Inventory analyses of dry and wet anaerobic digestion technologies for food waste management

Abstract

Dry anaerobic digestion (AD) has grown in popularity in recent years as an environmentally friendly form of food waste (FW) treatment. However, when compared to the wet AD, there appears to be a scarcity of information on environmental inventory evaluation. Therefore, the study aims to assess the life cycle inventory (LCI) of FW treatment in Malaysia through dry and wet AD plants and landfills. LCI entails identifying and quantifying all of the resources required for waste treatment, such as electricity, water, raw materials, and processed materials. In this study, all contaminants discharged into the atmosphere, including pollutant emissions into the air, soil, and water, and deficits arising from the inventory evaluation of FW treatment options were assessed. The system boundaries involve transportation, feedstock, biogas, electricity production, and bio-fertilizer processing. The scenarios for FW treatment were modeled and evaluated using the GaBi database and the functional unit is defined as the management of one ton of treated FW. The findings discovered the wet AD scenario depicts a drastic reduction in emissions of air (6.90E+01 kg) and freshwater (9.66E+03 kg) as compared to Scenario 1 (dry AD) and 3 (landfill). The number of pollutants generated from the analysis of Scenario 3, in which all waste is brought to a disposal site, indicates there is a massive exposure of air pollution (5.12E+03 kg) and freshwater contaminants (1.18E+06 kg) from landfills. Carbon dioxide and methane are the two most significant sources of emissions. To achieve a more accurate result, it is suggested by contrasting the value chain with the related studies conducted. Further, in the third phase of the life cycle assessment analysis, the life cycle impact assessment (LCIA), the statistics on elementary flows from the LCI are converted into environmental impact scores.