Assessment of the impact of food waste additions in livestock manure on ammonia (NH3) and carbon dioxide (CO2) emissions

Rapid global population growth has placed substantial pressure on food systems, leading to the intensification of agricultural practices and a concomitant increase in the production of waste from both crop production and livestock farming. In Türkiye, animal-derived protein requirements are primarily supply through poultry, cattle, and small ruminant farming. Improper management of manure, a primary by-product of animal production, is a major contributor to environmental degradation due to the release of gaseous pollutants such as ammonia (NH3) and carbon dioxide (CO2). Additionally, the processing of widely consumed agricultural commodities such as tea, coffee, and hazelnuts produces substantial quantities of organic by-products. These residues present potential for environmentally sustainable reuse. This study aimed to assess the effects of incorporating tea waste, coffee grounds, and hazelnut shells into various animal manures on NH3 and CO2 concentrations under laboratory-scale conditions. According to the result of the study, tea waste exhibited the highest efficacy in reducing NH3 concentrations, with reductions ranging from 54.5% to 61.9% in poultry manure, 62.7% to 68.6% in sheep manure, and 22.0% to 85.1% in cattle manure. In contrast, hazelnut shells were the most effective in mitigating CO2 concentrations, achieving reductions of 45.1% to 69.6%, 11.9% to 57.6%, and 13.1% to 64.4% in poultry, sheep, and cattle manure, respectively. Statistically significant differences (p < 0.05) were observed among the treatment groups for both gases across all manure types. Overall, the results demonstrate that tea waste is more effective in mitigating NH3 emissions, whereas hazelnut shells possess a stronger potential for reducing CO2 emissions.