TWE 414 Bioenergy Production Technologies PDF

TWE 414: BIOENERGY PRODUCTION TECHNOLOGIES Lecturer in Charge: Dr Tolulope E. KOLAJO Course Synopsis: A review of the basic mechanical, biological, chemical and thermal processes for converting biomass into biofu...

TWE 414: BIOENERGY PRODUCTION TECHNOLOGIES Lecturer in Charge: Dr Tolulope E. KOLAJO Course Synopsis: A review of the basic mechanical, biological, chemical and thermal processes for converting biomass into biofuels, e.g., briquetting, pelletisation, bio-digestion to produce biogas, trans- esterification to produce biodiesel, fermentation and alcohol distillation to produce bioethanol, gasification, and pyrolysis (i.e., torrefaction, carbonisation and full pyrolysis), etc. A review of traditional and modern charcoal production processes. A discussion of the advantages and disadvantages of the various technologies. Practical demonstration of the technologies and field visits to installation sites. Course Outline 1. Introduction: Biomass definition, types and sources. 2. Briquetting and Pelletisation: Machines, particle size reduction, process flow, product end use. 3. Pyrolysis and Gasification: Charcoal production, production of syngas, uses, environmental considerations, end products. 4. Biodiesel: Uses, Energy crops. Production pathways. 5. Bioethanol: 1st, 2nd and 3rd generation bioethanol. Biomass pretreatments and production techniques, pulping. 6. Biogas definition, sources of biomass for biogas, production pathways, practical production of biogas. 7. Conclusion. Revision.  LECTURE 1 INTRODUCTION Bioenergy is energy derived from biomass. Biomass is all organic material being either: The direct product of photosynthesis (for example plant matter such as leaves, stems, etc.) The indirect product of photosynthesis (for example animal mass resulting from the consumption of plant material). Biomass resources are potentially the world's largest and most sustainable energy source. The expected increase of biomass energy, particularly in its modern forms, could have a significant impact not only in the energy sector, but also in the drive to modernize agriculture, and on rural development. The share of biomass in the total final energy demand is between 7% and 27%. Sunlight is used by the biomass to synthesize nutrients for growth and also for synthesis of important compounds, like carbohydrates, lipids and proteins. These components may be converted to biofuels and various products in the frame of a biorefinery concept. Biomass covers all forms of organic material, including plants both living and in waste form, and animal waste products. It can be divided into two different categories: (i) waste materials or (ii) dedicated energy crops. Biomass waste materials include agricultural and forest residues, municipal solid waste (MSW), food processing waste and animal manure, among others. The value that can be obtained from these wastes cannot be ignored as an important bioenergy source. If effectively harnessed, biomass wastes can be used as raw material for the synthesis of high-value solid products and/or chemicals, as well as for reducing the energy consumption from non-renewable fossil fuel sources. Furthermore, the use of solid waste materials would also save landfill space and increase the value of the biomass resources. Different sources of Biomass: Agricultural Biomass refers to biomass grown on agricultural land, which is land area that is either arable, under permanent crops, or under permanent pastures, which includes all agricultural produce, regardless of the chemical composition (i.e., lignocellulosics, starch, oil seeds, etc.) and whether it is edible or not (i.e., food or energy crops). It can be further categorized into primary sources, grown as either crop or key product, such as sugarcane and short rotation energy plantations. This group of biomass comprises both herbaceous and woody biomass and is in the top three important biomass sources in the world. Secondary sources, as residues from the production processes, for example, sugarcane bagasse, rice husks, and corn stover. Sugarcane bagasse generated after juice extraction from the cane stalks in sugar mills is also used as a solid biofuel for production of steam and electricity required by the same sugar-production process. Tertiary sources are by-products, residues and wastes produced during and after production processes, for example, organic portions of municipal solid waste, sewage treatment sludge, wood waste, etc. These three source categories are abundantly represented in Nigeria. Forestry biomass: The world’s total forest area is 4.06 billion hectares (ha), about 31 percent of the total land area. This is equivalent to 0.52 ha per person – although forest areas are not geographically distributed evenly. The tropical region (45 percent) has the largest proportion of the world’s forests, followed by the boreal, temperate and subtropical domains. Forest biomass is the planet's most abundant source of renewable energy and makes up 44 percent of total forest carbon while soil organic matter (45 percent), and dead wood and litter, constitutes the remainder. The total living biomass in the world’s forests amounts to around 606 gigatonnes (Gt) or about 149 tonnes per ha and the highest biomass