Limites ambientais da produção de leite no Brasil: avaliação comparativa de métodos de Sustentabilidade Ambiental Absoluta

Abstract

Current production and consumption patterns overload ecological systems and push the Earth beyond the Holocene. In this context, integrating Planetary Boundaries (PB) into Life Cycle Assessment (LCA) termed Absolute Environmental Sustainability Assessment (AESA) transcends relative per-product evaluations by measuring impacts against absolute limits. The objective of this thesis was to adapt and apply AESA to dairy production systems in Brazil to analyze targets for absolutely sustainable production. A Systematic Literature Review (SLR) identified 42 empirical articles grouped into three clusters of AESA methods: LCIA-based method (51% of articles), PB-based method (21%), and ES-based method (16%). These methods were adapted and applied to free-stall, compost barn, and semi-confined systems. In the LCIA-based method, five impact categories (climate change, acidification, particulate matter formation, and freshwater and marine eutrophication) were analyzed via LCA using the Environmental Footprint method; in the PB-based method, elementary flows were multiplied by characterization factors (climate change, ocean acidification, and biogeochemical flows of phosphorus – P and nitrogen – N). Carrying capacity was allocated using Ability to Pay (ATP) and equal per capita (EPC) approaches combined with economic value (EV). In contrast, the ES-based method confronted demand (LCA impacts) with the supply of ecosystem services. The SLR indicated that the LCIA-based method stands out for its ease of application, the PB-based method requires greater analytical effort to report data in PB metrics, and the ES-based method offers greater scale flexibility and geographic resolution, although constrained by supply data. In the application using the LCIA-based method, all systems proved unsustainable for climate change regardless of allocation. Conversely, free-stall and compost barn systems were sustainable in the acidification and biogeochemical P flow categories, whereas the confined system only achieved sustainability in acidification under EPC+EV allocation. The worst performance occurred in the ES-based method, where most systems were unsustainable; only the semi-confined system achieved sustainability in N and P cycling categories. The findings pointed to impact reductions of up to 178-fold to operate within carrying capacity, a scenario that tends to generate economic viability challenges and encourages the adoption of more regenerative approaches. Thus, while improvement in LCIA and PB methods relies on reducing absolute impact, the ES-based method additionally demands an increase in carrying capacity.