A First Use of Oil- and Gas-Produced Water as a Medium for Algae
Water is the largest quantity resource other than land that will be needed for algal biofuel production. An estimated 50,000 acre-feet per year are projected to be needed for large (1,000- acre) growth facilities depending upon local climate (1). This can be compared to the total annual freshwater irrigation withdrawals in the U.S. of about 153,000 acre-feet per year (2)—a resource that is already stressed. One goal of the research conducted by the National Alliance for Advanced Biofuels and Bio-products (NAABB) consortium members is to show that algae cultivation need not impinge upon limited fresh water resources, particularly in arid regions. This requires the use of alternate resources including sewage wastewaters, brackish surface and ground waters, and oil- and gas-produced water.
Oil and gas production in this country currently brings about 800 billion gallons of brackish and saline water to the surface annually (3) along with the oil and gas. This amount is comparable to a weeklong flow of the Mississippi river at its mouth. This water has characteristics suitable for growth of marine algae; however, up to 98 percent of this water is routinely disposed as a waste product. Salinity of the water varies from near fresh (less than 1,000 ppm total dissolved solids, or TDS) to highly saline (greater than 100,000 ppm TDS, or three times typical seawater levels), and it contains bicarbonate and other micronutrients that can benefit algae. Some of it may be contaminated with oils, toxic metals, and chemicals from the oil production process and would require some pretreatment. In short, these large quantities of saline water that do not need to be pumped to the surface and are largely unused for other purposes have great potential economic value for algal biofuel production.
Researchers from Los Alamos National Laboratory and Eldorado Biofuels, both members of NAABB, have located and analyzed potential locations in New Mexico and Texas that are viable sources of produced water. The selected sources show consistent water quality, and permits to use the water from the sources are readily obtainable. Alfonse Viszolay of V.M. Technologies, a partner of Eldorado Biofuels, provided a treatment system that was used to remove organic contaminants and reduce toxic metal content and salinity from the produced water. Greg Wagner of LANL then tested bench-scale growth of Nannochloropsis Salina 1776, a salt-tolerant, oil-producing alga, in these treated waters.
In February, in collaboration with NAABB consortium member Texas AgriLife Research, the researchers conducted the first ever pilot-scale test of algae growth using water from an oil production well in Jal, N.M. The test was conducted by Lou Brown, project manager of the Pecos Algae Facility, at the Texas AgriLife Research facility at Pecos, Texas. The selected produced water was brackish water (12,000 mg/L TDS) with low free oil content. It was pretreated with UV/ozone oxidation to reduce dissolved organic concentrations and then flocculated with lime and coagulants to remove hardness, metals and some salinity.
Nannochloropsis salina algae were grown for two weeks in 80-gallon reservoirs using Pecos city water and the produced water as comparative media. Algae growth, productivity and water chemistry were closely monitored. Initial growth of algae with low concentrations of produced water was similar to city water, however, higher produced water concentrations became growth limiting. The researchers are now testing the hypothesis that high initial bicarbonate (greater than 400 mg/L), along with salinity increases (up to 40 mS/cm specific conductance) during growth were a cause of the limitation. Copper, iron, and zinc metal concentrations were similar in both media and, thus, were not likely causes of the limitation. Any of these metals can become toxic at levels beyond the tolerance of the algae.
Future work includes bench-scale testing at LANL and Texas Agrilife to be followed by a second pilot-scale test this fall. The treatment methods will be adjusted to improve algal growth, total biomass produced and oil yields. NAABB research is funded by the U.S. DOE’s Office of Biomass Program.
Authors: Enid J. Sullivan, Paul Laur
Technical Staff Member, Los Alamos National Lab;
Founder, El Dorado Biofuels
(1) Pate, Ronald, “Technoeconomics, siting, and resource use challenges for onshore algal biofuel production,” Wind, Sea, and Algae International Workshop, Maribo, Denmark, April 20-22, 2009.
(2) USGS, 2000. http://ga.water.usgs.gov/edu/wuir.html, accessed on 04/04/2011.
(3) Clark, C.E., and Veil, J.A., 2009. “Produced water volumes and management practices in the United States.” Report #ANL/EVS/R-09/1, Argonne National Laboratory for the U.S. DOE, September.