Tham khảo tài liệu 'biofuels, solar and wind as renewable energy systems_benefits and risks episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 12 A Framework for Energy Alternatives 313 in EROI can produce a large decrease in the net EROI for non-energy requirements. For energy production processes with significant non-energy requirements such as biofuels this suggests a low EROI can imply strong limitations on their ability to be scaled up Giampietro et al. 1997 Hill et al. 2006 . If we assume the Intermediate Boundary EROI for non-cellulosic ethanol from corn is in the neighborhood of Farrell et al. 2006 this implies net energy of .34 for every 1 unit of energy input. The corn-based ethanol Energy Return on Land Invested EROLI 11 633 MJ ha gross energy production equivalent to 3475 l per hectare . However the net energy per unit of land is only 2 908 MJ ha. At 2004 levels of gasoline consumption for the United States this is equivalent to consuming the net energy production of 42 ha of cropland per second. If the EROI of ethanol is reduced to a decrease of only 10 the net return on land decreases by 33 while the amount of land required to achieve this same net yield increases by 50 . Conversely an oil well requires equipment access roads etc. but pulls its bounty out of a comparatively small land area. This contrast has significant implications for the potential scale of biofuel production Giampietro et al. 1997 . In effect due to significant power density differentials replacing energy-dense liquid fuels from crude oil with less power dense biomass fuels will utilize 1 000- to 10 000-fold increases in land area relative to our existing energy infrastructure Cleveland 2007 . Though land is one limiting factor water may be another. In a forthcoming paper we use Multicriteria EROI analysis to define and quantify the EROWI Energy Return on Water Invested for various energy production technologies. Since water and energy may both be limiting we care about the Net EROWI which is a combined measure of EROI and EROWI for each technology. With the exception of wind and solar which use water only in .
