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Composting (Biological Conversion) (Process Description (1) Sorting (Trash…
Composting (Biological Conversion)
Aerobic Biological Conversion
Technical Parameters Concern
Temperature
The best degradation rates between 45 and 55° C
55° C maximize pathogen reduction but decrease the degree of microbial diversity
Aeration
Aeration provides oxygen to the aerobic organisms necessary for composting
Aerobic metabolism of microorganisms
To control temperature and remove the excess of moisture and gases
Moisture
Moisture content below 30-35% must be avoided since it causes a marked reduction of the microbiological activity and a premature end of the process due to exsiccation. Too much moisture should be avoided as it interferes with aeration by clogging the pores in the composting heap.
Carbon / Nitrogen Ratio
The optimal carbon/nitrogen (C/N) ratio in the starting material is around 25
A too low C/N ratio slows decomposition and increase nitrogen loss through ammonia volatilisation, especially at high pH and temperatures values.
A to high C/N ratio (>35) delays the process, since microorganisms must oxidize the excess of carbon until a more convenient C/N ratio for their metabolism is reached.
Anaerobic Biological Conversion
Paramater Factors
Temperature
Optimum at 35°C
Alkalinity and pH
pH – 6.8-7.3
Types of digester
batch, Fed-batch, continuous
Modes of operation
Modes of mixing
Anaerobic Digester
Reduces the pollution load of the waste
Anaerobic bacteria produce methane and carbon dioxide, both greenhouse gases
Methane is a gaseous fuel (natural gas) which can be burned directly or used to generate electricity
Digestion improves the fertilizer value of the waste
Treated effluent is less hazardous and easier to handle
Process Description
1) Sorting
Trash or other debris is removed from the wood or greenwaste
2) Grinding
Grinds wood and greenwaste
3) Composting
Windrows
4) Curing
Final stages of decomposition
5) Screening
Large chips is separated
Mohamad Saifullah Bin Abd Hamid 2017632158 Solid Waste 8B