There is immense potential of biomass energy in Southeast Asia due to plentiful supply of diverse forms of wastes such as agricultural residues, agro-industrial wastes, woody biomass, animal wastes, municipal solid waste, etc. Southeast Asia is a big producer of wood and agricultural products which, when processed in industries, produces large amounts of biomass residues.
The rapid economic growth and industrialization in Southeast Asian region is characterized by a significant gap between energy supply and demand. The energy demand in the region is expected to grow rapidly in the coming years which will have a profound impact on the global energy market. In addition, the region has many locations with high population density, which makes public health vulnerable to the pollution caused by fossil fuels.
Another important rationale for transition from fossil-fuel-based energy systems to renewable ones arises out of observed and projected impacts of climate change. Due to the rising share of greenhouse gas emissions from Asia, it is imperative on all Asian countries to promote sustainable energy to significantly reduce GHGs emissions and foster sustainable energy trends. Rising proportion of greenhouse gas emissions is causing large-scale ecological degradation, particularly in coastal and forest ecosystems, which may further deteriorate environmental sustainability in the region.
The reliance on conventional energy sources can be substantially reduced as the Southeast Asian region is one of the leading producers of biomass resources in the world. Southeast Asia, with its abundant biomass resources, holds a strategic position in the global biomass energy atlas.
Palm kernel shells is an abundant biomass resource in Southeast Asia
According to conservative estimates, the amount of biomass residues generated from sugar, rice and palm oil mills is more than 200-230 million tons per year which corresponds to cogeneration potential of 16-19 GW. Woody biomass is a good energy resource due to presence of large number of forests and wood processing industries in the region.
The prospects of biogas power generation are also high in the region due to the presence of well-established food processing, agricultural and dairy industries. Another important biomass resource is contributed by municipal solid wastes in heavily populated urban areas.
In addition, there are increasing efforts from the public and private sectors to develop biomass energy systems for efficient biofuel production, e.g. biodiesel and bioethanol. The rapid economic growth and industrialization in Southeast Asia has accelerated the drive to implement the latest biomass energy technologies in order to tap the unharnessed potential of biomass resources, thereby making a significant contribution to the regional energy mix.
Southeast Asia, with its abundant bioenergy resources, holds a strategic position in the global biomass energy atlas. There is immense biomass energy potential in Southeast Asian countries due to plentiful supply of diverse forms of biomass wastes, such as agricultural residues, woody biomass, animal wastes, municipal solid waste, etc. The rapid economic growth and industrialization in the region has accelerated the drive to implement the latest waste-to-energy technologies to tap the unharnessed potential of biomass resources.
Southeast Asia is a big producer of agricultural and wood products which, when processed in industries, produces large amounts of biomass residues. According to conservative estimates, the amount of biomass residues generated from sugar, rice and palm oil mills is more than 200-230 million tons per year which corresponds to cogeneration potential of 16-19 GW.
Rice mills in the region produce 38 million tonnes of rice husk as solid residue which is a good fuel for producing heat and power. Sugar industry is an integral part of the industrial scenario in Southeast Asia accounting for 7% of sugar production worldwide. Sugar mills in Thailand, Indonesia, Philippines and Vietnam generate 34 million tonnes of bagasse every year. Malaysia, Indonesia and Thailand account for 90% of global palm oil production leading to the generation of 27 million tonnes of waste per annum in the form of empty fruit bunches (EFBs), fibers and shells, as well as liquid effluent.
Woody biomass is a good energy resource due to presence of large number of forests in Southeast Asia. Apart from natural forests, non-industrial plantations of different types (e.g. coconut, rubber and oil palm plantations, fruit orchards, and trees in homesteads and gardens) have gained recognition as important sources of biomass. In addition, the presence of a large number of wood processing industries also generates significant quantity of wood wastes. The annual production of wood wastes in the region is estimated to be more than 30 million m3.
The prospects of biogas power generation are also high in the region, thanks to presence of well-established food-processing and dairy industries. Another important biomass resource is contributed by municipal solid wastes in heavily populated urban areas. In addition, there are increasing efforts both commercially and promoted by governments to develop biomass energy systems for efficient biofuel production, e.g. bio-diesel from palm oil.
Biomass resources, particularly residues from forests, wood processing, agricultural crops and agro-processing, are under-utilised in Southeast Asian countries. There is an urgent need to utilize biomass wastes for commercial electricity and heat production to cater to the needs of the industries as well as urban and rural communities.
