Quantitative assessment of the potential of rape straw resources as feedstock for biomass industry in Hunan Province

Rape (Brassica napus L.) straw has been one of the most important biomass resources in environmental protection and economic benefits, due to the high cellulose content and low utilization cost. A reasonable utilization rate can provide great contributions to the around-year feedstock supply for the biomass industries. However, it still lacks scientific and rational theoretical guidance on the utilization of straw resources. Most straws have been abandoned in the fields or directly burned, leading to severe environmental pollution and resource waste. Moreover, current straw utilization (such as returning straw to the field) can also exhibit certain negative effects. The waste of biomass resources has caused significant economic losses and ecological damage. It is a high demand to formulate the scientifically efficient straw utilization mode for the sustainable and green straw biomass industry. The high-value-added biomass products can be effectively converted for the environmentally and socio-economically friendly development of straw resources. Among them, Hunan Province can also share the potential of industrial utilization of the rape straw, due to the main producing area of rape in China. Therefore, the present study aims to explore the biomass yield potential and regional differences for the rational utilization of the rape straw resources in Hunan Province, in terms of biomass quality. Some recommendations were also given to utilize the rape straw for the future bioeconomy, according to the spatial heterogeneity of straw resources in the whole province. The results indicate that Hunan Province produced approximately 6.74 million tons of rape straw each year. The major production was concentrated in the northern region. There is significant heterogeneity in the feedstock quality of rape straw biomass across the province. All characterization indicators showed high coefficients of variation (CV > 0.50), indicating substantial variability. The differences in biomass quality were primarily represented in the heavy metal content, indicating a particularly high coefficient of variation (CV > 5.00). Additionally, there was notable variability in ash content (CV = 3.02), lignin content (CV = 1.17), cellulose polymerization (CV = 1.15), and cellulose crystallinity (CV = 0.56). Multiple measured indicators of rape straw feedstock quality were normalized, according to the biomass production potential index (BPPI) and membership functions. The rape straw was most suitable to produce hemicellulose-based products (the potential index was 0.58), especially from the northern Hunan region (the potential index was 0.60). Overall, the primary feedstock supply area can serve as the high yield potential and superior biomass quality in the northern Hunan region. The biomass and energy potential of rape straw can be expected to scientifically construct and develop green clusters of biomass industry. Hunan Province can maximize the efficiency and sustainability of biomass resources in the regions with the highest production potential, thereby contributing significantly to the development of a robust bioeconomy.