TABLE 4-1 Summary of Assumptions and Results of Studies for Life-Cycle Water Requirements for Open-Pond Algal Biodiesel


Assumptions Estimated Water Loss or Use


Study Case Fuel Productivity
(L/m2/yr)
Net
Evaporation
(cm/d)
Cultivation
(L/L)
Harvest (L/L) Fuel
Processing
(L/L)
Coproducts (%) Other Life-Cycle Water Use (L/L)

Harto et al. (2010)a

Low case

5.5

0

0

01

31

46

1

32

Base case

5.5

0.25

165

01

50

0

1

216

High case

2.6

0.42

575

01

80

0

0.58

656

Wigmosta
et al.
(2011)b

79.5 gal/yr production

0.46

0.06

438

01

N/Ab

0

0

438

200 gal/yr production

0.46

0.20

1613

01

N/Ab

0

0

1613

Yang et al. (2011)

100% harvest recycle

3.2

0.27

450

0

140

0

0

590

50% harvest recycle

3.2

0.27

450

1550

140

0

0

2140

No harvest recycle

3.2

0.27

450

3060

140

0

0

3650


aHarto et al.(2010) and Wigmosta et al.(2011) assumed 100 percent recycling of harvest water.

bWigmosta et al.(2011) did not estimate water use for processing algal biomass to fuels. They did not include water use upstream of algae cultivation (for example, water use for fertilizer production), but that amount is a small fraction of the total water requirement (Harto et al., 2010).
NOTES: L/L = liters water consumption per liter of biodiesel produced. As a comparison, life-cycle water use to produce gasoline from crude oil and oil sands has been estimated to be about 1.9-6.6 L/L.



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