Biomass as Renewable Energy Resource

biomass_resourcesBiomass 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

What is Biomass

Biomass comes from a variety of sources which include:

  • Wood from natural forests and woodlands
  • Forestry plantations
  • Forestry residues
  • Agricultural residues such as straw, stover, cane trash and green agricultural wastes
  • Agro-industrial wastes, such as sugarcane bagasse and rice husk
  • Animal wastes (cow manure, poultry litter etc)
  • Industrial wastes, such as black liquor from paper manufacturing
  • Sewage
  • Municipal solid wastes (MSW)
  • Food processing wastes

Biomass energy projects provide major business opportunities, environmental benefits, and rural development.  Feedstocks for biomass energy project 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 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.

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 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

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, 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.

Clean Cookstoves: An Urgent Necessity

Globally, three billion people in the developing nations are solely dependent on burning firewood, crop residues, animal manure etc for preparing their daily meals on open fires, mud or clay stoves or simply on three rocks strategically placed to balance a cooking vessel.  The temperature of these fires are lower and produce inefficient burning that results in black carbon and other short-lived but high impact pollutants.

These short-lived pollutants not only affect the persons in the immediate area but also contribute much harmful gases more potent than carbon dioxide and methane. For the people in the immediate area, their health is severely hampered as this indoor or domestic air pollution results in significantly higher risks of pneumonia and chronic bronchitis.

To remedy the indoor air pollution (IAP) and health-related issues as well as the environmental pollution in the developing world, clean cookstoves are the way to advance. But to empower rural users to embrace the advanced cookstoves, and achieve sustainable success requires a level of socio-cultural and economic awareness that is related directly to this marginalized group. The solution needs to be appropriate for the style of cooking of the group which means one stove model will not suit or meet the needs and requirements of all developing nation people groups.

Clean cookstoves can significantly reduce health problems caused by indoor air pollution in rural areas

Consideration for such issues as stove top and front loading stove cooking, single pot and double pot cooking, size of the typical cooking vessel and the style of cooking are all pieces of information needed to complete the picture.  Historically, natural draft systems were devised to aid the combustion or burning of the fuels, however, forced draft stoves tend to burn cleaner with better health and environmental benefits. Regardless of cookstove design, the components need to be either made locally or at least available locally so that the long term life of the stove is maintainable and so sustainable.

Now, if the cookstove unit can by powered by  simple solar or biomass system, this will change the whole nature of the life style and domestic duties of the chief cook and the young siblings who are typically charged with collecting the natural firewood to meet the cooking requirement.

Therefore the cookstoves need to be designed and adapted for the people group and their traditional cooking habits, and not in the reverse order. To assess the overall performance of the green cooking stoves requires simple but effective measures of the air quality. The two elements that need to be measured are the black carbon emissions and the temperature of the cooking device.  This can be achieved by miniature aerosol samplers and temperature sensors. The data collected needs to be transmitted in real-time via mobile phones for verification of performance rates.  This is to provide verifiable data in a cost effective monitoring process.

Biomass Energy Potential in Philippines

The Philippines has abundant supplies of biomass energy resources in the form of agricultural crop residues, forest residues, animal wastes, agro-industrial wastes, municipal solid wastes and aquatic biomass. The most common agricultural wastes are rice hull, bagasse, cane trash, coconut shell/husk and coconut coir. The use of crop residues as biofuels is increasing in the Philippines as fossil fuel prices continue to rise. Rice hull is perhaps the most important, underdeveloped biomass resource that could be fully utilized in a sustainable manner.

At present, biomass technologies utilized in the country vary from the use of bagasse as boiler fuel for cogeneration, rice/coconut husks dryers for crop drying, biomass gasifiers for mechanical and electrical applications, fuelwood and agricultural wastes for oven, kiln, furnace and cook-stoves for cooking and heating purposes. Biomass technologies represent the largest installations in the Philippines in comparison with the other renewable energy, energy efficiency and greenhouse gas abatement technologies.

