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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL TREATMENT OF MANURE AND ORGANIC RESIDUALS TO CAPTURE NUTRIENTS AND TRANSFORM CONTAMINANTS

Location: Sustainable Agricultural Systems Laboratory

Title: Near- and mid-infrared spectroscopic determination of algal composition

Authors
item Mulbry, Walter
item Reeves Iii, James
item Liu, Y
item Zhen, R
item Liao, W

Submitted to: Journal of Applied Phycology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 2011
Publication Date: January 4, 2012
Repository URL: http://handle.nal.usda.gov/10113/56731
Citation: Mulbry, III, W.W., Reeves, III, J.B., Liu, Y., Zhen, R., Liao, W. 2012. Near- and mid-infrared spectroscopic determination of algal composition. Journal of Applied Phycology. 24:1261-1267.

Interpretive Summary: Although algal cultivation and algae-based wastewater treatment systems have been in use for decades, there is renewed interest in such systems because of the potential use of the algal byproduct as a fertilizer or biofuel feedstock. Given the possible use of algal systems for treating varied sources of agricultural wastewater, robust and inexpensive methods of analysis for algal components are needed. At the present time, most algal samples are analyzed by conventional wet chemical methods, such as the Kjeldahl procedure for total N and P or by combustion techniques for total C or N. These procedures, while accurate, can be time consuming and expensive, and they generate chemical wastes. Infrared reflectance spectroscopy is an alternative method of analysis for determining the composition of a wide variety of materials ranging from forages and grains, food products, manure, and soil. Infrared spectroscopy can accurately and rapidly determine sample composition, while greatly reducing the waste associated with conventional analysis systems. The objective of this study was to investigate the feasibility of using near-infrared reflectance spectroscopy (NIRS) and mid-infrared reflectance spectroscopy (MIRS) to determine the composition of algal samples. Results showed that that NIRS and MIRS can accurately determine ash and total N concentrations, but not sugar or protein concentrations in algal samples. Results with the entire sample set (117 samples) also demonstrated that MIRS can accurately determine the P concentrations. Results with a 64 sample subset showed that NIRS and MIRS can accurately determine total lipid, concentrations, but not total fatty acid concentrations in algal samples.

Technical Abstract: The objective of this study was to investigate the feasibility of using near-infrared reflectance spectroscopy (NIRS) and mid-infrared reflectance spectroscopy (MIRS) to determine the composition of algal samples. We assayed a set of algal biomass samples (n=117), collected from algae turf scrubber systems by conventional means, NIRS, and MIRS for ash, sugar, protein, total N, and P. A subset of these samples (n=64) were assayed by conventional means and NIRS for total lipid and total fatty acid concentrations. We developed calibrations using a one-out cross validation procedure under partial least-squares regression. Calibration results with the entire sample set demonstrated that NIRS and MIRS can accurately determine ash (r square values= 0.990 and 0.994, respectively) and total N (r square values = 0.790 and 0.819, respectively) concentrations, but not sugar or protein concentrations in algal samples. Calibration results with the 117 samples also demonstrated that MIRS can accurately determine the P concentrations (r square value = 0.867). Calibration results with the 64 sample subset showed that NIRS and MIRS can accurately determine total lipid (r square values = 0.815 and 0.855, respectively), concentrations, but not total fatty acid concentrations in algal samples.

Last Modified: 12/25/2014
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