Bokashi : köksavfallshantering utan växthusgaser?

Abstract: EM Bokashi is a fermentative treatment used for kitchen waste, branded as a climate friendly alternative to compost with low or no greenhouse gas (GHG) emissions. This study aims to examine if these claims are true. This was done by examining if adding of Effective Microorganisms (EM) reduces GHG emissions (CO2, CH4 and N2O) during the fermentation phase of Bokashi. Additionally, a literature review over EM Bokashi was made to compare with household composts emissions. The experimental setup was three lines with four replicas, comparing adding of EM, adding of autoclaved EM and a blank with only kitchen waste added. Bokashi buckets were installed with gas ports in the lids for vial sampling. Samples was analysed for CO2, CH4 and N2O concentrations with gas chromatography. Additionally, C and N content, weight loss and moisture were measured together with leachate pH. The results show no significant difference between the treatments in total emissions. However, a trend for lower N2O emissions with EM Bokashi treatment was observed, and during the resting phase CH4 was significantly lower compared both to the Autoclaved and Control treatment. The review gave insufficient information to draw any conclusions of GHG emissions compared to compost. The fermentation phase release relatively low CH4 emissions, but the last step of Bokashi, (the soil factory step) have not been studied. That step is where the main degradation occurs, and therefor theoretically the step with the highest risk for GHG emissions. CO2 emissions seems to be similar for EM Bokashi and compost.