Abstract
As the growing world population drives demand for poultry meat and eggs, a surplus of poultry manure is produced, which, when applied to land, can lead to freshwater eutrophication and harmful algae blooms. To sustainably manage poultry manure, several waste-to-energy and soil amendment pathways have been developed, drawing from technologies such as pyrolysis, hydrothermal liquefaction, hydrothermal carbonization, and anaerobic digestion. To evaluate the “cradle-to-gate” life cycle impacts of the pathways, as well as how the introduction of these technologies affects the upstream and downstream markets for products, two different Life Cycle Assessments (LCA) methods are used. In an attributional LCA setting, direct land application has the lowest environmental impacts except prominently in the climate change and eutrophication categories, which are the categories for which its harms are most noticeable. In a consequential LCA setting, due to the consideration of offsets, direct land application only has the lowest energy resource use and ionizing radiation, while other technologies minimize all other impact categories. To meet environmental targets, the choice of management technology for poultry manure is significantly determined by the chosen system boundary, implying that careful consideration of environmental objectives is necessary for the circular economy.
