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12 Cards in this Set

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Composting

biological decomposition and stabilising of organic substrates

Aerobic composting

- most common type


-by-products of CO2, biomass, water and heat


-presence of oxygen increase micrbe growth rate 10 times

most common composting sysytems

- windrows


- static piles


- in-vessel

Windrows

-aeration is by natural convections due to temperature profile


-regularly mixed


-low cost but land intensive

Static pile

-aeration without disrupting pile.
-similar land usage

-aeration without disrupting pile.


-similar land usage

In- vessel

-plug flow of composted material with air  injection parallel.

-plug flow of composted material with air injection parallel.

Compost biology

1. mesophilic, thermophilic and maturation phases

1. mesophilic, thermophilic and maturation phases

Mesophilic phase

-mesophilic bacteria dominant (25-40 degrees)


-other organisms present

thermophilic phase

-thermophiic bacteria take over


- temperature rises at a slower rate



maturation phase

- temperature begins to decline


-mesophilic organisms dominate and finish composting process


-

Anaerobic digestion advantages

- no aeration cost


- less sludge production


- methane production

two stage treatment (Anaerobic)

1. acid forming bacteria(VFA formation)


2. methane production