PYROLYSED PRODUCTS FROM LIGNOCELLULOSIC WASTES: PRODUCTION, CHARACTERISATION AND THEIR EFFECT ON SOIL PROPERTIES, OKRA, INSECT AND MICROBIAL GROWTH

Abstract

This research work was conducted to produce biochar, bio-oil and bio-tar through thermo chemical conversion of three different lignocellulosic wastes biomass [cocoa pod husk (CP), Elephant grass straw (EG) and Empty palm fruit Bunches (EPB)] at three different pyrolysis temperatures: 400,500 and 600 °C. The physicochemical properties of the selected biomass were determined prior to pyrolysis. The three products obtained after the pyrolysis were: biochar (solid), bio-oil (liquid) and bio-tar (semi solid). For every kilogramme of biomass pyrolysed, the percentage yield of the biochar produced decreased as the pyrolysis temperature increased: 45.67, 41.00, 38.98%; 41.40, 37.69, 32.25%; 43.67, 37.20, 32.67% for CP, EG and EPB at 400, 500 and 600 °C respectively. The percentage yield of the bio-oil and bio-tar produced increased as the pyrolysis temperature increased: 32.47, 35.83, 39.42%; 30.27, 36.43, 41.83%; 22.07, 35.13, 37.47 for the bio-oil and 13.27, 14.56, 17.02%; 13.19, 15.35, 17.90%; 13.32, 13.87, 17.15% for the bio-tar CP, EG and EPB at 400, 500 and 600 °C respectively. Fourier Transforms Infrared (FTIR) spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), Elemental analysis and X-ray Diffraction (XRD) spectroscopy were used to characterized the biomass and the biochars while the bio-oil and bio-tar were characterized with FTIR and Gas Chromatography-Mass Spectroscopy (GC-MS). The FTIR spectra of the biochar showed IR absorption at 3414 cm-1 to 3392 cm-1( OH ), 2955 to 2918 cm-1, ( C-H ), 2330 to 2190 cm-1 ( C≡C ), 1635 to 1616 cm-1 ( C=C ), 1597 to 1570 cm-1 ( C-O ) and 1383 to 1340 cm-1 ( C-N ). The GC-MS analysis revealed that the most abundant compounds in the biomass feedstock bio-oils were: phenols (10.95%); mequinol ( 6.65% ); pyridine ( 0.91% ); carbamic acid ( 3.21% ); 3,5-dimethylphenol ( 4.14); 2-furanmethanol ( 2.03% ); 2,6-dimethoxy-phenol ( 3.70% ); trans-isoeugenol ( 2.19 ); 2,6-dimethoxy-phenol ( 7.71% ) and the most abundant compounds in the biomass feedstock (bio-tar) were n-hexadecanoic acid ( 19.30% ), pentadecanoic acid ( 7.23% ); oleic acid ( 3.95% ); 9-octadecenoic acid ( 2.89% ); phenol ( 8.40% ); 2-methoxy-mequinol ( 3.14% ); pyridine ( 0.25% ). Elemental analysis using Energy dispersive X-ray spectroscopy (EDX) as well as ultimate analysis indicated that the produced biochars contained more than five plant nutrients in appreciable quantity and the SEM revealed their porous structural nature while the XRD indicate the amorphous nature of the biochar as the temperature increased. The pH studies of the biochars revealed that produced biochar were slightly alkaline and range from 9.59 to 10.82 and the produced bio-oils were acidic and the pH value ranges from 2.29 to 4.71. Pot trial experiment was carried out to established the effectiveness of biochar as soil amendment, the result after the experiment showed that addition of biochar into the soil significantly increased both the physical and the chemical properties of the experimental soil compared to the control and the raw biomass. Okra yield was higher in the amended soil. Bioassay test of percentage inhibition of seed germination and percentage inhibition of seedling growth on the bio-oil at different pyrolysis temperature of seed of Tomatoes, Okra and Amaranthus showed that the bio-oils have considerable allelopathic potentials and the % inhibition was dose dependent. Antimicrobial studies of the biooil as well as bio-tar were carried out against bacteria and fungi. The bio-oil and bio-tar gave good antimicrobial result. The Minimum Inhibitory Concentration (MIC) was between 2.5 – 10% for bacteria and 10 - 20% for fungi. The percentage weight loss and % mortality of the bio-oils against termite were carried out. The result showed potent termiticidal and anti-feedant activity. Elephant grass biochar A ( 400 °C ) and B ( mixture of 500 and 600 °C ) were evaluated for removal of 3 NO from aqueous solution. Effects of pH, contact time, and concentration on nitrate ion on adsorption capacity were studied using batch adsorption technique. Langmuir and Freundlich models described the adsorption equilibrium data better than Temkin model. The maximum equilibrium amounts of 3 NO removed by biochar A and B are 104.17 and 42.37 mg/g, respectively. Pseudofirst order model gave the best fit of kinetic data. The adsorption process was feasible and exothermic. The combine adsorption data show that the biochar successfully removed nitrate ion from aqueous solution. The use of biochar as soil amender and the application of bio-oil and biotar as agrochemicals in green agriculture technology may be an alternative to the use of synthetic agrochemicals in soil fertility.