Teaching Energy Efficiency and Renewable Energy in a

Life Science Context

With Special Focus on Anaerobic Digestion for Organic Waste Conversion to Methane

Biofuel Curriculum OutlineFor the Teacher: The projects in this section are written in a manner that can be

incorporated into a science class's curriculum.

• http://www1.eere.energy.gov/biomass/pdfs/biofuel_production.pdf– National Science Education Standards by the National Academy

of Sciences – Technology Description Summary

• Direct combustion• Gasification (600-1000°C)• Pyrolysis (300-500°C)• Anaerobic digestion• Fermentation (sugar and starch)• Fermentation (cellulosic)• Biodiesel (plant seeds and algae).

Biofuel Production Curriculum: Project Ideas

– Project Ideas (including variables, equipment, resources, concerns, hints)

• What can be controlled to increase the efficiency of ethanol production? (variables: carbohydrate feedstock, temperature, yeast type)

• What kinds of biomass have the most heat energy in a given quantity? (calorimetry project)

• What type of “Biomass” will produce the greatest quantity of “biogases” by heating?

• What conditions provide the maximum yield of charcoal from biomass?• What conditions will produce the most efficient breakdown of paper

into sugars? (cellulase hydrolysis project)• What conditions would produce the most efficient conversion of algae

to a useful fuel? (Fuels from Micro-algae, 1989, SP-320-3396, Golden, Colorado: SERF )

• What is the most efficient way to produce biodiesel?• What conditions and/or biomass are best for producing methane? (a

sample anaerobic digestion project is provided in this presentation)

Biofuel Production Curriculum: science fair judging guidelines

• Evaluation Criteria:– Creative ability– Scientific thought– Engineering goals– Thoroughness– Demonstration of Scientific Skills– Clarity– Teamwork

BIOGAS

An Overview of Anaerobic Digestion for Methane Conversion

• A biogas recovery system is an anaerobic digester that converts organic wastes to renewable fuel (a mix of methane and carbon dioxide), liquid fertilizer, and sanitized solid residue (digestate).

• Combustion equipment may be used in a cogeneration unit to produce electricity, heat and hot water.

• A variety of “scrubbing” techniques are available to upgrade biogas for vehicle use.

Biochemical Reactions• ANAEROBIC DIGESTION involves a series of

chemical reactions in which carbon containing molecules are decomposed by microorganisms in an oxygen depleted environment.

• Each stage is completed by a physiologically unique bacteria population.

AD Biochemistry Schematic

Why Anaerobic Digestion?

• Net energy producing process• Yields value added end products: biogas, fertilizer,

sanitized bulk material.• Reduces solid waste volume and weight.• Reduces unpleasant odors• Destroys pathogens associated with organic waste.• Reduces atmospheric methane release (20-30x more

potent greenhouse gas than carbon dioxide). • Biogas combustion is “carbon neutral.”

Feed stocks for Anaerobic Digestion

• Animal manure Dairy, Cattle, Swine, and Poultry

• Field Residue• Food processing and packing wastes

Meat, Dairy, Brewery, etc…

• Municipal Solid Waste and Sewage Sludge• Pharmaceuticals and Organic Chemicals.• Pulp and Paper• Landfill Gas

Proprietary design by GHD, Inc [http://www.ghdinc.net/products.aspx]

400,000 Year Record of CO2 Concentration from Ice Core Samples and Projections for Next 100 Years

Source: Barnola et al., Ethridge et al., Keeling and Worf, Wigley et al.Carbon Dioxide Information Analysis Center , DOE (http://cdiac.esd.ornl.gov/)

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Long-Term Climate Change (cont.)

NOAA Slides by Forecast Systems Laboratory.

Climate Change Since the Industrial Revolution

Biogas Combustion is a Carbon Neutral Process

• Photosynthesis removes CO2 from the atmosphere.

• Respiration—and biogas combustion—returns CO2 to the atmosphere.

• Carbon completes a cycle

What is CVPS Cow Power™ ?CVPS Cow Power™ is a voluntary service that helps to promote development and reliance on renewable energy in Vermont, by creating a market for energy generated by burning methane from cow manure and supporting other renewable energy sources.

