There are currently many definitions of ecosystem services in use. Common for them is an aim to visualize contributions, assets and costs not traditionally covered by market valuations, thus often giving the ecosystems much lower value than their importance to economy. Emergy accounting, with its approach of donor values in contrast to receiver or market values, is one approach to assess contributions from the ecosystems and increase our understanding of the values of ecosystem services.

Other authors have connected the donor-side approach with a user side approach for ecological services. In this paper, we investigate the donor-side more in depth, and put up an emergy model with two possible main paths to assess the values for the ecosystem services: (1) the emergy values of the natural driving forces (DrivEES), such as sun, rain, wind and land cycle and (2) the emergy values delivered directly to the human society and economy (FuncESS, ecosystem function ecosystem services). The first approach can be assessed with the common calculation procedure of emergy accounting; the second includes more challenging feedback flows of different types. The implications of these different feedback flows are discussed in this paper. The Millennium Ecosystem Assessment terminology of supporting, providing, regulating and cultural ecosystem services relate primarily to the emergy FuncESS flows.