Incineration and co-combustion of waste: accounting of greenhouse gases and global warming contributions

Abstract

Important greenhouse gas (GHG) emissions related to waste incineration and co-combustion of waste were identified and considered relative to critical aspects such as: the contents of biogenic and fossil carbon, N(2)O emissions, fuel and material consumptions at the plants, energy recovery, and solid residues generated. GHG contributions were categorized with respect to direct emissions from the combustion plant as well as indirect upstream contributions (e.g. provision of fuels and materials) and indirect downstream contributions (e.g. substitution of electricity and heat produced elsewhere). GHG accounting was done per tonne of waste received at the plant. The content of fossil carbon in the input waste, for example as plastic, was found to be critical for the overall level of the GHG emissions, but also the energy conversion efficiencies were essential. The emission factors for electricity provision (also substituted electricity) affected the indirect downstream emissions with a factor of 3-9 depending on the type of electricity generation assumed. Provision of auxiliary fuels, materials and resources corresponded to up to 40% of the direct emission from the plants (which were 347-371 kg CO(2)-eq. tonne( -1) of waste for incineration and 735-803 kg CO(2)-eq. tonne(-1) of waste for co-combustion). Indirect downstream savings were within the range of -480 to -1373 kg CO(2)eq. tonne(-1) of waste for incineration and within -181 to -2607 kg CO(2)-eq. tonne(- 1) of waste for co-combustion. N(2)O emissions and residue management did not appear to play significant roles.

Pyrolysis and gasification of meat-and-bone-meal: Energy balance and GHG accounting

“…In full-scale operations, provision of materials includes chemicals and substances employed in the flue gas cleaning system. As explained earlier, these include CaO, CaCO 3 , Ca(OH) 2 , NaOH, according to what reported by Astrup et al (2009) for waste incineration. In addition, for the technologies B and C using fluidized bed reactor, a provision of 130 kg of silica sand per Mg ww was included.…”

“…Astrup et al, 2009). In the UOD approach, GHG emissions were quantified per Mg of MBM treated and aggregated to provide separate global warming factors (GWFs) for direct and indirect contributions, as shown in Figure 1.…”

“…Preferably, a full life cycle assessment should be carried out; however, the needed process and emission data are not yet available in literature as most of the processes are still in lab and pilot scale testing. For waste management technologies focusing on energy recovery, GHG emission accountings are very good indicators of the overall environmental performance because most of the environmental impacts are related to the energy processes, and emissions such as CO 2 very well represent these processes Fruergaard et al, 2009). …”

Case Study: Regional Supply of Fuel to Cement Industry – Evalutaion of a Regional Waste Treatment

“…Fly ash is generally not utilized, while the bottom ash is utilized in many countries, in order to save natural aggregates [2; 7]. Bottom ash can for example, be used for road construction [2]. The fly ash is often placed in a landfill, which in the future could lead to leakage of hazardous substances, for example heavy metals, to the surrounding environment [8].…”

“…However, the fluidized bed incinerators may enable more efficient energy recovery compared to grate fired incinerators. [2] Incineration of solid waste, both in grate fired and fluidized bed boilers, produces slags and ashes, formed by inorganic content in the waste [6]. Bottom ash and slags are solid residues formed in the combustion chamber, while fly ash is particles separated in the flue gas cleaning equipment [6].…”