Materials to prepare the bio-based films were soy protein obtained as by-product of soy oil industry, chitosan obtained from the skeleton of crustaceans and agar obtained from marine seaweeds.
Results showed that manufacture is the most contaminant stage for chitosan and agar films, whereas the extraction of raw materials is the stage with the highest environmental burden for soy protein films.
A “cradle-to-grave” perspective was considered with systems studied including raw material extraction, film manufacture and end of life.
Environmental burden
Soybeans cultivation contributes to the environmental burden in the land use category due to the use of glycerol, considered as by-product from biodiesel production, as plasticizer.
However, the end of life stage is the least pollutant phase for bio-based films due to their biodegradable nature allowing composting.
The raw material extraction stage considered the environmental load attributed to the process of obtaining raw materials, taking into account the additives employed.
The manufacture section included the environmental load related to the process of turning raw materials into films.
The end of life study centred on the environmental burden in the disposal of the film after use.
For polypropylene (PP) films, the end of life scenario was divided into landfilling (58%), recycling (21%), and incinerating (21%).
Most pollutant phase
In the case of SPI films, the extraction of raw materials is the most pollutant phase in land use.
Glycerol used in the film manufacture causes considerable impact in land use due to the fact that it is considered as by-product of the soybean oil production to obtain biodiesel, so its cultivation is considered and the environmental impact associated to land use is significant.
For agar films, environmental burden associated to land use is related to glycerol and the impact in the fossil fuels stage is associated to the electricity consumption in the manufacture phase.
The study said that future improvements in the extraction processes and optimization of the manufacture would help to increase environmental advantages of the materials that could be potential sustainable alternatives to petroleum-based films.
Film manufacture
Based on the findings, the BIOMAT research team from the University of the Basque Country (UPV/EHU)’s Polytechnic University School, Donostia-San Sebastian manufactured a film for food wrapping based on renewable resources and that was 100% biodegradable/compostable.
The biofilm can be secure-sealed thermally to surfaces such as polyethylene terephthalate (PET).
Sealing and mechanical properties of the manufactured biofilm are maintained at low temperatures (-20 ºC), not becoming a rigid and fragile film like certain conventional films.
Source: Journal of Cleaner Production
“Bio-based films prepared with by-products and wastes: environmental assessment”
Authors: I. Leceta, A. Etxabide, S. Cabezudo, K. de la Caba, P. Guerrero