Biodegradable Plastics: Energy Costs And Environmental Impact

Biodegradable plastics are an alternative to traditional plastics, which are made from fossil fuels. Biodegradable plastics are made from renewable and/or biodegradable resources, such as plants and food waste. They produce fewer greenhouse gas emissions than traditional plastics over their lifetime. However, the technology to produce biodegradable plastics is still in development, and it is important to consider the energy, environmental, and economic costs of these alternatives.

Biodegradable plastics are more energy-intensive to manufacture than traditional plastics

Bioplastics do produce significantly fewer greenhouse gas emissions than traditional plastics over their lifetime. There is no net increase in carbon dioxide when they break down because the plants that bioplastics are made from absorb the same amount of carbon dioxide as they grow. A 2017 study determined that switching from traditional plastic to corn-based PLA would cut U.S. greenhouse gas emissions by 25%.

Various researchers have undertaken extensive life cycle assessments of biodegradable polymers to determine whether these materials are more energy-efficient than polymers made by conventional fossil fuel-based means. While biodegradable plastics are more energy-intensive to manufacture, they have the potential to be more environmentally sustainable in the long run. This is because they are based on renewable and/or biodegradable resources, which can contribute positively to the end-of-life phase of products.

Overall, while biodegradable plastics may require more energy to manufacture, they have the potential to significantly reduce greenhouse gas emissions and contribute to a more sustainable future.

Fossil fuel energy is required to produce a kilogram of polyhydroxyalkanoate (PHA)

Biodegradable plastics are based on renewable and/or biodegradable resources, which can enable a positive contribution towards sustainable products. However, they can be more energy-intensive during their manufacturing phase than their conventional competitors.

Polyhydroxyalkanoate (PHA) is a carbon-neutral and valuable polymer that could be produced from many renewable carbon sources by microorganisms, making it a sustainable and environmentally friendly material. It is the most promising solution to the major ecological problem of plastic accumulation. The biodegradable and biocompatible properties of PHA make it highly demanded in the biomedical and agricultural fields.

The fossil fuel energy required to produce a kilogram of PHA is 50.4 MJ/kg, according to one estimate. Another estimate by Akiyama et al. places the value between 50-59 MJ/kg. The technology to produce PHA is still in development, and energy consumption can be further reduced by eliminating the fermentation step or by utilising food waste as feedstock. For example, the manufacturing of PHAs by fermentation in Brazil enjoys a favourable energy consumption scheme where bagasse is used as a source of renewable energy.

PHA is currently manufactured by bacterial fermentation directly from starch from genetically modified crops. Polymerisation occurs during the fermentation process and no additional synthesis steps are required. The bacteria deposit the PHA polyesters in their cell structures as energy storage reserves, and the resulting polymers only need extraction and isolation.

The fermentation step in the production of PHA can be eliminated to reduce energy consumption

Biodegradable plastics are made from renewable and/or biodegradable resources, which enable a positive contribution towards sustainable products in their material and end-of-life phases. However, bioplastics can be more energy-intensive during their manufacturing phase than their conventional competitors. For example, the fossil fuel energy required to produce a kilogram of polyhydroxyalkanoate (PHA) is estimated to be between 50 and 59 MJ/kg.

The technology to produce PHA is still in development, and energy consumption can be further reduced by eliminating the fermentation step. This is because the fermentation step in the production of PHA is energy-intensive and can be a significant contributor to the overall energy demand of the manufacturing process. By eliminating this step, the energy consumption associated with the production of PHA can be reduced, making it a more sustainable option.

The use of alternative crops other than maize, such as sugar cane from Brazil, is also expected to lower energy requirements. For instance, the manufacturing of PHAs by fermentation in Brazil enjoys a favourable energy consumption scheme where bagasse is used as a source of renewable energy.

Overall, while biodegradable plastics have the potential to be more sustainable than conventional plastics, it is important to consider the energy consumption associated with their production. By eliminating the fermentation step in the production of PHA, as well as exploring alternative feedstocks and renewable energy sources, the energy consumption of biodegradable plastics can be reduced, bringing them closer to being a truly sustainable alternative.

Using alternative crops to maize, such as sugar cane, can lower energy requirements

Biodegradable plastics can be more energy-intensive to produce than conventional plastics. However, they are still considered to be more environmentally sustainable because they produce fewer greenhouse gas emissions over their lifetime.

In addition, biodegradable mulch is considered a promising alternative to polyethylene film for improving maize productivity in rainfed agricultural areas. Field experiments in China's Loess Plateau found that biodegradable films could achieve a higher crop yield than polyethylene films when the precipitation is more than 600 mm and less than 800 mm. This suggests that biodegradable films can be a more environmentally friendly option in certain climatic conditions.

Bioplastics produce fewer greenhouse gas emissions than traditional plastics over their lifetime

Estimates suggest that the fossil fuel energy required to produce a kilogram of polyhydroxyalkanoate (PHA) is between 50 and 59 MJ/kg. However, this does not take into account the feedstock energy, which can be obtained from alternative sources such as food waste or sugar cane from Brazil, which is expected to lower energy requirements. For example, the manufacturing of PHAs by fermentation in Brazil uses bagasse as a source of renewable energy, resulting in a favourable energy consumption scheme.

Overall, while bioplastics may require more energy during their production, they have the potential to significantly reduce greenhouse gas emissions over their lifetime, especially when produced with renewable energy.

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