18.4.2 Feedstock Options

In China, the constraints of limited and decreasing arable land, as well as a huge population, are forcing the government to strike a balance between food security, energy security and environmental protection. Therefore, Medium — and Long-Term Development Plan for Renewable Energy in China clearly state that “Biofuel [production] must not compete with grain over land, it must not compete with food that customers demand, it must not compete with feed for livestock, [and] it must not inflict harm on the environment” [6]. To develop useful cellulosic energy crops, it is therefore important to have a basic understanding of available land and the competing needs in relation to crop production. Specifically, large scale cultivation of cellulosic energy crops is prohibited in China, unless it is done on marginal land. Therefore, because China is a large agricultural country, crop residues have been identified as the major cellulosic energy resource.

According to the survey and evaluation report on National crop straws, the theoretical annual yield of crop straws in China is 820 million tons (air-dry weight, 15% moisture) [7]. Corn, wheat and rice, which are the three most dominant grain crops, accounted for more than 75% of the total agricultural residue resources. Geographically, more than 50% of these straw resources are located in eight provinces (Sichuan, Henan, Shandong, Hebei, Jiangsu, Hunan, Hubei and Zhejiang) (Figure 19.1). The annual yield and percentage of straw contributed to the total resource is listed in Table 19.1.

The available amount of crop residue, estimated at 687 million tons, is less than the theoretical value because all harvest technologies will leave some stubble in the field. Furthermore, many of the collectable straw residues are already being used for fertilizer, feed, fuel, and industrial materials. Therefore, in addition to the 129 million tons of straw that is currently being used for fuel, it is estimated that an additional 215 million tons of straw could be utilized for biofuel production [7].

Eucalyptus, pine and poplar are three important, quick growing tree species that have been chosen for planting in China. This has given China the largest area of planted forest in the world, but the purpose of planting those lands is to provide environmental protection and fulfill industrial demand. Therefore, it is unacceptable to produce energy using these woods. However, forestry residues, including harvesting and wood processing wastes, forest management cuttings and small branches, shrub cuttings, economy forests, bamboo forests, shrubs growing under the primary trees and municipal green forest cuttings, can be used.

According to the seventh National Forestry Survey (2004-2008) [8], China processes 195 million ha of forest area with cover rate of 20.36% each year. Of this total, 64.2 million ha is for timber, 82.1 million ha is for protection forest, 20.4 million ha for economic forest,

1.8 million ha for firewood forest, 12.0 million ha for special-use forest and 14.6 million ha is for other uses. Based on these six forest categories, the total amount of available forest residues was estimated to be 368 million tons in 2008. Although it is expected that area of forest land in China will continue to increase, forestry residue resources are expected to remain stable for the next ten years due to many constraints, such as cutting regulations,

lack of industrial collection, processing capacity, environmental protection, and competing uses with other industrial production activities.

A national survey organized by Ministry of Land and Resources of People’s Republic of China on the national land resource indicated there are about 82.5 million ha of un­cultivated land of which 34 million ha, including waste land and winter-fallowed paddy land, could be made available for energy crop production. However, two critical points sought by the Chinese bioenergy market were that (1) non-food crops should be used for bioenergy production and, of even more importance, (2) neither yield nor the ability of cultivators to produce food should be threatened or reduced.

Sweet sorghum is an energy crop that can meet the requirements established for bioenergy in China. As a variant of conventional sorghum, sweet sorghum can be characterized as multiplatform crop capable of producing grain, sugar, and cellulosic straw. The production of sweet sorghum does not decrease the capability to produce grain from cultivated land since it can be rotated with conventional grain sorghum depending upon market forces. In addition, the high photosynthetic efficiency and excellent stress tolerance of sweet sorghum enables it to be grown on lower quality, drought prone or saline land. Potential grain and stalk yields for sweet sorghum in China range from 2.25 to 7.5 tonnes per ha and 40 to 120 tonnes per ha, respectively [9]. Sweet sorghum can produce one or two times more ethanol per unit land area than corn. Moreover, new sweet sorghum varieties (e. g., the Liaotian, Chuntian, or Nengsi series) with better geographic adaptability, high stalk yield, high brix, and tolerance to saline-alkali stresses have been developed by Chinese scientists. Currently, sweet sorghum is produced primarily in northern China, with the total production in 2008 being 2.5 million tonnes [10]. Therefore, as bioethanol production using advanced processing technologies improves, sweet sorghum would appear to be the most promising bioenergy crop for China.

China also has a very rich Miscanthus resource, which is being developed into a potential energy crop by Chinese research scientists and engineers. Based on average precipitation amounts, temperature ranges and other factors, areas in East, Central, South, and Southwest China are most suitable for Miscanthus production. It appears that production of Miscanthus can be an effective complement to sweet sorghum production, but due to the late start of energy crops research in China, Miscanthus studies are still in the initial stages of development.

Forestry residues could provide another cellulosic resource, but due to many existing obstacles including environmental protection policies, competing uses for industrial pro­cessing, high costs for collection, and natural conditions where forests exist, large scale use of these residues for energy production still faces many challenges. Therefore, wood energy crops will likely not be developed very fast for at least then next ten years.