Biomass energy plays a vital role in the nation’s energy supply. Nearly 30 percent of the energy for the 80 million people living in the Philippines comes from biomass, mainly used for household cooking by the rural poor. Biomass energy application accounts for around 15 percent of the primary energy use in the Philippines. The resources available in the Philippines can generate biomass projects with a potential capacity of more than 200 MW.

Almost 73 percent of this biomass use is traced to the cooking needs of the residential sector while industrial and commercial applications accounts for the rest. 92 percent of the biomass industrial use is traced to boiler fuel applications for power and steam generation followed by commercial applications like drying, ceramic processing and metal production. Commercial baking and cooking applications account for 1.3 percent of its use.

The EC-ASEAN COGEN Programme estimated that the volume of residues from rice, coconut, palm oil, sugar and wood industries is 16 million tons per year. Bagasse, coconut husks and shell can account for at least 12 percent of total national energy supply. The World Bank-Energy Sector Management Assistance Program estimated that residues from sugar, rice and coconut could produce 90 MW, 40 MW, and 20 MW, respectively.

The development of crop trash recovery systems, improvement of agro-forestry systems, introduction of latest energy conversion technologies and development of biomass supply chain can play a major role in biomass energy development in the Philippines. The Philippines is among the most vulnerable nations to climatic instability and experiences some of the largest crop losses due to unexpected climatic events. The country has strong self-interest in the advancement of clean energy technologies, and has the potential to become a role model for other developing nations on account of its broad portfolio of biomass energy resources and its potential to assist in rural development.

Bioplastics: Making an Informed Decision

bioplasticsPlastics are regarded by some as one of the greatest human inventions and continue to benefit society in more ways than one. However these benefits come at a high environmental cost as research has shown that “over 300 million metric tons of plastics are produced in the world annually and about 50% of this volume is for disposable applications, products that are discarded within a year of their purchase”.

About 50 percent of all plastics produced worldwide are disposed of within one year of being manufactured; now that is a critically important statistic when plastics have been known to have life spans over 500 years.  Infact, this is the main reason behind massive waste accumulation of plastics in landfills, drainage systems, water bodies etc. Moreover, plastic’s destruction is evident when in 2009, it was reported that an estimated 150 million tons of fossil fuels were consumed for the production of plastics worldwide.  Given all of these facts, it is no surprise that the pervasive use of non-biodegradable plastics has provoked many environmental and health concerns, especially in developing countries where plastic is often disposed of in unauthorized dumping sites or burned uncontrollably.

One result of this broadening awareness of the global plastic waste problem and its impact on the environment is the development of bioplastics.  Bioplastics are based on biomass derived from renewable resources and are in many cases more environmentally friendly than traditional petroleum based plastics. Currently, numerous types of bioplastics are under development, the most popular being “Polylactides, Polyglycolic acids, Polyhydroxyalkanoates (PHAs), aliphatic polyesters, polysaccharides”.

Basic Concepts and Misconceptions

Overall, in the Plastics Industry Trade Association’s 2012 Bioplastics Industry Overview Guide, it is stated that bioplastics that are both bio-based and biodegradable play an important role in further advancing the plastic industry as a whole.  Incredibly essential to note, is that within the above statement, it states, the importance of bioplastics that are both bio-based and biodegradable.  This statement implys that not all bioplastics are biodegradable and/or bio-based.  In fact, according to a 2011 industry report, there are many characteristics such as degradable, biodegradable, bio-based and compostable that are used to describe bioplastics. However, not every bioplastic is comprised of all of these features.  According to the report, this remains a common misconception as the public at large still lacks a clear understanding of the various bioplastic related terms.  For instance, it is commonly thought of that the terms bio-based and biodegradable are interchangeable. However not all bio-based plastics will degrade naturally. In fact, “many bio-based products are designed to behave like traditional petroleum-based plastic, and remain structurally intact for hundreds of years”.

