Industrial symbiosis: turning wastewater into an agricultural resource


Since resource scarcity and waste management are among the biggest issues of the century, the Water2REturn project decided to tackle them by establishing an industrial symbiosis between three key industrial sectors: agriculture, food processing and wastewater treatment. By transforming waste from one industry into raw materials that are reinjected into the market for others, the initiative creates new resources while avoiding waste.

Water2REturn, coordinated by BIOAZUL in Malaga (Spain), is funded under Horizon 2020, the European Commission’s research and innovation programme. In addition, it addresses the aims of the Commission’s Circular Economy Action Plan, adopted in 2015, which Member States agreed on more ambitious objectives. The plan, by setting minimum requirements to boost the efficient, safe and cost-effective reuse of water, asks for further industry innovation.

In this circular economy perspective, Water2REturn turns slaughterhouses’ wastewater treatment facilities into “bio-refineries” that enable the recovery and recycling of nutrients. The integrated system consists of a combination of technologies and processes in cascade, maximising the extraction of valuable products.

The nutrients extracted are then turned into value added products for agriculture and the agro-chemical industry. Three different types of raw materials are extracted from slaughterhouses’ wastewater and can be customisable according to the needs of the end user: nitrate and phosphate concentrate, hydrolysed sludge and algal biomass. These can be processed further to make agronomic products, such as fertiliser and biostimulants, ready to be commercialised.

The initiative aims to reduce wastewater discharge by 90%, save up to 40% of fresh water in the meat industry, recover up to 95% of the nutrients contained in the wastewater, and produce up to 4.19% of total chemical nitrogen-based fertilisers consumed in the EU.

There are multiple benefits to this industrial symbiosis strategy: on one side, it answers the concerns of water scarcity and resource recovery and responds to the needs of the agricultural sector to become more sustainable and more competitive due to an added source of revenue created by the generation of by-products. Moreover, it resolves slaughterhouses’ wastewater management problems through product valorisation. On the other side, it also reduces the environmental impacts of food production and promotes further uptake of circular processes in the sector.

A demo plant is set to be installed at an active slaughterhouse called “Matadero del Sur”, in Salteras, near Seville. This prototype will have a treatment capacity of 50m3 per day (one-third of the slaughterhouse’s 150m3 daily wastewater flow), and will be integrated with a water line, a sludge line and an algae line.