Features Manure Expo
Innovations in dairy manure and GHG research: A comprehensive approach

Cornell University and the New York dairy industry are working together to understand how dairy manure can impact a farm’s greenhouse gas (GHG) emissions and determine which strategies farmers can use to reduce their footprint, while maintaining profitable farm businesses that meet additional sustainability goals including air and water quality, soil health and biodiversity. With New York’s ambitious Climate Leadership and Community Protection Act and the dairy industry’s aggressive goals for environmental sustainability, Cornell is uniquely positioned as a leading research university and Land Grant Institution to study and develop innovative strategies and work with farmers to identify which of these will work in the northeast.

There are three important GHGs associated with agriculture – carbon dioxide, methane and nitrous oxide. When it comes to manure, however, we focus on methane and nitrous oxide. Methane on a dairy farm is primarily produced directly from the cow herself (enteric) and from the anaerobic storage of livestock manure. While nitrous oxide emissions occur in animal housing and during the handling and land application of manure and other associated field practices related to growing the forage and grain crops fed to those animals.

The cow
Cows produce enteric methane during the digestion process. As fermentation of feed takes place in the rumen, the byproducts of carbon dioxide and hydrogen are converted to methane by microbes (methanogens). Cows then release that methane by burping it out. There are feed additives that are designed to inhibit this process and therefore reduce enteric methane produced by the cattle. Cornell is currently in the process of building a state-of-the-art facility to investigate the effects of feed additives on enteric methane emissions over extended periods of time as these products interact with animal genetics, diet composition, and potential microbial adaptation.

Precision feeding is another strategy to reduce not only methane from the cow, but also nitrogen in her manure. By feeding rations that are more energy efficient, you can reduce excess energy fed and thereby keep more of that energy for the animal’s needs. This also means less is lost to byproducts like methane. Likewise, managing cattle diets for optimized protein and amino acids can reduce ammonia emissions and manure nitrogen, both of which can ultimately become nitrous oxide. The Cornell Net Carbohydrate and Protein System (CNCPS) is a cattle nutrition model that predicts feed utilization, animal performance and nutrient excretion for dairy and beef cattle using knowledge about feed composition, digestion, and metabolism in supplying nutrients to meet requirements. CNCPS is currently used to formulate diets for about 70 percent of the dairy cattle in the U.S. Version 7 of CNCPS has been in development for 13 years and evaluated internally on high producing lactating dairy cattle. Upon its release, nutritionists will be able to formulate more precise diets that maintain productivity while reducing N intake, excretion, and methane intensity. When implemented correctly, these diets can provide greater milk component yield, enhance energetic and N efficiency, and reduce the cost of the diets. Further, the model predicts enteric methane production with good accuracy while conducting diet formulation, allowing herd level methane inventories alongside nitrogen efficiency planning.

Manure storage and handling
To maintain compliance with the Clean Water Act and state and local regulations in the U.S., the number and volume of liquid manure storages has increased significantly in the last 20 years. While this is a clear benefit for water quality by reducing the need to spread manure during inclement weather that is conducive to runoff, these storages also create anaerobic conditions that result in methane gas production from the carbonaceous solids in livestock manure. Cornell’s Pro-Dairy Dairy Environmental Systems specialists are hard at work quantifying the impact of the GHG emissions from storages and are also researching and designing solutions. They are monitoring GHG emissions, sampling manure and building scale model storages to investigate potential additives and manure treatments that claim to reduce methane emissions from storages. The good news is that they have already identified some strategies that farms can do today to reduce the GHG footprint of their manure storage and handling. They are currently working to quantify the benefits of practices like separating manure solids before storage, reducing manure stored during the warmer months, covering separated liquids and flaring the methane captured by the cover, anaerobic digestion and biogas production, oxygenation and acidification.  

Manure application and crop management
Once manure is out of storage and being used as a soil amendment and nutrient source, the GHG focus for manure during field application shifts to nitrous oxide. In addition to reducing the need for importing fertilizer (and the associated GHG emissions from that), maximizing nitrogen availability of manure applied to cropland will reduce losses to the environment. Getting manure incorporated or injected as quickly as possible and applying it as close to (or during) crop utilization will reduce ammonia emissions significantly, but we are still learning what the ultimate impact is on nitrous oxide. In collaboration with the Soil Health Institute and researchers seven other research institutions, Cornell University is part of a project looking specifically at GHG emissions from manured field crop systems, called Dairy Soil & Water Regeneration: building soil health to reduce greenhouse gases, improve water quality and enable new economic benefits. This project funded through the Foundation for Food & Agriculture and matched by industry partners is led by the Dairy Research Institute. The project team is collecting data for six years to study soil health and manure management and its effects on greenhouse gas emissions, water quality and agronomic factors such as yield and forage quality.

By engaging in research on real dairy farms across the U.S. (in New York, Vermont, California, Wisconsin, Idaho and Texas) we will address research gaps about the GHG emissions from manured field crop systems, not just individual practices. This work is designed to engage and inform dairy producers by helping them select management alternatives that work for the crops, the environment and the farm’s bottom line while utilizing one of their most valuable resources: manure. •

If you want to see more innovation in the northeast around the sustainable use of manure, don’t miss the 2024 Manure Expo being hosted by Cornell Pro-Dairy and University of Vermont Extension on July 17-18 in Auburn, NY! Visit ManureExpo.com for more information.