Waste is the future!

About me

I am a doctoral student at Aalto University's Water and Environmental Engineering department, working in collaboration with The Finnish Environment Institute (SYKE). Last year I received an expenditure grant from the Gasum Gas fund for the first year of research into cultivation of fungal species in biogas wastewater. My overall aim is to develop an environmentally friendly method of nutrient recycling from biogas wastewater into a valuable product (e.g. biogas feedstock, fertilizer). This should improve the economics and sustainability of biogas production by creating a more circular economy.

During the past year I have had some success growing three of the five fungal species tested. Significantly, one species is also able to reduce the pH of the wastewater. Reducing the need for chemical pH adjustment.

Fungal species growing in diluted biogas wastewater

The broader context

Sustainable use of resources is important for our continued survival. To this end, reuse of waste is vital. Current EU policy aims to increase renewable energy, thus biogas production is likely to increase. This digestion process produces a slurry rich in nutrients. Water is removed from the slurry and returned to the biogas process or pre-treated using chemicals and discharged. Only a few biogas plants are able to make nutrient concentrate from this wastewater, resulting in a lost opportunity. This study seeks to exploit the nutrients in an environmentally friendly way.

SYKE has been working on growing algae in biogas wastewater to recycle inorganic nutrients into valuable biomass. My role is to find fungal species that can also grow in the wastewater. Fungi use organic nutrients for growth and would improve total nutrient removal.

Preliminary results

So far growth of the fungi is limited. We noticed that the fungi, which are used to optimal lab conditions, need to be slowly accustomed to the harsher environment of the wastewater. However, when cultivated in wastewater in which algae had been grown, growth was greatly improved. Pictures taken with a microscope showed dead algal cells aggregating with the fungi. This should help solve the problem of harvesting algal cells which are very small and tend to float.

Further optimization is needed (wastewater dilution, pH control and acclimatization of the fungi). But initial results are very promising and I am eager to test more species.

What I enjoy most

I get very excited when my fungi grow and changing from biology to engineering has been challenging but rewarding. I have enjoyed my first year immensely and look forward to new discoveries!

Text: Danielle Bansfield