Comprehensive Utilization of Straw: finding the other half of Agriculture

The picture shows that the straw is directly bundled and left the field by using agricultural machinery operation. Photo taken by Liang Baozhong

Editor's note: when it comes to the harvest season of autumn grain, the problem of straw burning has once again attracted the attention of all sectors of the community. In the spring and autumn of agriculture, half of the products are in the seeds and half in the straw. To expand the channel of comprehensive utilization of straw is to find the other half of agriculture, which is of great significance to solve the problem of agricultural non-point source pollution and promote the sustainable development of agriculture.

1. The way out: the utilization pattern of "five materials" is basically formed.

China produces nearly 600 million tons of straw every year, such a huge figure is accompanied by the continuous increase of grain production in our country. In the past, straw treatment has not become a follow-up problem of agricultural production as it is today. In the traditional planting technology, straw is a valuable production and living resources for farmers. After the autumn harvest, farmers will transport all the straw home, and the straw can be used for cooking, laying pens for pigs, cattle and sheep, and as roughage for livestock. In families with biogas digesters, biogas can be produced and then retted to make fertilizer. Today, with the change of rural energy structure, the function of straw as fuel is cancelled by natural gas and electric power, and with the increase of rural labor costs, the useless straw harvesting has become a burden on farmers.

Even rubbish is misplaced resources, of course, straw can not be useless. For the utilization of straw, the first thing is to return to the field. It is understood that most of the straw in developed countries is used to return straw to the field. For example, the United States produces 450 million tons of crop straw annually, and the amount of straw returned to the field accounts for 68% of the straw production. Straw itself comes from the land, straw returning can effectively increase the content of soil organic matter and improve soil aggregate structure and physical and chemical properties.

But returning to the field still can not consume the total amount of straw production each year, what should we do? Go back to your old business and make fuel, feed and biogas raw materials. At this time, the molding fuel is pressed into particles, blocks and rods under certain pressure, which has the advantages of high efficiency, cleanliness, easy ignition and zero carbon dioxide emission. it is a kind of high quality fuel and one of the main development directions of biomass energy at present. Straw as feed, not direct feeding, should go through the process of silage and yellow silage, that is, through fermentation to inhibit and kill a variety of microorganisms to produce useful metabolites, so that the feed with aromatic, sour, sweet and other taste, improve palatability.

Although it is the old method in the past, using industrial thinking and way to do agriculture has not only improved the efficiency of straw utilization, but also opened up ways of straw utilization. Most of the corn straw can be crushed and returned to the field or used as silage, and Gramineae straw such as wheat straw and rice straw is one of the excellent raw materials for cultivated grass saprophytic fungi, by matching with nitrogen sources such as cow dung, wheat bran, bean cake or rice bran, it can be used as a base material for edible fungus cultivation under suitable environmental conditions.

Straw as artificial board is a production technology that has made rapid progress in recent years, mainly using wheat straw, rice straw, corn straw, cotton straw, sunflower stalk and other wood-based panels, the properties can meet the national standard requirements of wood particleboard, and does not contain formaldehyde, but the current cost is slightly higher.

From being used only as rural energy and livestock feed in the past, it has been expanded to the field of "five-material" utilization, such as fertilizer, feed, edible fungus, fuel and industrial raw materials, and has gradually formed an ecological circular agriculture with the combination of agriculture and animal husbandry, such as breeding-biogas fermentation-planting-power generation, which has opened up a space for the comprehensive utilization of straw.

2. Difficulties: the cost of leaving the field to return to the field is high, and the collection, storage and transportation system is incomplete.

In a cycle of agricultural production, fruit and straw are the fruits of agricultural production, but fruit is the food that people cherish, and the value of straw as the other half of the achievement is often ignored. Although we have the use of "five materials", the phenomenon of burning straw still occurs from time to time.

