Measurement of Lipid Content of Garbage Compost Using Near Infrared Spectroscopy

Abstract

The determination of the lipid content of garbage compost by near infrared spectroscopy (NIRS) was investigated, because lipid content is known to be an inhibitor of plant growth and germination. The garbage compost samples, which were produced by electric garbage processors, were obtained from canteens in schools and factories, food service facilities, homes, restaurants, and a hospital. Lipid contents of the samples were spread over wide range (0.28-17.70%), and the main fatty acids in most samples were palmitic, stearic, oleic, and linoleic acids. The reflectance spectra of air-dried and milled compost samples were measured using a scanning monochromator. Second derivative spectra from 700 to 2500 nm and multiple regression analysis were used to develop calibration equations for lipid content. The main wavelength of the best calibration equations was 2310 nm, which was attributed to the absorption bands of the CH₂ stretch-bend combination of fatty acids. The standard error of prediction (SEP) of the best calibration was 1.24% . Although the fatty acid composition of the hospital sample was very different from others, it did not cause large errors in the estimates. In conclusion, NIRS is thought to be a practical method for evaluating plant inhibition caused by garbage compost.