Submitted to: California Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2008
Publication Date: 1/15/2009
Citation: Banuelos, G. J.J. Stapleton. 2009. Value-added Sustainability: Energy Crops for Biological Disinfestation and Remediation of Soils. California Agriculture. 63:41-46. Interpretive Summary: Long term phytomanagement of selenium(Se) is dependent upon acceptance and widespread use by end users, who are also concerned with economic returns from using a plant-based technology. Multi-year field studies were conducted with members of the Brassica family, e.g. canola, mustard, in different regions of the San Joaquin Valley in California. These plant species are also viable candidates for processing into biodiesel, as well as for managing soilborne pests as biofumigants while reclaiming selenium-polluted soils. In this regard, we observed deleterious effects on various soilborne fungi, nematodes, and even on emergence of different weed species after incorporating seed residual into the soil. Because canola and mustard oils extracted from the seed have a high energy content per unit weight and are two of the most efficient sources of bioenergy, we blended the vegetable oils with petrodiesel for operating irrigation booster pumps, and observed reduced concentrations of COx, CO2, and PM in the exhaust emissions. Coupling phytoremediation with biofumigation and biofuel production may provide California growers with a unique opportunity to increase the environmental and economic sustainability of developing energy crop systems grown for the remediation of Se.
Technical Abstract: Many of the Brassica plant taxa that are candidates for refining into biodiesel also possess qualities, which make them potentially useful for managing soilborne pests and/or managing Se-contaminated soils. Some of the plant species include: canola(Brassica napus) and mustard(Brassica juncea) that are planted in the westside soils of Central California(Oxalis silty clay form with naturally high levels of water soluble Se ranging from 0.15 to 1.2 mg/L). After growing the Brassica crops for the management of soluble Se, seed yields can be as high as 3.5 metric tons/ha. Preliminary oil yields extracted from the seeds on site ranged from 570-600L/ha. Creating a B20 biodiesel(20% vegetable oil blended with 80% diesel) successfully powered irrigation booster pumps after transesterification of the biofuel. We observed reductions of COx, CO2, PM, and observed questionable fluctuations in NOx content in the exhaust emissions. The byproduct from oil extraction was the residual seed meal from both canola and mustard. Incorporating the mustard seed residues at rates of 4-11 tons/acre produced deleterious effects on various fungi, nematodes, and prevented the emergence of ten different weed species. Likely, the high glucosinolate content (between 250-300 umol/g) was the family of compounds primarily responsible for exerting the observed biofumigation effects. The canola seed meal with a low glucosinolate content of 21 umol/g was not as useful as a biofumigant, but with a Se concentration between 1.85 and 2.0 mg/kg, it was available for use in dairy cow feed rations as a source of organic Se. These and other value-added products should be tested under different conditions and utilized in the widest possible range of crop taxa for maximum benefit to the environment and to the grower. The coupling of phytoremediation of Se with biofumigation, biofortification, and biofuel production may help protect the environment in an economical and sustainable manner.