Toward a Circular Economy Approach for Integrated Intensive Livestock and Cropping Systems
Manuel Taifouris, Mariano Martı́n
Abstract
The separation between cropping systems and livestock has caused an imbalance in the nutrients, increasing the environmental impact of both industries. In this work, an integrated system comprising intensive livestock and crop management is compared with traditional systems, from the economic and environmental points of view. A model for estimating energy and nutritional requirements of beef cattle, a waste treatment process, a nutrient recovery system, and crop management is integrated into a mathematical optimization framework. This integrated model allows relating the formulation of the feed of the animals with the composition of their feces, the necessary cultivation area, the crops, and the fertilizers required as well as carrying out the economic and environmental evaluation of the entire system, balancing the nutrients between both industries. Through the application of the model to a representative case study with 1000 animals, a 62% reduction in the environmental impact of the combined agricultural system has been achieved, with a 14% decrease in the profit compared to the nonintegrated system. The fertilizer formulation is optimized to add exactly the required amount of each nutrient to reduce nutrient pollution. 30% of the nitrogen and 56% of the potassium needed for the crops can be obtained from the livestock waste. The correct formulation of the feed can reduce the amount of phosphorus in the feces down to 0.01%. The results show that the integrated system makes it possible to significantly reduce the environmental impact, but it is still not economically promising yet.