Southeast Asian countries are yet to make optimum use of the additional power generation potential from biomass waste resources which could help them to partially overcome the long-term problem of energy supply. Technologies for biomass utilization which are at present widely used in Southeast counties need to be improved towards best practice by making use of the latest trends in the biomass energy sector.
In recent years, biopower (or biomass power) projects are getting increasing traction worldwide, however there are major issues to be tackled before setting up a biopower project. There are three important steps involved in the conversion of biomass wastes into useful energy. In the first step, the biomass must be prepared for the energy conversion process. While this step is highly dependent on the waste stream and approach, drying, grinding, separating, and similar operations are common.
In addition, the host facility will need material handling systems, storage, metering, and prep-yard systems and biomass handling equipment. In the second step, the biomass waste stream must be converted into a useful fuel or steam. Finally, the fuel or steam is fed into a prime mover to generate useful electricity and heat.
One of the most important factors in the efficient utilization of biomass resource is its availability in close proximity to a biomass power project. An in-depth evaluation of the available quantity of a given agricultural resource should be conducted to determine initial feasibility of a project, as well as subsequent fuel availability issues. The primary reasons for failure of biomass power projects are changes in biomass fuel supply or demand and changes in fuel quality.
Fuel considerations that should be analyzed before embarking on a biomass power project include:
Typical moisture content (including the effects of storage options)
Seasonality of the resource
Proximity to the power generation site
Alternative uses of the resource that could affect future availability or price
Range of fuel quality
Percentage of farmers contracted to sell residues
Accuracy is of great importance in making fuel availability assumptions because miscalculations can greatly impact the successful operation of biomass power projects. If biomass resource is identifies as a bottle-neck in the planning stage, a power generation technology that can handle varying degrees of moisture content and particle size can be selected.
Technologies that can handle several fuels in a broad category, such as agricultural residues, provide security in operation without adversely affecting combustion efficiency, operations and maintenance costs, emissions levels, and reliability.
Consistent and reliable supply of biomass is crucial for any biomass project
Consistent and reliable biomass resource supply to the facility
Presence of harvesting, processing and supply infrastructure to provide biomass in a consistent and timely manner
Biomass as an energy source is a system of interdependent components. Economic and technical viability of this system relies on a guaranteed feedstock supply, effective and efficient conversion technologies, guaranteed markets for the energy products, and cost-effective distribution systems.
The biomass system is based on the following steps:
The current use of agro biomass for energy generation is low and more efficient use would release significant amounts of agro biomass resources for other energy use. Usually, efficiency improvements are neglected because of the non-existence of grid connections with agro-industries.
Electricity generated from biomass is more costly to produce than fossil fuel and hydroelectric power for two reasons. First, biomass fuels are expensive. The cost of producing biomass fuel is dependent on the type of biomass, the amount of processing necessary to convert it to an efficient fuel, distance to the energy conversion plant, and supply and demand for fuels in the market place. Biomass fuel is low-density and non-homogeneous and has a small unit size.
Consequently, biomass fuel is costly to collect, process, and transport to facilities. Second, biomass-to-energy facilities are much smaller than conventional fossil fuel-based power plants and therefore cannot produce electricity as cost-effectively as the fossil fuel-based plants.
Agro biomass is costly to collect, process, and transport to facilities.
The biomass-to-energy facilities are smaller because of the limited amount of fuel that can be stored at a single facility. With higher fuel costs and lower economic efficiencies, solid-fuel energy is not economically competitive in a deregulated energy market that gives zero value or compensation for the non-electric benefits generated by the biomass-to-energy industry.
Biomass availability for fuel usage is estimated as the total amount of plant residue remaining after harvest, minus the amount of plant material that must be left on the field for maintaining sufficient levels of organic matter in the soil and for preventing soil erosion. While there are no generally agreed-upon standards for maximum removal rates, a portion of the biomass material may be removed without severely reducing soil productivity.
Technically, biomass removal rates of up to 60 to 70 percent are achievable, but in practice, current residue collection techniques generally result in relatively low recovery rates in developing countries. The low biomass recovery rate is the result of a combination of factors, including collection equipment limitations, economics, and conservation requirements. Modern agricultural equipment can allow for the joint collection of grain and residues, increased collection rates to up to 60 percent, and may help reduce concerns about soil compaction.
Biomass is a key renewable energy resource that includes plant and animal material, such as wood from forests, material left over from agricultural and forestry processes, and organic industrial, human and animal wastes. The energy contained in biomass originally came from the sun. Through photosynthesis carbon dioxide in the air is transformed into other carbon containing molecules (e.g. sugars, starches and cellulose) in plants. The chemical energy that is stored in plants and animals (animals eat plants or other animals) or in their waste is called biomass energy or bioenergy.
