The bioeconomy is a hot topic these days, right up at the top of policy agendas. It involves using renewable natural resources as a raw material. The circular bioeconomy introduces circularity into this concept: using what would otherwise be thrown away, using spent biological resources to regenerate ecosystems and minimising waste.

The ECESP website has a good selection of circular bioeconomy-themed content. This series will shine a spotlight on it.

Circular bioeconomy concept: biochar from sludge, for use in agriculture and other sectors

Bioforcetech: Phosphorus recovery from sewage sludge and organic waste: 

Bioforcetech aims to reduce energy and labour costs while reducing emissions and generating by-products (fertilisers) with added value. The company's vision is simple: instead of transporting "waste", machines are designed to transform organic streams into renewable energy and biochar right at the wastewater plant.

The process developed by Bioforcetech fits into the sludge treatment chain, with the Biodryer for biodrying and P-series pyrolysis. The two technologies can be installed independently, but the combination of the two processes guarantees an overall treatment with a net-zero energy approach.

The Biodryer uses the bacteria present in the sludge to produce heat, with about 75% reduction in volume, thus reducing the transport needed to dispose of the sludge to about a quarter, with a proportional reduction in pollution. Pyrolysis is a decomposition of organic material through the application of heat, from 350°C to 900°C, without adding oxygen, from which two co-products are obtained: synthesis gas and biochar.

The synthesis gas is combusted to obtain hot water that can be used to power the drying process, thus making both processes self-sustainable. The end result is OurCarbon®, biochar which is all that remains of the solid component of sludge. It is rich in segregated carbon and free of pollutants and pathogens and can be used in a wide variety of areas.

Results:

• With the treatment of - say - 7 000 tons per year, 400 trips by truck have been avoided, the sludge has been reduced to 560 tons/year and transformed into biochar, with 90% of the phosphorus recovered.
• The product can be used in agriculture and other sectors; it can even be used to enhance concrete.
• The process destroys harmful pollutants, including PFAS.
• Biochar sequesters carbon in the soil, as well as improving the soil itself.