Swiss biotech company AVA-CO2 has commissioned a pilot plant in Karlsruhe, Germany, to demonstrate its cleanphos process that recovers phosphorus from sewage sludge. First results will be made public later this year. AVA-CO2 is cooperating with two partners in the project: University of Hohenheim and the Project Group for Material Cycles and Resource Strategy at the Fraunhofer Institute for Silicate Research, both located in Germany.

The company said the technology could potentially be more efficient and cost-effective than existing phosphorus recovery methods. In the cleanphos process, municipal sewage sludge is converted into biocoal before the phosphate is isolated. Biocoal is formed by hydrothermal carbonisation (HTC) technology.

The process, said AVA-CO2, creates two commercially interesting products – fertilizer and phosphorus-free HTC-coal, or biocoal. In future, HTC-coal could be used as a substitute for lignite, or bituminous coal, which the company said would lead to substantial reductions in CO₂ emissions.

Burning lignite is a very polluting and CO₂-intensive means of electricity generation but is still the main technology in eastern Germany especially. Under plans notified in November 2015, Germany plans to close eight lignite-fired power plants between October 2016 and October 2019.

AVA-CO2 has been operating an industrial-scale HTC plant since October 2010. Subsidiary AVA Biochem uses HTC technology to produce hydroxymethylfurfural (4-HMF), a renewable alternative to petroleum-based materials which is used in specialty chemicals and pharmaceuticals.