Greenhouse Gas Emissions from Storage and Field Application of Anaerobic Digestate.

The increasing evidence that current climate change is caused by anthropogenic greenhouse gases has led to interests in alternative options for lowering GHG emissions. Anaerobic digestion (AD) of dairy manure is a promising solution that offers wide benefits as it deals with waste management, renewable energy and climate change mitigation. Measurements considering all potential sources of GHG emissions in AD and conventional manure management systems are clearly needed in order to assess environmental attributes associated with AD. As part of the Government of Canada's Agricultural Greenhouse Gases Program (AGGP, a contribution to the Global Research Alliance), we initiated a study on GHG mitigation strategies in dairy-cropping systems in fall 2011.   The objective of the research reported here is to assess the potential of an on-farm biogas system to reduce GHG emissions from stored manure and from soils after field application in Ontario. In the conventional manure management practice, manure from the barn enters an open storage tank, where it remains until required for land application as an organic fertilizer. On farm biogas systems have potential to reduce GHG emissions from manure storage tank and also through replacing fossil fuel use with biogas energy. In this system, manure from the barn enters the anaerobic digester where biogas and digestate are produced. The biogas is utilized for energy generation.  The digestate is stored in an open tank until needed on the land as an organic fertilizer. Methane emission from raw manure were measured using a micrometeorological method from July, 2010 to November, 2011 in a 160 cow dairy farm in Ontario. A biogas system became operational on this farm in August, 2012, and measurements of emissions from the digestate were conducted since then.  Agronomic studies are being conducted at two locations to quantify soil nitrous oxide emissions from digestate compared to raw manure application.  At the Elora Research Station, Elora, Ontario, Canada, we are investigating three liquid dairy manure application methods (surface application, incorporation following surface application, band injection), timing (fall vs. spring) and manure source (raw manure vs. digested manure) and their effect on emissions from corn. At Campus d'Alfred Research Station, Alfred, Ontario, Canada, we are examining GHG emissions from two soils (sandy loam vs. clay) receiving raw and digested manure in the fall or spring.  Here we will provide an overview of this project and present the results from the first 2 years focused on emissions from stored manure and from the cropping systems component of the project.