Background Over the past few years, livestock production has intensified, resulting in the generation of greater quantities of manure. Manure from farms represents a threat to the environment in the form of greenhouse gas (GHG) emissions and the release of excess nitrogen and phosphorus into the soil and water. There is thus a growing need for the agricultural sector to develop innovative means of managing manure or of using it differently. Furthermore, large areas of Spain are currently threatened by desertification, loss of soil fertility, salinisation and erosion. Climate change processes are also expected to result in a loss of carbon in the soil as temperatures rise. In this context, the impact of organic matter on the soil is highly relevant. Objectives The aim of this project was to demonstrate good practices in the management of agricultural organic waste that can help to reduce the environmental impact of cattle farms and reduce their GHG emissions. Project actions would focus on using agricultural waste for composting and methane production. The project planned to demonstrate an innovative system that mixes liquid manure from cattle farms with other types of organic waste (such as that from pigs and poultry). The aim was to produce a natural fertiliser and methane for energy recovery. The ultimate goal was for farmers to adopt these waste management strategies and thus avoid the use of other external resources and reduce the transportation of waste. The project would also promote the recovery of deteriorated soil through the application of compost. Results The project demonstrated a sustainable strategy for managing organic waste from farms in Galicia and Extremadura that includes composting and the production of biomethane. Such management practices can lower the environmental impact of manure. The project first carried out field research into the problem of waste management. A survey was conducted of 640 farms in the Spanish regions of Galicia and Extremadura. This research was useful in the selection of 18 farms where the pilot actions would take place – three cattle, three pig and three poultry farms in each region. The engaged farmers provided livestock waste (and vegetable waste as a supporting material), along with facilities for making compost and crop farms to check the fertilising capacity of the obtained compost. After analysing the slurry and soil, compost was produced under the guidance of the department of agricultural science at the University of Santiago de Compostela (USC) and other companies responsible for the operation and maintenance of the compost piles. The only materials used were those available in the farms selected. Compost piles were monitored throughout the process and amended when needed. Once the process was completed, the compost was applied to plots in varying degrees. The end results were analysed in comparison to control crops. The project demonstrated that adding compost improves crop yield though not to the extent that would have achieved through the use of an inorganic fertiliser. This result however can be explained by the already high organic content of the soils in the region. As a result, a single year is not sufficient to determine the benefits compost over other forms of fertilisation. A multi-year trial is required to effectively conclude that this method is better for the soil but still economically viable. The project concluded that higher profit margins or economic subsidies are necessary to compensate the work needed to produce compost. Increased soil biodiversity and reduction of GHG emissions are insufficient incentives for farmers to adopt a practice than adds to their workload. Parallel to the composting process, a biomethane pilot plant was installed at one farm in close cooperation with the USC and external companies in charge of the process. Tests were performed with poultry and pig manure. Though biomethanisation was shown to be a technically viable process, it is not economically advantageous. Considerable initial investments are needed for which the produced energy does not financially compensate. The project calculates that a plant would need to be at least 300 times larger than the pilot plant in order to generate sufficient energy to be profitable. The idea of a larger plant providing service to various farmers could be a feasible solution for this that is to be explored. Overall, both the tested processes were shown to help reduce GHG, offer a solution to waste management on farms and reduce the costs of inputs needed. The beneficiary will continue to promote composting of manure and biomethanisation on a large scale including advocating that farmers come together to jointly manage operations. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).