Ayhan Demirbas

Biomass resource facilities and biomass conversion processing for fuels and chemicals

Biomass resources include wood and wood wastes, agricultural crops and their waste byproducts, municipal solid waste, animal wastes, waste from food processing and aquatic plants and algae. Biomass is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles and providing process heat for industrial facilities. The conversion technologies for utilizing biomass can be separated into four basic categories: direct combustion processes, thermochemical processes, biochemical processes and agrochemical processes. Thermochemical conversion processes can be subdivided into gasification, pyrolysis, supercritical fluid extraction and direct liquefaction. Pyrolysis is the thermochemical process that converts biomass into liquid, charcoal and non-condensable gases, acetic acid, acetone and methanol by heating the biomass to about 750 K in the absence of air. If the purpose is to maximize the yield of liquid products resulting from biomass pyrolysis, a low temperature, high heating rate, short gas residence time process would be required. For high char production, a low temperature, low heating rate process would be chosen. If the purpose is to maximize the yield of fuel gas resulting from pyrolysis, a high temperature, low heating rate, long gas residence time process would be preferred.

Biodiesel fuels from vegetable oils via catalytic and non-catalytic supercritical alcohol transesterifications and other methods: a survey

Abstract Vegetable oil fuels have not been acceptable because they were more expensive than petroleum fuels. With recent increases in petroleum prices and uncertainties concerning petroleum availability, there is renewed interest in vegetable oil fuels for Diesel engines. Dilution of oils with solvents and microemulsions of vegetable oils lowers the viscosity, but some engine performance problems still exist. The purpose of the transesterification process is to lower the viscosity of the oil. Pyrolysis produces more biogasoline than biodiesel fuel. Soap pyrolysis products of vegetable oils can be used as alternative Diesel engine fuel. Methyl and ethyl esters of vegetable oils have several outstanding advantages among other new renewable and clean engine fuel alternatives. The main factors affecting transesterification are the molar ratio of glycerides to alcohol, catalyst, reaction temperature and pressure, reaction time and the contents of free fatty acids and water in oils. The commonly accepted molar ratios of alcohol to glycerides are 6:1–30:1.

Heavy metal adsorption onto agro-based waste materials: a review.

Adsorption has been proved to be an excellent way to treat industrial waste effluents, offering significant advantages like the low-cost, availability, profitability, easy of operation and efficiency. Biosorption of heavy metals from aqueous solutions is a relatively new process that has proven very promising in the removal of contaminants from aqueous effluents. Biosorption is becoming a potential alternative to the existing technologies for the removal and/or recovery of toxic metals from wastewater. The major advantages of biosorption technology are its effectiveness in reducing the concentration of heavy metal ions to very low levels and the use of inexpensive biosorbent materials. Metal adsorption and biosorption onto agricultural wastes is a rather complex process affected by several factors. Mechanisms involved in the biosorption process include chemisorption, complexation, adsorption-complexation on surface and pores, ion exchange, microprecipitation, heavy metal hydroxide condensation onto the biosurface, and surface adsorption.

Mechanisms of liquefaction and pyrolysis reactions of biomass

In the liquefaction process, the micellar-like broken down fragments produced by hydrolysis are degraded to smaller compounds by dehydration, dehydrogenation, deoxygenation and decarboxylation. These compounds once produced, rearrange through condensation, cyclization and polymerization, leading to new compounds. Thermal depolymerization and decomposition of biomass, cellulose, hemicelluloses and products were formed as well as a solid residue of charcoal. The mechanism of pyrolytic degradation of structural components of the biomass samples was separately studied. Cleavage of the aromatic C–O bond in lignin led to the formation of one oxygen atom products, and the cleavage of the methyl C–O bond to form two oxygen atom products is the first reaction to occur in the thermolysis of 4-alkylguaiiacol at 600–650 K. Cleavage of the side chain C–C bond occurs between the aromatic ring and the α-carbon atom.

