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Essay on Biomass
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Essay Contents:
- Essay on the Definition of Biomass
- Essay on the Main Sources of Biomass
- Essay on the Power from Biomass
- Essay on the Uses of Biomass
- Essay on the Biomass Programmes
- Essay on the Biomass and the Environment
Essay # 1. Definition of Biomass:
Any type of animal or plant material that can be converted into energy is called biomass. This includes trees and shrubs, crops and grasses, algae, aquatic plants, agricultural and forest residues plus all forms of human, animal and plant waste (1). When the material is used for energy production it becomes a biofuel. There are many forms of biofuel, existing in solid, liquid or gaseous categories.
An estimate of the world solid biomass standing in forests in 1979 was 1.8 x 1022 J. At that time this figure was comparable with the world’s proven natural gas and oil reserves. The same biomass figure is about 50 times the value of world primary energy consumption in 1995.
If the biomass values of grasslands and crops are included (although these are mainly used for food production—indirectly energy—rather than fuel supply) the solid biomass figure is about 200 times the global energy consumption. Biomass may be used in a number of ways to produce energy.
The most common methods are:
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1. Combustion
2. Gasification
3. Fermentation
4. Anaerobic digestion
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India is very rich in biomass. It has a potential of 19,500 MW (3,500 MW from bagasse-based congeneration and 16,000 MW from surplus biomass). Currently, India has 537 MW commissioned and 536 MW under construction. The facts reinforce the idea of a commitment by India to develop these resources of power production.
Following is a list of some States with most potential for biomass production:
1. Andhra Pradesh (200 MW)
2. Bihar (200 MW)
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3. Gujarat (200 MW)
4. Karnataka (300 MW)
5. Maharashtra (1,000 MW)
6. Punjab (150 MW)
7. Tamil Nadu (350 MW)
8. Uttar Pradesh (1,000 MW)
The potential available and the installed capacities for Biomass and Bagasse.
Essay # 2. Main Sources of Biomass:
The main sources of raw material that constitute biomass include:
a. Natural Vegetation:
In harvesting a natural vegetation site no energy costs are involved in clearing or replanting. Where an area may be unsuitable for agriculture the use of its vegetation for biomass would constitute a useful bonus biofuel source.
There still remains the necessary costs of harvesting the vegetation and transporting it to a user site. A disadvantage is that even in fertile locations the yields are low—about half of the value that might be obtained from customized energy plantations.
b. Energy Tree Plantations:
Trees and other types of lignocellulose materials may be grown specifically for burning as biofuels. By the choice of appropriate species, sites, planting densities and harvesting schedules biofuels can be grown at competitive costs. This process is sometimes referred to as “short rotation forestry“.
c. Specific Energy Crops:
Certain crops have high energy conversion efficiency. In appropriate locations, crops such as eucalyptus trees, rubber plants or sunflowers might be used because of their rapid growth and high energy content (3).
Such crops do not have to be consumable by humans or animals and the entire crop can be used, including leaves, stalks and roots. The stored chemical energy can be converted directly to heat by combustion or processed into liquid or gaseous fuels.
Energy farming, like other agricultural operations, requires large quantities of water. In the developed countries of the western world there is competition for the use of land, water and nutrients with various forms of food production, including animal farming.
An interesting economic issue is whether crops in growth command higher prices as fuel rather than food or fibre. Crop surpluses would provide low-cost biomass but is surplus food production the best overall use of the land and water?
There is a further potential disadvantage to the use of land-based energy farming. The hardy and fast- growing species required for energy use could become widespread nuisances if they escaped from the confines of the farm. They may then displace native plant species and impact on animal and insect life.
Also, the methods necessarily used to control infestations and disease in the energy plants, especially if they are monocultures, could have adverse effects on neighboring food production crops. The same soil plantation may be used for two species of plants with out-of-phase growth patterns.
If both species are in leaf together the leaf canopy cover profile is increased. Non-nitrogen-fixing crops can be grown side-by-side with legumes to reduce the need for nitrogenous fertilizers. Mixed cropping of this kind is less susceptible to damage by external parasites or predators than monoculture plantations.
There are some plants that produce high concentrations of “petroleum-like” products. These can be grown en masse and the “oils” extracted or squeezed out. Pilot schemes have been carried out in Mexico. Widespread energy farming on marginal land implies the need for some level of overall control.
A fast-growing plant that thrived in marginal conditions would create incentives to adapt the plant for food production. This is not necessarily bad but would create further pressure on land use for purely biomass reasons. In other words, the food versus biomass competition would increase.
