Accelerating demand for liquid fuel, together with concerns about anthropogenic influence on the environment and fossil fuels availability, resulted in an increasing interest in using renewable energy sources, which could be grown agriculturally. However, increasing demand for food and acceleration of land-use change have raised concerns about use of food-based bio-fuel (i.e. corn ethanol) and turned research to the direction of cellulosic feedstocks.
In order to analyze future possibility for using agricultural systems for bio-fuel production, we presenting here full carbon neutrality analysis of cellulosic feedstocks production. We used 17 years of data, which included measured fluxes of greenhouse gases (N₂O, CH₄), soil organic carbon concentration change and agronomical practices data, together with biomass yields to produce farm level life cycle analysis. We has analyzed four types of intensively managed annual cropping systems under corn-soybean-wheat rotation (conventional tillage, no till, low input, and organic), two perennial systems (alfalfa and poplar plantation), and one succesionnal system. We estimated potential biofuel yield and relative land – use requirements of each system. Additionally, we introduced environmental sustainability factor, describing ratio between carbon costs and energy yields of a biofuel production.
The poplar plantation showed the lowest GWP and potential fuel production. Fertilized (120 kg N ha^-1y^-1), early successional system showed the most positive effect on carbon sequestration with net global worming potential (GWP) of -714 ± 68 gCO₂ m^-2y^-1. Land requirements of that system were 10% larger than most productive system (in means of Lha^-1 of biofuel) in our analysis (alfalfa). The alfalfa perennial cropping system showed largest biofuel production rates of 2889 ± 64 Lha^-1y^-1 and net GWP of  -412 ± 52 gCO₂ m^-2y^-1.
From our analysis appears that use of alfalfa cropping system for biofuel feedstock production requires about 21 * 10⁶ ha of arable land (or ~16% of total arable land in U.S.) in order to reach U.S. legislative mandate for 16 billion gallons of ethanol per year from renewable sources by 2022. We emphasize potential for use of the marginal or abounded lands for feedstock production by successional systems.