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TWO STEP PROCESS FOR THE CONVERSION OF LIGNOCELLULOSIC MATERIAL INTO METHANE.

Objective

UNTREATED LIGNOCELLULOSE IS ONLY SLOWLY AND INCOMPLETELY TRANSFORMED INTO BIOGAS UNDER NORMAL ANAEROBIC DIGESTION.
THE PRIMARY AIM IS TO DEVELOP A MORE EFFECTIVE PROCESS FOR DEGRADATION OF LIGNOCELLULOSIC MATERIAL INTO METHANE, WHICH WILL MAKE IT MORE TECHNICAL/ECONOMICAL FEASIBLE TO USE STRAW AND OTHER LIGNOCELLULOSIC WASTES AND WASTE WATERS FOR COMMERCIAL PRODUCTION OF METHANE GAS. THE CONCEPT OF THE RESEARCH PROGRAMME IS BASED ON A CONVERSION OF LIGNOCELLULOSE IN TWO STEPS AND WOULD PRESUMELY INCREASE THE METHANE YIELD 30-50 %.
THE FIRST STEP IS PARTIAL DELIGNIFICATION WITH SPECIAL SELECTED FUNGI. THE SECOND STEP IS DEGRADATION OF THE RESULTING INTERMEDIATE PRODUCTS IN A ANAEROBIC REACTOR. CERTAIN PROCESS CONDITIONS FAVOURING THE TOTAL DEGRADATION TO METHANE MUST BE DETERMINED. THESE INCLUDE THE METHOD OF FERMENTATION, THE TYPE OF SUBSTRATE, THE FUNGI CULTURE AND THE REACTOR DESIGN.

PROGRESS AT BIOTECHNICA LTD :

PRELIMINARY WORK AT BTL HAS CONCENTRATED ON SCREENING WHITEROT FUNGI FOR THEIR ABILITY TO MODIFY AN UPGRADE LIGNOCELLULOSIC WASTES. BARLEY STRAW HAS BEEN CHOSEN AS A MODEL SUBSTRATE FOR THE INITIAL STUDY COMPRISING A TYPICAL FIBRE CONTENT OF 48-53 % CELLULOSE, 28-32 % HEMICELLULOSE AND 8-12 % PERMANGANATE LIGNIN.

STRAIN OF PHANEROCHAETE CHRYSOSPORIUM HAVE BEEN FOUND TO SUBSTANCIALLY DEGRADE BARLEY STRAW RESULTING IN 40-43 % WEIGHT LOSS OVER 55 DAYS, BUT WITH A CONCOMITANT REDUCTION IN REDUCING SUGAR AVAILABILITY IMPLYING NO IMPROVEMENT IN METHANE YIELD ON SUBSEQUENT ANAEROBIC DIGESTION. STRAINS OF PLEUROTUS OSTRATUS AND CYATHUS BERKLEYANUS DEGRADED THE STRAW MORE SLOWLY RESULTING IN 15-20 % WEIGHT LOSS OVER 55 DAYS, BUT WITH AN IMPROVED CELLULASE DIGESTIBILITY. LENTINUS EDODES AND LEPSITA SAEVA STRAINS COLONISED THE STRAW POORLY. ALTHOUGH LEPSITA IMPROVED THE CELLULASE DIGESTIBILITY OF THE STRAW AND SLOW GROWTH RATE OF THIS ORGANISM WOULD MEAN THAT IT WOULD BE RAPIDLY OVERGROWN BY ANY INDIGENOUS FLORA IN A NON-STERILE SYSTEM.

SUBMERGED FERMENTATION WORK HAS BEEN PERFORMED IN SMALL-SCALE STIRRED TANK REACTORS USING UNAMENDED STRAW AS SOLE SUBSTRATE. FUNGAL GROWTH HAS BEEN FOUND TO BE SLOWER IN SUBMERGED FERMENTATIONS AS SOLUBLE PRODUCTS ARE DILUTED FROM THE STRAW INTO THE SUSPENDING LIQUID.

AN 11 LITRE EXTERNAL CIRCULATION LOOP AIR-LIFT FERMENTOR HAS BEEN CONSTRUCTED FOR USE IN SUBMERGED FERMENTATIONS. INITIAL WORK HAS CONCENTRATED ON OPTIMIZING THE BIOCHEMICAL ENGINEERING PARAMETERS OF THIS REACTOR.

SMALL-SCALE PERCOLATION COLUMNS HAVE BEEN DESIGNED TO AMALGAMATE THE ADVANTAGES FROM SOLID SUBSTRATE AND SUBMERGED FERMENTATIONS. ON COMPLETION OF FUNGAL SCREENING AND STRAIN SELECTION WORK CAN PROCEED IN EXPANDING THE FERMENTATION TECHNOLOGY.

PROGRESS AT TECHNOLOGICAL INSTITUTE :

PRELIMINARY WORK AT TI HAS CONCENTRATED ON UPGRADING A CULTURE FEEDED WITH BARLEY STRAW AS THE SOLE SUBSTRATE.

AS INOCULUM WAS USED DIGESTED CATTLE MANURE MIXED WITH SLUDGE FROM ANAEROBIC REACTOR IN THE RATIO 10:1. IN THREE WEEKS THE SUBSTRATE WAS WHEY PERMEATE. FOR THE NEXT THREE MONTHS, THE CULTURE WAS FEEDED WITH BARLEY STRAW OF D 2.5 MM ONCE EVERY TWO WEEKS.

THIS CULTURE WILL BE USED AS INOCULUM FOR ANAEROBIC TEST OF FUNGAL TREATED STRAW DELIVERED BY BIOTECHNICA. THE TEST WILL BE USED TO DETERMINATE THE CORRELATION WITH THE CELLULASE DIGESTIBILITY ASSAY USED AT BIOTECHNICA. FURTHER THE CULTURE WILL BE USED IN A CONTROL FERMENTATION WHERE THE STRAW IS NOT PRETREATED WITH FUNGI.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Danish Technological Institute
Address
Gregersensvej
2630 Taastrup
Denmark

Participants (1)

Biotechnica Ltd
United Kingdom
Address
Chiltern Close
CF4 5DL Cardiff