Industrial uses of biomass.
Charcoal.
Ethanol.
Heat.
Combined heat and power (CHP).
Electricity.
Employment potential.
It is difficult to over-estimate the range of uses and importance of different traditional and modem forms of biomass products and residues in both the rural and urban sectors of developing countries. The industrial sectors of developing countries consume an average of 40 to 60% of commercial fossil fuel supplies and also use significant amounts of biomass fuels. These biomass fuels are often sold on the commercial market. Industry also provides roughly 25 to 35% of rural non-farm employment. {OTA, 1991}
Whilst biomass production and supply is almost exclusively rural, its use in the urban sector is highly diverse, economically important and energetically vital. The consumption of other, more convenient fuels (especially kerosene) is widespread; however, fuelwood remains the dominant source of energy in many developing countries.(box 1) Biomass is used mainly in the form of charcoal and fuelwood, but agricultural residues, including dung and
The uses of biomass include: physical- construction timber, poles (houses and fencing) and thatch; fibrous-mats and mixed with mud in hut walls; thermal- fuel for cooking, tobacco curing (requiring approx. 6-60 t of wood per t of cured tobacco produced, i.e. 90 to 900 GJ/t), tea/coffee drying, brick and tile making (roughly between 1,500 to 19,000 MJ/1000 bricks; 500 to 6,300 MJ/t for 3 kg bricks), paddy parboiling (4.17 GJ/t), gur making (24.95 GJ/t, brown sugar) rubber making, coconut, bakeries, tanneries/cloth makers and charcoal in metal production and processing, pulp for paper making, food preparation in shops and restaurants and shops, (table 8 for various types of industrial biomass use.)
There is a large potential for increasing the level of energy services from biomass sources through the adoption of modernised forms of bioenergy production and the use of energy-efficient equipment, without proportional increases in the amount of biomass use. Such strategies may make one unit of biomass work for longer e.g. cook more food from 1 kg of charcoal, or provide more services e.g. light, water pumping, milling, etc. per unit of biomass consumed, (see Hosahalli village section)
1 Biomass use in Bangladesh
|
In Bangladesh in 1988, biomass provided about 70% (519 PJ) of Bangladesh's energy, 20% of which was used by industry. The remaining 80% of total biomass fuel consumption was for domestic cooking, 45% of which was used in the urban sector and 65% in rural areas. Commercial fuels (mostly diesel and gas) provided about 220 PJ. Whilst most towns have piped gas supplies and many households are connected, consumption is often overestimated as many households which are connected still use charcoal and agricultural residues due to the cost of the gas and service facilities. {Ahsan Ul Haye, 1988} |
Charcoal use is wide-spread throughout developing countries, however, its increasing production and use is causing concern as unsustainable sources of wood are mined, destroying forests and eroding land. It is preferred by domestic users because of its convenience of use (small size, low weight) and quality of burning (constant heat, long lasting) compared to other accessible energy sources, such as firewood, crop residues and dung. It is preferred by industry and charcoal producers because of its energy density (about 30 GJ/t) and relative ease to transport compared to wood (small chunks which pack easily).
The charcoal industry often has a large infrastructure, based on an indigenous, if often unsustainable supply sources (i.e. forests & woodlands). Charcoal's low price and convenience for transport and use means that attempts to induce industrial and domestic users to switch from charcoal to other fuel sources, mainly fossil fuels, are unlikely to succeed in the near to medium term in many developing countries.
During the 1980's, however, due to increases in the efficiency with which charcoal was produced from wood, and the switch to plantation derived wood from natural sources, Brazil has been able to significantly increase its charcoal use. Brazil has been able to achieve this increase without increasing charcoal production from natural sources. The Brazilian charcoal industry is discussed in detail below.
Large amounts of charcoal are consumed in the reduction and heating of iron ore for pig iron production. In 1990, Brazil consumed over 36 Mm3 of charcoal of which 18.6 Mm3 was for pig-iron production. Before 1975, virtually all the charcoal was supplied from native forests with increasingly detrimental effects to the environment, mainly resulting from the destruction of natural forests. This essentially free energy source allowed Brazilian pig iron to become highly competitive in the world markets; it was finally recognised, however, that the continued exploitation of natural forests at such a rate was unsustainable. In an effort to establish sustainable wood production for the charcoal and pulp + paper industries the Government introduced tax incentives for the commercial growth of plantations in its 1965 Forestry Act.
