Biogas Digestionby

NARESH THAKUR

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.

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

• 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.”

Financial Incentives• Since 2003 USDA has awarded 37

million to anaerobic digestion systems

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

Other Countries use of Biogas

• Nepal• Africa• Ecuador• Sweden

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