The goal to reduce greenhouse gas (GHG) emissions has resulted in an increase in global efforts to develop renewable and sustainable technologies across key polluting sectors. Among these, the energy and agricultural industries are responsible for more than 85% of global GHG outputs, driven largely by fossil fuel consumption and methane emissions from livestock waste. Despite its environmental drawbacks, the agricultural sector offers opportunities for resource recovery, particularly through the utilization of livestock manure, which holds significant potential as an on-site energy source and nutrient reservoir. This research explores a closed-loop, manure-based hydrogen production system aimed at achieving energy autonomy and environmental sustainability on a dairy farm. Manure is first treated through anaerobic digestion to yield methane-rich biogas, which is subsequently converted to hydrogen via partial oxidation. The hydrogen is then used in a fuel cell to generate electricity, satisfying the farm’s operational energy needs. Concurrently, the digestate produced from the AD process is repurposed as a biofertilizer, reducing dependence on synthetic fertilizers and enhancing circular nutrient management. This system was simulated incorporating primary data from a conventional intensive dairy operation in Galicia, Spain. To evaluate the environmental performance of this integrated system, a life cycle assessment (LCA) was performed using 1 kg of fat and protein corrected milk (FPCM) as the functional unit, considering hydrogen and meat as co-products. Preliminary simulations indicate that the hydrogen generated surpasses the farm’s energy requirements, and the application of the digestate could substitute approximately 30% of the total fertilizer demand. The environmental analysis also revealed a 27% reduction in global warming per kilogram of FPCM. Similar downward trends were noted for other environmental impact categories, including terrestrial acidification, freshwater eutrophication, and marine eutrophication. Notably, fertilizer usage and manure-related emissions, identified as major environmental hotspots in conventional systems, showed substantial reductions within the proposed closed-loop configuration. As a conclusion, the proposed system is reported to have decrease the environmental impacts creating a sustainable and environmentally friendly loop.
Author Contributions
Conceptualization, A.T., G.F. and S.G.-G.; Methodology, A.T., G.F. and S.G.-G.; Software, A.T.; Validation, G.F. and S.G.-G.; Formal analysis, A.T.; Investigation, A.T. and S.G.-G.; Data curation, S.G.-G.; Writing—original draft preparation, A.T. and S.G.-G.; writing—review and editing, G.F.; visualization, A.T.; supervision, G.F. and S.G.-G.; project administration, S.G.-G.; funding acquisition, S.G.-G. All authors have read and agreed to the published version of the manuscript.
Funding
This research has been partially supported by the project CÓMBARO, which is being developed under the aid called by the Galician Food Quality Agency (Agacal) in 2023 for the execution of innovative projects of the operational groups of the European Innovation Association (EIP-Agri) and by NUTRITIVE (Grant agreement No. 10113540) project, being funded by the European Commission HORIZON-CL6–2023- ZEROPOLLUTION-02 and to the Cross-disciplinary Research in Environmental Technologies (CRETUS Research Center, ED431G 2023/12).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
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