In the countryside, there is an unimpressive but unignored thing – crop stalk （crop straw. Crop straw is an important biological resource in crop production systems. According to incomplete estimates, nearly 2 billion tons of straw are produced each year in the world. The use of crop straw involves not only thousands of households in the vast rural areas, but also sustainable development issues such as soil fertility, soil and water conservation, environmental security, and efficient use of renewable resources in the entire agro-ecosystem.
In the past, when the crops were harvested, the remaining stalks and stems could be used for waste, heating, and cooking. In addition to, it also can be used as litter for animals or animals feed.in the early, someone buried the straw into the biogas tank, which produced biogas and makes fertilizer. But now, the countryside is becoming more and more modern, coal, natural gas becomes the main fuel for cooking. And fertilizers are much more powerful than straw-smelling fertilizers. So the straw also changed from treasure to garbage. So farmers often choose to burn it. Due to the smog caused by burning straw, straw burning is prohibited throughout the country. However, it is not an effective way. At present, there are 900 million tons of straw produced each year in China, accounting for almost one-third of the world’s total. The utilization rate is less than 40%. What should be done with so many straws?
In fact, crop stalk can be applied to so many fields, such as biomass fuel, paper and pulp industry, electricity generation, straw returning to the field (SNPK), crop straw gasification, and building materials, etc.
Biomass pellet fuel
Straw pellet fuel is pressed by straw pellet machine under high temperature. Crop stalk pellet fuel is a new kind of fuel, and it is mainly made from corn straw, wheat straw, straw and other crops. The pellet fuel is produced by pressing a raw material such as wood chips and straws by a press roll and a ring die under normal temperature conditions. The density of raw materials is generally about 1100 kg / m 3, and the density of pellet is more than 1100 kg / m 3, which is convenient for transportation and storage, at the same time, the fuel performance of pellet fuel is greatly improved. The crop stalk pellet fuel is generally applied in the heating and cooking and power generation, etc. except for the pellet fuel, crop stalk also can be made into animal feed pellets with feed pellet mill.
paper and pulp making
Plant fiber is the basic raw material for the pulp and paper industry. According to international statistics, the wood fibers takes 90% share of the pulp fiber materials (excluding waste paper). In China’s pulp fiber materials, the proportion of wood is very small, and the proportion of non-wood materials such as grass is very high. China is the largest producer of straw pulp in the world. More than 75% of the non-wood pulp is produced in China. The straw fibers for pulp and paper making mainly include reed pulp, crop stalk pulp, bamboo pulp, bagasse pulp, straw pulp (wheat straw pulp), hemp pulp, cotton pulp, etc.
Straw returning to field
Mechanized straw returning technology is mainly based on mechanized operations such as mechanical crushing, breaking, deep ploughing and rolling, and the crop straw is crushed and directly returned to the soil. After the harvesting, the crop stalk is directly broken up with a straw returning machine, evenly sprinkled, and then turned into the soil with a rotary tiller.
From the current situation, because the high cost of straw stalk collection, returning to the field is the most economical, convenient and feasible solution. After the wheat harvest, the crop stalk is cut into sections on the spot, and the stubble is controlled to a height of about 5 cm. Filling the water in the field, after soaking crop stalk for a period of time, use the straw returning machine turn the straw into the ground. The ploughing and turning need to be repeated twice so that the straw is no longer in a group. After three or four days, the field can be transplanted. In foreign countries, many farms collect the crop stalks and make them into a large cylinder shape, which attracts many tourists to visit。
Material building
Building materials belong to the emerging field of straw processing and utilization. The technology uses straw stalk as raw material and uses molding equipment to make high quality low density, medium density and high density fiber board. Wheat straw stalk board is a new type of structural building material with high strength, corrosion resistance, fire retardant, no deformation, no cracking, beautiful appearance and low price. It is also possible to use the fiber and wood of the crop stalk as a filling material; using cement and resin to press various types of lighter partition boards as building materials. The building material is characterized by good compressive strength, light weight, fireproof and shockproof, low price and convenient installation.