The American Society for Testing and Materials (ASTM) defines biodegradable plastics as a plastic in which all the organic carbon can be converted into biomass, water, carbon dioxide, and/or methane via the action of naturally occurring microorganisms such as bacteria and fungi, in timeframes consistent with the ambient conditions of the disposal method (Compostable Plastics 101). This definition implies that there is a specific timeframe for the biodegradation to take place and merely fragmenting into smaller pieces, even if microscopic, does not make a material biodegradable.  This definition is commonly confused with the term degradable which is a broader term given to polymers or plastics that simply break down by a number or means, such as physical disintegration, chemical disintegration and biodegradation by natural mechanisms. After degradation, a degradable plastic can still remain in a smaller or fragmented form unlike that of a biodegradable plastic, which needs to completely biodegrade into water, carbon dioxide and/or methane. This distinction between terms results in polymers that are degradable but not biodegradable.

Another term that is commonly found to describe bioplastics is ‘compostable’. Compostable is defined by ASTM as “a plastic that undergoes biological degradation during composting to yield carbon dioxide, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials and leaves no visually distinguishable or toxic residues”. While the ASTM has specific standards for a plastic to be compostable such as biodegradation, eco-toxicity, and disintegration, the main difference between a plastic being compostable versus biodegradable is the rapid rate at which biodegradation, eco-toxicity, and disintegration occur. Therefore, in theory, all compostable plastics are biodegradable however, not all biodegradable plastics are compostable.

Finally, probably the most often confused term regarding bioplastics is the label, “bio-based”.  As defined by the US Department of Agriculture, the term “bio-based” refers to solely the raw materials of the plastic. According to the Department of Agriculture, bio-based materials that are those that are “composed in whole, or in significant part, of biological products or renewable domestic agricultural materials or forestry materials”. Since the majority, not all, of the materials have to be renewable, many bio-based plastics combine both petroleum-based materials with naturally based ones. For this reason, some researchers have suggested that a bio-based material may not technically be a sustainable product. Therefore, while the two terms are somewhat related, whether or not a product is bio-based is not an independent indicator of whether it is biodegradable.

Making an Informed Decision

This lack of understanding between the terms is a large issue that does not get much recognition.  Consumers are increasingly buying more and more bioplastics but are not fully being educated on the differences between the various different types of bioplastics on the markets. While as a whole, bioplastics may have many notable attributes making them excellent alternatives to traditional plastics, they are not considered flawless solutions. Some bioplastics encompass all of the above qualities while others may only hold one or two of these characteristics; meaning that there is a vast disparity between how environment-friendly different bioplastics might actually be.

Consumers often see the term bioplastic or a bio-based plastic and automatically assume that it will breakdown into the soil like leaves or grass once it is disposed of, when as discussed, this is often not the case. All in all, given the significant differences between the terms, it is very important for consumers to know that “bio-based,” “biodegradable” and “compostable” are individual attributes and be educated on what these characteristics actually mean. It is equally important for manufacturers to be educated on these differences and make proper labeling of their bioplastic products.

References

Biobased and degradable plastics in California. Retrieved from  this link

California Organics Recycling Council. (2011). Compostable plastics 101. Retrieved from this link

Confused by the terms biodegradable & biobased. (n.d.). Retrieved from this link

Divya, G., Archana, T., & Manzano, R. A. (2013). Polyhydroxy alkanoates – A sustainable alternative to petro-based plastics. Petroleum & Environmental Biotechnology, 4(3), 1-8. http://dx.doi.org/10.4172/2157-7463.1000143

Liu, H-Y. (2009). Bioplastics poly(hydroxyalkanoate) production during industrial wastewater treatment. Retrieved from ProQuest Digital Dissertations. (AAT 3362495)

Niaounakis, M. (2013). Biopolymers: Reuse, recycling, and disposal. Waltham, MA: William Andrew Publishing.

North, E. J., & Halden, R. U. (2013). Plastics and environmental health: the road ahead. Reviews on Environmental Health, 28(1), 1-8. doi: 10.1515/reveh-2012-0030

The Society of the Plastics Industry, Inc. (2012, April). Bioplastics Industry Overview Guide.

