Transcript GLOBAL WARMING - Agronomy Courses

Carbon Cycling
Production of
Greenhouse Gases in Livestock
Operations
GASES ASSOCIATED WITH GLOBAL WARMING
Current Rate of Half
concentration increase life
____Gas____
(ppmV) (%/yr) _(yr)_
Carbon dioxide
360
.5
150
Methane
1.7
.7
7-10
Nitrous oxide
.31
.2
150
Fluorinated
hydrocarbons
Water vapor
-
% of US
GHG
Relative
GHG contribution GH effect
emissions __%__ ( /kg) (_/mole)
81
55-60
1
1
10
15-20
62
22
7
5
310 310
2
-
-
-
-
• Sources
– Carbon dioxide
• Hydrocarbon combustion
– Methane
• Livestock, manure, wastewater treatment, landfills and fuel production
– Nitrous oxide
• Hydrocarbon combustion, industrial processes, denitrification of
manure and soil N
– Fluorinated hydrocarbons
• Refrigeration, dry cleaning, chemical manufacturing
– Water vapor
• Increased temperature from other GHG
LIVESTOCK AGRICULTURE’S ROLE IN
GREENHOUSE GASES
Emissions
Source
CH4
N2O
Total emissions, Tga/yr
535
17.5
Natural, Tg/yr
160
9.6
Anthropogenic, Tg/yr
375
8.0
Livestock, Tg/yr
103
6.2
Enteric, %
80
0
Manure handling, storage, 20
100
and application, %
A1
Tg = 1012g
*Monteny et al. 2001
GREENHOUSE GAS PRODUCTION IN LIVESTOCK
• Methane
– Produced by anerobic fermentation of carbohydrates in the
rumen, large intestine, or stored manure
– Produced by Methanogenic archea
• Methanogenic archea are associated with cellulolytic
bacteria and protozoa
– Methane producing mechanisms
• Acetate or methanol > CH4 + CO2
• CO2 + 4H2 > CH4 + H2O
• Formic acid + 4H2 > CH4 + 2H2O
– Effects
• Greenhouse gas
• Represents a loss of dietary energy
– 4 to 10% of dietary gross energy in ruminant animals
– 0.6 to 1.2% of dietary gross energy in swine
• Increases ATP production for microbial growth
• Carbohydrate
fermentation
– VFA and CH4
produced
from pyruvate
– Net production
• Glycolysis
(/ glucose)
2 ATP
2 NADH2
• Pentose PO4
pathway
(/pentose)
1.67 ATP
2 NADPH2
1 NADH2
1 pentose
ATP
ATP
ATP
ATP
ATP
• Metabolism in aerobic organisms
– Pyruvate
• Metabolized in the tricarboxyllic acid cycle producing
ATP, NADH2, FADH2 and CO2
– NADH2 and FADH2
• Oxidized in mitochondria by the electron transport
system producing ATP and H2O
– Metabolism of pyruvate and NADH2 by anerobic
microorganisms
VOLATILE FATTY ACIDS
• In animals
– Absorbed through wall of the rumen in ruminants or
large intestine of ruminants and nonruminants
– Metabolized by the animal for energy
• Main source of energy for ruminants
– Provide 70% of the energy in ruminants
– Production of different VFAs and methane vary with
diet
• Dietary factors that increase acetate production increase
CH4 production
• Dietary factors that increase propionate production
decrease CH4 production
• In manure
– Volatile fatty acids contribute to manure odor
• Acetic acid and propionic acid smell like vinegar
• Butyric acid smells like rancid butter
• Factors controlling fermentation endproducts
– Maximum ATP yields for the microorganisms
– Maintenance of Reduction-Oxidation balance
• In glycolysis, 2 NADH2 are produced per glucose.
– Must be oxidized to maintain Redox balance
– Electron acceptors
» Aerobic organisms
O2 > H 2 O
» Anerobic organisms
CO2 > CH4
Pyruvate > Propionate
Acetate > Butyrate
NO3 > NO2 > NH3
SO4 > S
– Redox balance in the rumen
• 2H (Reducing equivalents) produced:
– Glucose > 2 Pyruvate + 4H (as 2 NADH2)
– Pyruvate + H2O > Acetate + CO2 + 2H (as 1 FADH2)
• 2H accepted:
– CO2 + 4H2 > CH4 + 2H2O
– Pyruvate + 4H (as 2 NADH2) > Propionate + H2O
– 2 Acetate + 4H (as 2 NADH2) > Butyrate + 2H2O
– Fermentation balance
• High forage diets
– 5 Glucose > 6Acetate + Butyrate + 2Propionate + 5CO2
+ 3CH4 + 6H2O
– Acetate:Propionate = 3
– CH4:Glucose = .60
• High grain diets
– 3 Glucose > 2Acetate + Butyrate + 2Propionate + 3CO2
+ CH4 + 2H2O
– Acetate:Propionate = 1
– CH4:Glucose = .33
FACTORS AFFECTING METHANE AND VFA
PRODUCTION IN THE RUMEN OF RUMINANTS
• Dietary factors
– High forage levels of diet
• Promotes cellulose digesting bacteria in rumen
• Increases production of acetic acid and methane
• Decreases production of propionic acid
– High grain levels of diet
• Promotes starch digesting bacteria in rumen
• Increases production of propionic acid
• Decreases production of acetic acid and methane
– Fine grinding or pelleting of forage
• Decreases the amount of time the cattle spend chewing
• Decreases saliva flow and secretion of the buffer, sodium
bicarbonate.
