A Glance at Biomass Resources

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Biomass energy projects provide major business opportunities, environmental benefits, and rural development.  Feedstocks can be obtained from a wide array of sources without jeopardizing the food and feed supply, forests, and biodiversity in the world.

Agricultural Residues

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 thermochemical 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.

Animal Waste

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 manures. 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 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

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 Wastes

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.

Industrial Wastes

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 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.

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A Primer on Biofuels

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The term ‘Biofuel’ refers to liquid or gaseous fuels for the transport sector that are predominantly produced from biomass. A variety of fuels can be produced from biomass resources including liquid fuels, such as ethanol, methanol, biodiesel, Fischer-Tropsch diesel, and gaseous fuels, such as hydrogen and methane. The biomass resource base for biofuel production is composed of a wide variety of forestry and agricultural resources, industrial processing residues, and municipal solid and urban wood residues.

The agricultural resources include grains used for biofuels production, animal manures and residues, and crop residues derived primarily from corn and small grains (e.g., wheat straw). A variety of regionally significant crops, such as cotton, sugarcane, rice, and fruit and nut orchards can also be a source of crop residues. The forest resources include residues produced during the harvesting of forest products, fuelwood extracted from forestlands, residues generated at primary forest product processing mills, and forest resources that could become available through initiatives to reduce fire hazards and improve forest health. Municipal and urban wood residues are widely available and include a variety of materials — yard and tree trimmings, land-clearing wood residues, wooden pallets, organic wastes, packaging materials, and construction and demolition debris.

Globally, biofuels are most commonly used to power vehicles, heat homes, and for cooking. Biofuel industries are expanding in Europe, Asia and the Americas. Biofuels are generally considered as offering many priorities, including sustainability, reduction of greenhouse gas emissions, regional development, social structure and agriculture, and security of supply.

First-generation biofuels are made from sugar, starch, vegetable oil, or animal fats using conventional technology. The basic feedstocks for the production of first-generation biofuels come from agriculture and food processing. The most common first-generation biofuels are:

• Biodiesel: extraction with or without esterification of vegetable oils from seeds of plants like soybean, oil palm, oilseed rape and sunflower or residues including animal fats derived from rendering applied as fuel in diesel engines
• Bioethanol: fermentation of simple sugars from sugar crops like sugarcane or from starch crops like maize and wheat applied as fuel in petrol engines
• Bio-oil: thermo-chemical conversion of biomass. A process still in the development phase
• Biogas: anaerobic fermentation or organic waste, animal manures, crop residues an energy crops applied as fuel in engines suitable for compressed natural gas.

First-generation biofuels can be used in low-percentage blends with conventional fuels in most vehicles and can be distributed through existing infrastructure. Some diesel vehicles can run on 100 % biodiesel, and ‘flex-fuel’ vehicles are already available in many countries around the world.

Second-generation biofuels are derived from non-food feedstock including lignocellulosic biomass like crop residues or wood. Two transformative technologies are under development.

• Biochemical: modification of the bio-ethanol fermentation process including a pre-treatment procedure
• Thermochemical: modification of the bio-oil process to produce syngas and methanol, Fisher-Tropsch diesel or dimethyl ether (DME).

Advanced conversion technologies are needed for a second generation of biofuels. The second generation technologies use a wider range of biomass resources – agriculture, forestry and waste materials. One of the most promising second-generation biofuel technologies – ligno-cellulosic processing (e. g. from forest materials) – is already well advanced. Pilot plants have been established in the EU, in Denmark, Spain and Sweden.

Third-generation biofuels may include production of bio-based hydrogen for use in fuel cell vehicles, e.g. Algae fuel, also called oilgae. Algae are low-input, high-yield feedstocks to produce biofuels.

Solutions for Major Issues arising in Biomass Energy Projects

This article makes an attempt at collating some of the most prominent issues associated with biomass technologies and provides plausible solutions in order to seek further promotion of these technologies. The solutions provided below are based on author’s understanding and experience in this field.

1. Large Project Costs: The project costs are to a great extent comparable to these technologies which actually justify the cause. Also, people tend to ignore the fact, that most of these plants, if run at maximum capacity could generate a Plant Load Factor (PLF) of 80% and above. This figure is about 2-3 times higher than what its counterparts wind and solar energy based plants could provide. This however, comes at a cost – higher operational costs.
2. Technologies have lower efficiencies: The solution to this problem, calls for innovativeness in the employment of these technologies. To give an example, one of the paper mill owners in India, had a brilliant idea to utilize his industrial waste to generate power and recover the waste heat to produce steam for his boilers. The power generated was way more than he required for captive utilization. With the rest, he melts scrap metal in an arc and generates additional revenue by selling it. Although such solutions are not possible in each case, one needs to possess the acumen to look around and innovate – the best means to improve the productivity with regards to these technologies.
3. Technologies still lack maturity: One needs to look beyond what is directly visible. There is a humongous scope of employment of these technologies for decentralized power generation. With regards to scale, few companies have already begun conceptualizing ultra-mega scale power plants based on biomass resources. Power developers and critics need to take a leaf out of these experiences.
4. Lack of funding options: The most essential aspect of any biomass energy project is the resource assessment. Investors if approached with a reliable resource assessment report could help regain their interest in such projects. Moreover, the project developers also need to look into community based ownership models, which have proven to be a great success, especially in rural areas. The project developer needs to not only assess the resource availability but also its alternative utilization means. It has been observed that if a project is designed by considering only 10-12% of the actual biomass to be available for power generation, it sustains without any hurdles.
5. Non-Transparent Trade markets: Most countries still lack a common platform to the buyers and sellers of biomass resources. As a result of this, their price varies from vendor to vendor even when considering the same feedstock. Entrepreneurs need to come forward and look forward to exploiting this opportunity, which could not only bridge the big missing link in the resource supply chain but also could transform into a multi-billion dollar opportunity.
6. High Risks / Low pay-backs: Biomass energy plants are plagued by numerous uncertainties including fuel price escalation and unreliable resource supply to name just a few. Project owners should consider other opportunities to increase their profit margins. One of these could very well include tying up with the power exchanges as is the case in India, which could offer better prices for the power that is sold at peak hour slots. The developer may also consider the option of merchant sale to agencies which are either in need of a consistent power supply and are presently relying on expensive back-up means (oil/coal) or are looking forward to purchase “green power” to cater to their Corporate Social Responsibility (CSR) initiatives.
7. Resource Price escalation: A study of some of the successful biomass energy plants globally would result in the conclusion of the inevitability of having own resource base to cater to the plant requirements. This could be through captive forestry or energy plantations at waste lands or fallow lands surrounding the plant site. Although, this could escalate the initial project costs, it would prove to be a great cushion to the plants operational costs in the longer run. In cases where it is not possible to go for such an alternative, one must seek case-specific procurement models, consider help from local NGOs, civic bodies etc. and go for long-term contracts with the resource providers.

Contributed by Mr. Setu Goyal (TERI University, New Delhi) who can be reached at setu.goyal@gmail.com