Agricultural residues mainly refer to straw, stalks and husk of crops. In China, the main crops include rice, wheat, corn, beans, tubers, sorghum, coarse grains, oil bearing crops, cotton and sugarcane (Li et al, 2005). Presently, the usage of agricultural residues include cooking and heating in rural households, fertilizer, forage and the raw material of paper (Li et al, 2005). The forest residues are usually categorized into this type especially in agricultural areas. They come from fuel wood and waste of forest industries which are widely available in rural China but with unbalanced distribution (Li et al, 2001).

Agricultural residues can be identified as two types. Primary residues are the biomass generated during the harvest (e. g. rice straw, sugar cane tops) which are usually used as fertilizer or animal feed and are hard to collect (Bhattacharya et al, 2005). Comparably, secondary residues refer to the co-produced residues during the further processing after harvest such as rice husk and bagasse. Relatively large quantities of secondary residues are easy to get at the processing site without further transportation and handling cost (Li et al, 2005) and thereby are considered as a suitable biomass resource for commercial purpose of energy generation. Energy potential from agriculture is expected to be 5.31 EJ in 2010 (Bhattacharya et al, 2005). However, few

data are available about distribution between primary and secondary residues and further work is required here.

In general, agricultural residues are widely available in China but with unbalanced distribution among regions (Li et al., 2001). East and middle-south China have the largest portion of total production (in order of 10,000 tonnes/y) while Northeast China has the highest per capita pro­duction (in order of 100kg/y), which is shown in Table 4.1. For energy purposes, a three-stage calculation model has been developed by the National Development and Reform Commission (NDRC, 2008), the total production, the accessible amount and the energy potential. According to NDCR’s data for 2005, 0.3 billion tonnes of agricultural residues can be used for energy purposes which is equal to 0.15 billion tonnes standard coal.