DEVELOPMENT OF FERTILISER FROM BREWERY WASTE: HINTS FROM THE ALGAEBREW PROJECT

The use of mineral fertilizers for crop production is an unsustainable approach, negatively impacting the environment, soil health, and fertility. The AlgaeBrew project addresses these linear economy-based practices by managing brewery waste, which otherwise is fated to become a catalyst for soil, water, and environmental deterioration. AlgaeBrew aims to use brewery wastewater and brewer’s spent grains to cultivate Nannochloropsis spp. to produce eicosapentaenoic acid (EPA) for aquaculture feed and agricultural fertilizer using the defatted microalgae. For fertilizer production, defatted microalgae were blended with spent coffee grounds (SCG) using 0.5% xanthan gum as a binding agent to produce nine formulations through the wet granulation method. The C/N ratio was estimated for each formulation, and the formulation with 50% defatted microalgae and 50% SCG was finalized (C/N: 11). Phytotoxicity tests were conducted to examine the toxicity of fertilizer by using Lepidium sativum, Sorghum saccharatum, and Sinapis alba. Compared to control OECD soil, in S. alba, a higher germination index (GI) was observed for 1.2%, 2.5% and 5% of fertilizer applications. Whereas a higher GI in L. sativum was observed for control,1.25%, 2.5% and 5% of fertilizer application, and in S. saccharatum, for 2.5%, 10% and 15% of fertilizer application. These results depict the positive effect of novel fertilizer on GI. Moreover, upon root length analysis, no significant differences were noted in the root length of all tested plant species grown in control soil and lower concentrations of fertilizer. Furthermore, this formulation was also able to increase the water-holding capacity of the soil. As this is an ongoing EU ERA-NETs - SUSFOOD2 project, new fertilizer formulations are being developed using other brewery waste. In the future, ecotoxicological tests involving soil fauna organisms and plant pot experiments will be carried out to assess the fertilizer’s effect on plant health and soil rhizosphere microbiome (i.e. bacteria and protists). In conclusion, the AlgaeBrew strives to emphasize on zero-waste generation, circular bio-economy and agricultural sustainability.