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This post was last edited by qinweijun on 2012-5-10 11:29. I. Forest Energy Forest energy refers to the biomass energy provided by forest growth and forestry production processes; it mainly consists of firewood, as well as various residues from the forest industry. Forest energy plays an important role in rural energy use in our country. Before and after 1980, approximately 100 million tons of standard coal worth of forest energy was consumed in rural areas across the country, accounting for over 30% of the total rural energy consumption. In hilly, mountainous, and forested areas, more than 50% of the energy used for rural living comes from forest energy. Firewood comes from branches pruned during the growth of trees, waste materials from wood processing, as well as fuel forests dedicated to providing firewood. In 1979, the nationally available amount of firewood was 88.85 million tons, while the actual consumption was 181 million tons; thus, the demand for firewood was more than twice the available supply ； In 1995, a total of 143.229 million tons of forest energy was available; of this, more than 20 million tons could be obtained from firewood forests. Rural areas across the country consumed 213.39 million tons, resulting in a supply-demand gap of around 70 million tons. II. Crop straws Crop straws are by-products of agricultural production and also serve as a traditional fuel in rural areas of China. Straw resources are closely related to agriculture, particularly to crop production. Based on statistics from 1995, China’s annual output of crop straws was 604 million tons; of this amount, about 15% was used for fertilizer production and returned to the fields, with losses during collection accounting for the remaining portion, resulting in 513.4 million tons left over. The 513.4 million tons of crop straws available can be used not only as feed and industrial raw materials but also, to a large extent, as fuel for cooking and heating in rural households. Currently, the amount of straws used as energy in rural areas across the country is around 286.2 million tons; however, most of this is utilized in an inefficient manner, namely by being burned directly in stoves, with an efficiency rate of only about 10% to 20%. With the development of the rural economy and the increase in farmers’ incomes, regional disparities are gradually widening, and the proportion of commercial energy used in rural areas for domestic purposes is rising at a rapid pace. In fact, both an increase in farmers’ income and the ease of obtaining commercial energy can serve as incentives and motivations for them to switch to using commercial energy. In rural areas that are closer to commodity energy production regions or in affluent rural areas, commodity energies (such as coal and liquefied petroleum gas) have become the primary source of energy for cooking. Straw that is used in traditional ways becomes the first to be replaced, resulting in an increasing amount of straw being discarded in fields and burned there directly. In many areas, the amount of discarded straw already accounts for over 60% of the total amount of straw produced, which not only harms the environment but also wastes resources. Therefore, it is imperative to accelerate the transformation and utilization of straw into higher-quality forms. III. Livestock and poultry manure Livestock and poultry manure is also an important source of biomass energy. Apart from a small amount of direct burning in pastoral areas, livestock manure is mainly used as a raw material for biogas fermentation. The main poultry and livestock in China are chickens, pigs, and cows. The amount of manure available can be estimated based on factors such as the breeds of these animals, their body weight, and the amount of manure they produce. According to calculations, the total amount of livestock and poultry manure resources in our country is currently around 850 million tons, equivalent to more than 78.4 million tons of standard coal. Of this, cow manure accounts for 578 million tons, corresponding to 48.9 million tons of standard coal; pig manure amounts to 259 million tons, equivalent to 22.3 million tons of standard coal; and chicken manure totals 14 million tons, corresponding to 7.17 million tons of standard coal. Among fecal resources, the manure from large and medium-sized farms is more suitable for centralized development and large-scale utilization. At present, there are over 6,000 large and medium-sized cattle, pig, and chicken farms in our country, which produce more than 800,000 tons of manure, urine, and washing wastewater per day. The total amount of such waste across the country amounts to 160 million tons per year, which is equivalent to 11.575 million tons of standard coal. IV. Domestic Waste As cities grow in size and the process of urbanization accelerates, the amount of waste generated and accumulated in towns and cities in China is increasing year by year. In 1991 and 1995, the national generation of industrial solid waste was 588 million tons and 645 million tons respectively, while the amount of municipal household waste increased at a rate of around 10% per year during the same period. In 1995, China had a total of 640 cities, with 107.5 million tons of waste collected. Municipal domestic waste is primarily a mixture of household waste, waste from commercial and service industries, and a small amount of construction waste; its composition is relatively complex. It is mainly influenced by factors such as residents’ living standards, energy structure, urban development, green space coverage, and seasonal changes. The composition of waste in China’s large cities is showing a trend toward that of modern cities, with the following characteristics: first, the proportion of organic matter in the waste is close to 1/3 or even higher ； Secondly, food waste is the main component of organic matter ； Third, it has a high content of readily biodegradable organic matter. Currently, the calorific value of municipal waste in China is around 4.18 megajoules per kilogram (1,000 kcal per kilogram).