Many bio-plastic bags have no place in the garbage. They dissolve too slowly in oxygen-deficient environments like biogas plants and when incinerated they are a burden to the environment. A research project at the Austrian Centre of industrial Biotechnology (acib) hunts for enzymes, which accelerate degradation and avoid emissions. The aim is to reduce plastic mountains and replace conventional packaging by bio-based polymers.
Only very few know it and we all do it – bio-plastic bags have no place in organic waste collection bins. According to DIN standard EN 13432 biodegradability means that, after a fixed period of time, 90 % of a material have degraded to water, CO2 or biomass under defined temperature, oxygen and humidity conditions in the presence of bacteria or fungi.
Lately, part of the bio-waste in plastic bags has been introduced into biogas plants where anaerobic conditions (oxygen-deprived environment) generate biogas as a valuable energy source. “Under these circumstances bags from certain polymer types can only be degraded very slowly.
The bio-waste cannot be set free and the process is disrupted”, says Doris Ribitsch, scientist at the Austrian Centre of Industrial Biotechnology (acib). Together with a team in Tulln, she addresses the question if the decomposition of plastic labelled as bio-degradable such as customary bio-waste plastic bags, food packages or mulch foils could perhaps also work in fermentation plants.
Botox in Bio-sludge
First the scientists did some in-silico research. “We screened thousands of entries in an enzyme database to identify certain bacteria, which produce specific enzymes for the degradation of plastic”, says Ribitsch. After some years they were successful. “The bacterium Clostridium botulinum whose proteins are also present in Botox meets all requirements”, declares the scientist, “and small quantities of it are also present in bio-sludge”.
In order to enable the enzymes of bacteria to degrade plastic under anaerobic conditions in a large area, considerable engineering efforts are necessary.
In cooperation with ETH Zurich acib produced an optimized enzyme variant, which was introduced into a biogas testing plant. Up to this time there had been no information on how enzymes from this anaerobic microorganism work and so the scientists developed a method to measure the degradation process of polymers.
First experiments proved to be promising: the enzymes optimized in the lab scattered on the polymer layer and stimulated the degradation process. “Like a large shear they cut the long polymer chains in shorter and shorter pieces until only monomers, the smallest molecular parts, are left. These monomers are then metabolized by microorganisms. Thus, the plastic bags can completely be degraded and converted to valuable biogas together with the bio-waste”, explains Ribitsch.
Considering that about 12% of the worldwide plastic waste (about 45 million tons per year) are incinerated, this new process could mean a turning point for the permanent degradation of plastic. A subsequent project with a company partner is just about to start and two patents have already been filed.
Plastic from Renewable Resources
The new method is, however, only an intermediate step on the ecosensitive route to a plastic-free life. “As long as biologically degradable plastics cannot be recycled and reused properly the most reasonable solution is to gather them in biogas plants together with biogenic waste. Thus, the generated energy can at least be used for electricity, heating or bio-methane.”, says Ribitsch. In the long run the project results are expected to replace conventional packaging by bio-based polymers (from renewable resources), which degrade within some days. This would mean to close the carbon cycle and to avoid plastic waste.
If you are now worried that these new plastic bags will decompose on your way home from the shop rest assured. “To decompose they still would need the conditions of compost pile or a biogas plant”, says Ribitsch. No danger for your groceries – and for the environment either, that’s the plan.
Photos available without fees at:
Give credits to "FELMI Graz"
MA Martin Walpot | idw - Informationsdienst Wissenschaft
Complete skin regeneration system of fish unraveled
24.04.2018 | Tokyo Institute of Technology
Scientists generate an atlas of the human genome using stem cells
24.04.2018 | The Hebrew University of Jerusalem
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
25.04.2018 | Physics and Astronomy
25.04.2018 | Materials Sciences
25.04.2018 | Studies and Analyses