Spinning Corncobs into Socks Farming Plastics with “Green” Chemistry

Abstract

An underlying issue is how green exactly are these biomass-derived approaches? Corn production in the U.S. is subsidized and produced by intensive farming. As a consequence, it is inconclusive whether producing plastic from biomass really consumes less energy than making it conventionally. Moreover, the U.S. Department of Agriculture 10 year forecast (http://www.ers.usda.gov/briefing/corn/2005baseline.htm) projects that corn prices will rise because of increasing demand, and increased yield is to come from genetic engineering, gated by available water. If new markets for biopolymers emerge, we may be looking at a totally different demand and price structure.Dr. Tillman Gerngross, assistant professor of engineering at Dartmouth College, is not optimistic. Gerngross worked at Metabolix for several years and believes green chemistry is energy inefficient and will not result in notable cost savings. According to Gerngross, making a biopolymer still requires consumption of fossil fuels, so overall, not only the fossil fuels required to make the monomers but the farming and processing costs must be considered as well. “It is necessary to look at total energy consumption in the process,” Gerngross says. “What the previous work has shown rather convincingly is that the energy required to make these polymers far exceeds the energy required to make conventional polymers.” According to Gerngross, as oil prices increase, energy and processing costs go up as well. “In fact, they are very correlated, and that is because of the heavy dependence [on fossil fuels] of the corn wet-milling industry as well as the farming activity,” Gerngross says. “That is the case for PLAs. The economics for PHAs are even worse.” According to Gerngross, the more energy used, the more CO2 emissions. “In my view, these processes are not green at all,” Gerngross says.The greening of plastics involves more than just the production side. “Carbon is the basic building block of polymers,” says Dr. Ramini Nayaran, professor of chemical engineering, Department of Chemical Engineering and Material Science at Michigan State University. Narayan argues for plastics based on organic sources that use carbon sustainably. He cautions that before compostable biopolymers will have a real environmental impact, we must improve our waste-collection and disposal systems.