United States Department of Agriculture. (2006). Federal biobased products preferred procurement program. Retrieved from this link

Biorefinery Prospects in India

India has a tremendous biomass potential which could easily be relied upon to fulfil most of our energy needs. An estimated 50 MMT (million metric tonnes) of liquid fuels are consumed annually in India, but with the actual biomass potential and its full utilization, India is capable of generating almost double that amount per annum. These biomass estimates only constitute the crop residues available in the country and essentially the second-generation fuels since the use of first-generation crop bases fuels in such food-starved nations is a criminal thought.

Existing Technologies

Currently, there are various technologies available to process such crop residues and generate value products from them. However, essentially, they all revolve around two main kinds of processes, either biochemical or thermal.

The biochemical process involves application of aerobic/anaerobic digestion for the production of biogas; or fermentation, which results in the generation of ethanol. Both these products could be subsequently treated chemically and through trans-esterification process, leading to production of biodiesel.

Alternatively, the thermochemical processes involve either the combustion, gasification or pyrolysis techniques, which produces heat, energy-rich gas and liquid fuels respectively. These products can be used as such, or could be further processed to generate high quality biofuels or chemicals.

The Need

The estimated organized energy breakup for India is 40 percent each for domestic and transport sectors and 20 percent for the industrial sectors. The current share of crude oil and gases is nearly 90 percent for the primary and transport sectors and the remaining 10 percent for the generation of industrial chemicals. The escalating prices of crude oil in the international market and the resulting concern over energy security, has lead developing nations to explore alternative and cheap sources of energy to meet the growing energy demand. One of the promising solution for agrarian economies is Biorefinery.

The Concept

Biorefinery is analogous to the traditional petroleum refineries employing fractional distillation process for obtaining different fractions or components from the same raw material, i.e. the crude oil. Biorefinery involve the integration of different biomass treatment and processing methods into one system, which results in the production of different components from the same biomass.  This makes the entire chain more viable economically and also reduces the waste generated.

Typical Model of a Biorefinery

The outcome ranges from high-volume, low-energy content liquid fuels, which could serve the transportation industry needs, to the low-volume but high-value chemicals, which could add to the feasibility of such a project. Steam and heat generated in the process could be utilized for meeting process heat requirements. By-products like chemicals, fertilizers, pharmaceuticals, polymers etc are also obtained which provide additional revenue streams.

Benefits

Biorefineries can help in utilizing the optimum energy potential of organic wastes and may also resolve the problems of waste management and GHGs emissions. Wastes can be converted, through appropriate enzymatic/chemical treatment, into either gaseous or liquid fuels. The pre-treatment processes involved in biorefining generate products like paper-pulp, HFCS, solvents, acetate, resins, laminates, adhesives, flavour chemicals, activated carbon, fuel enhancers, undigested sugars etc. which generally remain untapped in the traditional processes. The suitability of this process is further enhanced from the fact that it can utilize a variety of biomass resources, whether plant-derived or animal-derived.

Applicability

The concept of biorefinery is still in early stages at most places in the world. Problems like raw material availability, feasibility in product supply chain, scalability of the model are hampering its development at commercial-scales. The National Renewable Energy Laboratory (NREL) of USA is leading the front in biorefinery research with path-breaking discoveries and inventions. Although the technology is still in nascent stages, but it holds the key to the optimum utilization of wastes and natural resources that humans have always tried to achieve. The onus now lies on governments and corporate to incentivize or finance the research and development in this field.

Biomass Conveyors: An Overview

Biomass_ConveyorA well designed biomass conveyor system should take into account the variability of the material and provide the consistent and reliable flow that is crucial to power generation. Depending upon the type of boiler and conversion system, the fuel is either transported directly to the powerhouse via a belt conveyor, or first processed in a chipper/grinder to produce a finer texture. For example, municipal solid waste is deposited into pits where cranes mix the refuse and remove any large, non-combustible items. Sometimes, it is further processed to remove ferrous materials, glass, and other non-combustible materials.

For large pellet-fired biomass system, rail dump method is very common where railway tracks are constructed to transport biomass. Station is specified for train and fuel receiving bins are typically located below the track and rail cars dump into bins, either directly or through a rotary dumper. Fuel received is then transferred by belt conveyors to the biomass storage bins. For small particle size, pneumatic conveying system offer greater flexibility in routing than traditional belt conveyors. Equipment specific to pneumatic systems include positive displacement blowers and rotary feeders that function as air locks.

