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ABO salinity presentation pnnl

  1. 1. Water Cost and Availability for Algae Cultivation- Salinity Issues ERIK R. VENTERIS AND MARK S. WIGMOSTA June 10, 2013 1 Spatial Modeling Research Engineer Richland, WA PNNL-SA-95574
  2. 2. June 10, 2013 2 Overview Key issues- water availability, quality, and associated costs Relevant PNNL Biomass Assessment Tool (BAT) capabilities (open ponds)- Algae productivity from climate and salinity data (M. Huesemann, PNNL) Evaporative water demand (met data, pond state simulation) Water source characterization, availability and costs Competitive freshwater salinity <2,000 mg L-1, relatively shallow <1,000 ft, municipal and/ or agricultural use Non-competitive saline water salinity generally too high for crops (>2,000 mg L-1), depth <3,280 ft Seawater- unlimited supply, salinity ~35,000 mg L-1, consistent ion chemistry This presentation- National trends in freshwater availability and groundwater salinity What is the best operating salinity to balance production value and water costs? For organism X and salinity of water source, what are supply and saline disposal costs (CAPEX and OPEX)? Note that we do not follow NRC model of freshwater + brackish mix
  3. 3. Competitive water (Fresh) Availability Details in Venteris et al., 2013, Environmental Science and Technology Strong E/W gradients, especially for southern half of the US 3
  4. 4. Salinity trends in competitive (fresh) waters Geostatistical simulation based on nearly 200,000 data points Patterns related to interaction between geology and climate Even waters defined as “fresh” have significant salt content 4
  5. 5. Salinity trends in non- competitive (brackish/ saline) groundwater Less data (21,000 data points), more clustering, more uncertainty Higher salinity waters related to sedimentary basins, oil-gas occurrence 5
  6. 6. June 10, 2013 6 Tradeoff Modeling- Operating Salinity What is best compromise between growth rate and water costs? As pond operating salinity goes up, in general- Algae growth rate and biofuel production decreases (Chlorella, N. salina) Total makeup water and associated costs decrease (blowdown) Smaller pipelines Fewer supply wells Less saline concentrate for disposal (by geologic injection or evaporation ponds) Costs based on pipelines (seawater) or wells and pipelines (ground waters) GIS models connect each farm site to optimal water source Calculate (biofuel production value – water costs) for range of salinities
  7. 7. Operating Salinity- N. salina and seawater June 10, 2013 7 4,654 485 Ha Unit Farm Sites
  8. 8. 16,024 485 Ha Unit Farms 38,678 485 Ha Unit Farms Operating Salinity- Chlorella and competitive waters June 10, 2013 8 Southwestern US Southeastern US 5-7 g kg-1 2-3 g kg-1
  9. 9. Operating Salinity- Chlorella and saline waters June 10, 2013 9 Southwestern US Southeastern US ~15 g kg-1 7-10 g kg-1 Use Chlorella or more salt-resistant species?
  10. 10. June 10, 2013 10 Conclusions, future directions Regional trends in salinity impact water availability and costs Understanding interactions between organism growth and water source geochemistry is critical. Elevated water source salinity and evaporation rates in SW require that ponds be operated at a higher salinities than in the SE. Many water issues remain to be addressed, including- Regulatory constraints on freshwater supplies and saline concentrate disposal Temporal trends in competitive uses (development, climate change, etc.) Brackish and saline groundwater sustainability (volumes, recharge etc.) Growth performance vs. pH, ion chemistry, etc. (for example, NaCl water vs. bicarbonate waters…)

Editor's Notes

  • Brief overview of PNNL’s efforts in water resource modeling.Discuss national patterns in groundwater salinityHow do these impact overall water costs? (Supply and concentrate disposal)
  • Freshwater availability model based on average discharge measured at stream gauges.Supply limited to 5% total dischargeEach dot is 485 ha unit farm, black supplied, gray unsupplied. Priority on water supply costsEW gradients
  • Low salinity waters in east and south east, some areas of upper Midwest, Pacific NorthwestSalinity of competitive waters much higher in the south west, Rockies, Great Plains.Saline concentrate disposal essentially unavoidable.
  • Non compete less information, generally deeper, higher salinity, etc.
  • As an approximation, utilization of non-compete waters requires roughly 2x increase in operating salinity.
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