Graphic: Eco-efficiency portfolio of various biowaste treatment processes (Ecology Index < 0 means environmental relief; Ecology Index > 0 means environmental impact; Cost Index: standardization of process-specific costs at the maximum value).
Compared biowaste treatment processes: (1) Composting, open | (2) Composting, closed | (3) Composting, partially closed | (4) Fermentation, batch process | (5) Fermentation, plug-flow process | (6) Wet fermentation | (7) Waste incineration plant | (8) Composting, membrane process.
Result: With good management of anaerobic digestion and composting plants, the environmental differences between the treatment alternatives – except for open composting – are small. Composting by encapsulation with a semi-permeable membrane cover (8) has the lowest ecology index and is therefore the process with the highest environmental impact when considering average plant operation, but is close to closed/partially closed composting and plug-flow/wet fermentation.