Dairy life cycle assessment puts spotlight on greenhouse gas emissions
Supporting Canada's leadership role and setting the stage for mitigation strategies
Posted: July 16, 2013
Few environmental issues in agriculture have driven as much interest and debate as the global discussion around greenhouse gas (GHG) emissions. Livestock production, particularly with ruminant animals, is identified as a contributor. There is mounting pressure to better understand and find ways to reduce the livestock GHG footprint, to meet new expectations and improve the sustainability of livestock industries for a successful future.
Now Canada has taken a major step forward to meet this challenge, with a broad science effort that includes a life cycle assessment of GHG emissions from dairy production. This assessment was conducted by Agriculture and Agri-Food Canada (AAFC) using the innovative 'Holos' modeling software program. It takes a comprehensive account of GHG emissions throughout the whole life of dairy cows, quantifying and breaking down the sources of emissions on dairy farms. This provides an in-depth picture of how dairy production contributes to emissions as well as the potential for mitigation strategies.
"Greenhouse gas emissions have become one of the most challenging and high profile issues facing livestock production globally, and dairy production has an important role," says Dr. Karen Beauchemin of AAFC Lethbridge, a lead researcher in the effort. "The dairy life cycle assessment, integrated with Holos, provides us with a baseline model of GHG emissions from dairy farms in Canada, along with a greater in-depth perspective on the efficiency and environmental impact of dairy production as it relates to those emissions. This gives us a clear idea of where we are today. It will help us develop strategies that can help minimize emissions while protecting the high production levels required to meet the demands of feeding a growing world."
The dairy life cycle assessment for Canada is one of the most sophisticated approaches of its kind completed to date anywhere, says Dr. Emma McGeough of AAFC Lethbridge, another lead researcher involved. "It gives us a very strong knowledge base to work from. The priority is to find approaches that make sense and work well for industry as well as from a GHG perspective. The good news is we are finding that the benefits on both sides often come down to efficiency. If we can find ways to improve dairy production efficiency to reduce GHG emissions, often there are productivity and economic advantages as well."
Meeting the challenge
The dairy life cycle assessment was a major undertaking conducted to capture a representation of the typical six year life span of the average dairy cow. It was based on a "whole farm system model" approach that involved examining all factors that contribute to GHG emissions on a typical Canadian dairy farm. This includes not only the emissions associated with the livestock themselves, but emissions associated with providing the feed for these animals. Also incorporated into the assessment are the factors involved with growing the crops to feed these animals.
"The advantage of the whole farm approach is that it allows you to see the complete picture," says Beauchemin. "Sometimes reducing GHG emissions in one part of a farming system can lead to an increase in emissions in another part of the system. We're interested in finding opportunities for a net overall reduction, which can only be identified definitively with the whole farm approach."
The researchers chose Quebec, as the province with the most dairy cows, as the location to base the life cycle assessment. Information was gathered to provide an accurate representation of real-world, average commercial values for dairy production in the province, including data from on-farm surveys, additional data and information from AAFC research centres in Quebec, and consultation with dairy advisors.
The project was structured to follow a representative group of calves from birth to their eventual cull from the farm while capturing information for the complete farm system - including all farm inputs and components. "Everything was designed to be realistic and representative of what was happening at a commercial level," says McGeough. "This would provide us with the baseline scenario we could then use to tie to potential mitigation strategies."
Holos tool drives sophistication
A critical tool providing a basis for the project was Holos. This whole-farm modeling software program was designed to estimate GHG emissions based on information entered for individual farms and is arguably the most sophisticated tool of its kind developed to date.
"Holos is a tool to estimate and reduce greenhouse gases from farms," says Shannan Little, AAFC Holos Coordinator. "It's a simple focus, but the tool itself is quite sophisticated. It's state-of-the-art in the world and it can be used in a number of different ways by everyone from producers to researchers to decision-makers at an industry-level. This opportunity to use Holos in life cycle assessment for livestock industries offers many advantages as we address GHG emissions and other issues related to sustainability."
The researchers used the real-world information gathered to develop values that could be used with Holos to generate a "simulated farm" model representing typical commercial conditions.
This model provided a sophisticated quantification of GHG emissions and a tool for running a variety of scenarios to project the impact of different changes to production approaches. Emissions were quantified and analysis was conducted on a milk basis - in other words, based on the emissions required to produce specific unit levels of milk. The researchers also quantified emissions on a per kg of beef basis, to account for the component of a dairy farm that produces beef from veal and cull cows.
