If you want to feel good about what you do in your work, and you aren't yet into plasticulture, take another look. We'll be needed more and more. That's the inevitable conclusion to be made after seeing what plastics can do for food production, and realizing that so many people still go hungry or don't eat properly.
The American Society for Plasticulture held its National Agricultural Plastics Congress from March 5-8 in Charleston. Most of this meeting dealt with fresh produce - tomatoes, lettuce, cucumbers, berries and melons - but the principles apply to other crops as well, and as world population grows, we'll need more and more help from plastics to feed us all.
Plasticulture is the science of using plastics to help grow food, and a science it certainly is. The meeting included 46 papers, mostly from university agricultural scientists, that reported the latest developments in such things as mulch (between the plants), high and low tunnels (over the plants) and greenhouses, as well as irrigation pipe and tubing.
Here are some highlights:
Smart Mulch. Mulch film warms the soil, prevents weed growth below it, and sometimes channels water toward the plants. It can be as thin as 0.6 mil up to 2-3 mils, depending on what resins are used, how many plantings it can survive, and how it is eventually removed. Often, the thickness is limited by strength, as the film needs enough after use to enable it to be pulled off the ground without tearing. But the original use of simple monolayer black film now has new twists: mulch that repels insects, mulch whose color reflects upward and increases production, and clear film that allows the soil to get so hot that it kills underground pests without the use of soil fumigants.
Burn, poly, burn. An impressive paper showed a video of a portable furnace capable of burning just about any ag-plastic waste - film, baler twine, drip tubing - with minimal cleaning, and sending the energy (via hot water) to heat greenhouses, tunnels, animal buildings and other structures on the farm. Such agricultural waste is a serious economic as well as environmental problem now.
Drip, drip, drip. Water supply has come a long way beyond the big spray devices we see out in rural areas that seem to waste so much water. Irrigation, especially drip irrigation (thin plastic tubing with ``leaky'' fittings at regular intervals), avoids most evaporation and gets the water where the roots are, a major issue in water-short areas. One paper showed how white tubing avoids overheating delicate transplants by reflecting more of the sun's energy during the day.
It's not just water any more. Hydroponics, the science of growing plants in water without soil, needs plenty of plastic. It is not as simple as it sounds, because roots need air, too, and growers have to adjust water levels and the fertilizers that the water carries, based on the type and growth stage of the plants. Hydroponic products avoid earthborne pests, are available year-round, and often look as well as taste better, which helps offset the original investment.
It's not just PE, either. Although polyethylene is the usual material for all these products, additives have become very important. Many papers dealt with different colors, stabilizers, wave-length managers, promoters of degradability and even additives to protect other additives. As for other resins, one speaker showed how polyurethane films were much tougher and held in enough heat to justify their cost in some cases.
Lettuce go to the South Pole. The most unusual of all the papers was one from the University of Arizona, which showed the greenhouse that they developed for use at the NSF Research Station at the South Pole. They need the fresh foods for nutrition as well as variety, but this project had a psychological aim as well; in this barren and hostile environment, it feels good to see something growing, and there is an observation room in this greenhouse so the researchers can do just that. And as if that weren't enough for the Arizona team, they are now working on a facility to grow produce on Mars, just in case we ever set up a colony there.
ASP wants more members, and the plastics industry could do more with and for them. Details are available on the group's Web site, www.plasticulture.org.
Griff is a consulting engineer based in Bethesda, Md.