Biogas Digestion by Michael Klima mklima@yahoo.com.

Biogas Digestionby

Michael Klimamklima@yahoo.com

What is Biogas Digestion?• Biogas Digestion is the process of taking

biogas to produce electricity, heat, or hot water

• Biogas means a gas formed by carbon dioxide and methane from breakdown of organic materials such as manure.

What is a Digester?• Digester is a vessel or container where the

biogas process takes place. Bacteria breaks down manure or other waste products to create biogas. Products may be fed into the chamber such as manure or the container could be used to cover a place that is already giving off biogas such as a swamp or a landfill.

History of Biogas

Reasons of Interest in Biogas Anaerobic Digester systems

• Improved Technology in systems has led to reliability

• Good way to manage manure given the odor and environmental concerns associated with manure

• Government has subsidized programs for systems

• Potential to sell credits to utilities and utilities continue interest in green energy

Biogas Process

Design of a Digester

How Digester Works

• Temperature must be kept between 65 degrees and 150 degrees

• 4 Types of bacteria breakdown the waste– Hydrolytic breaks organic material to simple

sugar and amino acids– Fermentative then converts to organic acids– Acidogenic convert to carbon dioxide,

acetate, and hydrogen– Methanogenic produces biogas

Combined Heat and Power

• Also known as cogeneration• Using the heated water for other

purposes such as heating buildings or creating additional energy

Sources of Biogas

• Wetlands• Sewage Sludge• Landfills• Plant Material• Animal Waste

TYPES OF BIOGAS DIGESTER SYSTEMS

Number of United States Operating Anaerobic Digesters by

Technology

• Complete Mix Digester – Are larger vessels that can either be above or below ground. They are used for larger amounts of manure

• Plug Flow Digester- Is used for ruminant animal manure and requires little maintenance. Better for smaller operations

• fixed film digester – “a tank designed as part of a manure management system to handle manure up to 3 percent solids. The digester is temperature controlled and a media is placed inside the digester. This design allows the microbial populations to attach to the media and grow as a biofilm (fixed film), thus preventing the microbes from being removed with the effluent”

• temperature-phased anaerobic digester (TPAD) – “two tanks designed as part of a manure management system. The digesters are heated, the first digester in the thermophilic temperature range and the second digester in the mesophilic temperature range. This will maximize biological activity for the destruction of volatile solids, methane production and odor reduction.”

• covered lagoon digester – “an anaerobic lagoon is commonly used when manure has less than 2 percent solids. Decomposition of the manure occurs, methane is produced and effluent odor is reduced. The lagoon is covered with a gas-tight cover to capture the biogas.”

• A landfill gas-to-energy – “consists of a series of wells drilled into the landfill. A piping system connects the wells and collects the gas. Dryers remove moisture from the gas, and filters remove impurities. The gas typically fuels an engine-generator set or gas turbine to produce electricity. The gas also can fuel a boiler to produce heat or steam. Further gas cleanup improves biogas to pipeline quality, the equivalent of natural gas. Reforming the gas to hydrogen would make possible the production of electricity using fuel cell technology.”

US Government Involvement

Regulations

• On March 20, 2009 revised the new source performance standards to limit when owners/operators of stationary combustion turbines using biogas had to install emission controls and/or pretreatment systems to remove sulfur compounds

• Biogas is recognized as an advanced biofuel under 42 U.S.C.A. § 7545

Financial Incentives• Since 2003 USDA has awarded 37

million to anaerobic digestion systems

EPA AGSTAR Study of Two farms

Parameter With anaerobic digestion

Odor Substantial reduction

Greenhouse gas emissions Methane—substantial reduction (3.03 tons per cow-yr on a carbon dioxide equivalent basis) Nitrous oxide—No evidence of

emissions with or without anaerobic digestion

Ammonia emissions No significant reduction

Potential water quality impacts Oxygen demand—substantial reduction (8.4 lb per cow-day) Pathogens—substantial reduction (Fecal coliforms: ~99.9%) (M.

avium paratuberculosis: ~99%) Nutrient enrichment—no reduction

Economic impact

Significant increase in net farm income ($82 per cow-yr)

Benefits and Concerns

Benefits of Biogas Digester Systems

• Odor Reduction by using raw manure• If Ammonia, a by-product of process,

is captured can be used to help plant growth by injecting it into the ground

• Reduction of Electricity for Farms • Carbon Dioxide generated from biogas

digester systems creates less greenhouse gas then methane gas used in initial process

Biogas Digester System Concerns

• Releases Nitrogen and ammonia into the atmosphere both of which hazardous

• Can release Hydrogen Sulfide a very toxic gas

• Methane released can create explosive atmosphere

• Should raw materials get into water supply can contaminate the water

• Transportation is of a concern because methane is explosive although new technology may allow it to be stored in powder form