In a typical biomass thermal power plant, the initial process in the power generation is biomass fuel handling. A railway siding line is taken into the power station and the biomass is delivered in the storage yard. It is then unloaded from the point of delivery by means of wagon tippler. It is rack and pinion type. The biomass is taken from the unloading site to dead storage by belt conveyors. The belt deliver the biomass to warehouse.

The transfer points inside the warehouse are used to transfer biomass to the next belt. The belt elevates the biomass to breaker house. It consists of a rotary machine, which rotates the biomass and separates the light inorganic materials (viz. plastic or other incombustible particles) from it through the action of gravity and transfer it to reject bin house through belt. The belt further elevates the biomass until it reaches the crusher through belt. In the crusher a high-speed 3-phase induction motor is used to crush the biomass according to the requirement, for gasification size range is usually upto 15-20mm, while for biomass-fired boiler, size of 50mm is acceptable. Biomass rises from crusher house and reaches the dead storage.

Cost-effective production of biomass energy is very much dependent on efficient handling of available biomass sources, as well as the efficiency of each process. An important, but often overlooked, area is the efficient receiving of different types and different capacities of biomass as it enters the plant and then conveying this material to the production equipment.  In many cases, the space available for biomass handling is limited.

Receiving equipment can be installed in a pit or at the ground level. The size and volume of the receiving pocket can be suited to vehicle volumes or turn-around times. The receiving pit can be used as small buffer biomass storage or as an emergency or mixing pocket.

Belt conveyors are an economical and reliable choice for transferring biomass over long distances at high capacities with lower noise levels. Designs range from simple, open configurations to totally closed and washable conveyor galleries. Well engineered conveyors have the maximum safe distance between support legs to minimize the cost of civil construction as well as reducing the number of obstructions on the ground.

Chain conveyors are a reliable choice for transporting unscreened or dusty biomass, or when the available space is limited. Screw conveyors are a very economical alternative for transporting biomass over short distances.

Biomass conveyors are an integral feature of all biomass conversion routes

Nowadays, automated conveyor systems are getting traction around the world. Fully automated fuel handling systems employ a biomass storage bin that can hold upto 50 tons (or more) of biomass. The bin is filled by a self-unloading truck with negligible or no onsite staff assistance. From the biomass storage bunker, the fuel is fed automatically to the boiler by augers and conveyors. The fully automated system is a good match for biomass plants where maintenance staff has a large work load and cannot spend much time working with the biomass conversion plant.

Pellet-based hopper systems offer low costs for both installation and operation. In a modern biomass pellet boiler system, fuel is stored in a relatively low-cost grain silo and automatically fed, with no operator intervention, to the boiler or boilers with auger systems similar to those used for conveying feed grain on farms.

The fuel-handling system uses electric motors and is run by automated controls that provide the right amount of fuel to the combustion chamber based on facility demand. Such conveyor systems require minimal maintenance, around 20-30 minutes daily, for ash removal and maintenance of motors and augers, estimated to be about 20-30 minutes per day.

Bioenergy Resources in MENA Countries

The Middle East and North Africa (MENA) region offers almost 45 percent of the world’s total energy potential from all renewable sources that can generate more than three times the world’s total power demand. Apart from solar and wind, MENA also has abundant biomass energy resources which have remained unexplored to a great extent.

According to conservative estimates, the potential of biomass energy in the Euro Mediterranean region is about 400TWh per year. Around the region, pollution of the air and water from municipal, industrial and agricultural operations continues to grow.  The technological advancements in the biomass energy industry, coupled with the tremendous regional potential, promises to usher in a new era of energy as well as environmental security for the region.

The major biomass producing countries are Egypt, Yemen, Iraq, Syria and Jordan. Traditionally, biomass energy has been widely used in rural areas for domestic purposes in the MENA region, especially in Egypt, Yemen and Jordan. Since most of the region is arid or semi-arid, the biomass energy potential is mainly contributed by municipal solid wastes, agricultural residues and industrial wastes.

