Abstract:
An accurate prediction of energy supply potential has great significance for the development of straw biomass resources. In particular, the spatial-temporal scale of data has an important influence on prediction accuracy. This research aims to investigate the prediction accuracies of the grey system theory GM (1, 1) and its extended form on the standard coal quantity of straw at different time scales (7, 10, 12, and 15 years) and different spatial scales (China, Beijing-Tianjin-Hebei Region, and Hebei Province), in order to determine the optimal model and data time scale at each spatial scale. Furthermore, the main factors were also determined to affect the prediction accuracy. The standard coal quantity was predicted in each region from 2021 to 2030. The results showed that: 1) The grey Verhulst model performed the best to predict the standard coal quantity at all spatial scales, where the 10-year prediction accuracy was significantly better than that of 7, 12, and 15 years. Moreover, the fitting precision of the standard coal quantity of collectible straw for the main and grain crops in China was 99.56% and 99.52%, respectively, which were higher than those in the Beijing-Tianjin-Hebei Region (98.88% and 98.68%) and Hebei Province (98.99% and 98.65%), respectively. 2) The standard coal quantity of collectible straw for the main and grain crops in China was mainly affected by the sown area and yield per unit area. The correlation coefficient between the standard coal quantity and the sown area was 0.993, and 0.969 for the main and grain crops, respectively, which were higher than those in the Beijing-Tianjin-Hebei Region (-0.709 and 0.401), and Hebei Province (-0.463 and 0.602). By contrast, the standard coal quantity of collectible straw for the main and grain crops in the Beijing-Tianjin-Hebei Region and Hebei Province were mainly affected by the cereal yield per unit area. The correlation coefficient between the standard coal quantity of collectible straw for the main and grain crops and the cereal yield per unit area in China were 0.974 and 0.969, respectively, which were both lower than those in the Beijing-Tianjin-Hebei Region (0.979 and 0.985), and Hebei Province (0.985 and 0.981). 3) The prediction of the grey Verhulst model with the 10-year data showed that the standard coal quantity of collectible straw for the main and grain crops of China was basically stable in the next 10 years (from 2021 to 2030), compared with 2020. It infers that the standard coal quantity of collectible straw for the main and grain crops of China reached 297.3, and 256.9 million tons, respectively, in 2030. More importantly, the standard coal quantity of collectible straw for the main and grain crops gradually increased in the Beijing-Tianjin-Hebei Region and Hebei Province during the period 2021 to 2030. Moreover, the growth rate of the standard coal quantity of collectible straw for the grain crops was higher than that for the main crops between 2021 and 2030. The finding can provide a strong reference to predict the energy potential for the development practice by grey system theory.