Green chemistry, an emerging scientific approach, focuses not just on a final product, but also on coproducts and production processes that are sustainable.
It’s a familiar concept in agriculture. A cornfield yields more than grain; it also produces corn stover and cobs. Farmers have to consider soil health and nutrient needs, not just how much corn they can produce.
Green chemistry is revealing exciting opportunities to use agricultural products in innovative, high-value applications. Some may take decades to be viable, others a handful of years and some have
already emerged.
Sugar-fermented chemicals
Succinic acid, a four-carbon molecule, is a chemical feedstock for food, pharmaceuticals, surfactants, detergents, plastics, clothing fibers and biodegradable solvents. Because all living things make succinic acid through natural sugar fermentation, the biomass-derived chemical is a potential alternative to petroleum-based chemicals. As petrochemical prices continue to climb, bio-based alternatives become more attractive.
Biomass can be converted to mixed-alcohol fuels using the MixAlco process. It is a biological method for converting any biodegradable material such as crop residue, manure or municipal solid waste into useful chemicals such as acetic, propionic and butyric acid and alcohol biofuels, which can be used for heat and energy.
Ag-fiber composites
Mixing renewable fibers with other materials to make biocomposites is not new. In fact, horse hair was used to strengthen plaster in home construction around the turn of the 20th century. Today ag-based materials are mixed with traditional or bio-based resins to make building materials, packaging and other biocomposite products. Minnesota plastic manufacturers surveyed say they are interested in bioproducts if price and performance are competitive with petro-based plastics. (see story page 5)
PLA in cups to clothes
A polymer made through starch fermentation, Polylactic acid (PLA) was introduced several years ago and is gaining popularity. The compostable polymer is used in a wide variety of items such as cups, food packaging and clothing. Wal-Mart recently announced that some of its produce will be sold in PLA containers. While heat resistance remains a challenge, PLA items are popular when “bio-based” and “sustainable” are selling points.
Bacteria-made polymers
Science is revealing a new kind of agriculture used to make polyhydroxy-alkanoates or PHA. Feeding ag coproducts to bacteria will produce PHA, a polymer that can be used in soaps, lotions, personal-care items and cleansers. Researchers are investigating bacteria strains that may produce polymers more efficiently.
Protein plastic
It’s possible to make a fast-food-meal toy that kids can eat. While it may not be recommended, protein-based plastics for injection molding can be made from feedstocks such as soy protein. Cooking utensils and other household products have been made from protein plastic and there could be a wider variety of products in
the future.
Soy copolymers
Green chemistry is yielding plastics through copolymerization using soybean oil. The renewable copolymers could replace petroleum-based plastic in products such as cold-beverage bottles.
Green roofs
Soy polymers are being blended with agricultural fibers to produce rigid roof shingles. The biobased materials are an alternative to petro-based shingles.
These are just a few examples of products that may be used in small volumes but have high value. If they reach markets where consumers are concerned about the product’s origins and sustainability, they can compete on more than price.