The possibility of making plastic from corn stems from a growing interest in sustainable alternatives to traditional petroleum-based plastics. Exploring plant-derived materials for plastic production is a significant area of focus, aiming to reduce reliance on finite fossil resources and develop renewable options for common products.
Understanding Bioplastics
Bioplastics are plastic materials created from renewable biomass sources, such as vegetable fats, corn starch, or recycled food waste. Polylactic Acid (PLA) is the most common type derived from corn. Unlike conventional plastics that originate from crude oil or natural gas, PLA is a plant-based polymer. While corn is a primary source, PLA can also be produced from other fermentable sugars found in sugarcane, tapioca root, cassava, or sugar beet pulp.
The Manufacturing Process
The transformation of corn into PLA plastic begins with the extraction of starch from corn kernels through a process called wet milling. Enzymes or acids are then introduced to the starch, converting it into simple sugars, primarily dextrose. These sugars undergo fermentation, typically with the help of microorganisms such as Lactobacillus bacteria, which convert the dextrose into lactic acid. Once lactic acid is produced, it is further processed into a cyclic dimmer called lactide. Finally, these lactide molecules are linked together to form long chains of polylactic acid, resulting in the final PLA resin, which can then be used to create various plastic products.
Properties and Applications
PLA plastic exhibits several distinct properties suitable for diverse applications. It is a thermoplastic, meaning it can be molded and reshaped when heated to its melting temperature, typically ranging from 130 to 180 °C. PLA has a glass transition temperature between 60 and 65 °C. While somewhat brittle, its mechanical properties are comparable to conventional plastics like polystyrene or PET. PLA finds widespread use across various industries, including packaging (such as food containers, drinking cups, and disposable cutlery), 3D printing filaments, and medical applications like dissolvable sutures, medical implants, and drug delivery systems.
Environmental Considerations
While corn-based plastics offer environmental advantages, their end-of-life management requires specific conditions. PLA is biodegradable and compostable, but it typically requires industrial composting facilities with high temperatures, moisture, and oxygen levels to break down efficiently. It does not readily decompose in conventional landfills or typical home composting systems, where conditions are not optimal for degradation and it can produce methane if discarded without adequate oxygen. The production of corn-based PLA results in lower greenhouse gas emissions and consumes less non-renewable energy compared to petroleum-based plastics. However, growing corn for plastic feedstock raises concerns regarding land use, water consumption, and the use of fertilizers and pesticides; its overall environmental footprint must be considered across its entire lifecycle.