(325d) A Decision-Making Tool for the Design and Evaluation of Waste Management Systems in Livestock Facilities

The agricultural industry generates large amounts of organic waste, representing a challenge in terms of management, treatment, and disposal. Livestock activities are a powerful industry required to cover the food demands of the population. As a result, it is one of the main producers of organic waste, containing an excessive amount of nitrogen and phosphorus. Inadequate management and disposal of these residues in certain areas leads to nutrient pollution in soil and water causing many environmental issues, including harmful algal blooms (HABs), dead zones and hypoxia, nitrates in drinking water, and byproducts of water treatment (dioxins), representing potential threats to human health [1]. In addition, organic waste pollution of can make land unavailable for crop activities requiring expensive remediation processes to mitigate nutrient pollution, which has a negative economic impact [2].

Currently, in concentrated animal feeding operations (CAFOs), the manure is collected and stored as a liquid or slurry in waste storage ponds specifically designed for this purpose, or in tanks. After storage, a common practice is the land application of the waste with the aim to employ the manure nutrient content as fertilizer [3]. However, the continued land application of manure in the surroundings of CAFOs can lead to nutrient pollution [4], causing various effects on human health, the environment, and the economy as mentioned before. Additionally, one of the major nutrient management difficulties is the high-water content of manure, making transportation of waste to nutrient deficient locations difficult and expensive. Therefore, appropriate and cost-effective on-site livestock manure management strategies must be implemented to achieve an environmentally sustainable operation of livestock facilities.

This work describes the development of a design and assessment tool based on techno-economic models to aid decision-makers in selecting the optimal nutrient recovery and valorization technologies from livestock waste. This approach is based on the operational conditions which define each livestock facility, capital cost availability, and the targeted environmental benefits. The goal is to provide a customized solution for each individual facility by evaluating different nutrient recovery and product valorization alternatives through a multi-criteria analysis framework and reach a satisfactory trade-off between economic and environmental goals. The technologies considered for nutrient recovery range from simple mechanical separation techniques such as filtration and centrifugation units to chemical processing units such as struvite formation, for obtaining products with a different quality to be used as fertilizers [5, 6]. All technologies concentrate the product nutrient content, facilitating its transportation and distribution to potential customers. In addition, the proposed tool recommends decision-makers an optimal preliminary process design and cost of the selected technology as a function of the facility operating parameters.

Hence, this tool informs decision-makers regarding cost-effective actions for nutrient pollution control and prevention from a diverse cadre of organic wastes. This allows the development of end-of-life alternatives for organic waste reuse/recycling and the recovery of valuable products.

References

[1] Aguirre-Villegas, H. A.; Larson, R. A. Evaluating greenhouse gas emissions from dairy manure management practices using survey data and lifecycle tools. J. Cleaner Prod.2017, 143, 169−179.

[2] Bylund, F.; Collet, E.; Enfors, S.; Larsson, G.A Compilation of Cost Data Associated with the Impacts and Control of Nutrient Pollution; Technical Report; U.S. Environmental Protection Agency, 2015.

[3] United States Department of Agriculture (USDA), Agricultural Waste Management Systems. Agricultural Water management Field Handbook, 2009.

[4] United States Department of Agriculture (USDA), “Planning Considerations” Agricultural Water management Field Handbook, 2009.

[5] Martín-Hernández, E.; Sampat, A.; Zavala, V.; Martín, M. Optimal integrated facility for waste processing. Chem. Eng. Res. Des. 2018, 131, 160-182.

[6] León, E.; Martín, M. Optimal production of power in a combined cycle from manure based biogas. Energy Conv. Manage. 2016, 114, 89-99.