It would seem sensible to think in terms of integrated growth mixed cropping, in which energy crops are developed alongside crops for food, fertilizers and chemicals. The vertical distribution of primary productivity and biomass formation in forest is shown in Fig 24.18.
Essay # 3. Power from Biomass:
Almost all life forms need sunlight for their energy (some creatures in volcanic ocean trenches use geothermal energy). Photosynthesis by green plants converts large amount of sunlight into biological material- grass, trees etc.—which are rich in energy and form the basis of food chains for other creatures.
Human society derives products such as wood or alcohol from these basic photosynthetic materials and uses them to meet various human needs. The fossil fuels which we use at the moment are products of photosynthesis many million of years ago and form an “energy bank” on which our present society is drawing heavily.
Biomass is used extensively throughout the world today. The use of fuel wood, crop residue or cow dung for cooking is widespread in developing countries as a free good and is usually the only option for their rural poor.
The use of biomass is not, however, restricted to the poor of the Third World. For instances, the US obtains as much energy from biomass as it does from nuclear power, while Sweden derives 14 per cent of its primary energy from biomass.
The biomass resources are very large, the amount stored annually worldwide is equivalent to ten times the total world annual energy use. The total stored biomass in the world has an energy content equal to that of all the world’s proven fossil fuel reserves.
Table 24.4 shows the potential for biomass to supply the energy demand of different regions of the world. Europe would be able to supply only half its energy demand even if it used all of its fertile land for energy production, while North America would need over half of its fertile land to meet its present energy demand.
This is due partly to the inflation of the present demand for primary fuels because of inefficient use, but also, in the case of Europe, by a population density of around 1/2 ha/person of fertile land.
South America is best placed to supply its energy needs from biomass, needing only about 3 per cent of its fertile land to supply 35 GJ/Cap p.a. Central America would need one-fifth of its fertile land.
Asia would need to use two-thirds of its fertile land for energy crops and would, if it did so, have severe problems of food supply. Africa would need about one-eighth of its fertile land, which could be acceptable if agricultural productivity improved.
No one really thinks that any region would rely exclusively on biomass for its energy supply, but the data in Table 24.4 do show clearly the very large potential in many areas of the world.
There are four major attractions in the use of biomass; it is an indigenous resource in most parts of the world; it provides stored energy unlike most renewable sources; it is very flexible in use; and, during its growth, it captures CO2.
It also makes use of agricultural skills which are to be found throughout the world, and provides rural employment and thus, unlike most other energy technologies, does not increase the drift from rural to urban areas.
Essay # 4. Uses of Biomass:
The simplest use of biomass is to burn it and the most common biomass used this way is wood, but corn stalks, cow dung and many other agricultural residues are also burnt on open fires for cooking, heating and other social purposes. The fireplace is usually formed by three stones, on which the cooking pot, or whatever, is balanced. Both the fuel and the stones are gathered locally, so the only cost is in time.
The next step in sophistication is to heat the wood in an enclosed space to make charcoal which is a very convenient fuel. It is much lighter than wood and so is much more easily transported. It burns without fumes and so is favoured in urban areas, but it is a processed fuel, sold commercially to those who can afford it.
In many parts of the world, animal—and sometimes human—wastes are used in biogas plants. The anaerobic digestion of these wastes produces a methane-rich gas and leaves behind a benign residue which makes an excellent compost.
There are millions of farms or village-sized biogas plants in operation around the world, particularly in China and India. But collecting waste from animals which roam freely can be so time-consuming that biogas production is no longer worthwhile and it is only really practicable where animals are kept in pens.
None the less, enough gas to satisfy the family’s cooking and lighting needs can be produced from the waste of the livestock owned by a typical peasant farmer.
This is particularly true where fairly rapid cooking is the norm, as with the Chinese wok. In general, the richer the farmer, the more animals the family will have and hence the more likely it is that a biogas plant could supply the family with its cooking and lighting needs.
In the industrialised countries and the urban conurbations of developing countries, the use of biomass would need to be on an industrial scale, far removed from farm or village sized charcoal or biogas plants. Just as farms can burn their own straw or dispose of animal waste in biogas plants, so municipalities could install waste burning and land-fill gas plants for energy production.
The full potential of biomass as an energy source could, however, only be achieved by the use of energy crops and the associated processing plants.
The two major ways of processing woody biomass from energy crops are bio-conversion by a fermentation process and thermal conversion, usually by anaerobic heating. Table 24.5 shows the products which can be derived from these processing steps.
