Biogas - An overview -养殖--中国农资供销网

Biogas - An overview

时间：2009-12-18 11:54:51来源：作者：大山

By Brian Sexton, Alberta Agriculture, food and rural development - This article provides a brief overview of the principles and economics of producing biogas as a by-product of hog production.

Biogas - An overview - By Brian Sexton, Alberta Agriculture, food and rural development - This article provides a brief overview of the principles and economics of producing biogas as a by-product of hog production.

What is Biogas?

Biogas consists of about 60 to 80 percent methane, 20 to 40 percent carbon dioxide, and trace amounts (1 to 2 percent) of other compounds such as hydrogen sulfide, ammonia, and water vapour. The gas is similar to natural gas and is produced as a byproduct from the biological breakdown of organic material. In the agriculture industry, biogas can be produced from livestock manure.

How To Produce Biogas

Digester
The digester is an airtight tank with heating coils and, in some systems, a mechanical mixer. As manure enters the digester, it is mixed with the contents and heated to a temperature of 35°C or higher, depending on the type of digester. At this temperature, anaerobic bacteria multiply and feed on the volatile solids found in the manure. The byproduct of this feeding is biogas. Oxygen is poisonous to anaerobic bacteria so an oxygen free environment in the digester is important. As the gas is produced, it rises above the manure to the top of the digester where it is collected into the piping system.

Appliances
With minor modifications to equipment, such as increasing the jet size, biogas can be used in many natural gas appliances such as water heaters and furnaces. Other appliances include compressor engines found on refrigerators and air conditioners. The gas can also be used to supply heat to the digester.

Co-generators
Biogas can be used to power co-generation units, which produce both heat and electricity. The heat can be used on site for heating buildings and/or the digester. The electricity can be used on site or sold to the grid.

Effluent Storage and Handling
Most livestock operations have a manure storage in place. Therefore, rather than constructing a new storage, the effluent is simply stored in the existing storage. Digested manure contains fewer solids than raw manure and is therefore less stressful on handling equipment such as pumps and agitators.

Manure Treatment and Green Energy

As a result of the digestion process, digested manure contains fewer pathogenic organisms and is less odourous than raw manure. The resulting effluent can be stored and land applied without concern for odour nuisances. Pathogen transfer potential is also reduced.

Is It Worth It?

Manure digestion has not been practiced in Alberta for several years. Past digesters were often not economically and/or technically feasible. Modern day digesters are technically feasible but the economic viability is questionable. With a number of biogas facilities being built in Western Canada, the economic feasibility of biogas production will soon be apparent. The set up cost of a digester is usually the limiting factor for potential biogas producers. The capital cost of a biogas system can range from hundreds of thousands of dollars to over a million dollars.

Compatibility

Manure digestion works best with livestock operations that produce liquid or slurry manure. Hog and dairy operations are well suited for biogas production. For economic viability, the bigger the operation, the better. Information from the United States suggests hog operations larger than 1000 pigs and dairy operations larger than 300 cows are best suited for biogas production.

Where Do I Start?

If you are seriously considering implementing biogas production on your farm, you should contact a firm that specializes in biogas facilities, or Alberta Agriculture for more information.

How Much Biogas Can I Produce?

The following is a calculator for estimating the amount of biogas your operation can produce. The calculator is a guideline only and should not be used for design purposes.

1. Choose the biogas production number that applies to your operation?Example: 600 sow farrow to finish operation, choose Farrow to Finish HogsCubic metres biogas/hog/year Farrow to Finish720Farrow to Wean222Farrowing174Weaner24Feeder78

2. Multiply the number of animals by biogas production number?Example: 600 hogs * 720 m3 biogas / hog / yr = 432000 m3 biogas / year 3. Multiply the result by the numbers below?____________ * 2 kWh/ m3 biogas = _________ kWh of electricity per year
____________ * 12.6 MJ/ m3 biogas = _________ MJ of heat per year

Print Version

Download Printable PDF version - 435 KB

Reproduced Courtesy Alberta Agriculture, Food and Rural Development
To visit their web site, click a link below.

For More Information
Brian Sexton , E.I.T.
#100, 5401 - 1st Avenue South
Lethbridge, Alberta T1J 4V6
Phone:(403) 381-5885
Fax:(403) 381-5806

E-mail: brian.sexton@gov.ab.ca

The user of this information agrees to the terms and conditions in the terms of use and disclaimer.
Copyright ?2001 - 2002 Her Majesty the Queen in the Right of Alberta. All rights reserved.