Municipal solid wastes represent the best source of biomass in Middle East countries. Bahrain, Saudi Arabia, UAE, Qatar and Kuwait rank in the top-ten worldwide in terms of per capita solid waste generation. The gross urban waste generation quantity from Middle East countries is estimated at more than 150 million tons annually. Food waste is the third-largest component of generated waste by weight which mostly ends up rotting in landfill and releasing greenhouse gases into the atmosphere. The mushrooming of hotels, restaurants, fast-food joints and cafeterias in the region has resulted in the generation of huge quantities of food wastes.

In Middle East countries, huge quantity of sewage sludge is produced on daily basis which presents a serious problem due to its high treatment costs and risk to environment and human health. On an average, the rate of wastewater generation is 80-200 litres per person each day and sewage output is rising by 25 percent every year. According to estimates from the Drainage and Irrigation Department of Dubai Municipality, sewage generation in the Dubai increased from 50,000 m3 per day in 1981 to 400,000 m3 per day in 2006.

The food processing industry in MENA produces a large number of organic residues and by-products that can be used as biomass energy sources. In recent decades, the fast-growing food and beverage processing industry has remarkably increased in importance in major countries of the region. Since the early 1990s, the increased agricultural output stimulated an increase in fruit and vegetable canning as well as juice, beverage, and oil processing in countries like Egypt, Syria, Lebanon and Saudi Arabia.

The MENA countries have strong animal population. The livestock sector, in particular sheep, goats and camels, plays an important role in the national economy of respective countries. Many millions of live ruminants are imported each year from around the world. In addition, the region has witnessed very rapid growth in the poultry sector. The biogas potential of animal manure can be harnessed both at small- and community-scale.

Overview of Biomass Pyrolysis

Biomass pyrolysis is the thermal decomposition of biomass occurring in the absence of oxygen. It is the fundamental chemical reaction that is the precursor of both the combustion and gasification processes and occurs naturally in the first two seconds. The products of biomass pyrolysis include biochar, bio-oil and gases including methane, hydrogen, carbon monoxide, and carbon dioxide.

The pyrolysis process consists of both simultaneous and successive reactions when organic material is heated in a non-reactive atmosphere. Thermal decomposition of organic components in biomass starts at 350 °C–550 °C and goes up to 700 °C–800 °C in the absence of air/oxygen. The long chains of carbon, hydrogen and oxygen compounds in biomass break down into smaller molecules in the form of gases, condensable vapours (tars and oils) and solid charcoal under pyrolysis conditions. Rate and extent of decomposition of each of these components depends on the process parameters of the reactor temperature, biomass heating rate, pressure, reactor configuration, feedstock etc

Depending on the thermal environment and the final temperature, pyrolysis will yield mainly biochar at low temperatures, less than 450 0C, when the heating rate is quite slow, and mainly gases at high temperatures, greater than 800 0C, with rapid heating rates. At an intermediate temperature and under relatively high heating rates, the main product is bio-oil.

Slow and Fast Pyrolysis

Pyrolysis processes can be categorized as slow or fast. Slow pyrolysis takes several hours to complete and results in biochar as the main product. On the other hand, fast pyrolysis yields 60% bio-oil and takes seconds for complete pyrolysis. In addition, it gives 20% biochar and 20% syngas.  Fast pyrolysis is currently the most widely used pyrolysis system.

The essential features of a fast pyrolysis process are:

  • Very high heating and heat transfer rates, which require a finely ground feed.
  • Carefully controlled reaction temperature of around 500oC in the vapour phase
  •  Residence time of pyrolysis vapours in the reactor less than 1 sec
  • Quenching (rapid cooling) of the pyrolysis vapours to give the bio-oil product.

Advantages of Biomass Pyrolysis

Pyrolysis can be performed at relatively small scale and at remote locations which enhance energy density of the biomass resource and reduce transport and handling costs.  Heat transfer is a critical area in pyrolysis as the pyrolysis process is endothermic and sufficient heat transfer surface has to be provided to meet process heat needs. Biomass pyrolysis offers a flexible and attractive way of converting organic matter into energy products which can be successfully used for the production of heat, power and chemicals.

