Warming weather changes the chemical composition of oat hulls.

The current threats of climate change are driving attention away from the petrochemical industry towards more sustainable and bio-based production processes for fuels and speciality chemicals. These processes require suitable low-cost starting material. One potential material assessed here is the oat hull. Its overall chemical composition has so far not been fully characterized. Furthermore, it is not known how it is affected by extreme weather events. Oat hulls (Kerstin and Galant varieties) grown during 'normal' weather years (2016 and 2017) are compared to the harvest of the warmer and drier year (2018). Standard methods for determination of plant chemical composition, with focus on carbohydrate composition, are utilized. Oat hulls grown in 'normal' weather conditions (2017) are rich in lignocellulose (84%), consisting of 35% hemicellulose, 25% lignin and 23% cellulose. Arabinoxylan was found to be the major biopolymer (32%). However, this composition is greatly influenced by weather variations during the oat growth phase. A lignocellulose reduction of 25% was recorded in the warmer and drier 2018 harvest. Additionally, a 6.6-fold increase in starch content, a four-fold increase in protein content and a 60% decrease in phenolic content was noted. Due to its high lignocellulose composition, with an exceptionally large hemicellulose fraction, the chemical composition of oat hulls is unique among agricultural by-products. However, this characteristic is significantly reduced when grown in warmer and drier weather, which could compromise its suitability for use in a successful biorefinery.