Recycling of Agricultural Film: the Green Development of "White pollution"

Editor's note: after the autumn harvest, before the next production cycle, in addition to straw needs to be treated, the last crop of used agricultural film should also be cleaned up and recycled in time. The recycling of agricultural film can not only effectively solve the problem of "white pollution", but also realize "turning waste into treasure", which is of great significance for promoting the sustainable development of agriculture.

1 Now: heavy use, light recycling, agricultural film residues lead to "white pollution"

In the late 1970s, China introduced the first agricultural plastic film. Since then, with the unremitting efforts of agricultural science and technology workers throughout the country, agricultural plastic film has been widely used in China and has gradually become the fourth largest agricultural production material after seeds, pesticides and fertilizers. After more than 30 years of development and application, plastic film mulching has become one of the most important agronomic techniques in China, especially in Northwest China. In Gansu Province, a typical dry farming area in China, with the application of agricultural plastic film, agricultural scientific and technological personnel have successfully developed and popularized the dry farming techniques of autumn plastic film mulching, top plastic film mulching and hole sowing with full film covering. Thanks to the adjustment of grain structure and large-scale popularization of dry farming technology in Gansu Province, the grain production in Gansu Province not only bid farewell to the history of grain shortage completely, but also realized grain self-sufficiency.

How can a piece of plastic film make the originally arid and barren land play such a huge food production potential? Yan Changrong, a researcher of the Institute of Agricultural Environment and Sustainable Development of the Chinese Academy of Agricultural Sciences, who has been studying agricultural plastic film for a long time, believes that plastic film mulching has the functions of warming, water conservation, fertilizer conservation, improving soil physical and chemical properties, improving soil fertility, inhibiting weed growth and alleviating diseases, which can help promote crop growth and development and increase yield.

"Plastic film mulching can increase the average daily temperature of soil by 3 to 5 degrees, change the circulation process of water and reduce the evaporation of ineffective water, which is very important to ensure the growth of some crops in China, especially in arid areas." Yan Changrong said, But at the same time, Our research found, After decades of application, Agricultural plastic film residual film pollution area and plastic film use area is completely coincident.

What kind of pollution will agricultural film residues produce? In this regard, the reporter learned in the interview, if the plastic film residue in the soil, first of all will destroy the structure of the soil, leading to soil hardening; secondly, will affect the growth and development of seeds, even affect the quality application of some crops, such as peanut although it is an excellent feed, but due to the agricultural film residue in the soil will lead to the continuous evaporation of water, affecting the growth and utilization of peanuts.

In view of the misunderstanding of the current agricultural plastic film residue pollution problem, Yan Changrong believes that qualified PE plastic film does not contain plasticizers, and the problem of plasticizer in soil has nothing to do with plastic film; at the same time, there is no evidence that some components in farmland plastic film will enter our food chain.

2 way out: put an end to ultra-thin plastic film, improve recycling rate

A few days ago, at the on-site meeting on promoting comprehensive utilization of agricultural plastic film held in Lanzhou, representatives from key application provinces and regions of plastic film generally believed that recycling waste plastic film was an arduous task, and the prevention and control strategy of "walking on two legs" must be adopted for source control and efficient recycling.

"First of all, when producing plastic film, we should strictly formulate corresponding standards. For example, put an end to ultra-thin plastic film. Only when the thickness and stretching degree of plastic film are enough can we pick up ten pieces. We should prepare for recycling at the beginning." Xinjiang production and construction corps agricultural technology extension station senior agronomist Yuan Yamei said.

Xinjiang is the province with the largest area of agricultural plastic film use in China. Plastic film is widely used in the production process of cotton, processed tomato, corn, vegetables and other crops. At the same time, it is also one of the regions with serious plastic film residue pollution in China. In recent years, on the basis of increasing support from the state, Xinjiang has also continuously increased capital investment in the recycling and utilization of waste agricultural film on farmland. Pilot demonstration construction of pollution control has been carried out in 40 counties and cities in Xinjiang, especially propaganda and guidance for enterprises to produce plastic film with thickness of more than 0.01 mm, encouraging farmers to use thickened plastic film, actively promoting plastic film mulching methods conducive to recycling, and promoting the recycling of residual film from the source. In 2014, Xinjiang also issued a mandatory local standard for polyethylene blown agricultural ground cover film.

In fact, it has become a realistic choice for many provinces to improve the quality standard of plastic film, improve the recovery rate and strengthen the supervision and management of the whole process of plastic film application through legislation. Establish and improve the system of plastic film recovery and processing, and take the road of resource reuse. In view of farmers 'weak awareness of environmental protection and other problems, Hebei has won funds through various channels on the basis of publicity and training in various forms to support the application of standard thickness agricultural film and the recycling of waste agricultural film. Heilongjiang Province has established 15 demonstration projects of agricultural cleaner production of residual plastic film by actively striving for it. In the two plains, focusing on one county, the waste plastic processing plant has been reconstructed, expanded or newly built, and the surrounding areas are driven by radiation; In several central towns of each county, enterprises set up waste agricultural film recycling stations to recover waste plastic film with compensation, and uniformly package and transport them to processing plants for renewable resource utilization.

