Small-scale biodigesters in a tropical semi-arid region: Impacts on emissions and water, energy and food security

• An energy-water-food nexus framework for biodigesters in small farms was analyzed. • LCA demonstrated low emissions in the construction of the biodigester. • Biogas demonstrates economic benefits through LPG substitution. • Replacing firewood with biogas helps reduce respiratory problems. • The importance of alternative energy sources for families in semiarid areas was analyzed. Due to the growing search for natural resources to meet human needs, interest has arisen in developing technologies based on the Water-Energy-Food (WEF) nexus. The implementation of biodigesters on small farms is an initiative that aligns with global agendas and the WEF nexus concept. This research aimed to evaluate the integration of a small-scale biodigester prototype locally referred to as " biodigestor sertanejo ," on the water, energy, food, and environmental security of smallholder farmers in the semi-arid region of northeastern (NE) Brazil. Primary data were obtained from semi-structured questionnaires. A physical-chemical analysis of the digestate as a biofertilizer was also carried out. The emissions from the biodigester were analyzed using the life cycle assessment method. The use of biodigesters to treat animal waste has positively impacted the lives of families by reducing the proliferation of diseases and the contamination of water resources. Replacing firewood with biogas for cooking also helped reduce the number of cases of respiratory diseases in families by 10.9 %. It was also found that domestic savings of around USD 201.3 per year resulted from the switch to biogas energy. Another benefit was using the digestate from the biodigester as an organic fertilizer, which increased food production. Environmental analysis showed that using manure for biogas production emits fewer greenhouse gases than applying it directly to crops or leaving it in open fields. This work provides insights for better management of water and energy resources in a semi-arid region and can support public policies and investments. The results also demonstrate how this technology enhances food security for local populations, which could serve as an incentive to expand its use.