A new natural resource balance indicator for terrestrial biomass production systems

Managing the efficient use of land is a key aspect, especially for a sustainable biomass-based economy. Due to the complexity in accounting all inputs for biomass production, land use efficiency analysis is usually performed without completeness, for instance, considering only fossil fuels. The objective of this paper is to introduce a new indicator, called Overall Net Annual Exergy Production (ΔEP), which considers the total biomass production from a land, the cumulative consumption of non-local resources (e.g. fossil fuels), and the natural primary biotic resource production that is deprived due to the land use, through exergy (which is the amount of useful work that can be obtained from a resource). We applied this indicator to seven agricultural case studies, composed by one or more crops, and located at different areas of the World. The case study composed by potato and wheat was the only one to generate negative ΔEP (−27.4 GJex/ha year), while the case studies that were composed by at least one C4 plant (maize or sugarcane) in the rotation or permanent crops (palm fruit) produced positive ΔEP. The latter had the highest ΔEP (+329.7 GJex/ha year). This indicator was able to give a more holistic overview of the natural resource balance of biomass production systems in comparison to the indicators commonly used in literature (e.g., net energy value), contrasting with the landʹs natural state, through a simple equation, and making use of data already available in literature.