The traditional approach to feed formulation in pig production is based only on minimising cost to reach nutrient requirements and does not consider environmental factors. To reduce the overall impacts of pig production, new methods have been developed that incorporate environmental impacts of feed ingredients into the feed-formulation process of eco-friendly diets. The objective of this study was to evaluate impacts of eco-friendly pig diets on slurry characteristics and associated gas emissions (i.e. methane production and ammonia volatilisation). Two diets were compared: a control diet that followed standard practices used on commercial farms and an eco-diet formulated with an eco-friendly formulation method. Twenty pigs fed one of the two experimental diets were housed individually in metabolism cages equipped for measuring feed and water intake and collecting excreta. The collected slurries were characterized for pH, dry matter (DM), organic matter (OM), total carbon (C), and total nitrogen (N) and used to determine the biochemical methane potential (BMP) and ammonia volatilisation under storage conditions. The eco-diet increased the excretion of DM, OM, C and N per pig per day without influencing growth performance. It also increased the BMP of slurry per pig per day.