Environmental assessments of biological treatments of biowaste in life cycle perspective: A critical review

Abstract

Municipal biowaste is a major environmental issue. Life-cycle assessment is a valuable tool to assess recycling options, and anaerobic digestion and composting have performed adequately. However, reviews indicate several discrepancies between studies. Thus, we critically review 25 life-cycle assessments of the composting and anaerobic digestion of municipal biowaste. Our objective is to identify decisive factors, methodological gaps and processes that affect environmental performance. We generally identified methodological gaps in expanding systems borders. In energy systems, the replaced energy source did not consider power generation or dynamic regulation. All studies adopted mixed energy sources or marginal approaches. Agroecosystems included the carbon sequestration potential and compensation for the production of synthetic fertilizers only. A limited range of scientifically proven benefits of compost use has been reported. In general, studies provided a limited account of the effects of use on land emissions, but contradictory assumptions emerged, mainly in modelling synthetic fertilizer compensation. Only three studies compensated direct emissions from the use of synthetic fertilizers, and none included indirect emissions. Further studies should include an analysis of the additional benefits of compost use, compensate for the effects of emissions from synthetic fertilizer use on land and mix attributional and consequential approaches in energy system expansion.

Environmental impact assessment of organic fraction of municipal solid waste treatment by anaerobic digestion in Sri Lanka

“…Similar to the observations of Vieira and Matheus (2019), we observed that fugitive methane emissions and digestate generation were major environmental concerns in this study. Therefore, direct gaseous emissions and the discharges of nutrients from liquid slurry need to be minimized.…”

“…Vieira and Matheus (2019) showed that anaerobic digestion displayed the best environmental performance due to its precise anaerobic conditions and methane caption. In analysing seven different municipal food waste systems in Australia, Edwards et al (2018) found that anaerobic digestion-based systems had a better environmental performance for global warming potential compared to composting and landfills.…”

Comparison of local and centralized biowaste management strategies – A spatially-sensitive approach for the region of Porto

“…In most of these studies, GHG emissions are usually most favorable for AD, followed by incineration or composting and finally landfill as the worst option (Bernstad and La Cour Jansen, 2012;Morris et al, 2013Morris et al, , 2017. Depending on the country and the methodology, detailed study results vary significantly, reflecting the dependencies of GHG emissions on local conditions such as the city layout, carbon intensity of the electricity grid (Vieira and Matheus, 2019) and potential carbon credits from (productive) land application. Salemdeeb et al (2018) found that, for current electricity grids, incineration can achieve even more negative emissions across the life cycle than AD with composting generating net positive emissions.…”

Economic and Ecological efficiency with respect to Waste Treatment Policies: Literature Review

“…Here the focus is on minimizing costs of collection, input costs for firms and transportation costs (Berglund 2003). The life cycle analysis has been employed to this issue (Bernstad & Jansen 2011;Brogaard & Christensen 2016;Finnveden & Ekvall 1998;Finnveden et al 2000;Hansen et al 2006;Hauschild et al 2013;Maria & Micale 2015;Sharma & Chandel 2017;Vieira & Matheus 2019).…”