The BIOTECH Plants
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Institutional level BIOTECH plant (left) and market level BIOTECH plant (right). Source: HEEB (2009) |
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| The BIOTECH Roadshow. Source: F. HEEB (2009) |
BIOTECH is a nodal agency of the Ministry of Non-Conventional Energy Sources in Kerala, South India (MUELLER 2007). BIOTECH has been developing and installing biogas plants that generate biogas from domestic biodegradable waste like cooked food waste, vegetable waste and waste water from kitchen (1 m3 for a 3 to 5 member family meets about 50 % of cooking needs, MUELLER 2007) (see picture above). BIOTECH has also developed reactors for the decentralised anaerobic digestion of organic market waste or municipal solid or slaughterhouse waste. The electricity generated from the decentralized plants for market wastes is used for street lightning and distributed to households.
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| Schematic plan of a BIOTECH market level plant. The sketch is not drawn to scale, but the proportions have been considered as far as possible. a) Inlet tank for feedstock. b) Digester tank. c) Effluent tank. d) Effluent storage tank. e) Effluent pump. f) Gasholder drum. The drum is stabilized by a guide pole in the middle and is floating in a water jacket outside the digester. g) Biogas pipe. h) Gas Scrubber. i) Biogas generator j) Drainage connection for excess effluent Source: HEEB (2009) |
As the ARTIs, the BIOTECH market level plants are based on a floating-drum design including a recirculation loop to optimise moisture content (HEEB 2009). The feedstock (often market wastes) is put in the inlet tank from where it is flushed into the main digester tank for anaerobic digestion (3 m diameter and 3 m depth, HEEB 2009). To increase the retention time for solids, there is a baffle in the middle of the tank and orthogonal to the flow direction. The baffle holds back unsuspended solid compounds of the waste, whereas liquids can easily flow over (much like septic tanks or biogas digesters, see also factsheet (see also small scale digesters or biogas settlers). This leads to an increased retention time for unsuspended solids and therefore to an improved decomposition of this compounds. The digested liquor (digestate) flows into the effluent tank from where a pump, run with electricity of the produced biogas, transports it up into an overhead storage tank. From the tank, the digestate is then used to flush the feedstock from the inlet tank into the digester tank avoiding the need of fresh water for flushing (HEEB 2009).
