3. Sanitary landfill with gas recovery (figure 5) or aerobically managed SWDS, is used to dispose 8% of global waste. These SWDS must have controlled placement of waste, as well as permeable cover material; leachate drainage system; regulating pondage; and gas ventilation system. Aerobically managed SWDS can recover >90% of methane to, either flare it or, use it to fuel industrial boilers; generate electricity; or to produce a substitute natural gas. In developing countries, this captured methane emissions can be turned into CERs (Certified Emissions Reductions) that are traded and sold to industrialised countries to meet their emission reduction targets. CERs, however, sold cheaply (€0.30/CER in 2019) and are no longer a compliance unit in the EU.
Aerobically managed SWDS equally avoid leachate leakage, although liners can be damaged beyond repair and leachate can still pollute the soil. Additionally, SWDS's land requirements are proving difficult to meet by land-strapped municipalities. Many countries are therefore moving away from landfills; the EU, for instance, is targeting a maximum landfilling rate of 10% by 2030.
Policies / measures / instruments to move forward:
- Regulation aimed at restricting the amount of landfilled waste
- Economic instruments to discourage landfilling
- Regulation aimed at promoting landfill alternatives such as recycling and energy recovery
4. Energy recovery (figure 6) is an alternative to landfilling for GHG emissions avoidance. It turns post-recycling waste into energy -be it heat, electricity or biofuels- using thermal (combustion), thermochemical (pyrolysis) or biological (anaerobic digestion) processes.
Combustion, the more common process in energy recovery, reduces GHG emissions, despite being a source of CO2. This is because only CO2 emissions resulting from oxidation of fossil carbon in waste (plastics, rubber etc) are considered net emissions, whereas CO2 emissions from biogenic carbon (ie paper, food and wood waste) are not. Methane emissions from combustion processes are the result of incomplete combustion (like in open burning) and hardly occur in controlled processes where combustion efficiency is very high. There are other emissions from combustion that don't affect global heating but air quality and they are trapped to nearly 99% with air pollution control.
Pyrolysis avoids GHG and polluting emissions since no combustion takes place, being the external energy-supplying system the only emission source of GHG in the pyrolysis plant. This makes pyrolysis the most environmentally friendly energy recovery technology, since anaerobic digestion still generates methane, and a residue that needs to be landfilled.
Energy recovery is a key step towards zero landfill. The IPCC calculates that "the maximum rate of incineration that could be implemented was 85% of the waste generated". This means that energy recovery alone cannot deliver a zero landfill solution - it's not a target either - and needs to work in conjunction with other waste management practices. Countries successfully implementing zero landfill are using a combination of recycling and energy recovery (figure 7), whereby the recycling rate is at 50+%.
Policies / measures / instruments to promote energy recovery:
- Regulation aimed at improving air quality
- Regulation aimed at promoting energy recovery
- Economic incentives to support waste-generated electricity
- Government support for construction of energy recovery plants combined with standards for energy efficiency
IN SHORT
GHG emissions and environmental degradation arising from current waste disposal methods can be avoided by introducing waste management practices and zero landfill policies achieved by means of energy recovery and recycling (figure 8).