• Allows rumen pH to decrease
• Decreases growth of cellulolytic bacteria
• Decreases production of acetic acid and methane
• Increases production of propionic acid
– Increasing forage maturity
•
•
•
•
•
•
Causes more chewing
Increases saliva flow and secretion of buffer, sodium bicarbonate
Increases rumen pH
Increases growth of cellulolytic bacteria
Increases production of acetic acid and methane
Decreases production of propionic acid
– Feeding fats containing unsaturated fatty acids
• An unsaturated fatty acid is a fatty acid that has one or more
double bonds in the chain
• The rumen bacteria use hydrogens to saturate (replace double
bonds with hydrogens) unsaturated fatty acids
• Example
H
H
H C C C C COOH
H H H H
Unsaturated fatty acid
H+
H H H H
H C C C C COOH
H H H H
Saturated fatty acid
• Results
– Decreased acetic acid and methane production
– Increased propionic acid production
• Important to feed no more than 5% fat to ruminants
– Feeding ionophores
• Antibiotics that include
– Monensin, sold as Rumensin
– Lasalocid, sold as Bovatec
• Increase propionic acid production
• Decrease acetic acid and methane production
• Production factors
– Rate of gain
• Regardless of diet, ruminants produce methane each day at a
maintenance level
– Every day the cattle or sheep is on the farm, they produce more
methane
• The faster an animal grows or the more milk is produced, the
lower the amount of methane produced per unit of meat or milk
produced
Methane production
EFFECTS OF MILK PRODUCTION ON
METHANE PRODUCTION/KG MILK
1200
800
CH4, gm/d
400
CH4, gm/kg
milk
0
0 10 20 30 40 50
Milk production, kg/d
Clemons and Ahlgrimm (2001)
CH4, g/day = 59 + 4.9 kg milk/day + 1.5 BW, kg
PROJECTED IMPACTS OF USE OF
CONVENTIONAL OR ORGANIC-BASED DAIRY
PRODUCTION TO MEET REQUIREMENTS FOR
U.S. POPULATION IN 2040
Milk production, kg/yr x 109
Lactating cows, x 106
Milk production, kg/cow x 103
Total dairy pop., x 106
Total land reqd, ha x 106
GHG emissions, kg/yr x 109
Capper et al. (2008)
System
Conventional Organic
101
101
6.58
8.23
15.3
12.3
14.0
17.5
10.3
13.4
121
136.7
ANNUAL GHG EMISSIONS FROM DIFFERENT
CATTLE PRODUCTION SYSTEMS
Cow-calf
Enteric CH4
Manure CH4
Total CH4
N2O
CO2
Total GHG
Total GHG
Cow-calf Stocker Feedlot - Feedlot Dairy
CO2 equivalent, kg/head/yr
1140
1725
743
1167 1828
34
48
12
34 1075
1175
1773
755
1201 2903
1487
1721 1294
1490
1800
127
380 1245
252
742
2788
3874 3294
2944
5444
CO2 equivalent, kg/kg product
20.6
14.4
5.7
15.5
1.1
*Phetteplace et al. (2001)
N2O PRODUCTION
• Nitrification of NH3 to NO3
Nitrosomas spp.
NH4+
– Requirements
Nitrobacter spp.
NO2-
NO3-
• Aerobic conditions
• Warm temperatures
• High C:N ratio
• N2O is produced during denitrification of NO3
NO3NO2NO
N 2O
N2
– Requirements
• Anerobic conditions
– Wet, compacted soils
– Manure stacks
• Warm temperatures
• High C:N ratio
– Amount associated with livestock production is directly
related to amounts of N excreted.
FACTORS AFFECTING N2O PRODUCTION
• Diet
– Nonruminants
• Amounts of protein fed
– Increased protein = increased N excretion
• Amino acid balance
– Poor amino acid balance = increased N excretion
– Ruminants
• Amounts of protein fed
– Increased protein = increased N excretion
• Ratio of degraded to undegraded protein in the rumen
– Increased protein degraded in rumen = increased N excretion
• Ratio of degradable protein to digestible carbohydrate in
the rumen
– High proportion of degradable protein to digestible
carbohydrate = increased N excretion
» Digestible carbohydrate is needed to convert degraded
NH3 into microbial protein
• Amino acid balance
– Poor amino acid balance = increased N excretion
• Manure handling
– Storage losses
Anerobic
Slurry
Stockpiled
lagoon
CH4
Total GHG
Dominant gas
earthen pond Deep litter Compost
Relative emissions
10
8
6
1
Very high
4
2-3
1
CH4
CH4
CH4 & N2O
N2O
– Application losses
• Injection > Surface application