High tunnels and hydroponics are extensions of the fossil fuel supply line. The plastic covering requires barrels of petroleum and gallons of natural gas both for feedstock and the energy to manufacture.
The support structures require energy for manufacture and for mining in the cases of aluminum or steel. The mixtures require energy.
These are not sustainable, they are not green; they are not environmentally safe.
“Polyethylene covers on high tunnels and greenhouses make a significant contribution to the growing problem of waste plastics. ... Most of these plastic films are produced from low-density polyethylene (LDPE #4) resins.”
For a round style high tunnel — 20 feet wide by 12 feet high by 48 feet long — it takes approximately 50 feet of 40-foot wide of 6 mil, 4-year plastic. From data at Plastics Europe this can be figured to be more than a couple of barrels of crude oil every four years.
This is not a large greenhouse either in length or width so the energy requirements and waste problems would be magnified.
It is important to understand that high tunnels and hydroponics do not offer a sustainable alternative in a world where access to oil and natural gas are requiring more and more energy to extract; in a world where obtaining fossil fuels requires more and more environmentally dangerous practices.
This does not even consider the carbon and other greenhouse gas emission required for the materials, manufacture, transportation and installation of high tunnels.
My point is not to negate their use as much as to require honesty in the promotion of them.
High tunnels and hydroponics as industrial gardening are neither a sustainable answer to our food needs nor a back to basics. It is a sideways move to business as usual.