Composting and compost utilization: accounting of greenhouse gases and global warming contributions

Abstract

Greenhouse gas (GHG) emissions related to composting of organic waste and use of compost was assessed from a waste management perspective. The GHG accounting for composting includes use of electricity and fuels, emissions of methane and nitrous oxide from the composting process, and savings obtained by the use of the compost. The GHG account depends on waste type and composition (kitchen organics, garden waste), technology type (open systems, closed systems, home composting), the efficiency of off-gas cleaning at enclosed composting systems, and the use of the compost. The latter is an important issue and is related to the long term binding of carbon in the soil, to related effects in terms of soil improvement and to what the compost substitutes; this could be fertilizer and peat for soil improvement or for growth media production. The overall Global Warming Factor (GWF) for composting therefore varies between significant savings (-900 kg CO 2 -equivalents tonne -1 wet waste (ww)) and a net load (300 kg CO 2 -equivalents tonne -1 ww). The major savings are obtained by use of compost as a substitute for peat in the production of growth media. However, it may be difficult for a specific composting plant to document how the compost is used and what it actually substitutes for. Two cases representing various technologies were assessed showing how GHGs accounting can be done when specific information and data are available.

Determination of the energy and environmental burdens associated with the biological treatment of source-separated Municipal Solid Wastes

“…This is the case of the AD plant, which is beneficial in terms of energy production, but it will be penalized by the refuse transport to a landfill and its decomposition due to greenhouse gas emissions. Also, compost utilization has a beneficial effect 46 on those plants with the higher productivity per mass of OFMSW. However, in this work, LCA is only used to demonstrate that a new functional unit should be used in the assessment of the environmental impact of the biological treatment of source-separated P r e -p r i n t…”

Material Resources, Energy, and Nutrient Recovery from Waste: Are Waste Refineries the Solution for the Future?

“…The refinery process comprised two reactors: in the first reactor waste was heated by injection of hot water to about 75 °C for approximately 0.5-1 hours, then cooled to about [50][51][52][53][54][55] °C before entering the second reactor where enzymes were added (about 5 kg t -1 MSW) resulting in hydrolysis and break-down of bonds in the organic materials, thereby suspending organic materials in the liquid phase (44). The retention time was about 10-16 hour.…”

Anaerobic degradation of municipal organic waste among others composting techniques improves N cycling through waste-soil-plant continuum

“…The remaining part is stable organic matter that have been reported to have the potential of binding C with soil when applied on land for 100-1000 years resulting in considerable reductions of CO2 emissions to the atmosphere (Boldrin et al, 2009;Favoino and Hogg 2008). Therefore, it can be concluded that ANC con- …”

“…For such waste, optimized biological processes or means for waste reduction, reuse and recovery would be preferable. These processes convert the green waste or food leftover in to organic fertilizers such as compost (Favoino and Hogg, 2008;Hargreaves et al, 2008b;Boldrin et al, 2009Kumar, 2011) that may fulfill the increasing demand of chemical fertilizers for crop production in Pakistan, which is about 13% annually (Pakistan Bureau of Statistics, 2016).…”