A FARM SYSTEM APPROACH TO ANALYZE GREENHOUSE GAS (GHG) MITIGATION STRATEGIES FOR RUMINANT PRODUCTION SYSTEMS

Agriculture is a significant emitter of GHGs. Especially ruminant production systems that contribute substantially to global warming due to the enteric fermentation. Ruminant production systems are often integrated in mixed farm systems, including arable production, grassland systems and possibly energy production, which may provide opportunities for mitigation of GHGs when considered as a whole system. The paper analyzes systematically the GHG mitigation potentials of a mixed farm system, which represents a typical farm in northeastern Germany by modeling interactions and substance flows between different subsystems within a model farm. The following mitigation strategies are compared: 1) increased milk production per dairy cow, 2) integration of a biogas plant. The results show that the integration of the biogas plant has the greatest mitigation effect, followed by increased performance of the dairy system. Each mitigation practice has specific uncertainties which determine the overall results substantially. Uncertainties in the biogas mitigation option are due to emissions from the digestate spread to the fields. In option 2 the mitigation of methane production due to increased milk production per animal is partly compensated by increased methane emissions per animal and increased emissions due to feed production. The integration of the biogas system requires additional land to be cultivated, which may lead to induced emissions and thus lower the positive GHG effect.