valuable materials. Local governments are addressing these challenges through a
variety of strategies, as listed in this section, to divert waste from landfills and
recover and repurpose valuable and/or toxic materials.
ANAEROBIC DIGESTION
Microorganisms are used to break down biodegradable material and sewage
sludge in the absence of oxygen.
Pros
■ It is a renewable energy source.
■ Systems can either be located at sources of biowaste (e.g., large farms) or
at centralized facilities.
■ It reduces or eliminates the energy footprint of waste treatment plants.
■ It reduces the methane emission from landfills.
■ Nutrient-rich digestate (leftovers) can be used as fertilizer.
■ It is suited for organic material and is commonly used for industrial
effluent, wastewater, and sewage sludge treatment.
■ It reduces the amount of organic matter, which might otherwise be
destined to be dumped at sea (by some countries) or in landfills or burned
in incinerators.Cons
■ Systems are expensive if installed on individual farms.
■ There are transportation and additional labor costs if farmers need to
transport biowastes to a centralized facility.
■ Nutrient conservation may be undesirable on a farm with excess nutrients
to manage.BURNING, INCINERATION, OR ENERGY RECOVERY
Incineration is a waste treatment process that involves the combustion of
substances contained in waste materials. Incineration of waste materials converts
the waste into ash, flue gas, and heat. The United States incinerates 15% of its
wastes whereas France, Japan, Sweden, and Switzerland incinerate more than
40% of their wastes and use the heat to generate electricity.