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In a montado farm, commonly found in the South Portugal, human activities benefit from important fluxes of renewable resources. In this study, traditional economic and emergy evaluations are compared to determine their potential contributions to understanding this complex system and applied to a case study of a farm. This allows us to determine how each method values local natural resources and purchased factors of production and services in an empirical context. Results show that the montado farm has a renewable component evaluated at 27% of the total social costs of the system and that the work of natural resources is undervalued in economic budget accounting. Economic evaluation's relative value of purchased factors and services is three and half times higher than their emergy share. We propose that complementing economic budget accounting with emergy accounting provides a benchmark to evaluate the environmental contribution to agricultural and farming systems. In this way, factors external to markets can be evaluated for farming systems, bringing to economic analysis a full evaluation of resources, including the bio-geophysical system's contributions to wealth, enlarging total economic value of resources with a donor perspective enabling a better informed and comprehensive accounting to attain sustainable economic decisions and public policies.