POST-PURPLE · Prevention, correction, and valorization of exhaust flows from urban photobiorefineries

The challenge of promoting zero waste and zero pollution strategies in industrial sectors still lacks optimal technological solutions. In the EU, waste management is an essential part of the transition towards a circular economy . In the case of urban biorefineries , their problem is doubled because their feedstock is the waste itself. It is important to remark that in Europe there are more than 26,000 urban wastewater treatment plants (WWTP) that process wastewater from 539 million inhabitants , and more than 5,800 municipality waste treatment plants dealing with the organic fraction of the municipally solid waste (OFMSW) to treat about 229 thousands of tonnes . The urban biorefinery sector represents a significant source of greenhouse gas (GHG) emissions. In the waste sector, landfills and wastewater make up about 20 % of global methane anthropogenic emissions . Furthermore, the sector of wastewater treatment accounts for 0.8% of the total energy use in the EU and was responsible, in 2018, for 0,86% of the total EU GHG emissions. Most of these off-gases (CO2, NOx, CH4, VOCs and NH3) are discarded into the atmosphere or treated in conventional purification plants to avoid emissions but generate a new waste. Nearly 8% of global anthropogenic GHG emissions are N2O and WWTP account for 3.2% of this figure. Regarding solid waste treatment, most of 35 % of the organic fraction is typically discarded without being reused. In this context, achieving zero pollution and zero emissions represents a significant challenge, highlighting the need for environmentally and circular-oriented technologies. While bio-based technologies have made considerable progress in advancing circularity, the standardization and validation of processes that convert waste into valuable products beyond composting are still in development. Current technologies like biogas and biofuel production, bioplastics, biopolymers, nutrient recovery, and biochar production illustrate the successful integration of circular approaches. However, further R&D is needed to enhance these technologies, increase scalability, and boost their market integration within the circular economy. In POST-PURPLE project, innovative biobased technologies will be developed to fully realize the valorization potential of urban biorefineries’ waste. This will enable the production of high-value products such as carotenoids, Ω-3, coenzyme Q-10, microbial proteins, and fortified irrigation water. Additionally, these technologies aim to reduce diffuse emissions and optimize the treatment of wastewater and OFMSW in urban biorefineries. POST-PURPLE offer a promising battery of solutions to reduce exhaust gas flows, vapors, and odors, as well as to minimize diffuse emissions to air and water. Our technologies will transform gas, solid and liquid waste into valuable resources, supporting a zero-waste strategy and a zero-pollution goal. Ultimately, POST-PURPLE will make a step change in the enhancement of the sustainability of urban refineries minimising their environmental impacts. The solutions developed will aim: 1. to capture up to 95% of CO2 (108.3k Tonnes of CO2eq/year, considering the implementation of POST-PURPLE solutions in the industrial-scale plants in WWTPs and OFMSW plants with AD), N and P as well as to get a reduction of up to 90% of VOCs and NH3 emissions. 2. To convert more than 95% of the solid rejects of OFMSW into circular biochar (3,5 Ton/year) and syngas (10,5 Ton/year). 3. to produce novel added-value products from urban wastes, such as food-grade microbial protein (1.25 kg/Ton OFMSW), carotenoids (3.7 kg/Ton OFMSW), Ω-3 fatty acids (2.3 kg/Ton OFMSW), Q-10 coenzyme (10 g/Ton OFMSW), green methanol (71 kg/m3Biogas), organic fertilizers (0.2 kg/m3WW), and irrigation water (0.65 m3/m3WW)