(btw, this information is copyright by the Queen’s Printer for Ontario)
Plasticulture, The Use of Plastic in Agriculture
Plastic is an important new tool in agriculture. It is improving productivity, shortening the growing season and facilitating crop cultivation in non-traditional growing areas. It is also providing new storage systems for forages, and grain crops.
This factsheet will deal with plastic films as they apply to forages and grains.
In 1991, it was estimated that 2000 tonnes (4.4 million lbs) of plastic films were used for the storage of Canadian forages and grains. This is approximately 8% of the 24,000 tonnes (53 million lbs) of plastic film used in the agricultural and construction sectors. To keep this in perspective, it was only 1.2% of the total plastic film used in Canada in 1991.
Traditional storages for forages and grain have been made from steel, wood, and concrete. The use of plastic films will continue to grow because of:
- the low capital cost
- the flexible storage options
- extending the life of existing storages by using plastic film liners
- the marketing of crops stored in plastic film packages
There are five main options for farmers:
- re-use them for other purposes
- recycle them
- bury them
- send them to a land fill
- use them as a fuel source
Currently, plastic film (wrap) has no widespread secondary use on the farm. However, one possibility would be in pillows for free stalls. Current materials for pillows include straw and ground-up rubber tires.
Haylage bags can be reused 2 to 3 times if you are careful with them. Plastic agricultural grade film from bags, tubes and sheets can be reused for covering piles of wood & hay, machinery, and for protective liners for horizontal silos. The amount of reuse will depend on the severity of tears and holes in the plastic.
Recreational use of plastic film includes water slides, toboggans, kids’ forts plus 100 other uses your kids will come up with. Have fun with plastics and your kids, but make sure what they are planning is safe.
Recycling means moving plastic from the agricultural waste stream back into the manufacturing process. To make recycling a reality, one must have a system or infrastructure in place. The following are the basic components of any such system:
For recycling to be effective, one must collect a lot of material, from many farms. However, used plastic film is bulky and cannot be transported very effectively.
To reduce transport cost for this bulky material the farmer can use a farm type small square baler that uses tine forks for cross feeding into the baling chamber to compact the plastic on the farm.
(Figures 1 & 2) Feed the plastic into the baler by spreading the plastic into a windrow and driving the baler into the plastic. Make windrows approximately (1 m x 0.6 m deep) 3 feet by 2 feet high. Do not hand feed plastic into baler! This could cause serious injuries if feet or hands become tangled in the plastic. Large round balers can also be used, however the resulting size and shape of bale is too hard to handle. One may also have plastic compacted at a commercial compactor (Figure 3). The resulting compacted volume could be reduced to 15% of the original bulky volume (Figure 4).
Agricultural plastic film is mainly low density polyethylene. Sorting of this material is needed because there are different plastic products and additives. For example, plastic wrap is 0.5 to 1 mil thick and has tacifiers (glue) compared to tube plastic which is 4 to 15 mil thick with no tacifiers.
Agricultural plastic films must be cleaned before being converted into pellets for film or formed into moulded products like plastic lumber and fence posts. Incoming plastics must be inspected for contamination and are accepted or rejected depending on the level of contamination. Contamination includes dirt, sand, stones, grease, vegetation, water, other types of plastic, glue, tape and ultraviolet (UV) light degradation. If the film has lost its flexibility and is crinkly, it has serious ultraviolet light damage. UV damage can severely limit the recyclability of agricultural plastic film.
Plastic films are then chopped in a grinder, washed to remove contaminates, then fed into an extruder where heat and pressure melt the plastics. The molten plastic is extruded into fine strands, then cooled and chopped into pellets. These pellets are used by manufacturers to make new plastic film products.
Some plastic film is chopped then melted and formed directly into moulded products.
For agriculture, plastic films could be recycled back into plastic film. This is the best since there is no need to develop a market for the recycled plastic.
Plastic Moulded Products
Here are several options for molded products such as; landscape timbers, fencing, planking for farm pens, roadside posts, benches, picnic tables and pallets (Figure 5). All these options require a marketing plan for selling the new products.
On farm burial of your own clean plastic film (agricultural waste) is an option. However, this method is not recommended since it would be hard to recover the material in the future and seepage of contamination into the ground water may occur if crop matter is trapped in the plastic.
Land fills are the most common method of handling municipal solid and agricultural film waste world wide.
From a farmer’s point of view, the problems with this option are that:
- landfills are filling up, resulting in less sites available.
- tipping fees range from $ 80 to $ 160 a ton
- some municipal landfills may not accept agricultural plastic film waste
Energy recovery is another option that other countries have available for plastic films and for solid wastes. In the U.S. there are 136 energy recovery plants with another 100 plants planned by the year 2000. In Germany, energy recovery is gaining interest as a waste management option. Table 1 lists the energy values for various materials.
Currently, energy recovery is not an option for agricultural plastics in Ontario. However, it may be possible to ship the agricultural plastics to the United States for energy recovery, recognizing there would be a substantial cost in transportation and possible tipping fees.
While energy recovery of solid wastes can reduce volume by 95%, plants require high-temperature burning and pollution control equipment to control air pollutants.
The critical considerations for energy recovery, are the cost of collection, transportation, reprocessing and pollution control.
The Ontario Ministry of Agriculture, Food and Rural Affairs has been involved in test projects and pilot collection days with recyclers to work out the problems of cleaning plastic films and possible end use products. With fine tuning, 97% recovery of plastic films into pellets for remanufacturing is possible. These pellets could then be used for making recycled film in a 50/50 blend with virgin pellets, garbage bags, ground cover sheets, luggage, weather stripping, etc. Preliminary results indicated that during processing, stretch wrap curls up on its self, is hard to wash, water and dirt is trapped, and extruding filter screens tends to plug up. These results indicate that process adaptations will be needed to make agriculture plastic film into pellets or flakes for remanufacturing.
The results of using agriculture plastic film to manufacture plastic lumber is very promising. Some problems are: the material being too wet and dirty to handle, and brown stripes caused by the burning of silage and haylage residues in the plastic. Modification of the process to handle wet material by adding a drier or collecting only dry plastic and using darker colouring may solve these problems.
The major problems associated with agricultural film are:
- Inability to keep the material clean
- Ultraviolet degradation
- High cost of collection and sorting
- Lack of reliable end use market.
Efforts are under way to collect and recycle agricultural plastic films throughout the world. These problems will be solved in the near future. Currently, the best recommendation for Ontario farmers is to store the plastic film for future off farm recycling.
Steps in Off-Farm Recycling
- Once the plastic film is removed, shake it to get contaminants off (dirt, haylage, water, ice, etc.). Separate strings from the plastic.
- Store plastic films immediately indoors. This will keep it from further contamination and sunlight. Some farmers are storing plastic in hay wagons inside machinery sheds.
- Keep plastic clean and dry.
- Bale or compact into small square bales for easier handling, storing and transporting. Note: Bale only with plastic string not jute.
- Send to pilot recycling project in baled or loose form.
- Store for future full scale recycling program.
NOTE: If more than 5% of the weight is contaminants, the plastic film will NOT BE ACCEPTED for recycling.