Current U.S. Examples• Central Vermont of 158,000

customers 4,000 have agreed to pay a small premium to use biogas energy

• Panda Ethanol Plant in Texas• Columbia Boulevard Wastewater

Treatment Plant in Portland, Oregon produces 1.5 million kilowatts of energy per year

Other Countries use of Biogas

• Nepal• Africa• Ecuador• Sweden

Nepal

• Since 2003 Nepal has built 94,425 small biogas plants for individual use

• One plant costs approximately $593 USD (2009 estimate)

• Nepal has subsidized half the cost for farmers willing to build these biogas plants

• Nepal has targeted farmers with at least one cattle and owns a small piece of land

Benefits from Nepal's Prospective

• Saves from deforestation because main source of Nepal’s farmers power is wood burning

• Has created 13,000 jobs since 2003 for those who build these small plants

• Reduces air pollution because biogas burns cleaner then wood

• Improves women and girls lives because the plants reduce overall work by about 3 hours then collecting and cooking with fire wood leaving more time for education

Africa

• Biogas distributors cost about $50 per family

• Currently Nigeria is working on a biogas project that will provide gas to 5,400 people and cost $300k

Ecuador Biogas Sewage Project

• A large education complex called Santa Maria del Fiat did not have proper sewage system and would simply dump waste in open spaces. This contaminated underground water sources and created sever odors

• The project built a biogas digester that processed both human and animal waste

Ecuador Biogas Sewage Project Continued

• The school also built a water reclamation system

• During school year the 500 students waste is used to produce over 40% of the school’s gas electricity. Power is also produced in the summer from local farmer’s animal and vegetable waste

• The school sells the fertilizer by product and uses the fertilizer in the schools own orchid

Sweden Biogas Train• Train runs on entrails of slaughtered

cows• Costs 20% more to run on methane then

diesel right now• Sweden is 10 times ahead of its European

counter parts for binding goals the European Commission as setup for use of bio-products by the end of the year 2010

• Sweden also has 65 fleet of biogas buses

Conclusions• Biomass counts for only 4% of

United States yearly energy use• Biogas works best on small scale

operations• Has technology improves we will

be able to use methane gas more efficiently

• Good way to put human and animal waste to good use

Notes-Citations• Slide 3-http://www.biogas.psu.edu/terminology.html• Slide 4-http://www.biogas.psu.edu/basics.html• Slide 5-http://www.energyrevolution.co.za/biogas/biogas-history• Slide 6- http://www.epa.gov/agstar/documents/2010_digester_update.pdf• Slide 7-http://www.hydropur.be/anglais/Assainissement%20et%20biogaz /biogas

%20principle.html• Slide 8-http://www.clearhorizonsllc.com/html/products/diagram.htm• Slide 9-http://www.oregon.gov/ENERGY/RENEW/Biomass/biogas.shtml• Slide 10-http://www.epa.gov/chp/basic/index.html• Slide 11-http://www.epa.gov/chp/basic/index.html• Slide 12- Various sources see• Slide 13-No need for citation

Notes-Citations Continued • Slide 14-http://www.epa.gov/agstar/documents/2010_digester_update.pdf• Slide 15-http://www.biogas.psu.edu/terminology.html• Slide 16-http://www.biogas.psu.edu/terminology.html• Slide 17-http://www.biogas.psu.edu/terminology.html• Slide 18-http://www.biogas.psu.edu/terminology.html• Slide 19 -http://www.oregon.gov/ENERGY/RENEW/Biomass/biogas.shtml# Landfill_Gas• Slide 20- No Citation needed• Slide-21- SO2 EMISSION LIMIT FOR UNITS BURNING BIOGAS ADDED TO NSPS FOR• STATIONARY COMBUSTION TURBINES (19 NO. 4 Air Pollution Consultant 2.13)• Slide 22-http://www.epa.gov/agstar/documents/2010_digester_update.pdf• Slide 23- http://www.epa.gov/agstar/documents/nydairy2003.pdf

Notes-Citations Continued • Slide 24-No citation needed• Slide 25-http://animalagteam.msu.edu/Portals/0/anaerobic.pdf• Slide 26-http://www.biogas.psu.edu/Safety.html• Slide 27-http://www.nytimes.com/2008/09/24/business/businessspecial2/

24farmers.html• Slide 28-No need for a citation• Slide 29-http://www.bspnepal.org.np/achievements• Slide 30-http://www.bspnepal.org.np/target-group• Slide 31 – Borders and Environment by Andrew P. Morriss and E. Roger Meiners 39

Envtl. L. 141)• Slide 32-http://sgp.undp.org/download/SGPCaseStudiesBook.complete.pdf• Slide 33-http://sgp.undp.org/download/SGPCaseStudiesBook.complete.pdf• Slide 34-http://news.bbc.co.uk/2/hi/science/nature/4373440.stm• Slide 35-http://tonto.eia.doe.gov/kids/energy.cfm?page=biomass_home-basics-

k.cfm