A 50-Year Comparison of the Carbon Footprint and Resource Use of the US Swine Herd: 1959-2009

Over the past 50 years, the US pig industry has reduced significantly its environmental impact and natural resource use nearly 50 per cent across the board per 1,000 pounds of dressed carcass produced, according to Garth Boyd of Camco in a report for the US National Pork Board.
calendar icon 31 March 2013
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The purpose for this scientific project was to conduct parallel life cycle assessments to evaluate the impact of increased production efficiency in the US swine industry on the environment and resource use over the past 50 years (1959 to 2009). The project models every aspect of pork production from cradle (upstream emissions and resource use associated with feed production) to finished market hogs at the farm gate (production of the live animal ready to be transported to harvest). The functional unit used for comparison is 1,000 pounds of hot dressed carcass weight.

A process-based deterministic model was used to model the flow of pigs through the US swine industry by animal age-gender subclass for both the US breeding and market hog herds. The model was designed to estimate feed, water, energy, land and crop nutrient resources required to support the population. Furthermore, estimates were made of manure and global warming gases (carbon-equivalents, CO2e) produced annually. Each population flow was based on the yearlong flow of pigs through each age-gender subclass from 1 December to 30 November of the following year as published by USDA. Then, the authors estimated the dynamics of the population using known/published biological parameters representative typical of production practices of the era.

Results from the population flow model yielded the number of average animal-days in a year for each age-gender subclass in the population. Knowing the number of animal-days made it possible to estimate resource requirements such as feed and water. From this point, it was a natural progression to determine crop requirements using annual crop yield and input data from inputs such as pesticides, energy and irrigation. Emission factors were obtained for each process, including but not necessarily limited to, swine life functions, cropping, feed processing, feed transportation and manure storage.

The US swine industry produces pigs far more efficiently today (2009) than in 1959. The number of hogs marketed has increased 29 per cent (87.6 million in 1959 to 112.6 million in 2009 after removing market hogs imported directly to harvest) from a breeding herd that is 39 per cent smaller. The efficiency gain is even more impressive when measured against the total dressed carcass weight harvested. Dressed carcass yield leaving the farm has nearly doubled in 50 years from 12.1 billion pounds to 22.8 billion pounds. This increase in productivity has resulted in an increase of 2,231 pounds (2.5 times) of carcass harvested annually per sow-year. Today, it takes only five hogs (breeding and market) to produce the same amount of pork that required eight hogs in 1959.

A near doubling of pork output at the farm gate has only required a 25 per cent increase in annual feedstuffs. As a result, feed efficiency as measured over the entire population, including maintenance of the breeding herd, has improved 33 per cent from 6.6 pounds of feed per pound of dressed carcass weight produced at the farm gate to just 4.4 pounds of feed. This improvement is attributable to many factors including increased average daily gain, dietary changes, improved feed conversion, a smaller breeding herd and fewer numbers of idle pigs in the breeding herd.

Increased crop yields have resulted in a 59 per cent decrease in the total amount of land required resulting in a 78 per cent decrease in the amount of land required per 1,000 pounds of dressed carcass produced. This gain in efficiency, while primarily due to improved crop yields, is also a result of by-product feed use (eg. dried distiller’s grain solubles (DDGS) and soybean meal (SBM)). Dietary changes based on improved feed milling and ration formulation have most likely played a role as well.

Much like feed utilisation, total water demand for animal consumption has increased only 11 per cent from 32.7 million gallons in 1959 to 36.2 million gallons in 2009. This has resulted in water consumption dropping from 2.7 gallons per pound of dressed carcass to 1.6 gallons, a 41 per cent improvement. Most likely this improvement is due to a reduction in the size of the breeding herd and animals going to harvest at a much younger age today than in 1959.

The carbon intensity also known as the carbon footprint (CO2e) of US swine production to the farm gate has increased 23 per cent in the past 50 years - 45.7 million metric tonnes (MMT) to 56.1MMT. This is to be expected given the increase in the number of pigs going to market and compares very favourably to the 88 per cent increase in dressed carcass weight production during the same period.

As a result, the carbon footprint per pound of dressed carcass produced has been reduced 35 per cent from 3.8kg per CO2e to 2.5kg per CO2e. This highlights the positive impact of improved efficiency in the total swine production chain on resource use.


The US swine industry has managed to stabilise its overall resource demand over the past 50 years. This feat is remarkable because pork production, as measured by pounds of dressed carcass leaving the farm gate, has nearly doubled in that same period.

What the swine industry has been able to accomplish very successfully over the past 50 years is to reduce significantly its environmental impact and natural resource use nearly 50 per cent across the board per 1,000 pounds of dressed carcass produced.

Further Reading

You can view the full report by clicking here.

May 2012

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