There is no consensus on the scope or definition of “Material and Energy Flow Analysis” (MEFA). At first glance, this method might simply entail undertaking both a Material Flow Analysis (MFA) and an Energy Flow Analysis (EFA). And in fact, some authors do exactly that (Alfonso Piña and Pardo Martínez 2014). Haberl and colleagues (Haberl et al. 2004) developed a conceptual MEFA framework that not only included MFA and EFA, but that also looks at human appropriation of net primary production (HANPP), in order to understand the land use changes that accompany the material and energy flows.

However, there is no clear unified “materials and energy” approach and within this review MEFA is therefore not considered its own accounting method. Instead, like others, MEFA is considered an umbrella term to refer to the accounting method categories that involve materials and/or energy flows.

It should be noted that undertaking both a material and an energy flow analysis yields a number of advantages. Most importantly, these two flows embody the entirety of the human-environmental interaction and they are furthermore closely related. A large share of the energy used in cities can be traced back to fossil fuels and biomass. At the same time, energy is required to move the material flows through an urban space. The same mass balancing principles apply to energy, which similarly cannot be created or destroyed within a system.