Biomass energy is becoming increasingly important, owing to the decreasing supply of fossil fuels and growing environmental problems. Hydrothermal carbonization (HTC) is a promising technology for producing solid biofuels from agricultural and forestry residues because of its lower fossil-fuel consumption. In this study, HTC was used to upgrade red jujube branch (RJB) to prepare hydrochar at six temperatures (220, 240, 260, 280, 300, and 320 °C) for 120 min, and at 300 °C for 30, 60, 90, and 120 min. The results showed that the energy recovery efficiency (ERE) reached maximum values of 80.42% and 79.86% at a residence time of 90 min and a reaction temperature of 220 °C, respectively. X-ray diffraction results and Fourier transform infrared spectroscopy measurements show that the microcrystal features of RJB were destroyed, whereas the hydrochar contained an amorphous structure and mainly lignin fractions at increased temperatures. Thermogravimetric analysis shows that the hydrochar had better fuel qualities than RJB, making hydrochar easier to burn.

Tea (Camelliasinensis var. sinensis) is a widely consumed caffeine-containing beverage, however the Camellia genus also includes other species, which are consumed as tea in their local growing regions. Presently, HPLC analysis assessed 126 unique Camellia germplasms belonging to three Camellia species, C. sinensis var. pubilimba Chang (Csp), C. gymnogyna Chang (CgC) and C. crassicolumna Chang (CcC). Theobromine was the predominant purine alkaloid in all species, representing over 90% of purine alkaloids in Csp and CgC, and 50% in CcC. Significant variability existed in purine alkaloid patterns both between and within species, and some germplasms possessed highly unique alkaloid profiles. Sensory evaluation and quality composition analysis of green tea products produced from the three Camellia species suggested their unsuitability for use in tea production due to their unpalatable flavor. The results of this study revealed the differences in purine alkaloids and main quality components between Camellia species and tea, which contributed to understand why tea, rather than other Camellia species, has become a popular beverage in the world after long-term artificial selection. In addition, unique alkaloid profiles suggest usefulness of these germplasm resources in future breeding of decaffeinated tea plant varieties and alkaloid metabolism research.