Life cycle assessment and modeling approaches in silvopastoral systems: A case study of egg production integrated in an organic apple orchard

This paper aimed to assess the environmental impacts of two organic silvopastoral farms in Austria, using a Life Cycle Assessment approach. The two farms (F1, F2), with egg production integrated into an apple orchard, were compared to standard practices for each product. The functional unit was '1 kg fresh Class I apples' and '1 kg fresh Class I eggs'. The assessment covered two scopes: cradle-to-farm gate and cradle-to-retail for each product. Effects on climate (including carbon sequestration in the soil and woody biomass), eutrophication potential (EP), acidification potential (AP), and land occupation (LO) were assessed. Feed, manure, and land were three resource loops included in the system boundary. Two modeling approaches were used from cradle-to-farm gate for distributing the impacts of the entire system between apples and eggs: model 1 (M1) used economic allocation, while model 2 (M2) divided the system into two subsystems. Results varied considerably by model. M1 consistently showed higher impacts for apples and considerably lower for eggs compared to M2. At farm gate, the carbon footprint (CF) ranged from 0.09 to 0.17 kg CO₂-eq/kg apple and 0.19-1.62 kg CO₂-eq/kg egg across all analyzed systems and models. Carbon sequestration reduced emissions by 22-42% for apples and by 0.4-39% for eggs. Sequestration was mainly associated with the carbon contributions from plant biomass from apple production (84-99%), with manure contributing 0.7-9%. EP ranged from 0.19 to 1.7 g PO₄-eq/kg apple and 0.7-35 g PO₄-eq/kg egg and AP ranged from 0.8 to 2.9 g SO₂-eq/kg apple and 2-36 g SO₂-eq/kg egg across all analyzed systems and models. LO ranged from 0.3 to 0.6 m²/kg apple and 0.8-9 m²/kg egg across all analyzed systems and models. Post-harvest activities accounted for up to 29% of the total impacts for EP and AP, and up to 57% for CF from cradle-to-retail. In general, the impacts per kg egg or kg apple in F1 and F2 were lower in most impact categories relative to their reference systems, driven mainly by management factors and the production phase of the value chain. Further development of modeling approaches is needed.