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.
ABO salinity presentation pnnl
Water Cost and Availability forAlgae Cultivation- Salinity IssuesERIK R. VENTERIS AND MARK S. WIGMOSTAJune 10, 2013 1Spatial Modeling Research EngineerRichland, WAPNNL-SA-95574
June 10, 2013 2OverviewKey issues- water availability, quality, and associated costsRelevant 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 costsCompetitive freshwatersalinity <2,000 mg L-1, relatively shallow <1,000 ft, municipal and/ or agricultural useNon-competitive saline watersalinity generally too high for crops (>2,000 mg L-1), depth <3,280 ftSeawater-unlimited supply, salinity ~35,000 mg L-1, consistent ion chemistryThis presentation-National trends in freshwater availability and groundwater salinityWhat 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
Competitive water (Fresh) AvailabilityDetails in Venteris et al., 2013, Environmental Science and TechnologyStrong E/W gradients, especially for southern half of the US 3
Salinity trends in competitive (fresh) watersGeostatistical simulation based on nearly 200,000 data pointsPatterns related to interaction between geology and climateEven waters defined as “fresh” have significant salt content4
Salinity trends in non- competitive(brackish/ saline) groundwaterLess data (21,000 data points), more clustering, more uncertaintyHigher salinity waters related to sedimentary basins, oil-gas occurrence 5
June 10, 2013 6Tradeoff Modeling- Operating SalinityWhat 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 pipelinesFewer supply wellsLess 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 sourceCalculate (biofuel production value – water costs) for range of salinities
Operating Salinity- N. salina and seawaterJune 10, 2013 74,654 485 Ha Unit Farm Sites
16,024 485 Ha Unit Farms38,678 485 Ha Unit FarmsOperating Salinity- Chlorella and competitive watersJune 10, 2013 8Southwestern US Southeastern US5-7 g kg-1 2-3 g kg-1
Operating Salinity- Chlorella and saline watersJune 10, 2013 9Southwestern US Southeastern US~15g kg-17-10g kg-1Use Chlorella or more salt-resistant species?
June 10, 2013 10Conclusions, future directionsRegional trends in salinity impact water availability and costsUnderstanding interactions between organism growth and water sourcegeochemistry is critical.Elevated water source salinity and evaporation rates in SW require that pondsbe 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 disposalTemporal 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…)