"the direct return of straw to the field needs the cooperation of several conditions: first, the straw should be crushed and pressed, mixed and buried to return to the field, the second is reasonable irrigation, and the third is to increase nitrogen fertilizer." Bi Yuyun, a researcher at the Institute of Agricultural Resources and Agricultural regionalization of the Chinese Academy of Agricultural Sciences. If the straw is not crushed or crushed completely, it will be returned to the field directly, and the straw will accumulate on the surface of the soil, affecting the growth of the next crop. At present, straw crushing mainly adopts the way of agricultural machinery operation, which will increase the fuel consumption of the harvester, and the comprehensive operating cost per mu will also increase, which has become a burden for farmers. According to a survey conducted by the Ministry of Agriculture, the subsidy standards of individual provinces and cities that have introduced subsidy policies are obviously on the low side. For example, the subsidy standard of returning straw to fields in some provinces and regions is only 1020 yuan per mu, which is equivalent to about 1 inch of the actual cost of returning fields, while farmers have to bear the cost of returning straw to fields on their own.

In fact, the collection, storage and transportation system of straw is not complete, which leads to the high cost of straw leaving the field, which is also an important factor affecting the comprehensive utilization of straw. According to the investigation and calculation of the Ministry of Agriculture in Beijing, Tianjin, Hebei and its surrounding areas, as well as eight provinces (cities and regions) such as Heilongjiang and Jilin, the cost of returning straw to the field is about 9% to 15% of the net income of crops in a single season, and the cost of leaving the field is about 15% to 30%. As a result, farmers are not willing to return their fields and their enthusiasm is not high. At present, there is a shortage of rural labor, and the value of straw is large but cheap. the straw handled by a labor force may only be sold for more than ten yuan a day, but the daily wage for this worker is hundreds of yuan, which is really not high. Some farmers in Northeast China said helplessly: "if you don't burn the straw, you can't grow the field." take away the straw, and take the straw for free. And the use of baler operation means an increase in cost.

Beijing-Tianjin-Hebei region has gradually stepped up air control efforts in recent years. Haze has accelerated the adjustment of energy structure in North China, and biomass fuel has shown its environment-friendly advantages, which gives opportunities for the development of biomass fuel and supporting gas appliances industry. Moreover, with the gradual maturity of technology, the thermal efficiency of biomass stoves has generally increased from 60% to more than 70%, with a maximum of 80%, which is a very suitable product for cooking and heating in rural areas. however, with the continuous decline of coal prices, the status of biomass fuel is awkward. Last year, the price of coal in China fell below 500 yuan per ton, and this year it may fall below 400 yuan per ton, while the factory price of biomass briquette fuel is 250,350 yuan per ton, and the ex-factory price per ton of molded fuel after processing is about 800,000yuan. This has led to the departure of some users.

The cost of leaving the field to return to the field is high, the collection, storage and transportation system is incomplete, and there is no advantage in the price of biomass fuel, which are the bottlenecks to be faced with whether the straw can be used effectively.

3. Outlook: make good use of both the government and the market

On October 10 this year, the national conference on comprehensive utilization of crop straw was held in Shijiazhuang City, Hebei Province. The participants generally said that the comprehensive utilization of straw is a cause that has broad prospects and benefits the country and the people, and governments at all levels are trying to make a difference.

Beijing has comprehensively adjusted its planting structure. In view of the plots that cannot be mechanically operated in the mountainous and semi-mountainous areas, the planting of food crops will be reduced in an orderly manner from this year, so as to solve the problem of straw utilization in the mountainous and semi-mountainous areas from the source. Hebei Province plays the role of pilot and demonstration, requiring township governments to unify the collection, storage and transportation of scattered straw in Luquan District. Each village sets up a collection and storage point, and the village committee is responsible for collecting and storing scattered straw, bundling and transporting it to the processing plant to produce pressed straw. For every 1 ton of straw collected, the district financial subsidy to the village committee is 50 yuan, and the processing plant is responsible for the transportation fee, 20-30 yuan per ton. In view of the fact that there is still no price advantage in the government subsidized straw lump, we should actively explore the new mechanism of fuel processing and purchase. That is, farmers provide straw raw materials by themselves, and enterprises charge a processing fee of 100 yuan per ton after processing, or farmers pay 2 tons of straw to the lump station, and the station provides 1 ton of straw lumps to farmers free of charge, and about 0.8 tons of straw lumps processed by enterprises are recycled by enterprises and suppliers. In this way, farmers, governments and enterprises are connected together to become a community of interests, and it also forms a virtuous circle from straw recycling to processing to use.