Carbon Cycling Production of Greenhouse Gases in Livestock Operations

GASES ASSOCIATED WITH GLOBAL WARMING Current Rate of Half % of US GHG Relative concentration increase life GHG contribution GH effect ____Gas____ (ppmV) (%/yr) _(yr)_ emissions __%__ ( /kg) (_/mole) Carbon dioxide Methane Nitrous oxide Fluorinated hydrocarbons Water vapor 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 CH 4 N 2 O Total emissions, Tg a /yr Natural, Tg/yr Anthropogenic, Tg/yr Livestock, Tg/yr Enteric, % 80 0 Manure handling, storage, and application, % A 1 Tg = g *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 > CH 4 + CO 2 CO 2 + 4H 2 > CH 4 + H 2 O Formic acid + 4H 2 > CH 4 + 2H 2 O –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 CH 4 produced from pyruvate –Net production Glycolysis (/ glucose) 2 ATP 2 NADH 2 Pentose PO 4 pathway (/pentose) 1.67 ATP 2 NADPH 2 1 NADH 2 1 pentose ATP

Metabolism in aerobic organisms –Pyruvate Metabolized in the tricarboxyllic acid cycle producing ATP, NADH 2, FADH 2 and CO 2 –NADH 2 and FADH 2 Oxidized in mitochondria by the electron transport system producing ATP and H 2 O

–Metabolism of pyruvate and NADH 2 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 CH 4 production Dietary factors that increase propionate production decrease CH 4 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 NADH 2 are produced per glucose. –Must be oxidized to maintain Redox balance –Electron acceptors »Aerobic organisms O 2 > H 2 O »Anerobic organisms CO 2 > CH 4 Pyruvate > Propionate Acetate > Butyrate NO 3 > NO 2 > NH 3 SO 4 > S

–Redox balance in the rumen 2H (Reducing equivalents) produced: –Glucose > 2 Pyruvate + 4H (as 2 NADH 2 ) –Pyruvate + H 2 O > Acetate + CO 2 + 2H (as 1 FADH 2 ) 2H accepted: –CO 2 + 4H 2 > CH 4 + 2H 2 O –Pyruvate + 4H (as 2 NADH 2 ) > Propionate + H 2 O –2 Acetate + 4H (as 2 NADH 2 ) > Butyrate + 2H 2 O –Fermentation balance High forage diets –5 Glucose > 6Acetate + Butyrate + 2Propionate + 5CO 2 + 3CH 4 + 6H 2 O –Acetate:Propionate = 3 –CH 4 :Glucose =.60 High grain diets –3 Glucose > 2Acetate + Butyrate + 2Propionate + 3CO 2 + CH 4 + 2H 2 O –Acetate:Propionate = 1 –CH 4 :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 + H H H H H C C C C COOH H H H H H H H H Unsaturated fatty acid 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

EFFECTS OF MILK PRODUCTION ON METHANE PRODUCTION/KG MILK CH 4, g/day = kg milk/day BW, kg Clemons and Ahlgrimm (2001)

PROJECTED IMPACTS OF USE OF CONVENTIONAL OR ORGANIC-BASED DAIRY PRODUCTION TO MEET REQUIREMENTS FOR U.S. POPULATION IN 2040 System Conventional Organic Milk production, kg/yr x Lactating cows, x Milk production, kg/cow x Total dairy pop., x Total land reqd, ha x GHG emissions, kg/yr x Capper et al. (2008)

Cow-calf Cow-calf Stocker Feedlot - Feedlot Dairy CO 2 equivalent, kg/head/yr Enteric CH Manure CH Total CH N 2 O CO Total GHG CO 2 equivalent, kg/kg product Total GHG *Phetteplace et al. (2001) ANNUAL GHG EMISSIONS FROM DIFFERENT CATTLE PRODUCTION SYSTEMS

N 2 O PRODUCTION Nitrification of NH 3 to NO 3 Nitrosomas spp. Nitrobacter spp. NH 4 + NO 2 - NO 3 - –Requirements Aerobic conditions Warm temperatures High C:N ratio N 2 O is produced during denitrification of NO 3 NO 3 - NO 2 - NO N 2 O N 2 –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 N 2 O 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 NH 3 into microbial protein Amino acid balance –Poor amino acid balance = increased N excretion

Manure handling –Storage losses Anerobic Slurry Stockpiled lagoon earthen pond Deep litter Compost Relative emissions CH Total GHG Very high Dominant gas CH 4 CH 4 CH 4 & N 2 O N 2 O –Application losses Injection > Surface application