A wide range of biomass feedstocks can be used in pyrolysis processes. The pyrolysis process is very dependent on the moisture content of the feedstock, which should be around 10%. At higher moisture contents, high levels of water are produced and at lower levels there is a risk that the process only produces dust instead of oil. High-moisture waste streams, such as sludge and meat processing wastes, require drying before subjecting to pyrolysis.

Furthermore, the bio-char produced can be used on the farm as an excellent soil amender as it is highly absorbent and therefore increases the soil’s ability to retain water, nutrients and agricultural chemicals, preventing water contamination and soil erosion. Soil application of bio-char may enhance both soil quality and be an effective means of sequestering large amounts of carbon, thereby helping to mitigate global climate change through carbon sequestration.  Use of bio-char as a soil amendment will offset many of the problems associated with removing crop residues from the land.

Biomass pyrolysis has been garnering much attention due to its high efficiency and good environmental performance characteristics. It also provides an opportunity for the processing of agricultural residues, wood wastes and municipal solid waste into clean energy. In addition, biochar sequestration could make a big difference in the fossil fuel emissions worldwide and act as a major player in the global carbon market with its robust, clean and simple production technology.

Agricultural Wastes in the Philippines

The Philippines is mainly an agricultural country with a land area of 30 million hectares, 47 percent of which is agricultural. The total area devoted to agricultural crops is 13 million hectares distributed among food grains, food crops and non-food crops. Among the crops grown, rice, coconut and sugarcane are major contributors to biomass energy resources.

The most common agricultural wastes in the Philippines are rice husk, rice straw, coconut husk, coconut shell and bagasse. The country has good potential for biomass power plants as one-third of the country’s agricultural land produces rice, and consequently large volumes of rice straw and hulls are generated.

Rice is the staple food in the Philippines. The Filipinos are among the world’s biggest rice consumers. The average Filipino consumes about 100 kilograms per year of rice.  Though rice is produced throughout the country, the Central Luzon and Cagayan Valley are the major rice growing regions. With more than 1.2 million hectares of rain-fed rice-producing areas, the country produced around 16 million tons of rice in 2007. The estimated production of rice hull in the Philippines is more than 2 million tons per annum which is equivalent to approximately 5 million BOE (barrels of oil equivalent) in terms of energy. Rice straw is another important biomass resource with potential availability exceeding 5 million tons per year across the country.

With the passing of Biofuels Act of 2006, the sugar industry in the Philippines which is the major source of ethanol and domestic sugar will become a major thriving industry. Around 380,000 hectares of land is devoted to sugarcane cultivation. It is estimated that 1.17 million tonnes of sugarcane trash is recoverable as a biomass resource in the Philippines. In addition, 6.4 million tonnes of surplus bagasse is available from sugar mills. There are 29 operating sugar mills in the country with an average capacity of 6,900 tonnes of cane per day. Majority is located in Negros Island which provides about 46% of the country’s annual sugar production.

The Philippines has the largest number of coconut trees in the world as it produces most of the world market for coconut oil and copra meal. The major coconut wastes include coconut shell, coconut husks and coconut coir dust. Coconut shell is the most widely utilized but the reported utilization rate is very low.  Approximately 500 million coconut trees in the Philippines produce tremendous amounts of biomass as husk (4.1 million tonnes), shell (1.8 million tonnes), and frond (4.5 million tonnes annually).

Maize is a major crop in the Philippines that generates large amounts of agricultural residues. It is estimated that 4 million tonnes of grain maize and 0.96 million tonnes of maize cobs produced yearly in the Philippines. Maize cob burning is the main energy application of the crop, and is widely practiced by small farmers to supplement fuelwood for cooking.

Cogeneration of Bagasse

Cogeneration of bagasse is one of the most attractive and successful energy projects that have already been demonstrated in many sugarcane producing countries such as Mauritius, Reunion Island, India and Brazil. Combined heat and power from sugarcane in the form of power generation offers renewable energy options that promote sustainable development, take advantage of domestic resources, increase profitability and competitiveness in the industry, and cost-effectively address climate mitigation and other environmental goals.

