Assessing Environmental and Economic Sustainability: Valorizing Grape Stems for Animal Feed Production

This study evaluated an innovative strategy for valorizing grape stems (GS) from the winery industry as an animal feed ingredient from both environmental life-cycle and economic perspectives. Two processes for GS-based feed ingredient production were compared: one using hydrolyzed GS and the other using nonhydrolyzed GS, alongside the conventional animal feed production process. Using primary pilot-scale data for GS-based feed ingredient production and secondary data for animal feed production, life-cycle assessments, and economic analyses were conducted. Results showed that hydrolyzing GS leads to 3.8 times higher impacts on human health compared to the nonhydrolyzed variant, primarily due to NaOH and electricity usage, although this difference becomes negligible at the animal feed production stage. Incorporating GS-based feed ingredients was found to reduce the environmental impacts of animal feeds, primarily due to reductions in other ingredients. Economically, producing nonhydrolyzed GS-based feed ingredient proved more feasible, with a net present value of €-106,766 for a plant with a capacity of 1000 kg/d. GS valorization scenarios yield lower environmental impacts than landfilling and composting, although not compared to incineration, which offers notable energy recovery potential. This study suggests adopting GS valorization in animal husbandry to support a circular economy, providing insights for stakeholders.