GLOBAL WARMING • Distribution of solar radiation entering the atmosphere – 20% reflected by the atmosphere – 20% absorbed by the atmosphere – 51% is absorbed by the earth – 9% is reflected by the earth and dust • Distribution of emitted infrared radiation – 17% escapes atmosphere – 83% is held and re-emitted • Maintains atmospheric temperature • Increased concentrations of CO 2 , CH 4 and other gases increase amounts of infrared radiation that is trapped and re-emitted – Increases atmospheric temperature
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GLOBAL WARMING Distribution of solar radiation entering the atmosphere –20% reflected by the atmosphere –20% absorbed by the atmosphere –51% is absorbed.
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GLOBAL WARMING• Distribution of solar radiation entering the atmosphere
– 20% reflected by the atmosphere– 20% absorbed by the atmosphere– 51% is absorbed by the earth– 9% is reflected by the earth and dust
• Distribution of emitted infrared radiation– 17% escapes atmosphere– 83% is held and re-emitted
• Maintains atmospheric temperature• Increased concentrations of CO2, CH4 and other gases increase
amounts of infrared radiation that is trapped and re-emitted– Increases atmospheric temperature
UNDERSTANDING GLOBAL WARMING
EVIDENCE FOR GLOBAL WARMING
• Since 1860– CO2 concentration in atmosphere has increased by 24%
– CH4 concentration in atmosphere has doubled
– Mean global temperature has increased by 2oF• 10 hottest days on record have occurred since 1980
ENVIRONMENTAL EFFECTS OF GLOBAL WARMING• Average temperature will increase by 2 to 6oF in next century• An increase in extreme weather events
– Droughts, floods etc.– Concern for insurance industry
• Sea levels will increase .5 to 3 feet– Threaten coastal resources, wetlands, and islands– Saline water will pollute water supplies of coastal cities
• Increased range of diseases associated with tropical climates– Malaria, dengue fever, and yellow fever will occur at higher latitudes
• Heat stress and death of humans and animals– Particularly a concern in elderly
• Increases air conditioning needs– Angus cattle?
• Rapidly reproducing species of weeds, rodents, insects, bacteria and viruses may occur at higher latitudes
• Crop may be susceptible to new insect and disease problems• Reduced forest health and changes in tree species
GASES ASSOCIATED WITH GLOBAL WARMING Current Rate of Half % of US GHG Relative concentration increase life GHF contribution GH effect____Gas____ (ppmV) (%/yr) _(yr)_ emissions __%__ ( /kg) (_/mole)Carbon dioxide 360 .5 150 81 55-60 1 1Methane 1.7 .7 7-10 10 15-20 62 22Nitrous oxide .31 .2 150 7 5 310 310Fluorinated hydrocarbons - - - 2 - - -Water vapor - - - - - - -
– 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
• In manure– Volatile fatty acids contribute to manure odor
• Acetic acid and propionic acid smell like vinegar• Butyric acid smells like rancid butter
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 HH C C C C COOH 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
N2O PRODUCTION• N2O is produced during denitrification of NO3
– Occurs under anerobic conditions• Wet, compacted soils• Anerobic lagoons
– 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 Lagoons > Slurries > Compost
STRATEGIES TO REDUCE GHG EMISSIONS ASSOCIATED WITH LIVESTOCK PRODUCTION
• Production system manipulation– Limit management approaches that just maintain ruminant
animals with little production• Example - Backgrounding cattle
– Maximize reproductive efficiency– Maximize disease control and herd health
• Dietary manipulation– Nonruminants
• Manage diet to minimize N excretion and waste– Review N section
» Do not feed excess protein» Balance for amino acids» Use crystalline amino acids to create the ‘ideal’ protein» Use phase feeding with 4 or more phases» Use split sex feeding» Limit feed waste» Promote lean growth through genetic manipulation or feed
additives:Ractopamine
– Ruminants• Maximize the proportion of grain in the diet
– Effects» Reduces CH4 production» Increases incorporation of NH3 into microbial protein Reduces urinary N» Increases rate of gain Reduces lb GHG/lb gain
– Effects » Increases incorporation of amino acids into animal protein Reduce N excretion
» Reduces GHG/lb product by increasing productionReduces CH4/lb product by 4%
• Manage protein nutrition to minimize N excretion– Review N strategies– Strategies
» Reduce CP of diet Reducing CP concentration of dairy cow from 17.5 to 12.5% CP:
Reduce N2O by 78%» Lower the Rumen Degradable Protein:Undegradable protein ratio» Increase energy concentration of the diet» Use crystalline amino acids to balance amino acids of lactating
dairy cows
• Manipulation through manure handling and storage– Effects of manure storage method Anerobic Slurry Stockpiled lagoon earthen pond Deep litter Compost Relative emissions CH4 10 8 6 1Total GHG Very high 4 2-3 1Dominant gas CH4 CH4 CH4 & N2O N2O– Effects related to:
• C:N ratio of the manure Separated Farm yard Deep litter manure without manure with bedding bedding C:N 10 20 CH4 (g/cow/7 weeks) 26 3 N2O (mg/cow/7 weeks) 866 42 GHG (CO2 equiv./cow/7 wk) 878 82• O2 exposure
– Reduces CH4
• Surface area– Increased surface area increases gas release – Covers reduce gas release
– Methane capture and use• Requirements
– Anerobic, air-tight structure– pH control
» pH 6.8 – 7.0– High temperature
» 95oF– Can not have a high concentration of NH3
– Expense» $400 - $500/animal for large dairies (<3700 cows)» $1200/animal for small dairies (<500 cows)
• Production Swine Dairy Beef PoultryGas yield, cubic ft/lb solids 12 7.7 15 8.8Energy production, BTU/hr/animal 103 568 775 5.25Animals needed to heat a 1500 ft2 house 535 99 72 10714
• Manipulation through manure application– Frequent application of manure
• Prevents anerobic decay• Traps C in soil organic matter or released to atmosphere as
CO2
– Timing of manure application• Avoid application in later winter and early spring
– Plant growth is slow» Little uptake of NO3
– Soils are water-logged» Anerobic conditions promote denitrification of NO3 to
N2O– Method of application
• Injection of manure reduces all N emissions by 90%• Band application of surface produces more N2O than uniform
surface application
• Manipulation of GHG through carbon sequestration– Plants sequester C, reducing atmospheric CO2 – Amounts of C sequestered
Crop tons C/acrePasture 1.0Range .12Hay land .5Grain 2.0Trees 3.7
– Potential• U.S. grazing lands = 524 million acres• C sequestered = 60 million tons = 1.6 x all C emissions from all agriculture
– C sequestered may be increased by:• Incorporation of legume forage species in pastures
– Producers may economically benefit from increased C sequestration by selling C credits to industries producing Greenhouse Gases• 1 C credit = 1 ton C sequestered beyond a base value before
improved management
= 3.67 tons CO2 removed from the atmosphere
• Credits sold through markets– Chicago Climate Exchange