Biodiesel from vegetable oils via transesterification in supercritical methanol

Transesterifications of six vegetable oil samples in supercritical methanol were studied without using any catalyst. Methyl esters of vegetable oils have several outstanding advantages among other new-renewable and clean engine fuel alternatives. The variables affecting the methyl ester yield during the transesterification reaction, such as molar ratio of alcohol to vegetable oil and reaction temperature, were investigated. Compared to no. 2 Diesel fuel, all of the vegetable oils are much more viscous, while the methyl esters of vegetable oils (biodiesels) are slightly more viscous.

Calculation of higher heating values of biomass fuels

Abstract Calorific values (higher heating values, HHV) of 16 biomass samples obtained from different Turkish sources were determined experimentally and calculated from both ultimate and proximate analyses. The HHV (MJ kg−1) of the biomass samples as a function of fixed carbon (FC, wt%) was calculated from the following equation: HHV = 0.196(FC) + 14.119 for which the correlation coefficient was 0.9997. The calorific values calculated from this equation showed a mean difference of 2.2%.

Agricultural based activated carbons for the removal of dyes from aqueous solutions: a review.

This review evaluates a number of different agricultural waste adsorbents and types of dyes. Certain wastewater containing different dye contaminants causes serious environmental problems. Recently, growing research interest in the production of carbon based has been focused on agricultural by-products. Low cost adsorbents derived from agricultural wastes have demonstrated outstanding capabilities for the removal of dyes from wastewater. Therefore, low cost agricultural waste adsorbents can be viable alternatives to activated carbon for the treatment of contaminated wastewater. The use of cheap and eco-friendly adsorbents have been studied as an alternative substitution of activated carbon for the removal dyes from wastewater. The dye adsorption capacities of agricultural waste adsorbents vary, depending on the characteristics of the individual adsorbent, the extent of surface modification and the initial concentration of adsorbate.

An Overview of Biomass Pyrolysis

The pyrolysis is degradation of biomass by heat in the absence of oxygen, which results in the production of charcoal, liquid, and gaseous products. The pyrolysis process can be divided into three subclasses: conventional pyrolysis, fast pyrolysis, and flash pyrolysis. The hemicelluloses break down first at temperatures of 470 to 530 K, cellulose follows in the temperature range 510 to 620 K, and lignin is the last component to pyrolyze at temperatures of 550 to 770 K. If the purpose is to maximize the yield of liquid products resulting from biomass pyrolysis, a low temperature, high heating rate, short gas residence time process would be required. For a high char production, a low temperature, low heating rate process would be chosen. If the purpose was to maximize the yield of fuel gas resulting from pyrolysis, a high temperature, low heating rate, long gas residence time process would be preferred.

Production of Biodiesel from Algae Oils

Abstract A macroalga (Cladophora fracta) and a microalga (Chlorella protothecoides) samples were used in this work. Most current research on oil extraction is focused on microalgae to produce biodiesel from algal oil. The biodiesel from algal oil in itself is not significantly different from biodiesel produced from vegetable oils. Algal oils, as well as vegetable oils, are all highly viscous, with viscosities ranging 10–20 times those of no. 2 diesel fuel. Transesterification of the oil to its corresponding fatty ester is the most promising solution to the high viscosity problem. Fatty acid (m)ethyl esters produced from natural oils and fats is called biodiesel. Generally, methanol has been mostly used to produce biodiesel as it is the least expensive alcohol. The oil proportion from the lipid fractions of Chlorella protothecoides is considerable higher than that of Cladophora fracta. The higher heating value of Chlorella protothecoides (25.1 MJ/kg) also is higher than that of Cladophora fracta (21.1 MJ/kg). The average polyunsaturated fatty acids of Chlorella protothecoides (62.8%) also are higher than those of Cladophora fracta (50.9%).

Fuel properties and calculation of higher heating values of vegetable oils

Abstract The physical, chemical and fuel properties of vegetable oils were investigated in this work. Combustion heats, determined as higher heating values (HHVs), of vegetable oil samples obtained from different Turkish sources were determined experimentally and calculated from chemical analyses. The HHV (kJ g −1 ) of the oils as a function of saponification value (SV) and iodine value (IV) was calculated with the equation: HHV = 49.43 − [0.041(SV) + 0.015(IV)], for which the correlation coefficient was 0.9999. The HHVs calculated from this equation showed a mean difference of 0.0067%.