stock per hectare was in regions with tropical forests – with figures above 200 tonnes per ha in South America and Western and Central Africa. Forestry residues obtained from sound forest management can enhance and increase the future productivity of forests. Recoverable residues from forests have been estimated to have an energy potential of about 35 EJ/yr. A considerable advantage of these residues is that a large part is generated by the pulp and paper and sawmill industries and thus could be readily available. A major advantage of forest biomass is that it is intrinsically connected to several industries and could be directly combusted in boilers and other equipment, or used in co-combustion with fossil fuels for power generation. In direct combustion, the biomass is burned in open air or in the presence of excess air at extreme temperatures, and the stored chemical energy of the biomass is converted into heat. This leads to the emissions of CO2 and other harmful substances, however, the amounts are still less than those caused by the combustion of fossil fuels. A major problem with forest biomass utilization is the vastness of forests and the complexity of forest biomass compilation. Thus, lack of access to these resources is a severe concern in the sustainability of direct electricity generation using forest biomass. Furthermore, the waste resources generated during these activities are generally far from industrial and residential areas. To solve these concerns, forest biomass-based industries be located within a 120km radius of forests. However, this requires a significant financial investment and storage space. By-products, Residues, and Waste can be defined as biomass from defined side streams from agricultural, forestry, and other related industrial operations (FAO, 2004), and organic residues from municipal solid wastes. The use of residual biomass and wastes as bioenergy feedstock has various benefits but also disadvantages. Benefits include a decrease in pollution and fire risks, a decrease in production costs and environmental burdens related to the main produce, a reduction in trash accumulation, and a decrease in transportation costs because the waste is often gathered in specific radia. On the other hand, drawbacks include price volatility, uncertain long-term supply when viewed as by-products, market competition with other raw materials, the possibility of soil depletion (due to exportation of minerals and carbon matter), as well as other environmental effects. Energy crops: Dedicated energy crops in land specifically devoted for, and intercropping with non-energy crops. This is a new concept for the farmer, which will have to be fully accepted if large-scale energy crops are to form an integral part of farming practices. Factors to be considered are: land availability, possible fuel versus food conflict, potential climatic factors, higher investment cost of degraded land, land rights, etc. The most likely scenario would be the use of about 100-300 million ha, mostly in developed nations, where excess food production exists. (Assignment: Write on Types of Energy crops, biofuels that can be produced from energy crops, advantages and disadvantages of production of biofuels from energy crops). Aquatic Biomass refers to plant or animal material that has formed in water, such as algae (microalgae and macroalgae), seaweed and other aquatic plants. Algae can grow in different types of waters including fresh, saline, brackish water and even in wastewater from different sources, such as agricultural water, treated industrial wastewater, aquaculture wastewater, water from oil and gas drilling operations, and so on. Due to this, they can be considered a very promising biomass feedstock with very interesting growth potential in the near future. This group of biomasses are also seen as a promising renewable biomass feedstock for the production of fuels and chemicals because of their higher photosynthetic efficiency, higher biomass production, and faster growth under a wide variety of environmental conditions compared to lignocellulosics. Their utilization could also reduce greenhouse gas emissions by up to 90%. Algae composition contrasts widely from that of lignocellulosic biomass types. While lignocellulosics are made up of cellulose, hemicellulose, lignin, and varying amounts of inorganics and organic extractive compounds, algae consist of different types of carbohydrates in combination with various proteins, lipids, and inorganic material. Algae can be further distinguished according to their cell structure into prokaryotes and eukaryotes; classes of which are under investigation for possibilities of hydrothermal liquefaction processing. Wet Wastes: Wet waste biomass includes food wastes, sewage sludge from municipal wastewater treatment plants, manure slurries, different organic wastes from industrial processes and the biogas obtained by the decomposition of organic matter in the absence of oxygen of any of the above feedstock resources. The transformation of this waste into energy or value-added products can generate additional incomes for rural areas, besides reducing waste-disposal problems. Fig. 1: Different types of Biomass feedstock Fig. 2: Classification of Biomass sources Fig. 3: Biomass Processing Pathways