A quick glance at popular biomass resources
What is Biomass
Biomass comes from a variety of sources which include:
Wood from natural forests and woodlands
Agricultural residues such as straw, stover, cane trash and green agricultural wastes
Crop residues encompasses all agricultural wastes such as bagasse, straw, stem, stalk, leaves, husk, shell, peel, pulp, stubble, etc. Large quantities of crop residues are produced annually worldwide, and are vastly underutilised. Rice produces both straw and rice husks at the processing plant which can be conveniently and easily converted into energy.
Significant quantities of biomass remain in the fields in the form of cob when maize is harvested which can be converted into energy. Sugar cane harvesting leads to harvest residues in the fields while processing produces fibrous bagasse, both of which are good sources of energy. Harvesting and processing of coconuts produces quantities of shell and fibre that can be utilized.
Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. These residues could be processed into liquid fuels or thermochemically processed to produce electricity and heat. Agricultural residues are characterized by seasonal availability and have characteristics that differ from other solid fuels such as wood, charcoal, char briquette. The main differences are the high content of volatile matter and lower density and burning time.
There are a wide range of animal wastes that can be used as sources of biomass energy. The most common sources are animal and poultry manure. In the past this waste was recovered and sold as a fertilizer or simply spread onto agricultural land, but the introduction of tighter environmental controls on odour and water pollution means that some form of waste management is now required, which provides further incentives for waste-to-energy conversion.
The most attractive method of converting these organic waste materials to useful form is anaerobic digestion which gives biogas that can be used as a fuel for internal combustion engines, to generate electricity from small gas turbines, burnt directly for cooking, or for space and water heating.
Forestry residues are generated by operations such as thinning of plantations, clearing for logging roads, extracting stem-wood for pulp and timber, and natural attrition. Harvesting may occur as thinning in young stands, or cutting in older stands for timber or pulp that also yields tops and branches usable for biomass energy. Harvesting operations usually remove only 25 to 50 percent of the volume, leaving the residues available as biomass for energy.
Stands damaged by insects, disease or fire are additional sources of biomass. Forest residues normally have low density and fuel values that keep transport costs high, and so it is economical to reduce the biomass density in the forest itself.
Wood processing industries primarily include sawmilling, plywood, wood panel, furniture, building component, flooring, particle board, moulding, jointing and craft industries. Wood wastes generally are concentrated at the processing factories, e.g. plywood mills and sawmills. The amount of waste generated from wood processing industries varies from one type industry to another depending on the form of raw material and finished product.
Generally, the waste from wood industries such as saw millings and plywood, veneer and others are sawdust, off-cuts, trims and shavings. Sawdust arise from cutting, sizing, re-sawing, edging, while trims and shaving are the consequence of trimming and smoothing of wood. In general, processing of 1,000 kg of wood in the furniture industries will lead to waste generation of almost half (45 %), i.e. 450 kg of wood. Similarly, when processing 1,000 kg of wood in sawmill, the waste will amount to more than half (52 %), i.e. 520 kg wood.
The food industry produces a large number of residues and by-products that can be used as biomass energy sources. These waste materials are generated from all sectors of the food industry with everything from meat production to confectionery producing waste that can be utilised as an energy source.
Solid wastes include peelings and scraps from fruit and vegetables, food that does not meet quality control standards, pulp and fibre from sugar and starch extraction, filter sludges and coffee grounds. These wastes are usually disposed of in landfill dumps.
Liquid wastes are generated by washing meat, fruit and vegetables, blanching fruit and vegetables, pre-cooking meats, poultry and fish, cleaning and processing operations as well as wine making.
These waste waters contain sugars, starches and other dissolved and solid organic matter. The potential exists for these industrial wastes to be anaerobically digested to produce biogas, or fermented to produce ethanol, and several commercial examples of waste-to-energy conversion already exist.
Pulp and paper industry is considered to be one of the highly polluting industries and consumes large amount of energy and water in various unit operations. The wastewater discharged by this industry is highly heterogeneous as it contains compounds from wood or other raw materials, processed chemicals as well as compound formed during processing. Black liquor can be judiciously utilized for production of biogas using anaerobic UASB technology.
Municipal Solid Wastes and Sewage
Millions of tonnes of household waste are collected each year with the vast majority disposed of in open fields. The biomass resource in MSW comprises the putrescibles, paper and plastic and averages 80% of the total MSW collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the engineered landfill.
At the landfill sites, the gas produced, known as landfill gas or LFG, by the natural decomposition of MSW (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of MSW can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.
