-150 L day-1 hot water heater infrared heater electrical generator 150-300 L meal-1 ~1,200 L day-1 = biogas production gas lights 200-300 L hr-1 cook stove

Usage estimates from GTZ

1000 L kWh-1

• Produces a renewable, alternative fuel from

locally available resources

• Mitigates health and environmental safety

problems associated with waste disposal in Alaska

• Reduces fossil fuel demands in rural Alaskan

communities, lowering high fuel expenditures and fuel transportation risks

Biogas Technology Benefits

• Produces fertilizer for Alaskan agricultural efforts
• Counteracts the greenhouse effects of methane previously released directly into the atmosphere
• Empowers local and individual contributions to mitigating the global greenhouse effect
• Puts Alaska at the head of cold-adapted digestors globally and makes Alaska one of the initiating areas

to use digestors in the USA

Questions?