"Comprehensive utilization of plastic film and pollution control is a systematic project, with many influencing factors, wide aspects involved and great difficulty in treatment." Wang Yanliang, deputy director of the Department of Science, Technology and Education of the Ministry of Agriculture, said that in order to do a good job in the treatment of agricultural plastic film pollution, agricultural departments at all levels throughout the country should fully summarize and popularize good experiences and good practices in various places, continuously intensify their efforts, and strive to achieve the recovery and comprehensive utilization rate of agricultural film in the current season by 2020.

3 Future: Actively carry out research on the application of degradable films

In addition to supervision, management, recycling and recycling, developing degradable plastic film to replace PE plastic film is the best way to explore and solve the problem of residual plastic film pollution in farmland, which can solve the problem of plastic film residue from the source. However, the application of degradable plastic film still faces a series of problems and challenges.

"although it has been tested in our local area for more than four years, due to too many influencing factors, further tests and comparisons may be needed." Liu Hongjin, an agronomist at the Rural Ecological Energy Environmental Protection Station in Inner Mongolia Autonomous region, said that degradable plastic film has little environmental pollution, but the cost is high, resulting in higher product prices than ordinary plastic film, which brings some difficulties to popularization. Tang Jirong, director of the Agricultural Ecological Environment Protection and Management Station in Gansu Province, said, "due to different climatic environments and different conditions of agricultural production, the requirements for the degradation time of plastic film in different places are also different. For example, Gansu vigorously promotes the autumn film mulching technology, which is not sown until March or April of the following spring after film mulching in autumn, while some degradable plastic films are automatically degraded before sowing time, so they cannot be used at all. "

The reporter also learned in the interview that at present, there are still some problems in domestic degradable plastic film, such as insufficient stability of products, poor initiative of degradation and so on.

"due to the complexity of degradation and application of degradable plastic film, the degradable plastic film of the same formula has different degradation performance to different crops in different places, so it can only be widely used through application research." Yan Changrong believes that the research and development of degradable plastic film should make a breakthrough in raw materials, formula, and touch technology. in addition, the use of biodegradable plastic film should be organically combined with regions and agricultural production conditions. it is necessary to strengthen the research on the adaptability of plastic film mulching technology and actively explore new ways to solve "white pollution".

Agricultural film recycling has to go through three hurdles.

◇ thickness, toughness up to standard ◇ financial subsidies ◇ waste agricultural film has a future

For the current situation of agricultural production in China, in addition to some areas with conditions to try to promote degradable agricultural film, most of them are mainly agricultural film recycling, so what conditions are needed to recover agricultural film?

First of all, agricultural film in thickness, toughness to meet certain requirements, too thin agricultural film strength is poor, fragile, after the use of a production cycle in the soil surface is broken, recovery is basically impossible. In accordance with the 1992 formulation of China's "polyethylene blow molded agricultural ground covering film" production standard (GB13735-92), the minimum thickness of agricultural plastic film is 0.008 mm, and the limit deviation is allowed to float up and down 0.003 mm, at present, some provinces and cities in China encourage the promotion of plastic film with a thickness of 0.01mm, which can be used for many years, and suitable for a variety of film uncovering technology, but also in line with the conditions of agricultural film recycling.

Secondly, at present, farmers are encouraged to recycle plastic film by themselves. most agricultural film use provinces have agricultural film recycling stations in each township, and farmers collect agricultural film and send it to the recycling point. Compared with the agricultural film scattered in the field in the past, it takes a certain amount of labor to recover the agricultural film, so it is very important for financial subsidies to encourage the recycling of old film. Yuzhong County of Lanzhou City has adopted the practice of replacing the old with the new. Since 2013, the province, city and county have been subsidizing the use of plastic film at the provincial, municipal and county levels. On average, 6 kg of plastic film is used in one mu of dry land, about 70 yuan, the financial subsidy is nearly 2/3 yuan, and the individual spends 25 yuan. This kind of financial subsidy is called "index film", that is, the purchase index of recycling old film for new film must be 2 ∶ 1. Take 6 kg new film as an example. It takes farmers 12 kilograms of old film and 25 yuan to buy it. To some extent, this measure not only increases the enthusiasm of farmers to recycle agricultural film, but also reduces the cost burden of thick agricultural film. "since the implementation of the trade-in policy, agricultural films with a thickness of less than 0.008 mm have basically disappeared in the market of our province." Yuzhong County agricultural ecological environment protection management station director Zhang Guangquan said.

Third, the recycled waste agricultural film should have a place to go and should not be polluted again. It is understood that there are two main ways of comprehensive utilization of waste plastic film: one is to crush and clean the recovered waste plastic film, produce recycled plastic particles through hot melting and extrusion, use recycled particles for deep processing, and produce PE pipes, plastic containers, drip irrigation belts, etc. Second, the recycled waste plastic film is directly crushed and mixed with a certain proportion of slag to produce recycled products such as well circle, manhole cover, tree grate for urban greening and so on. The waste plastic film is stored in the recycling points of villages and towns, and the recycling enterprises will recover and pull away at a certain cost, and the enterprises will bear the transportation costs at the same time.

From plastic film picking up to recycling to resource reuse, this is a production chain of agricultural film recycling. If the market-oriented operation mechanism can be gradually improved, the "white pollution" caused by agricultural film will also be solved.