Greenhouse Gas Emissions Reduction Potential of An On-Farm Biogas System.

Stored livestock manure is a source of methane (CH₄) emissions, a potent greenhouse gas (GHG). Manure management accounts for 12% of the total agricultural GHG emissions in Canada.  The objective of this research is to assess the potential of an on-farm biogas system (i.e. anaerobic digestion) to reduce GHG emissions from a 160 cow dairy farm in Ontario, Canada. In aconventional dairy operation, 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 the potential to reduce GHG emissions from the manure storage and also through replacing fossil fuel use with biogas energy. With most on-farm anaerobic digestion systems, manure from the barn enters the mesophilic digester where biogas and digestate are produced. The biogas is utilized for energy generation. The digestate undergoes solid/liquid separation withthe liquid being stored in an open tank until needed as an organic fertilizer for land application. Quantifying and comparing net GHG budgets of farm manure management systems through life cycle analysis (LCA) on biogas and conventional systems will assess environmental impacts and quantify the potential GHG emission reductions within the agricultural sector. Methane emissions from conventional manure management were measured using a micrometeorological method from July, 2010 through November, 2011 at which time a biogas system was installed. The biogas system became operational in August, 2012, and measurements of CH₄ emissions from the digestate are now being conducted. Preliminary results show the average CH₄ flux density observed was 272 μg m^-2 s from untreated manure and 50 μg m^-2 s from digestate which have been subsequently used in an initial LCA.. The energy generated was calculated using the 500 kW h nameplate capacity of the biogas system, but will be updated with actual production. The preliminary results from the LCA will be presented.