Biodigesters Against Global Warming
by Catherine LaineOctober 17th, 2006
It sounds like the start of a silly joke. What comes out of both ends and contributes to global warming? Cow burps and flatulence.
Not very funny, but neither is the fact that the methane in these bovine outbursts is 20+ times more powerful as a greenhouse gas than CO2. How much gas are we talking about anyway and is it just cows? A lot and no. Here is data for the United States.
Methane Emissions from Enteric Fermentation (Gigagrams)
| Livestock Type | 1990 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 |
| Beef Cattle | 3,961 | 4,124 | 4,047 | 4,045 | 3,973 | 3,923 | 3,919 | 3,930 |
| Dairy Cattle | 1,375 | 1,255 | 1,251 | 1,265 | 1,283 | 1,282 | 1,290 | 1,300 |
| Horses | 91 | 93 | 94 | 93 | 94 | 95 | 95 | 95 |
| Sheep | 91 | 64 | 63 | 58 | 56 | 56 | 53 | 50 |
| Swine | 81 | 88 | 93 | 90 | 88 | 88 | 90 | 90 |
| Goats | 13 | 10 | 10 | 10 | 10 | 10 | 10 | 10 |
| Total CH4 | 5,612 | 5,634 | 5,557 | 5,561 | 5,505 | 5,454 | 5,458 | 5,475 |
Note: Totals may not sum due to independent rounding.
Source: Environmental Protection Agency
The above numbers unfortunately do not include gas produced from the decomposition of manure. Here are that data from the EPA.
Methane Emissions from Manure Management (Gigagrams)
| Animal | 1990 | 1997 | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 |
| Dairy Cattle | 545 | 639 | 662 | 700 | 692 | 715 | 722 | 748 |
| Beef Cattle | 153 | 152 | 149 | 150 | 149 | 148 | 147 | 146 |
| Swine | 622 | 780 | 874 | 837 | 812 | 826 | 843 | 808 |
| Sheep | 9 | 6 | 6 | 6 | 5 | 5 | 5 | 5 |
| Goats | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Poultry | 128 | 127 | 130 | 125 | 125 | 129 | 126 | 127 |
| Horses | 27 | 28 | 28 | 28 | 28 | 29 | 29 | 29 |
| Total CH4 | 1,485 | 1,733 | 1,850 | 1,846 | 1,813 | 1,853 | 1,873 | 1,864 |
Note: Totals may not sum due to independent rounding.
Source: Environmental Protection Agency
But there is a silver lining to this … um … gaseous cloud. Biodigesters can be used to trap methane released from the decomposition of manure. Rather than escaping into the atmosphere, the captured biogas can be used as fuel for heating, cooking and electricity generation very much like propane or natural gas would be. Additional benefits from biodigester usage are reduced odor (which people living downwind greatly appreciate), sterilized fertilzer and protection of nearby water sources from fecal contamination (also pleasing to the neighbors).
While biodigesters can greatly reduce manure as a source of the greenhouse gas, methane, they do nothing for the not-so-jokeworthy problem of burps and flatulence.
January 11th, 2010 at 1:27 am
Just a thought, is it possible to tap this methane gas and package it? It can work wonders.
Consolata