Impact of physical pre-treatment of source-sorted organic fraction of municipal solid waste on greenhouse-gas emissions and the economy in a Swedish anaerobic digestion system

Importance of food waste pre-treatment efficiency for global warming potential in life cycle assessment of anaerobic digestion systems

“…In this study, the biomass intended for the biogas production was the slurry and the composition was set according to the mass transfer coefficients presented in Table 4. The default BMP value calculated from the composition was 373 ml CH 4 /g VS which was significantly lower than similar biomass BMP determined in laboratory batches (Carlsson et al, 2015;Davidsson et al, 2007). The original C bio and values were therefor adjusted to give a higher BMP value in the result, estimated at 514 ml CH 4 /g VS.…”

“…For the fifth scenario -80 high TS, a case with higher TS concentration of the slurry (15% TS), corresponding to less water addition during digestion, was modeled. In a systems perspective, this means less energy consumption of the slurry digestion and digestate transportation processes, which was shown to have a high impact in a previous study (Carlsson et al, 2015).…”

“…The reference case is reflected in scenario 80 ref and corresponds to high efficiency and performance level achieved today. Following Carlsson et al (2015); 80% of TS was recovered in the slurry, TS content in the slurry was 10% and the slurry contained low amounts of contaminants, allowing the digestate to be applied on land (corresponding to the "good" slurry quality). For the less efficient pre-treatment -scenario 70-10% more of initial waste TS was refused assuming the slurry composition did not change and the quality was still "good".…”

“…In practice, modelling of the pre-treatment depends on the modelling tool and data available and thus differs between studies (Carlsson et al, 2015;Naroznova et al, 2013). As reflected in Naroznova et al (2013), modeling in EASETECH is mass-balance based and requires transfer coefficients for each material fraction to be specified.…”

“…It is, however, of importance to investigate the environmental impacts of different efficiencies and the possible consequences on the AD system. Previous LCA studies investigating the environmental impacts of FW pre-treatment efficiency have come to different results regarding the impact of losses of organic material to refuse (Carlsson et al, 2015;Naroznova et al, 2013). These studies were performed as case-studies with special focus on Swedish and Danish conditions, respectively, and were performed using different approaches for modelling marginal heat and electricity.…”