Environmental impact

The environmental impact of bioplastics is often debated, as there are many different metrics for "greenness" (e.g., water use, energy use, deforestation, biodegradation, etc.) and tradeoffs often exist.The debate is also complicated by the fact that many different types of bioplastics exist, each with different environmental strengths and weaknesses, so not all bioplastics can be treated as equal.

The production and use of bioplastics is sometimes regarded as a more sustainable activity when compared with plastic production from petroleum (petroplastic), because it requires less fossil fuel for its production and also introduces fewer, net-new greenhouse emissions if it biodegrades. The use of bioplastics can also result in less hazardous waste than oil-derived plastics, which remain solid for hundreds of years.

Petroleum is often still used as a source of materials and energy in the production of bioplastic. Petroleum is required to power farm machinery, to irrigate crops, to produce fertilisers and pesticides, to transport crops and crop products to processing plants, to process raw materials, and ultimately to produce the bioplastic. However, it is possible to produce bioplastic using renewable energy sources and avoid the use of petroleum.

Italian bioplastic manufacturer Novamont states in its own environmental audit that producing one kilogram of its starch-based product uses 500 g of petroleum and consumes almost 80% of the energy required to produce a traditional polyethylene polymer. Environmental data from NatureWorks, the only commercial manufacturer of PLA (polylactic acid) bioplastic, says that making its plastic material delivers a fossil fuel saving of between 25 and 68 per cent compared with polyethylene, in part due to its purchasing of renewable energy certificates for its manufacturing plant.

A detailed study examining the process of manufacturing a number of common packaging items from traditional plastics and polylactic acid carried out by Franklin Associates and published by the Athena Institute shows that using bioplastic has a lower environmental impact for some products, and a higher environmental impact for others. This study, however, does not factor in the end-of-life environmental impact of these products, including possible methane emissions from landfills due to biodegradable plastics. This could affect the assessment of the environmental impact of bioplastics compared to traditional plastics.

While production of most bioplastics results in reduced carbon dioxide emissions compared to traditional alternatives, there is concern that the creation of a global bioeconomy required to produce bioplastic in large quantities could contribute to an accelerated rate of deforestation and soil erosion, and could adversely affect water supplies. Careful management of a global bioeconomy would be required.

Other studies showed that bioplastics result in a 42% reduction in carbon footprint.

On October 21, 2010, a group of scientists reported that corn-based plastic ranked higher in environmental defects than the main products it replaces, such as HDPE, LDPE and PP. In the study, corn-based plastics created more acidification, carcinogens, ecotoxicity, eutrophication, ozone depletion, respiratory effects and smog than the synthetic-based plastics they replaced[7]. However the study also concluded that biopolymers trumped the other plastics for biodegradability, low toxicity, and use of renewable resources.

The American Carbon Registry has also released reports of nitrous oxide caused from corn growing which is 310 times more potent than CO₂. Pesticides are also used in growing corn-based plastic[8].

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