Paper milling wastewater

The pulp and paper industry are ranked as the third world’s largest consumer of water and, consequently, produces high amounts of organic rich wastewater. It is, however, the sixth largest polluter in the world after the oil, cement, leather, textile, and steel industries. The environmental impact of pulp and paper industry is of particular concern since the industry emits a variety of gaseous, liquid, and solid wastes to the surroundings. Although efficient wastewater treatment systems combined with biogas production are available in paper industry, the environmental impact of organic fraction is still significant. This is because approximately five liters of water are being released into rivers per each kg of recycled cardboard. In addition, little is known on the efficiency of the current systems to eliminate the toxicity attributed to the presence of organic compounds. Nevertheless, an interesting opportunity can emerge from these wastes if they can be converted into value-added by-products.

Literature studies have shown the potential of paper mill side stream as a source of suitable carbon that could be upgraded to PHAs. Some systems based on pure cultures are able to accumulate up to 90% of PHA and are available at industrial level, but this is only based on high values and pure substrate and not from paper mill waste streams. The use of mixed cultures (MMC) can be an alternative to pure culture, but still present drawbacks, such as, lower PHA content than those achieved with pure cultures, non-homogeneous distribution of PHA content in cells, and difficulty to implement the PHA production systems in the already existing wastewater treatment plants facilities. Moreover, toxic solvents (e.g. chloroform, methanol) are often used in MMC, resulting in high production costs while contributing a negative impact to the environment. Therefore, the development of more economical and environmentally friendly downstream processes is critical.

INGREEN will provide sustainable pilot scale integrated biotechnological plants and protocols validated in industrial environments to produce safe biomasses enriched in PHA from paper mill to be used as prebiotics for animal and as promising alternative to conventional plastic for the packaging industry. As there is limited knowledge on the application of PHAs as polymer for packaging industry, INGREEN will provide a sustainable exploitation route of PHA enriched biomasses alternative to conventional biodegradable plastic production. In addition, INGREEN processes and production methodology will enhance anaerobic fermentability and biomass storing accumulation capability compared to the competing ones. Thermal Hydrolysis at specific temperature will enhance biodegradability of paper milling biomass and release sugar/starch and volatile fatty acids (VFAs) needed for subsequent fermentation processes. The obtained VFAs is required as precursors to the conversion to PHB/PHV/PHA. For safe environmental impact, INGREEN will improve the downstream phase by reducing the use of toxic solvents to achieve a more economic and eco-friendly procedure to fully exploit the potential of paper mill side streams for the sustainable production of well characterized PHA with high purity grade