Sewage is a source of biomass energy that is very similar to the other animal wastes. Energy can be extracted from sewage using anaerobic digestion to produce biogas. The sewage sludge that remains can be incinerated or undergo pyrolysis to produce more biogas.
Biomass pellets are a popular type of biomass fuel, generally made from wood wastes, agricultural biomass, commercial grasses and forestry residues. In addition to savings in transportation and storage, pelletization of biomass facilitates easy and cost effective handling. Dense cubes pellets have the flowability characteristics similar to those of cereal grains. The regular geometry and small size of biomass pellets allow automatic feeding with very fine calibration. High density of pellets also permits compact storage and rational transport over long distance. Pellets are extremely dense and can be produced with a low moisture content that allows them to be burned with very high combustion efficiency.
Biomass pelletization is a standard method for the production of high density, solid energy carriers from biomass. Pellets are manufactured in several types and grades as fuels for electric power plants, homes, and other applications. Pellet-making equipment is available at a variety of sizes and scales, which allows manufacture at domestic as well industrial-scale production. Pellets have a cylindrical shape and are about 6-25 mm in diameter and 3-50 mm in length. There are European standards for biomass pellets and raw material classification (EN 14961-1, EN 14961-2 and EN 14961-6) and international ISO standards under development (ISO/DIS 17225-1, ISO/DIS 17225-2 and ISO/DIS 17225-6).
The biomass pelletization process consists of multiple steps including raw material pre-treatment, pelletization and post-treatment. The first step in the pelletization process is the preparation of feedstock which includes selecting a feedstock suitable for this process, its filtration, storage and protection. Raw materials used are sawdust, wood shavings, wood wastes, agricultural residues like straw, switchgrass etc. Filtration is done to remove unwanted materials like stone, metal, etc. The feedstock should be stored in such a manner that it is away from impurities and moisture. In cases where there are different types of feedstock, a blending process is used to achieve consistency.
The moisture content in biomass can be considerably high and are usually up to 50% – 60% which should be reduced to 10 to 15%. Rotary drum dryer is the most common equipment used for this purpose. Superheated steam dryers, flash dryers, spouted bed dryers and belt dryers can also be used. Drying increases the efficiency of biomass and it produces almost no smoke on combustion. It should be noted that the feedstock should not be over dried, as a small amount of moisture helps in binding the biomass particles. The drying process is the most energy intensive process and accounts for about 70% of the total energy used in the pelletization process.
Schematic of Pelletization of Woody Biomass
Beforefeeding biomass to pellet mills, the biomass should be reduced to small particles of the order of not more than 3mm. If the pellet size is too large or too small, it affects the quality of pellet and in turn increases the energy consumption. Therefore the particles should have proper size and should be consistent. Size reduction is done by grinding using a hammer mill equipped with a screen of size 3.2 to 6.4 mm. If the feedstock is quite large, it goes through a chipper before grinding.
The next and the most important step is pelletization where biomass is compressed against a heated metal plate (known as die) using a roller. The die consists of holes of fixed diameter through which the biomass passes under high pressure. Due to the high pressure, frictional forces increase, leading to a considerable rise in temperature. High temperature causes the lignin and resins present in biomass to soften which acts as a binding agent between the biomass fibers. This way the biomass particles fuse to form pellets.
The rate of production and electrical energy used in the pelletization of biomass are strongly correlated to the raw material type and processing conditions such as moisture content and feed size. The The average energy required to pelletize biomass is roughly between 16 kWh/t and 49kWh/t. During pelletization, a large fraction of the process energy is used to make the biomass flow into the inlets of the press channels.
Binders or lubricants may be added in some cases to produce higher quality pellets. Binders increase the pellet density and durability. Wood contains natural resins which act as a binder. Similarly, sawdust contains lignin which holds the pellet together. However, agricultural residues do not contain much resins or lignin, and so a stabilizing agent needs to be added in this case. Distillers dry grains or potato starch is some commonly used binders. The use of natural additives depends on biomass composition and the mass proportion between cellulose, hemicelluloses, lignin and inorganics.
Due to the friction generated in the die, excess heat is developed. Thus, the pellets are very soft and hot (about 70 to 90oC). It needs to be cooled and dried before its storage or packaging. The pellets may then be passed through a vibrating screen to remove fine materials. This ensures that the fuel source is clean and dust free.
The pellets are packed into bags using an overhead hopper and a conveyor belt. Pellets are stored in elevated storage bins or ground level silos. The packaging should be such that the pellets are protected from moisture and pollutants. Commercial pellet mills and other pelletizing equipment are widely available across the globe.
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