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The objective of this study is to propose models of livelihoods symbiosis between freshwater aquaculture operations and vegetable farming. This model functioned as the way to reuse water and nutrients discharged from aquaculture activities, which caters for vegetable farming. The efficiency of the model is to minimize a large amount of solid waste disregarded directly to the receiving source, which was 315.098 kg. The quality of wastewater had been improved after releasing to the source. Total amount of carbon (TOC), nitrogen and phosphorus was 7.56%, 8.27% and 0.64% respectively, all of which meet the standard index of waste disragrded directly into the environment. In addition, the model also brings the additional income for households with 24.9 million VN dong after every fish breeding in comparison with traditional farming model.

Background Economic benefit has been analyzed for the yield of farming products when designing a farming system, while waste treatment also generates profitable energy products for this system. The economic factor is decisive in decision-making for applying waste treatment solutions for a small-scale farming system. A household farming system in the Mekong Delta generates many kinds of organic wastes, but most of the agricultural waste resources are disposed of into the environment. Methods This study approaches an analysis of economic–environmental–energy (EEE) efficiency for waste treatment of an integrated livestock-orchard (LO) system on a household scale in the Mekong Delta. This novel analysis method is based on the energy content of biomass and its cost. The EEE efficiency is optimized to gain objective functions regarding energy yield efficiency, system profit, and CO2 sequestration for the treatment model. The algorithms are built for optimizing these objective functions. Results The optimization results show the treatment model of pyrolysis and pelleting gain all the objective functions with high efficiency. The model is efficiently applied for the LO system that generates more than 100 kg of orchard residues and 3000 kg of pig manure. The system with a charcoal oven and pellet machine is capable to gain energy efficiency due to its potential biofuel products, such as biochars and pellet products. A treatment model of composting, pyrolysis, and pelleting gives the best performance of overall EEE efficiency. Conclusions This work has proven economic benefits from integrating biogas tank, charcoal oven, and pellet machine in an integrated LO system. The system contributes not only for reducing CO2 emissions but also for supplementing secondary renewable bioenergy, as well as for increasing incomes and thus supporting livelihoods for the local farming households.