Starch, biodegradable plastics

All of these factors mean that production of PHA in plants will likely be more expensive than starch. However, considering that starch costs about 0.25 US /kg, even tripling the production cost of PHA compared to starch would make PHA in plants at least five times cheaper than PHA obtained from bacterial fermentation and most likely the cheapest biodegradable plastic made from renewable resources. 

Castronuovo D, Candido V, Margiotta S, Manera C, Miccolis V, Basile M, D Addabbo T (2005) Potential of a corn starch-based biodegradable plastic film for soil solarization. Acta Hort (ISHS) 698 201-206... 

Should all plastics that are made in the future be biodegradable Biopolymers, such as proteins and starches, are used to produce one type of biodegradable plastic. Find out more about biodegradable plastics. How are they made, and how do they break down What are the risks and benefits ... 

At this point little is known about the interrelationships between composition, structure, starch-degradation and physical disintegration properties of starch-plastic composites. Continued work towards development of a laboratory assay for biodegradability will eventually result in the establishment of a sufficient database to elucidate these relationships, allowing development of a host of starch-containing plastic products for both existing and new markets. 

Biodegradable plastics have been used on an industrial scale since the end of the 1990s when BASF launched Ecoflex . This is a fossil-based, man-made polyester but yet is completely biodegradable due to its chemical structure. This structure is also the reason why Ecoflex combines excellent mechanical properties with the good processability of synthetic thermoplastics. Ecoflex is the preferred blend partner for bio-based and biodegradable polymers, which typically do not exhibit good mechanics and processability for film applications by themselves. Ecoflex therefore is a synthetic polymer that enables the extensive use of renewable raw materials (e.g., starch). 

Bionolle is a typical biodegradable plastic. Currently, each raw material is made from petroleum, but we are developing more environmentally friendly green plastics. The first approach is to produce plastics from monomers such as succinic acid by biological methods. The second approach is to make hybrid compounds of Bionolle and natural resources like starch. The typical chain of materials for Bionolle is shown in Fig. 1. 

Tokiwa Y., Takagi S., Koyama M. Starch-containing biodegradable plastic and method of producing same. American patent US5256711 (1993). 

Starch offers several potential advantages as a raw material for plastics applications. It is annually renewable, obtained from a variety of plant sources and is a low-cost material. Interest in its use in biodegradable plastics is also driven by the inherent biodegradability of starch and the ubiquity of microorganisms capable of utilizing starch as a carbon source. 

One of the industrially available natural polymers for the manufacture of biodegradable plastics materials is starch. Starch is produced and stored by various types of plants. The differing properties of various starches result from their different proportions of amylose (linear starch chains) and amylopectin (branched starch chains). 

In 2006, there are around 30 major companies worldwide that are actively involved in developing biodegradable plastic materials. The synthetic biopolymers market is dominated by large, global and vertically integrated chemical companies such as BASF, DuPont, and Mitsubishi Gas Chemicals. The starch and PLA sectors contain mainly specialist biopolymer companies such as Novamont, NatureWorks, Rodenburg Biopolymers and Biotec, which were specifically established purely to develop biodegradable polymers. 

Starch-based biodegradable plastics are used for manufacture of various types of bags and sacks including, refuse sacks, shopping bags and compost bags. 

Biopolymer Technologies (Biop) offers a starch-based material containing an additive consisting of a vinyl alcohol/vinyl acetate copolymer. In 2005, the company transferred production of its bioplastics from The Netherlands to Schwarzheide in Germany and invested 7m in a new plant there, increasing its production capacity to 10,000 tonnes per annum. The announcement followed the decision earlier in 2005 by BASF to produce its Ecoflex biodegradable plastic, one of the components of Biop s Biopar resins, at the Schwarzheide site. 

Loose-fill packaging was one of the first successful areas of application for starch-based biodegradable polymers. Loose-fill starch-based foam is used for packaging consumer products as an alternative to polystyrene and polyethylene. While, biodegradable plastics have made some inroads into these markets, the future prospects for their growth in loose-fill are not so exciting as they are in some other areas of packaging. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

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