Why does CVPS offer Cow Power?• To reduce reliance on non-renewable energy• To create new income streams to participating farmers.• To reduce water quality impacts and odors associated with manure.• To reduce bedding costs by using dry byproducts of the process in place of

sawdust or other bedding • To sanitize waste by destroying harmful pathogens like E. Coli• To create high quality agricultural fertilizer• To responsibly address the problem of Global Climate Change

How does CVPS Cow Power generate electricity?• Dairy Cows provide the raw substrate material—manure!• Microbial communities convert substrate to methane gas.• A pipe delivers the gas to an engine. The gas is burned to generate

electricity, which is fed onto the CVPS electrical system.

Where does the money for CVPS Cow Power™ go?

• Customers who choose to buy their electricity through Cow Power pay an extra 4¢ per kilowatt hour for their electricity.

• Customers may buy 25%, 50%, or 100% of their electricity through Cow Power.

• CVPS pays the farmer the market price for the energy + the 4¢/kWh for the environmental benefits of the generation.

• If not enough kilowatt-hours are available from participating farms, CVPS will either purchase Renewable Energy Certificates, or deposit payments into the CVPS Renewable Energy Development Fund

• CVPS does not profit from the Cow Power program

(more details at http://www.cvps.com/cowpower/faq.shtml)(or call 800-649-2877).

Methane Projects in Vermont

• CVPS Cow Power– Blue Spruce Farm (1500 cows, >1.3 million

KWH/year)– Green Mountain Dairy (1000 cows: 1.8

million KWH/year)– Montagne Farm (700 cows, 1.4 million

KWH/year).– At least 2 other farms in planning

(estimated total power: 5 million KWH/year)

• Essex Junction Wastewater Treatment Facility• Coventry landfill biogas project (5.7 million

KWH/year)

Energy Content: How Biogas Compares

• Biogas contains about 60%-80% methane.• When burned, a cubic foot of biogas yields

about 10 Btu of heat energy per percentage of methane composition. For example, biogas composed of 70% methane yields 700 Btu (0.2 KWH) per cubic foot. (3,412 Btu = 1KWH)

• In contrast, natural gas—a fossil fuel—yields 1000 Btu per cubic foot.

What is the Energy Yield Potential of Anaerobic Digestion?

• The average American home consumers 11,000 KWH/yr (EIA), therefore the three operational digesters on Vermont farms (3200 cows) supplying 4.5 million KWH/yr, provide enough electricity to power 410 homes.

• According to USDA there were 9.1 million dairy cows in 2006 (average 120 cows/farm), enough waste to theoretically power 1,165,937 homes.

• There are 124.5 million homes in the U.S.A (DataPlace.org). Diary farms could theoretically provide carbon neutral energy for 1% of residential power use.

What is the Greenhouse Gas Reduction Potential of Anaerobic Digestion?

• 9.1 million cows × 4.5 million KWH/3200 cows = 12.8 billion KWH• 12.8 billion KWH/yr × 1 ft3 biogas/0.2 KWH = 64 billion ft3 biogas• Since biogas is about 70% methane, anaerobic digestion on dairy

farms can theoretically prevent about 44.7 billion ft3 of methane from escaping to the atmosphere.

• Methane is about 25x more potent as a greenhouse gas than CO2.

therefore, the methane reduction is equivalent to preventing the release of 1.1 trillion ft3 of CO2.

• 1.1 trillion ft3 of CO2 × 28.3L/1 ft3 = 31 trillion L CO2.

• 1 mole of a gas has a volume of 22.4 L at STP. Therefore, 31 trillion L CO2 is equivalent to 1.4 trillion moles CO2.

• 1.4 trillion moles CO2 × 0.028 kg/1 mole = 39 billion Kg CO2

Conclusion:

• Intensive and widespread application of anaerobic digestion on dairy farms in the USA would be equivalent to preventing 39 billion Kg of CO2 from escaping to the atmosphere, on an annual basis.

• Humans add about 4.1 trillion Kg of carbon dioxide equivalent greenhouse gases annually to the atmospher (EIA).

• AD technology on US dairy farms could reduce that figure by 1%. • Similar benefits, in terms of carbon neutral energy and reduction of

potent greenhouse gas emissions, could be achieved by expanding the application of AD technology to wastewater treatment, MSW, food processing, pharmaceutical waste, landfills, etc…

A Simple “Desktop Digester” http://www.re-energy.ca/t-i_biomassbuild-1.shtml

Schematic “Desktop Digester” http://www.re-energy.ca/pdf/biogas-generator.pdf

Desktop Digester showing the red tub used to maintain a 35 ºC warm water bath, heated with aquarium heaters