Conversion of diluted mixed urban bio-wastes into sustainable materials and products in flexible purple photobiorefineries


The EU generates almost 140 million tonnes of urban biowaste every year. Around 75 percent of this is sent for incineration or landfilled and has a major environmental impact. It is also a lost opportunity as much of this waste has the potential to be recycled. The main reason why the various waste streams are not recycled is that current methods of valorisation has a low performance, a high carbon footprint and most nutrients are dissipated. The waste streams are also highly heterogeneous and diluted, meaning that efforts to separate them at source are difficult.

In an effort to address this challenge and recover the potential from these urban wastestreams, DEEP PURPLE project aims to demonstrate a method of transforming diluted urban bio-wastes, including mixed waste streams, the organic fraction of municipal solid waste, waste water and sewage sludge into a sustainable source of feedstock for various bio-industries.

It will use an innovative approach, implemented by using a novel Multi-Platform Biorefinery Concept (Biomass, Cellulose and Biogas). This will replace current destructive and polluting practices.



The overall objective of DEEP PURPLE is to develop and demonstrate the viability of the concept of a versatile, integrated and flexible multi-platform biorefinery capable of extracting and recovering high added-value compounds from urban waste streams.

Within this, DEEP PURPLE has a number of specific objectives.

  • It will reduce the amount of waste currently going for incineration or landfilled, by recycling and re-using almost 60 percent of the primary sludge and nearly 85 percent of the secondary sludge produced at a wastewater treatment plant.
  • It will attempt to reduce the amount of organic waste going to landfill, by converting the biogas that can be produced by the organic fraction into high-added value products such as ectoine.
  • It will develop a range of bio-based products – slow-release fertilisers, polyesters for film applications, packaging applications, cosmetics and a ‘self-healing’ additive for concrete, all of which will offer improved environmental performance.

DEEP PURPLE aims to deliver a number of impacts. It seeks to:

  • Establish new interconnections between companies and other sectors to build new value chains. These will feature actors that have not previously worked together in a value chain and is likely to see cooperation between waste management companies and those in the fields of packaging, construction, fertilisers and cosmetics.
  • Develop five new bio-based value chains which will involve developing industrial symbiosis models between municipal waste managers and end users in three different sectors.
  • Demonstrate the viability of converting the bio-based intermediate products obtained into five consumer-oriented products. These will have greater overall sustainability than existing alternatives, will perform as well and will meet a clear market demand.

Project achievements & milestones

Alkalinity is the key parameter for treatment of domestic wastewater
Resources, 20 July 2020
DEEP PURPLE's latest article shows that the efficient treatment of domestic wastewater by purple phototrophic bacteria is determined by alkalinity. The study contrasted it to the oxidation state of the organic material. Read article