Inside the emissions picture
The results of the baseline scenario show three types of GHG emissions related to dairy farms. Methane accounts for 58 percent of emissions, nitrous oxide makes up 39 percent of emissions and carbon dioxide comprises the remaining 3 percent of emissions.
Among emissions by farm component, 68 percent are related directly to the cattle, 30 percent to soils and crops, and 2 percent to energy use.
Among the specific emissions sources, by far the greatest of these is enteric methane emissions at 47 percent. This is followed by soil and crop nitrous oxide emissions at 25 percent, manure methane emissions at 10 percent and manure nitrous oxide emissions at 8 percent. The remainder includes indirect nitrous oxide emissions at 7 percent, soil carbon dioxide emissions at 2 percent, and carbon dioxide emissions from energy use at 1 percent.
Examples of new opportunities
Based on this information several pathways have stood out for the researchers as they look toward potential mitigation strategies.
Nutritional strategies. The nutritional aspect in particular appears to be one of the greatest opportunities, says Beauchemin. "When you consider all of the factors that contribute to emissions on a dairy farm, almost 50 percent of the emissions are actually from the digestion of feed by the cow - what we call enteric methane emissions. This shows us that how we feed the animals, the type of feed and how the animal digest the feed has a huge impact on the overall emissions. There has been a lot of research done on nutritional strategies and there is more research we can do to further our knowledge specific to emissions, so this appears to be a promising area to make progress."
There is a growing body of knowledge showing that nutritional approaches that result in enteric methane reduction often also improve overall feed efficiency, says McGeough. "The economic incentive for reducing GHG emissions alone hasn't been there at the producer level. This has the potential to change in the future as opportunities such as offset programs take hold. However, both in the short and long-term anything that reduces emissions and also has clear other benefits for the producer is a big plus. Those 'win-wins' are what we're looking for."
With the baseline scenario in place and integrated with the Holos program, the researchers plan to continually use this as a tool to evaluate the GHG implications of different approaches, as new research is conducted and new information becomes available. One key area they are examining is the impact of additional fats to the diet. "Previous research has suggested that additional fat can mitigate methane emissions, so that is one example of a component we want to look at more closely."
Overall, the researchers want to examine many different nutritional and feeding strategies. Different forages, different grains, different portions and ratios - anything that might yield new insight to better understand how different feeding approaches impact emissions. "Even if we find that some of these different approaches increase emissions that is still good for us to know," says. "Every bit of new data we have improves our knowledge base and improves the modeling scenarios we can run using the Holos program."
Nitrogen efficiency. Another early focus on the nutritional side is finding ways to improve efficiencies in the nitrogen cycle as it relates to use by the animal and manure used as a resource for fertilizer. "One of the indications we uncovered with Holos is that there's often excess nitrogen in the system," says Little. "That's an example of something producers may not be focusing on as much, where we can look at options such as protein sources to improve that."
Reproductive management. From a management perspective, another opportunity that stands out for the researchers is fertility – specifically, the potential to improve reproductive rate and replacement rate. "When you look at the investment in feeding and caring for animals over a period of time, there is a huge impact when you lose an animal or when the fertility rate is lower," says McGeough.
She has already led one study using the Holos program that confirmed reducing the dairy cow replacement rate significantly reduced the GHG footprint of milk production. "The benefits are multiplied when coupled with other mitigation strategies and would also be expected to improve farm profitability."
Improving consistency. Another approach the researchers are pursuing is to look for differences between the practices at dairy farms with the best statistics versus those with lower performance results. "That's often a good starting point toward identifying the best approaches," says McGeough. "We can then use the Holos model to run scenarios and help lead us down the right path."
Driving research. The program also has benefits for helping identify priorities for further research, says Little. "For example, we see now just how big of a target enteric methane is, compared to other components, and that's helping drive a push for new knowledge on that component."
Canada in the big picture
The findings of the life cycle assessment reinforce that Canada's dairy sector is among the most efficient and productive in the world, says Beauchemin. "We have very high yielding cows and very fine-tuned diets. Our emissions per kilogram of milk are low when you compare us to other countries."
However, while the industry is already highly efficient, the assessment and ongoing use of Holos can add value by helping Canada maintain a leadership position and continue to strengthen its competitive advantages. "Some of our farms do better than others," says Beuchemin. "This tool can help bring everyone up to the same level and make sure we're being as efficient as we can be as production approaches and options continue to evolve. There's always going to be a drive to have solid benchmarking and keep getting better. This is an important step in that process."
Find more information on Holos on the AAFC website.
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