Technical Development of Waste Sector in Sweden: Survey

MASTER’S THESIS IN ENVIRONMENTAL STRATEGIES RESEARCH
and handling and for safe use in land applications” (Golueke et al., 1955; Golueke,
1972; Diaz et al., 1993).
Composting is one element of an integrated solid waste management strategy that can be applied to
mixed municipal solid waste (MSW) or to separately collected leaves, yard wastes, and food wastes.
The four basic functions (Tchobanoglous & Kreith, 2002) of composting are (1) preparation, (2)
decomposition, (3) post-processing, and (4) marketing. Composting is a common waste treatment
technology for garden waste or organic waste fraction. Composting has some limitations like;
composting is suitable for organic or biodegradable waste, so that during the biological process it can
degrade waste as fertilizers. Huge land area is need for composting process and emission control is
hard to control in the process.
Anaerobic Digestion:
Anaerobic digestion (AD) is a biological process and achieved with the help of microbes in the
absence of oxygen. Anaerobic digestion usually takes place in an enclosed reactor with controlled
and favorable environment maintaining temperature, moisture content, pH value etc. In the chamber
biogas and compost residue are produced as a final product, while biogas can be used as fuel for
electricity, compost can be used as organic fertilizer based on nutrient content. Biogas; consists of
methane (ranging 55% to 70%) and carbon dioxide (CO 2 ) is produced from the process after 2-3
weeks. Anaerobic digestion is more preferred, as it has lower environmental impacts however, AD
needs special type of waste feed (organic waste) for the treatment process, which might be
problematic pre-sorting or recycling has not been done at household level. Only organic waste is
managed by anaerobic digestion process. AD with energy recovery facilities requires more waste
preprocess for better efficiency.
(ii) Thermal Waste Treatment Technology (Incineration)
Incineration is an advanced thermal process. Combustion process takes place at the presence of
oxygen at temperature of about 850 o C. Waste is then converted to flue gas carbon dioxide, water and
non-combustible materials called bottom ash. Flue gas is used to generate heat and electricity
through boiler and after cleaning the flue gas, gas is emitted to the atmosphere. Figure 8 shows the
schematic diagram of incineration process. The process produces heat and electricity, however in the
study total electricity conversion value is considered as the energy potential of the incineration
process. Therefore, total heat value of the process is converted as the energy value and due to similar
data output for two different treatment processes (P-G & Incineration) only electricity potentials is
considered for the study.
Depending on the thermal treatment process, volume pollutants are exposed to the environment.
Incineration primarily takes place at the presence of air which produces huge volume of CO 2 .
Incineration of MSW has two process stages, i.e. a) burning of MSW and b) cleaning of flue gas. In
the first stage, wastes are collected and stored in the refuse bunker. Wastes are then feed to the
refuse hopper through the crane and combustion takes place at the furnace. Flue gas and bottom ash
are produces from the combustion of MSW. The burnt-out grate slag (bottom ash) is discharged
KUNGLIGA TEKNISKA HÖGSKOLAN
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