Bioplastics from sewage

The first kilogram of PHA, which is made from sewage by bacteria, was recently presented in the Netherlands. This completely biodegradable plastic is the result of a pilot project that offers many industrial opportunities and environmental benefits. A similar project has been running for some time in Brussels.

North Brabant

A trial during the Phario project, which took place at the Bath sewage treatment plant in the Dutch district of Rilland, shows that it is possible to obtain new and sustainable raw materials from sewage. Sludge, which is the residual product from the purification of sewer water, can be converted in this way into a durable product: fatty acids are filtered from the sludge and mixed with bacteria that convert them into biopolymers, which form the basis for bioplastic. Although it was a small-scale trial, it was the first time this technique had ever been used.

In this way, the Dutch water boards (local government bodies responsible for water management in their areas) and their partners showed that PHA can be produced and marketed successfully on a production scale. This test also gave them considerable practical knowledge and experience about the market for bioplastics. There is a study underway to see how much demand there is and what buyers are willing to pay for bioplastic products compared to plastics made from petrochemicals. The first batch must in any case demonstrate the quality that can be achieved.

At present, several kilograms per week are produced, but this can be scaled up to 2,000 tonnes per year.

Brussels

A pilot system at the Aquiris water treatment plant in Brussels has been successfully been turning waste water into bioplastic since 2010. This sewage treatment plant also used bacteria for producing biopolymers. The plant claims that the sewage from the 1.1 million people of Brussels could potentially produce some 20,000 tonnes of bioplastics per year. After the pilot project Aquiris will work with investors to scale-up the project.

PHA’s potential

PHA (polyhydroxyalkanoate) is an environmentally friendly material that degrades under natural conditions within a year, unlike petroleum-based plastics, which need several decades to decay. The material is quite expensive to produce conventionally. But by letting bacteria make it from waste water, the cost of production should fall.

The market for PHA is growing steadily. At the moment, PHA is used, amongst other things, to make surgical suture threads, for consumer product packaging and for agricultural plastic. Worldwide demand for PHAs is expected to grow. In time, PHA may even contribute to a solution for the 'plastic soup' accumulating in the oceans.

An additional advantage of bioplastic, which is made of sewage by bacteria, is that it does not compete with food production. Conventionally-produced PHA bioplastic, however, does as it is made from agricultural products.

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