Life cycle assessment of biowaste treatment – Considering uncertainties in emission factors

Abstract

The present paper provides an environmental assessment and ranking of different treatment options for the organic fraction of municipal solid waste (OFMSW), which is a biowaste that typically contains food- and green-waste. The main biochemical treatment systems for OFMSW are composting (by-product: fertilizer) and anaerobic digestion (by-products: biogas and digestate), which are often combined in practice. Total impact scores as evaluated by means of Life Cycle Assessment (LCA) with the Ecological Scarcity Method range from 8 to 31 eco-points for Germany (EPG) per kg treated OFMSW with “Global Warming” and “Main Air Pollutants” (such as NH3) as main environmental impacts. In spite of significant uncertainties in the available emission data, the subsequent application of a Monte Carlo Analysis provides a robust ranking of the treatment systems. The analysis reveals that the transportation distance is a crucial factor to increase the ecological benefit of an OFMSW treatment system. Consequently, decentral structures with short transportation distances (e.g. 17 km) as well as an optimal plant operation mode are more important to reduce emissions than the choice of the treatment system itself. Further research should focus on monitoring campaigns to generate better representative operational datasets for the different types of OFMSW treatment plants such as plug-flow or batch digestion systems as well as for the composting technologies.

Keywords

• Life cycle assessment
• OFMSW treatment
• Anaerobic digestion
• Biogas
• Ecological scarcity method
• Monte Carlo analysis