Bio-conversion processing has been known for thousands of years and is used to produce those important solar products—beer, wine, and spirits. In the Brazilian bio alcohol programme a process similar to distilling spirits is used to ferment sugar cane and distill the ethanol; in the US, grain is used for the same purpose.
To ferment woody biomass, produced by coppicing energy plantations, its cell structure must first be broken down by hydrolysis, acids or enzymes to allow fermentation to proceed efficiently.
There are four basic thermal conversion processes:
The oldest is direct combustion in air to produce heat. This can range from the domestic wood fire to large power stations fuelled by peat, coconut fibres and other waste products.
Pyrolysis is the process of heating biomass in the absence of air and as it reduces wood to charcoal, it produces gaseous and liquid products which, in the traditional charcoal kilns are vented into the air. In fact, they are valuable products and in modern pyrolysis plant they are collected and used (Fig. 24.19).
The third thermal conversion process is the liquefaction of biomass to produce bio-oil which can be burnt to produce heat and power or can be upgraded to petrol or diesel fuel. Rapeseed oil, for instance, is becoming quite widely used as a transport fuel, either on its own or as an additive to diesel.
The fourth process is gasification, which produces either or both, medium heating value (MHV) or low heating value (LHV) gas. Each has a different chemical make-up, but they can both be burnt in air to give heat and power or they can be used as chemical feedstock. MHV gas can be synthesised into methanol and LHV gas into ammonia, both of which are important in the chemical industry.
Essay # 5. Biomass Programmes:
Biomass programmes can be divided into three broad classes. There are those which are cost-effective on purely financial accounting grounds, there are those in the demonstration stage which can or could become cost-effective and there are those which may never become cost-effective, but which bring such significant non-monetary benefits that they deserve continuing support.
This last category is the most difficult to appraise. It includes many social forestry and agroforestry projects. If the cost/benefit analysis includes only commercial transactions, then many projects seem quite unviable.
However, their social and economic developmental benefits, though unquantifiable for accounting purposes are extremely important and often provide justification for continuing and even expanding or replicating them.
The second category includes many programmes for the development and dissemination of improved cooking stoves, small biogas plants in many parts of the world and the production of fuels by gasification or briquetting. The viability of these schemes depends crucially on local conditions, in agriculture as well as in social and economic structures.
Biomass energy or products have no general cost, only local costs determined by local conditions and the cost/benefit analysis determined by outside agencies may be quite different from the costs and benefits perceived by local people.
If these programmes are to be promoted by international agencies, an essential pre-condition for success is patience in working with and listening to local people so that the programme may be tailored to best meet their needs in their situation.
The first category, that of biomass projects judged on purely commercial grounds, is appropriate for Europe and other industrialized areas. Even so, it is not easy to produce definite cost-effectiveness judgements for them because there are so many ‘spin-off’ benefits.
These lie in maintaining a vigorous rural economy and in improving the environment by replacing fossil fuels (whose price does not include the cost of environmental externalities) with biomass fuels.
The costs, in Sao Paulo in Brazil, of producing hydrous alcohol for mixing with petrol are shown in Table 24.6. The Revenues at set at $ 0.18/liter and the residue(bagasse) from the process can be sold at the equivalent of $0.02/liter.
The process is profitable on its operating costs, but makes a loss if the opportunity costs are included. The rate of return on investment and hence the opportunity cost, depends on the financial circumstances of the time and changes with the economic climate.
The price of alcohol is set in relation to the cost of petrol, which depends on the international price of oil and the pricing policies of oil companies and Brazilian Government.
The attractiveness of using sugarcane for alcohol rather than sugar production depends on the world price of sugar. However, if the large Brazilian producers were to switch from alcohol to sugar production there would be such a glut on the world market that prices would tumble.
It has been estimated that up to 10 GW could be produced from the bagasse residues from alcohol production and there are proposals in Sao Paulo to use it as a solid fuel for power stations. This would transform the economics of the alcohol programme. Electricity could be produced at under $0.045k Wh and alcohol sold at $0.15/litre making it competitive even at $15/bbl for oil prices.
The biomass programme is the US is also very effective and biomass could be a major component of the US energy mix. Table 24.7 shows the energy which could be supplied annually on a commercial cost-effective basis if the target cost can be met.
It is clear that many of these potential resources are at, or close to, commercial viability. Technical developments, particularly those permitting increases in scale are still needed but the major obstacles are structural and institutional. The exploitation of these resources requires the recreation of new industries and this takes time, even when the technical and economic conditions are favourable.
