Phytoremediation of Selenium Contaminated Soil, and Water Produces Biofortified Products and New Agricultural Byproducts

Authors: Banuelos, Gary

Submitted to: CRC Press
Publication Type: Book / Chapter
Publication Acceptance Date: 3/15/2008
Publication Date: 1/15/2009
Citation: Banuelos, G. Chapter 4. Phytoremediation of Selenium Contaminated Soil, and Water Produces Biofortified Products and New Agricultural Byproducts. p. 57-70 in Banuelos, G. and Z.Q. Lin (eds.) Development and Uses of Biofortified Agricultural Products. CRC Press, Boca Raton, FL. 2009.

Interpretive Summary: The use of green plants and associated microbes for environmental remediation has been called "phytoremediation". This green technology is being developed for the cleanup/management of metal(loid)-contaminated soils and waters via the processes of phytoextraction, phytovolatization, and phytostabilization. Scientists at the WMRU have determined that potential crops used for the phytoextraction of Se in Central California include members of the Brassica family, e.g., broccoli, canola, and Indian mustard. They hypothesized that by using these types of plants for managing soluble Se from soil and drainage waters, high value products such as Se-enriched animal feed or Se-enriched vegetables can also be produced. In addition, other commodity byproducts can also be generated, such as using extracted oil from canola and mustard seeds for the production of biofuel. Oleaginous crops, e.g., Brassica, are considered to be potential alternative fuel sources for diesel-powered engines, which perform well using a biofuel blend with chemical and physical properties similar to those of commercial-grade diesel fuel. In addition, after the oil has been extracted from Brassica seeds, residual seed by-products are also of value as Se-enriched feed meal, organic fertilizer, and even as a biological herbicide. This chapter discusses the derivation and novel production of Se-fortified products and other potential byproducts that were developed primarily from Brassica species and alternative crops grown for the management of natural-occurring Se in soils and waters in the Westside of Central California.

Technical Abstract: Based upon these processes-phytoextraction, phytovolatization and phytostabilization-a plant management remediation strategy for selenium (Se) has been developed for the Westside of Central California. Multi-year field phytoremediation studies were conducted between 2002-2007 on Se-tainted field sites located at Red Rock Ranch, Five Points, CA, and at the USDA-ARS research facility in Parlier, CA to evaluate Se-remediation strategies and the subsequent production of viable plant products. The soil in the experimental area at RRR was classified as an Oxalis silty clay loam (fine montmorillonitic, thermic Pachic haploxeral with a well developed salinity profile), and the soil and shallow groundwaters in this area contain natural-occurring concentrations of soluble Se as high as 1 mg/L. Members of the Brassica family, Brassica napus (canola), B. oleracea (broccoli), and B. juncea (mustard) were some of the predominate oil plant species used for the vegetation management of Se. At the end of their respective growing seasons, various new agricultural products were developed from the harvest of these plants that are of economical value to the growers utilizing the phytomanagement strategy. Examples of these products are as follows: 1)Selenium-enriched broccoli with concentrations between 3-5 mg/kg that can be used as a source of supplemental dietary Se for human nutrition; 2)Selenium-enriched canola biomass (12 metric tons/ha) with concentrations ranging from 3-4 mg/kg that can be used for supplementing Se in the sheep and dairy industry; 3) Canola and mustard seed (2 tons/acre)under high salt and B growing conditions from which Brassica oil (120 gallons/ton)was extracted at a conservative rate 6-8 tons per day at Red Rock Ranch; 4)BD 20 biofuel blend was produced (after transestrification) for operating diesel-powered equipment on the farm site; and 5)Se-enriched canola seed meal (2 mg/kg) was produced and usable in daily feed rations for dairy cows. We have demonstrated that we can produce cash-value agricultural products, e.g., Se-enriched broccoli, biodiesel, and Se-enriched animal fodder, that should encourage growers to accept and use phytoremediation as a green strategy for managing Se in problematic soils and waters in a sustainable manner.