Ashley J. Belle

Ashley Belle






Participant: PROMISE AGEP Research Symposium, 2014

Ashley J. Belle

Department: Environmental Science and Technology
Institution: University of Maryland- College Park



Feasibility of Small-scale Anaerobic Digestion Improves for Dairy Farmers through Forage Radish Cover Crops Co-digestion

The main challenges to U.S. anaerobic digestion installation have been the large capital investment and lack of information on predicted biogas production. This research investigates using forage radish, a sulfur-rich winter cover crop, as a co-digestion feedstock in a dairy manure-based anaerobic digester in order to increase economic viability for small to mid-sized dairy farmers by augmenting their biogas production in the winter months, when fuel demand is the greatest. Forage radish does not compete with other food crops and greatly enhances soil nutrient management. It has been shown that these benefits are still realized when the above ground biomass of the radish is harvested and therefore can be used as a co-digestion feedstock. The objectives of this research are to determine: 1) how the sulfur content of the radish contributes to hydrogen sulfide (H2S) production in the biogas and whether its presence inhibits methane (CH4) production and 2) the optimal substrate ratios (forage radish to dairy manure) and inoculum volume for CH4 production using biochemical methane potential experiments. Our results revealed that CHproduction increased as radish inputs were increased from 0% to 100% (by volume) in dairy digesters when added with a non-limiting volume of inoculum (~90%), with 100% radish producing 162% more methane than digesting only dairy manure. However, digesters containing larger radish inputs also produced more H2S. Methanogenesis in dairy digesters did not appear to be adversely effected by the sulfur content of the forage radish, with increases in CH4 production being uniformed to radish additions.



Ashley J. Belle is a doctoral candidate in the Department of Environmental Science and Technology at the University of Maryland-College Park, where she is specializing in ecological technology design. Her research focuses on methane production and iron-sulfur dynamics in dairy anaerobic digesters utilizing forage radish cover crops as a co-feedstock. She has designed, constructed, and operated pilot-scale complete mixed digesters, which can be utilized as a better predictor of biogas potential for real world applications. Ashley received a Bachelor of Science (2004) in Chemistry from Dillard University and was an intern for two summers in the NSF Research Experience for Undergraduates Program. Prior to pursuing graduate studies, she also completed a yearlong internship with the U.S. EPA in the Office of Water and the Office of Environmental Information. As a Louisiana Board of Regents Fellow at Louisiana State University, Ashley received a Master of Science (2007) in Environmental Sciences with a concentration in Environmental Toxicology and was awarded the Dr. Joseph D. Martinez Memorial Award for her outstanding contributions to environmental science research. Ashley has also served as an Environmental Scientist with the LA Department of Environmental Quality, where she conducted inspections of permitted facilities to determine compliance with state regulations and responded to environmental emergencies. Currently, Ashley is a member of the American Society of Agricultural and Biological Engineers and recently was awarded first place for presenting her dissertation research in their graduate student oral competition at the Northeast regional conference.



Since the pre-industrial era, methane emissions have increased globally by 148%. Livestock manure management is responsible for 25% of the anthropogenic methane emissions related to agricultural activities, with dairy cattle listed as the highest emitter of all domestic animals. Through the AgSTAR program, anaerobic digestion (AD) technology is being promoted to farmers as a mechanism of capturing the methane gas generated from animal manures and utilizing it as an on-farm renewable fuel source. Burning of methane-rich biogas releases carbon dioxide into the atmosphere, which is 21 times less potent of a greenhouse gas, thus minimizing methaneemissions. However, AgSTAR estimates that AD technology is only economically viable to farms with over 500 dairy cattle, thus making this technology inaccessible to the small to mid-size dairy farmer who is limited by animal waste capacity. This research aims to optimize the biogas potential of dairy digesters by determining the suitability of co-digesting with forage radish, a sulfur-rich winter cover crop that would normally frost-kill. Forage radish is an ideal cover crop because it does not compete with other food crops and it greatly enhances nutrient management as nitrogen and phosphorus are extracted from the soil depth by the crop. Use of the co-feedstock, forage radish, has the potential to enhance biogas production in the wintertime when the demand for fuel is particularly high in the United States.



  1. Belle, A.J., Lansing, S., Weil, R. 2013. Forage radish cover crops increases methane production in dairy digesters (conference proceedings). Northeast Agricultural and Biological Engineering Conference. Altoona, PA. June 16-19, 2013.
  2. Belle, A.J., Lansing, S., Weil, R. 2013. A case study: Harvesting of forage radish cover crops for co-digesting in dairy manure anaerobic digesters. Northeast Sun Grant Anaerobic Digestion Workshop. Beltsville, MD. June 6, 2013.
  3. Belle, A.J., Lansing, S., Weil, R. 2013. Forage radish cover crops increases methane production in dairy digesters. The Clark School Engineering Sustainability Workshop 2013. University of Maryland, College Park, MD. April 22, 2013.
  4. Belle, A.J., Lansing, S., Weil, R., Felton, G. 2012. Creating renewable energy through sustainable nutrient management practices (poster). Science for Biomass Feedstock Production and Utilization National Conference. New Orleans, LA. October 2-5, 2012.
  5. Belle, A.J., Lansing, S., Weil, R., 2011. Enhancing methane production in dairy manure-based anaerobic digesters through co-digestion with forage radish cover crops (poster). 10th Annual American Ecological Engineering Society Conference. Asheville, NC. May 23-25, 2011.

Disclaimer: Information on this page has been provided by and is owned by the student presenter.


Please Comment! Leave a Reply.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


Get every new post delivered to your Inbox.

Join 156 other followers

%d bloggers like this: