Hongmin DONG1*, Zhiping ZHU1, Yongxing CHEN1 and Hongwei XIN2
1Institute of Agricultural Environment and Sustainable Development, Chinese Academy of Agricultural Sciences, 12, Zhongguancun South Street, Beijing 100081, CHINA; 2Department of Agricultural and Biosystems Engineering, Iowa State University, Ames, Iowa, USA. *Email: Donghm@mail.caas.net.cn
Introduction
Animal husbandry has become one of the pillar industries in rural
economy and an important source of increasing farmer’s income in China.
The animal production value reached 1,217.4 billion Yuan, accounting for 33.6% of the Chinese agriculture production in 2004. According to the data by FAO, in 2004 the meat, egg and milk production in China accounted for 28.2%, 45.3% and 3.7%, respectively, of the world production. The number of swine, cattle, sheep and poultry in stock accounted for 49.7%, 8.0%, 18.7% and 27.8%, respectively, of the world figures. Associated with the rapidly increasing animal production are environmental challenges. As the animal production grows, livestock facilities tend to be more concentrated with larger amount of animal waste discharged. Animal manure changes from valuable resources to waste because of improper management and application. Consequently, animal manure management is considered one of the environmental priority issues in China. The objective of this paper is to describe the current state of pollution and emission controls in China, and to identify the challenges and opportunities.
Material and methods
A multitude of sources were reviewed for this overview. Data sources on animal production were from China official statistical data, while
information on production parameters, housing types and manure
management systems were from a field survey by the research group led by Dong (Liu and DONG, 2006).
Findings on current state
(1) In 2005 fresh animal manure production in China was estimated to be 3.0 billion tons, which was about 2.24 times the industrial and
municipal solid waste output (1.34 billion tons). The average manure load is approximately about 24 tons of manure over the country’s farmland of 1.837 billion Mu or 122 million hectares. The highest provincial average
manure N load was 127 kg N per ha, although the N load was much higher in some areas. Also because of the low profit of the livestock industry and poor transport means, 80% of the large and medium-sized farms are located in densely populated areas in Eastern China and around major cities. Furthermore, most of the farms lack effective pollution-prevention facilities. Consequently, animal production has become one of the largest pollution sources in China.
(2) The Chinese government has paid more attention to prevention of pollution from livestock production, thereby ensuring sustainable agricultural development. The National Strategy on Pollution Prevention and Control from Livestock Production was issued by the State Environmental Protection Agency (SEPA) in 2001. In 2003 the national discharge standards for pollutants from livestock production was established. The major parameters of discharge standards are lists in Table 1.
Table 1. Threshold values of average daily pollutant concentrations of discharged waste water in China
Parameters BOD5
Threshold 150 400 200 80 8.0 1000 2.0
(3) The Ministry of Agriculture (MOA) of China is implementing an Eco-household Project for promoting sustainable agricultural
development. This program focuses on using biogas and solar energy as supplementary measures to increase farmer’s income while improving their living environment. By the end of 2005, the number of household biogas digesters had reached 17 million with a total biogas production of 6.5 billion m3. Ten percent of the rural families have the opportunity to use biogas. The number of large-scale biogas digesters for manure treatment had reached about 2000. This program will mitigate pollution from animal manure to some extent.
(4) A variety of manure treatment and utilization systems, such as compost and biogas digester, have been applied to meet the requirement of different scales of animal farms in China. However, the extent of utilization is limited. In recent years, combined treatment and utilization systems for animal manure have been
increasingly developed to meet the need of large-scale animal operations. The process includes pre-treatment of various raw materials, selection of better technical parameters for improved digestion, after-treatment of effluent for discharge, reuse and land application. Great improvements have been made in this type of system. Solid and liquid separator is widely used to reduce the solids content of slurries and thus required volume of digesters.
Combined anaerobic-aerobic technologies are being adopted on large-scale farms located in the land-limited areas. Sequential batch reactors (SBR) are applied to treat the effluent of anaerobic
digesters. However, the high operation cost has limited the extension of this technology to medium- and small-scale animal farms. Membrane technology is under investigation. The Chinese Academy of Agricultural Sciences (CAAS) is exploring the application of membrane technology in animal manure treatment. Land
application is one of the most widely accepted ways to utilize nutrition in animal manure. However, excess nitrogen and
phosphorus from animal residues have caused increasingly serious non-point pollution of soil and waters.
Conclusions
With the development of intensive animal production, large- and medium-scale biogas digesters and combined treatment systems have become a priority. A variety of technologies on further treatment and/or utilization of effluent from anaerobic digesters have been explored. However, a large gap in terms of the cost and the rate of industrialization or
commercialization exists between the current technologies and the requirement. How to reduce the cost of manure treatment and utilization remains a challenge facing the Chinese researchers and farmers.
References
China Livestock Statistical Yearbook. 2004. China Agricultural Press, Beijing, China. (in Chinese).
Liu Ling, Dong Hongmin , Jiang Guifang and Tao Xiuping. 2006. Handbook on Mnaure treatment and pullution contral for Animal production Park. China Agricultural Press, Beijing, China. (in Chinese).