Biodegradable plastic
As a result, Imperial Chemical Industries (ICI UK) successfully produced PHB at a yield of 70% using the strain Alcaligenes latus.
[9] Production efforts slowed dramatically due to the undesirable properties of the PHA produced and the diminishing threat of rising oil prices soon thereafter.
[9] In 1983, ICI received venture capital funding and founded Marlborough Biopolymers to manufacture the first broad-application biodegradable plastic, PHBV, named Biopol.
In 1996, Monsanto discovered a method of producing one of the two polymers in plants and acquired Biopol from Zeneca, a spinout of ICI, as a result of the potential for cheaper production.
[11] As a result of the steep increase in oil prices in the early 2000s (to nearly $140/barrel US$ in 2008), the plastic-production industry finally sought to implement these alternatives to petroleum-based plastics.
The biosynthesis of PHA is usually driven by depriving organisms of certain nutrients (e.g. lack of macro elements such as phosphorus, nitrogen, or oxygen) and supplying an excess of carbon sources.
[20] PHA can be further classified into two types: Polylactic acid is thermoplastic aliphatic polyester synthesized from renewable biomass, typically from fermented plant starch such as from maize, cassava, sugarcane or sugar beet pulp.
[27] Other biodegradable plastic processes such as polyethylene terephthalate (PET) have been found to release CO2 and water as waste products produced by the degrading microorganisms.
Petroleum-based plastics are derived from petrochemicals, which are obtained from fossil crude oil, coal or natural gas.
[31] Polycaprolactone has gained prominence as an implantable biomaterial because the hydrolysis of its ester linkages offers its biodegradable properties.
The French standard is based on the "OK compost home certification scheme", developed by Belgian certifier TÜV Austria Belgium.
A plastic is considered biodegradable if it can degrade into water, carbon dioxide, and biomass in a given time frame (dependent on different standards).
While oxo-degradable plastics rapidly break down through exposure to sunlight and oxygen, they persist as huge quantities of microplastics rather than any biological material.
[48] Therefore, products that are classified as “biodegradable” but whose time and environmental constraints are not explicitly stated are misinforming consumers and lack transparency.
Clear and accurate labelling is needed so that consumers can be confident of what to expect from plastic items, and how to properly use and dispose of them.
[50] On the other hand, composting of these mixed organics (food scraps, yard trimmings, and wet, non-recyclable paper) is a potential strategy for recovering large quantities of waste and dramatically increasing community recycling goals.
The use of biodegradable plastics, therefore, is seen as enabling the complete recovery of large quantities of municipal solid waste (via aerobic composting and feedstocks) that have heretofore been unrecoverable by other means except land filling or incineration.
[citation needed] They contain salts of metals, which are not prohibited by legislation and are in fact necessary as trace-elements in the human diet.
Oxo-biodegradation of low-density polyethylene containing a proprietary manganese-salt-based additive showed 91% biodegradation in a soil environment after 24 months.
[56] There is also much debate about the total carbon, fossil fuel and water usage in manufacturing biodegradable bioplastics from natural materials and whether they are a negative impact to human food supply.
They report making a kilogram of PLA with only 27.2 MJ of fossil fuel-based energy and anticipate that this number will drop to 16.6 MJ/kg in their next generation plants.
In contrast, polypropylene and high-density polyethylene require 85.9 and 73.7 MJ/kg, respectively,[67] but these values include the embedded energy of the feedstock because it is based on fossil fuel.
[64] Gerngross assesses that the decision to proceed forward with any biodegradable polymer alternative will need to take into account the priorities of society with regard to energy, environment, and economic cost.
Technology to produce PHA, for instance, is still in development today, and energy consumption can be further reduced by eliminating the fermentation step, or by utilizing food waste as feedstock.
"[69] Many biodegradable polymers that come from renewable resources (i.e. starch-based, PHA, PLA) also compete with food production, as the primary feedstock is currently corn.
ASTM International defines methods to test for biodegradable plastic, both anaerobically and aerobically, as well as in marine environments.
The specific subcommittee responsibility for overseeing these standards falls on the Committee D20.96 on Environmentally Degradable Plastics and Bio based Products.
In order to comply with the standards biodegradable plastic must degrade to a wax which contains no microplastics or nanoplastics within two years.
[78] Similarly, a study conducted in 1999 investigated how the oil seed rape plant can be genetically modified to produce PHBVs.
Previous research indicated that both Rre37 and SigE proteins are separately responsible for the activation of PHB production in the Synechocystis strain of cyanobacteria.
