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May 2006 10 hits: 444 times

China has/kloc-0.5 billion mu of arable land, and the annual output of crop straw exceeds 600 million tons. But for many years, straw has become a problem for scientists.

Straw burning has become a public hazard.

Liu Changyue, a senior engineer of Hebei Academy of Sciences who has been engaged in agricultural research for a long time, said in an interview that the most direct impression of straw treatment is that it is burned in large quantities in the field, which is particularly prominent in eastern China. Every year after the summer harvest and the autumn harvest, the fields are full of flames and smoke, and sometimes the smoke makes people almost suffocate. Airports and highways are often closed due to burning straw, and the losses are incalculable. According to statistics, China has/kloc-0.50 billion mu of arable land, and the annual output of crop straw reaches 600 million tons, including straw/kloc-0.80 billion tons, corn 220 million tons, wheat/kloc-0.65438 billion tons, and the output of sweet potato vine, rape stalk, soybean stalk, sugarcane stalk, sorghum stalk, peanut seedling and peanut shell all exceeds. In order to solve this problem, the Ministry of Agriculture and other six ministries jointly issued a document in April this year, calling for strengthening the comprehensive utilization of straw and prohibiting incineration. How to develop and utilize straw has become one of the major issues in the development of contemporary agriculture.

Liu Changyue said that the reason why straw has become a "public hazard" that everyone hates is related to the low utilization rate of straw in rural areas in China for a long time. Due to the low level of productivity, low level of science and technology, unreasonable industrial structure and other reasons, the main ways of using straw in rural areas in China are as follows: first, using original straw as feed, farmers feed livestock directly, but the existing problems are low intake and low digestibility of livestock; Second, as an industrial raw material, it is used for papermaking or building materials, but there are environmental pollution problems; The third is composting, but this is limited by the site; The fourth is to crush the straw and return it directly to the field. Returning straw directly to the field has advantages and disadvantages. At present, due to the insufficient fineness of straw crushing, the effective transformation period of straw in soil is long, which may even bring inconvenience to land cultivation and affect crop growth. Generally speaking, the disadvantages outweigh the advantages.

In recent years, the state has organized scientific and technological forces to explore the comprehensive utilization of straw. By using physical means such as cutting, crushing and granulating, chemical means such as alkalization, acidification and ammoniation, and microbial means such as silage, fermentation and enzymolysis, the utilization rate of straw has been improved, but in general, it has not fundamentally changed the situation, and there are still problems such as high cost, uneconomical, difficult to master technology and inadaptability.

Find the crux, find the way out

Although there are many reasons for the low comprehensive utilization rate of straw, Liu Changyue believes that the low density of straw itself is the most important and direct reason. According to reports, the natural density of straw is usually 30 ~ 50 kg per cubic meter, so "fluffy" raw materials are not conducive to transportation and storage, affecting its deep processing or secondary development and utilization. Therefore, the key to solve the "bottleneck" of comprehensive utilization of straw is to first carry out high-density compression of straw. Only by high-density compression of straw can we create favorable conditions for the next development and recycling.

In recent years, some domestic research institutions have cooperated with farms to tackle key problems, and used mechanical means to carry out different degrees of compression tests on straw. The results show that straw compressed feed not only improves the nutritional level, but also is beneficial to circulation. From 1998, "Luquan Straw Development Experimental Field" in Hebei Province took the lead in undertaking the key scientific research project of "Straw Comprehensive Utilization" in Hebei Province. Corn and other straws are used as raw materials, which are compressed into block feed at high pressure and high temperature, so that the straw is compressed to a high density of 0.8 ~ 1 ton per cubic meter, which is not only convenient for storage and transportation, sterilization and insect prevention, but also difficult to burn, and the nutritional level is higher than the original.

Liu Changyue said that China is a big country in agriculture and animal husbandry, and compared with developed countries, the proportion of animal husbandry is low. With the improvement of people's living standards, the dietary structure will be inclined to milk, meat and eggs, which puts forward greater requirements for animal husbandry, and the great development of animal husbandry needs rich feed resources. Facing the contradiction of serious grassland degradation and desertification, insufficient forage supply and difficult collection and utilization of leaf resources, the development potential of coarse fodder for animal husbandry with straw as raw material is huge. Ruminants such as cattle and sheep must eat coarse feed such as straw. Taking cattle as an example, according to the statistics of 200 1, the number of cattle in China is 65.438+0.5 billion, and the annual demand for roughage is 450 million tons, especially for large-scale and intensive farming. In the field of straw development and utilization, there are 300-500 million tons of idle resources every year; As far as the market is concerned, there is a business opportunity of10 billion, and the comprehensive utilization of straw is promising.

According to estimates, every 10,000 tons of straw compressed feed can be used for aquaculture, and 3,000 to 4,000 cows can be fed a year. The weight gain of beef cattle increased by 15%, the production and income of dairy cows increased by 16%, and the milk fat rate also increased by 0.2%. At the same time, most of these feeds will form feces, which can be used to make biogas on the one hand, and about 1 10,000 tons of organic fertilizer can replace chemical fertilizer on the other hand, becoming an important industrial chain for developing ecological agriculture. Practice has proved that straw is the most extensive, abundant, cheapest and better roughage resource, so it is urgent to speed up the industrialized production and modern circulation of roughage with straw as raw material.