There is, however, the problem of agricultural prices. Between 1980 and 1987, maize varied from $ 1.41 per bushel to $3.16 per bushel. By-product prices can vary by a factor of three. These variations are caused by market responses to worldwide supply and demand and are thus very difficult either to control or to predict.
There is thus a considerable risk that biomass industries will go through periods of unprofitable operation as world agricultural prices fluctuate and they will need some assurance of stability through long-term financing and/or guaranteed pricing.
There is a very active programme of research, development and demonstration of biomass technologies in the European Union. Contemporary European biomass resources are estimated at 455 Mt p.a. and could rise to 820 Mt p.a. in the future.
The breakdown of these resources is shown in Table 24.8:
The research programme of the European Commission has identified a wide range of crops which could be suitable for energy cropping.
These are shown in Table 24.9:
Of the species shown in Table 24.9 the front-runners for commercial energy cropping are sorghum for southern and central areas, eucalyptus for southern regions and poplar and willow for northern Europe. The costs of these resources are expected to be about 27-30 ECU/dry tonne in production, which is low enough to ensure that the end products of the bio or thermal conversion processes are cost-competitive.
Biomass production for non-agricultural purposes could be an important part of the European Common Agricultural Policy (CAP). Unless alternative profitable non-food uses for land can be found, the CAP schemes for limiting agricultural production will mean that it is abandoned, with all the consequent social and environmental costs.
About 20 million hectares of agricultural land and 10-20 million hectares of marginal land are likely to become available for biomass production by 2010 so using it to produce biomass could provide the employment needed to maintain rural economies.
Bio-energy, in the 21st century, could equal the present output of the North Sea oil fields or all the nuclear power stations so far installed and so could provide a significant fraction of the EU’s demand for energy. It would also confer significant environmental benefits.
The distinctive characteristic of the European programme is its emphasis on an integrated approach to the use of biomass. The output is seen as a set of products, each of which contributes to the profitability of the enterprise, rather than focusing just on energy and treating others as by-products.
The biomass industry can be targeted to meet needs in various sectors of industry, agriculture and energy in the different regions of Europe. The European programme has set target dates for demonstrating and commercializing the range of technologies needed for this integrated approach (Table 24.10).
Essay # 6. Biomass and the Environment:
Photosynthesis results in the absorption of carbon dioxide and the emission of oxygen, so the growth of plants counteracts the anthropogenic emissions of carbon dioxide from fossil fuels. The reduction in the area of high productivity plants in the tropical forests and grasslands is a cause for concern in its effect on the natural carbon cycle.
The planting of trees is often regarded as a means of counteracting the increasing atmospheric concentrations of carbon dioxide. During their growth, the trees do absorb carbon dioxide, but this is re-emitted, possibly accompanied by methane, when they die and decay.
David Hall has argued powerfully (Table 24.11) that the sustainable application of biomass within the commercial energy sector requires the substitution of biofuels for fossil fuels and has presented a scenario for the reduction in global CO2 emissions which might be achieved by this substitution.
It is clear that biomass could offset much of the human-made emissions of CO2 and play a very significant role in stabilising the global climate while allowing the increase in energy use which is essential if the people of the developing nations are to have good quality of life.
The substitution of fossil-fuels by biomass energy sources has a number of environmental advantages other than reducing CO2. Biomass contains little or no sulphur, so the acid emissions of sulphur compounds is avoided. The production of nitrogen oxides can also be reduced considerably.
Burning biomass as, for instance, on a garden bonfire can produce large quantities of noxious chemicals, some of which are carcinogenic, but if burning is properly controlled, in a furnace with flue gas cleaning, the overall acid emissions can be very small. The more advanced processing of raw biomass can be designed to emit very little into air, water, or land.
A biomass industry would significantly benefit the rural environment. It produces compost and that, together with the improved agronomic practices, would help condition and stabilise the soil and avoid the desertification and forest fires beginning to occur in Southern Europe.
Social and political benefits would also accrue from the widespread use of biomass. The creation of profitable and sustainable rural employment would reduce the drift to urban areas and to maintain the vitality of rural communities Biomass can be produced and used locally in most parts of the world, avoiding the concentration of supply which characterizes fossil fuels.
The promotion of local self-sufficiency and the geographical diversity of supply for trade will contribute to a more stable world-political environment to the benefit of all countries, but particularly to the Third World.