Similar to water resources, plants grown as open systems require significant fertil­izer loads to optimize biomass yield (Table 2). Brazilian sugarcane utilizes as little as 20% of applied nitrogen [34]; the remainder is largely lost to water supplies with the attendant negative impact on the surrounding environment [14]. The require­ment for nutrient complexity within soil often requires crop rotation and precludes year-over-year high biomass productivities available with closed-system bioreactors.

To the extent that growth can be separated from production, rapid CO2 fi xation is possible in an Electrofuels approach with low nutrient requirements, since relatively little biomass is produced per volume of fuel. These requirements are further dimin­ished through nutrient recycling within the biorefinery. At least some other advanced biofuels systems also address this issue; notable examples include slow growing woody biomass (with no external nutrient requirements) and other closed system photobioreactors [49, 60].