By Blake Jackson
Researchers at Penn State, along with collaborators from Iowa State University and Roeslein Alternative Energy, are exploring innovative management practices in dairy farming that could reduce nutrient pollution and greenhouse gas emissions.
The study focuses on continuous cover-keeping fields vegetated year-round and anaerobic digestion, a process that converts manure and plant biomass into biogas. When combined, the team calls these approaches “Grass2Gas.” The research simulated a large Pennsylvania dairy farm to compare the environmental footprint of Grass2Gas practices with conventional management.
Using lifecycle assessment, which accounts for all resources and activities from start to finish, the study found that anaerobic digestion of manure with grassy biomass could lower the carbon footprint of milk production by more than 20% on average.
However, the researchers noted that to reduce water and air pollution fully, careful tradeoffs and adjustments are necessary.
“It has been suggested that promoting perennial plant species for nutrient management and converting manure and biomass into biogas with anaerobic digestion, which can be upgraded to renewable natural gas or directly burned in a generator to produce electricity and heat, can support sustainability on Pennsylvania dairy farms - and we wanted to see if that is true,” said study senior author Christine Costello, assistant professor of agricultural and biological engineering in the College of Agricultural Sciences at Penn State.
“We found that it could be true, but our research highlights the complexities of integrating anaerobic digestion into farm systems, including the impact on soil biogeochemistry and nutrient balances.”
The study found mixed results regarding water quality. While continuous cover reduces nutrient runoff, growing more vegetation for anaerobic digestion often requires importing feed, which can offset water quality benefits elsewhere. Adjusting herd size to match available feed showed minimal milk loss, comparable to current levels of milk wasted in the supply chain.
“The main takeaway from the study is that agricultural and environmental scientists, engineers and policymakers should think about crop and livestock production and energy technology as one interconnected system,” Costello said.
“When we think about adding an energy-production technology - in this case, anaerobic digestion - to a farm, we really need to think about how the residual materials - in this case, digestate - will be handled.”
The project is funded by the USDA’s Agriculture and Food Research Initiative, Sustainable Agricultural Systems Program, under the National Institute of Food and Agriculture.
Photo Credit: gettyimages-lishanskyphotography
Categories: Pennsylvania, Education