Carbon conservation strategy for the management of pig slurry by composting: Initial study of the bulking agent influence

The intensification of the livestock production systems implies a potential environmental risk, associated with the great generation of animal wastes and slurries and their storage and management. Manure management is associated with considerable emissions of ammonia (NH3) and greenhouse gases (GHG). However, the potential for GHG mitigation is highly dependent on the waste treatment strategy considered. This laboratory study aims to evaluate the influence of the type of bulking agent used on the potential reduction of the carbon dioxide (CO2) emission, dealing with carbon (C) conservation when the solid fraction of pig (Sus scrofa domesticus) slurry is managed by composting. For this, a composting experiment in batch reactors was run with four mixtures elaborated using the solid fraction of pig slurry (SPS) and different materials (maize (Zea mays) stalks, barley (Hordeum vulgare L.) straw, cotton (Gossypium hirsutum) gin and garden prunings) as bulking agents. The potential C conservation in the mixtures was evaluated by determining the CO2 emissions; the evolution of the mixtures, the thermal profile developed and the thermodynamics of the process were also studied. The mixtures elaborated with cotton gin and garden prunings showed the fastest temperature development, and also the highest CO2 emissions. However, the use of maize stalks as bulking agent reduced CO2 emissions due to its slow degradability: this could constitute a suitable strategy to promote C conservation during the management of pig slurry by composting.The research has been funded by the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/under REA grant agreement n° 289887, and the results and conclusions achieved reflect only the author’s view - the Union not being liable for any use that may be made of the information contained therein. This work has been also supported by a ‘Juan de la Cierva’ contract to Dr. Bustamante (Spanish Ministry of Science and Innovation) co-funded by the EU through the Social Funds.Peer reviewe