RESEARCHERS at the University of Arkansas are attempting to help the U.S. dairy industry decrease its carbon footprint.
In 2007, Americans consumed approximately 17.4 million metric tons of fluid milk — not including milk used in dairy products such as cheese, yogurt and ice cream. The dairy industry has set a goal to reduce greenhouse gas emissions 25% by 2020.
The University of Arkansas researchers' "cradle-to-grave" life-cycle analysis of milk will provide guidance for producers, processors and others in the dairy supply chain and will help these stakeholders reduce their environmental impact while maintaining long-term viability.
"Based, in part, on growing consumer awareness of sustainability issues in our food supply chain, the U.S. dairy industry is working to further improve the environmental performance of its production processes and supply chain in a way that is also economically sustainable," Greg Thoma, professor of chemical engineering at the university, said. "Our analysis provides a documented baseline for their improvement efforts. It is a source for understanding the factors that influence environmental impact."
Thoma and an interdisciplinary team of Arkansas researchers looked at all facets and stages of milk production, from the fertilizer used to grow the animal's feed to waste disposal of packaging after consumer use. Specifically, their life-cycle analysis focused on seven areas:
1. Farm production and processes;
2. Farm-to-processor transportation;
3. Processor operations, packaging and distribution;
4. Retail operations;
5. Consumer transportation and storage;
6. Post-consumer waste management, and
7. Overall supply chain loss and waste.
The researchers found that for every kilogram of milk consumed in the U.S. per year, 2.05 kg of greenhouse gases, on average, are emitted over the entire supply chain to produce, process and distribute that milk. This is equivalent to approximately 17.4 lb./gal., they said.
The greenhouse gases were measured as carbon dioxide equivalents and included methane, refrigerants and other gases that trap radiation.
According to the researchers, the largest contributors to the footprint were feed production, enteric methane — gas emitted by the animal itself — and manure management.
The researchers identified areas where the dairy industry can reduce its impact within feed and milk production, processing and distribution, retail and the supply chain. They focused on farms, where processes for feed production, handling of enteric methane and manure management varied greatly and, therefore, represent the greatest opportunities for achieving significant reductions.
The researchers also suggested widespread nutrient management strategies that link inorganic fertilizer use with the application of manure for crop production. They recommended dry lot and solid storage systems as preferred manure management strategies, rather than anaerobic lagoons and deep bedding.
Methane digesters, which biologically convert manure to methane and capture it as an energy source, should be a high priority for larger dairy operations, Thoma said.
At the processor and distribution level, greater emphasis on truck fleet fuel usage and consumption of electricity will reduce emissions, the researchers said. Implementing standard energy efficiency practices focused on refrigeration and compressed-air systems, motors and lighting will also lead to reductions. Likewise, processing plant fuel reductions can be achieved through improved steam systems and continued energy efficiency improvements in other operating practices.
With packaging, emission reductions could come from improved bottle designs that result in less material use. Specifically, changing the bottle cap manufacturing process from injection molding to thermoforming may lower the environmental impact.
Finally, the researchers recommended a careful examination of transport distances to realize greater optimization and efficiency of trucking routes. They also suggested transport refrigeration systems that use fewer refrigerants.
The University of Arkansas researchers — Rick Ulrich, professor of chemical engineering; Darin Nutter, professor of mechanical engineering; Jennie Popp, professor of agricultural economics and agribusiness, and Marty Matlock, professor of biological and agricultural engineering, in addition to Thoma — partnered with researchers at Michigan Technological University. The study, "Carbon & Water Footprint of U.S. Milk, From Farm to Table," was published in April as a special issue of the International Dairy Journal.
A new European Union-supported network aims to improve the measurement of methane emissions from ruminants, among other things.
More than 50 scientists from more than 20 countries in Europe have joined forces in the METHAGENE network that will compile existing knowledge from existing research projects on genetics and methane emissions from cows, goats and sheep.
Jan Lassen with the department of molecular biology and genetics at Aarhus University in Denmark and Yvette de Haas, a researcher at Wageningen University in the Netherlands, will lead the project.
"The scientists in the network represent research projects with budgets totaling 39 million euros, and we are all using different methods to measure the climate-forcing methane that is emitted by cows when they digest their food in the rumen. The measuring methods that are ultimately used for the genetic selection of the cows with the lowest methane emissions are different, and in the network, we will be standardizing the methods and extracting the full potential of existing data," Lassen explained.
He has studied methane emissions from dairy cows in recent years, and preliminary results indicate that there is a link between methane emissions and feed utilization.
"There are correlations between the cows that are good at utilizing feed and the amount of methane they emit. A high feed efficiency gives lower methane emissions," Lassen said, acknowledging, though, that he is not yet able to make a genetic selection that can ensure a low methane yield while also maintaining high reproduction and milk yield.
The inability to select for a low methane yield is something the METHAGENE project may able to remedy.
"I have measurements from around 2,000 cows, but the network combined will have far more data that we can then explore. We can all contribute to the creation of a joint data set, and this is an advantage for all the network partners," Lassen said.
In addition to measuring methane emissions from cows using a sniffer device that sits above the cows at the automatic milking station, where they are fed concentrate, Lassen will use milk samples to calculate the methane emission from cows.
"I am working with other scientists from Aarhus University in another research project where we use milk samples to see if we can find a link in these to methane emission. The setup with milk samples is far easier to work than the sniffer method," Lassen said, explaining that what they are testing for is a link between the cow's respired air and the milk profile in terms of fatty acid composition, metabolites and proteins.