According to World Alliance for Decentralized Energy (WADE) report on Bagasse Cogeneration, bagasse-based cogeneration could deliver up to 25% of current power demand requirements in the world’s main cane producing countries. The overall potential share in the world’s major developing country producers exceeds 7%. There is abundant opportunity for the wider use of bagasse-based cogeneration in sugarcane-producing countries. It is especially great in the world’s main cane producing countries like Brazil, India, Thailand, Pakistan, Mexico, Cuba, Colombia, Philippines and Vietnam. Yet this potential remains by and large unexploited.

Using bagasse to generate power represents an opportunity to generate significant revenue through the sale of electricity and carbon credits. Additionally, cogeneration of heat and power allows sugar producers to meet their internal energy requirements and drastically reduce their operational costs, in many cases by as much as 25%. Burning bagasse also removes a waste product through its use as a feedstock for the electrical generators and steam turbines.

Most sugarcane mills around the globe have achieved energy self-sufficiency for the manufacture of raw sugar and can also generate a small amount of exportable electricity. However, using traditional equipment such as low-pressure boilers and counter-pressure turbo alternators, the level and reliability of electricity production is not sufficient to change the energy balance and attract interest for export to the electric power grid.

On the other hand, revamping the boiler house of sugar mills with high pressure boilers and condensing extraction steam turbine can substantially increase the level of exportable electricity. This experience has been witnessed in Mauritius, where, following major changes in the processing configurations, the exportable electricity from its sugar factory increased from around 30-40 kWh to around 100–140 kWh per ton cane crushed. In Brazil, the world’s largest cane producer, most of the sugar mills are upgrading their boiler configurations to 42 bars or even higher pressure of up to 67 bars.

Technology Options

The prime technology for sugar mill cogeneration is the conventional steam-Rankine cycle design for conversion of fuel into electricity. A combination of stored and fresh bagasse is usually fed to a specially designed furnace to generate steam in a boiler at typical pressures and temperatures of usually more than 40 bars and 440°C respectively. The high pressure steam is then expanded either in a back pressure or single extraction back pressure or single extraction condensing or double extraction cum condensing type turbo generator operating at similar inlet steam conditions.

Due to high pressure and temperature, as well as extraction and condensing modes of the turbine, higher quantum of power gets generated in the turbine–generator set, over and above the power required for sugar process, other by-products, and cogeneration plant auxiliaries. The excess power generated in the turbine generator set is then stepped up to extra high voltage of 66/110/220 kV, depending on the nearby substation configuration and fed into the nearby utility grid. As the sugar industry operates seasonally, the boilers are normally designed for multi-fuel operations, so as to utilize mill bagasse, procured Bagasse/biomass, coal and fossil fuel, so as to ensure year round operation of the power plant for export to the grid.

Latest Trends

Modern power plants use higher pressures, up to 87 bars or more. The higher pressure normally generates more power with the same quantity of Bagasse or biomass fuel. Thus, a higher pressure and temperature configuration is a key in increasing exportable surplus electricity.

In general, 67 bars pressure and 495°C temperature configurations for sugar mill cogeneration plants are well-established in many sugar mills in India. Extra high pressure at 87 bars and 510°C, configuration comparable to those in Mauritius, is the current trend and there are about several projects commissioned and operating in India and Brazil. The average increase of power export from 40 bars to 60 bars to 80 bars stages is usually in the range of 7-10%.

A promising alternative to steam turbines are gas turbines fuelled by gas produced by thermochemical conversion of biomass. The exhaust is used to raise steam in heat recovery systems used in any of the following ways: heating process needs in a cogeneration system, for injecting back into gas turbine to raise power output and efficiency in a steam-injected gas turbine cycle (STIG) or expanding through a steam turbine to boost power output and efficiency in a gas turbine/steam turbine combined cycle (GTCC). Gas turbines, unlike steam turbines, are characterized by lower unit capital costs at modest scale, and the most efficient cycles are considerably more efficient than comparably sized steam turbines.