Satellite images used to investigate straw distribution to improve usage

China produces over 1 billion tons of straw each year, but it is not all being used. As much as 35% of the straw, a byproduct of agricultural production, is discarded or burned directly in the field. Researchers believe finding a cost-effective way to recycle and use the straw could help reduce air pollution and provide a valuable renewable energy reserve.

To help pinpoint areas where straw could be better utilized, Mou et al. used satellite imagery for the first time to map the distribution of winter wheat and straw in Qihe County, a region with ideal farming conditions 350 kilometers south of Beijing, China. Previously, researchers had only made estimations of straw quantity based on the amount of grain harvested.

To calculate where this straw was distributed, the researchers analyzed a series of satellite images during different vegetation growth stages using the weighted normalized difference vegetation index (NDVI), an indicator of vegetation biomass calculated with near infrared and visible light aerial images. This method allowed them to better differentiate between winter wheat and other land covers than with an unweighted NDVI.

The results were compared with survey data and were found to agree with an error of 1.27%. The researchers hope their findings can help with site selection for future straw recycling sites and factories, as well as provide more timely information on straw distribution.

“The spatial distribution of straw obtained in this study is being applied to a rapid survey of straw, which can be obtained several months earlier than the statistical data,” said co-author Yuguang Zhou.

Source: “Estimating winter wheat straw amount and spatial distribution in Qihe County, China using GF-1 satellite images,” by A. Huawei Mou, B. Huan Li, C. Yuguang Zhou, D. Yongjun Zheng, E. Renjie Dong, and F. Jinxin Cao, Journal of Renewable and Sustainable Energy (2020). The article can be accessed at https://doi.org/10.1063/5.0033639 .