The water consumption and water withdrawal required for transportation via bio-oil and biomass fuel (methane) produced in this production path­way are calculated based on the methodology presented by King and Web­ber [33]. Consumption and withdrawal are defined as:

“Water consumption describes water that is taken from surface wa­ter or a groundwater source and not directly returned. For example, a closed-loop cooling system for thermoelectric steam power genera­tion where the withdrawn water is run through a cooling tower and evaporated instead of being returned to the source is consumption. Water withdrawal pertains to water that is taken from a surface water or groundwater source, used in a process, and (may be) given back from whence it came to be available again for the same or other pur­poses. To determine the water consumption or withdrawal for each input, the amount of each energy or material input is multiplied by the water equivalent for that input.” [33].

and the water withdrawal intensity, WWI, is defined as:

WW

WWI =

кво ‘ EEB0 + Vbmf + FEbmf)

where WC is the water consumed per liter of growth volume processed, WW is the water withdrawn per liter of growth volume processed, VBO and VBMF are the volumes of bio-oil and biomass fuel (methane) produced per liter of growth volume processed, FEBO and and FEBMF are the fuel economy values for transportation via bio-oil (28 miles/gallon, 11.8 km/L)
and methane fuels (0.2 miles/standard cubic foot, 0.01 km/L). Thus, these metrics are calculated as the water required (consumed or withdrawn) for operating the production pathway shown in Figure 1 divided by the total distance that could be traveled using the bio-oil and the biomass fuel pro­duced (assuming typical conversion efficiencies). The water consumption and water withdrawal include direct water inputs (e. g., water supplied to the growth volumes) and indirect water inputs (e. g., water used during nitrogen fertilizer production and electricity generation), thereby yield­ing a second-order water analysis. The energy return on water investment (EROWI) is a similar metric for evaluating water intensity [9,34] and can be calculated from the data in this study that are reported in Tables 3A and 4A. However, this metric does not consider the energy quality of the fuels produced, and therefore the WCI and WWI were used as the main metrics for evaluating water intensity in this study.

5.3 RESULTS