The ongoing debate on global warming has left some people convinced that human activity is seriously impacting climate change while others are skeptical and dismissive. Whether global warming is real or imagined, knowing the carbon footprint or energy use of your poultry operation can help you reduce the amount of energy use and improve your bottom line.
Human activities, including modern agriculture, contribute to greenhouse gas (GHG) emissions. Only 6.4% of U.S. GHG emissions come from agriculture. Of this 6.4%, beef cattle accounted for about 37%, dairy cattle 11.5%, swine 4.4% and poultry 0.6% (Fig. 1). While the figures for poultry production appear to be low, understanding how these GHG are generated and what we can do to further reduce poultry’s footprint remains important in today’s challenging times.
Greenhouse gasses of concern
GHGs of particular concern (Fig. 2) include carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), hydroflorocarbons (HFCs), and sulfur hexafluoride (SF6). Within the agricultural sector, N2O, and CH4 are of primary concern as they occur naturally in agriculture, while the other are considered anthropogenic and not typically associated with agricultural sources.
There are several other gasses that are of interest because they are precursors of the other GHG. These include nitrogen oxide (NOx), ammonia (NH3), non-methane volatile organic compounds (NMVOC) and carbon monoxide (CO).
The EPA estimated that in 2008 about 15% of GHG emissions were CH4 and N2O, of which 36% and 77%, respectively, were directly attributable to agriculture.
Over the past several years, the term “carbon footprint” has often been used in conversations as public debate heightens on responsibility and mitigation practices that can be used to stem the threat (real or perceived) of global climate change. To the man in the street the term is a general reference to the sum of gaseous emissions that are relevant to climate change associated with any given human activity.
The ISA Research Report in 2007defines it as follows: “The carbon footprint is a measure of the exclusive total amount of CO2 emissions that are directly or indirectly caused by an activity or is accumulated over the life stages of a product.”
A carbon footprint involves not only CO2 emissions but also includes N2O and CH4 emissions which are expressed in CO2 equivalents (CO2e). A CO2e is the concentration of CO2 that would give the same levels of radiative properties as a given amount of CO2. This is calculated over a specified time period and must be stated whenever a global warming potential (GWP) is stated.
The GWP is a measure of how much a given mass of GHG is estimated to contribute to global warming. For example, GWP over 100 years for N2O is 298. This means that the emission of 1 million tons of N2O is equivalent to 298 million tons of CO2 over 100 years. The GWP over 100 years for CH4 is 25.
Greenhouse gasses and the poultry industry
Much of the CO2e that is generated from the poultry industry is primarily from the utilization of fossil fuels. This may be from purchased electricity, propane use in stationary combustion units such as furnaces and incinerators and diesel use in mobile combustion units such as trucks, tractors, etc. and generators that are used on the farm.
Aside from the N2O and CH4 emitted from fossil fuel used on poultry farms, these gases are also emitted from manure during handling and storage. Nitrous oxide and CH4 emissions are dependent on management decisions about manure disposal and storage as these gases are formed in decomposing manures as a by-product of nitrification/ de-nitrification and methanogenesis, respectively.
In animal agriculture, the greatest contribution to CH4 emissions is enteric fermentation (21%) and manure management (8%). When comparing the distribution of CH4 emissions from enteric fermentation among animal types (Fig. 3), poultry had the lowest amount with 0.57lbs (0.26kg) CH4 per animal per year when compared to dairy cattle with 185-271lbs (84-123kg) CH4 per animal per year and swine with 10.5lbs (4.8 kg) CH4 per animal per year.
For manure management, CH4 emissions are generated as a result of the decomposition of manure under anaerobic conditions. These conditions occur readily when large numbers of animals are managed in a confined area resulting in the generation of a large amount of manure.
The majority of poultry production systems handle manure as a solid, and the manure tends to decompose under aerobic conditions generating less CH4 than would be generated under anaerobic conditions. The main cause of agricultural increases in N2O emissions is from the application of nitrogen fertilizers and animal manures.
The EPA (2005) reported that manure from all livestock is a contributor to N2O emissions with poultry accounting for 9% of manure nitrogen. Indirect emissions result from volatile nitrogen losses primarily in the form of NH3 and NOx. The amount of excreted organic nitrogen mineralized to ammonia during manure collection and storage depends on time and temperature.
In the case of poultry, uric acid is quickly mineralized to ammonia nitrogen which due to its volatility, is easily diffused into the surrounding air.
How can the industry address carbon footprint?
As the poultry industry moves towards becoming a more energy efficient and sustainable industry, it is important to have an understanding of the carbon footprint of each segment of the industry. Reductions in the carbon footprint of the poultry production will require the identification and adoption of on-farm management practices and technological changes in production and waste management that can result in positive net changes for producers and the environment.
Study results put the poultry industry in a favorable light when compared to other protein sources. It was recently reported that one pound of chicken meat resulted in the emission of 7.05 lbs. CO2e, while a report from a swine study indicates that 8.8 lbs. CO2e was emitted to produce one pound of pork.
Reducing energy use on the farm
From all indications, the majority of GHG gases generated from the poultry industry occur during the production stage (i.e. the grow-out, pullet and breeder farms), specifically propane and electricity use. The poultry industry continues to work on improving efficiency when using fossil fuels in an effort to reduce GHG emissions.
Improvements in energy use on poultry farms have to be approached on an individual basis. There are a number of actions that can be taken to reduce the use of fossil fuel, specifically propane on the poultry farms.
- For those houses that are not constructed with solid walls, enclosing and insulating curtain openings will reduce heat loss from the houses thereby reducing propane use.
- Installing attic inlets will allow the utilization of the attic area as a solar energy collector.
- Adding insulation to the walls and ceilings will reduce heat loss.
- Installing circulatory fans will reduce temperature stratification and using radiant heaters for brooding instead of gas heaters is not only more economical but is also more efficient.
- Energy efficient models of generators and incinerators should be selected as these will pay for themselves quickly with the amount of energy they conserve.
- Incandescent lights should be replaced with compact fluorescent lights to help reduce electricity use and costs.
Developing alternative energy sources
Currently, there are a number of alternative energy sources that could be considered, the most common are solar, wind and biomass. While these alternatives may eventually prove effective, they remain in the proving stage and are expensive to implement.
A considerable amount of poultry litter is generated annually in the U.S., approximately 10.2 million tons. A large amount of this litter is applied to crop lands and pastures as a means of soil amendment. The litter in poultry houses could alternatively be used as renewable energy source.
Reducing methane and nitrous oxide
Methane production from animal manures increases with increased temperature. This is where the majority of the CH4 emitted during poultry production. Prolonged litter storage can increase CH4 emissions and should be avoided when possible. To reduce the N2O emissions, nitrification inhibitors can be added to the poultry litter.
Genetic selection and nutrition
Other ways of becoming more efficient are through improving growth rate and feed efficiency. The poultry industry has consistently improved growth rate and feed efficiency through genetic selection and nutrition when compared to other animal production systems.
The scale of the U.S. poultry sector is vast and even small impacts can add up. Therefore, the industry needs to be vigilant and continue the excellent progress it has made in reducing emissions and making the industry more sustainable.