The consequences of this Act have been far reaching as 1t stipulated target percentages of total production (not quantities) which had to be reached within specified time periods (table 7). Presently all pulp and paper and 34% of charcoal production is plantation-derived, the wood being provided from an estimated 4 to 6 Mha of plantations, mostly Eucalyptus. By 1995, the plantation-derived charcoal percentage is required to rise to 100% according to Brazilian regulations; however, the effective total will only be around 80% due to a stipulated allowance for charcoal production from forest residues (see table 7).
Estimates of present plantation areas are complicated by the abandonment of young plantations which had been registered under the Act, or the death of parts of plantations (hence also resulting in lower than predicted productivities.) It is now believed that between 4 and 6 Mha of commercial plantations are in operation, with an increase of between 0.2 and 0.45 Mha/yr. since 1970. {de Jesus, 1990; Rosillo-Calle, 1992}.
Pandey {1992} has estimated a net area of plantations in Brazil (1990) of 6.1 Mha. This is dependant on the success rate for the establishment of plantations having been maintained at the 87% success level ascertained from the 1981-82 inventory of plantations. {Pandey, 1992} It may be reasonable to expect this success rate to have increased as the results of continuing R&D are incorporated into plantation management techniques, and hence net plantation areas may actually be higher than suggested. Charcoal production. The efficiency with which wood is converted to charcoal has also benefited from the Brazilian regulations since the large iron and steel producing companies have been forced to obtain reliable supplies of plantation charcoal. This has inevitably led to many of them investing in the development of large plantation and charcoal production facilities. Such competition has resulted in the need for increased yields, efficiency and benefits from economies of scale. Most charcoal is still produced using internally heated beehive kilns (mud or brick, taking 9-50 m3 wood), the technology of which is up to 100 years old and is often inefficient. (Ch.4, carbonisation) There is considerable room for improvement in efficiency, perhaps to over 30% of the weight of the original wood being converted to charcoal, so also reducing costs. Present conversion efficiencies are often below 20% by weight.
Larger kiln sizes can allow partial mechanisation of the charcoal making process by using forklift trucks to load and unload the kilns allowing faster overall production cycle times. For example, the 300 m3 kilns now used by CAF in Bahia state can be loaded, carbonized and unloaded in 7 days, resulting in significant savings in labour and more socially acceptable weekly work patterns. The carbonisation process is also much more closely controlled increasing the efficiency of conversion. Many of the larger kilns also allow tar and oil recuperation which is sold as low-grade fueloil; this practice also results in less environmental damage from the leakage of these oils into surrounding soils.
Costs of wood production for charcoal are highly dependant on the original cost of the land, soil type, yield and relief. Harvesting costs can increase by up to 75% depending on the steepness of the land. The four main cost components in charcoal production i.e. wood yields, harvest, carbonisation and transport, usually result in production costs above 1992 US$ 25 per m3 charcoal (about US$ 3.5/GJ). Transport costs are generally above US$ 0.0125 per m3.km, and thus for average transport distances of about 300 km, total minimum delivered charcoal costs about 1992 US$ 4/GJ. In general, costs for industrially produced and delivered charcoal are in the range US$ 3.8 to 4.4 per GJ (US$ 27 to 31 per m3). {Rosillo-Calle et al, 1992}
Whilst the present political instability of this country makes continued monitoring impossible, detailed data obtained previously highlights many important aspects of industrial charcoal production in a poor developing country. It is thus included here.
In many countries, the demand for energy in the cities is having adverse effects on the livelihoods of the rural inhabitants who reside near the source of biomass to be exploited as a fuel. In Somalia, for example, the capital city Mogadishu consumed about 42,000 t fuelwood in 1983 or about 0.5 t/capita. Mogadishu's fuelwood production for domestic consumption was estimated to be about 17,000 t's, institutional (hospitals, schools, prisons, military) and for the industrial sector (e.g. lime production) more than 29,000 t's. In contrast to Brazil where most of charcoal production is industrial, 95% of Somalian charcoal produced was consumed for cooking, and was mainly derived from small scale artisanal production, generally of low efficiency. Households in Mogadishu spent on average about 10% of all household expenditure on fuel, one third of which was for charcoal.
The concentrated urban purchasing power in Somalia and elsewhere (large centralised market) made it economically possible to transport fuels over long distances, and therefore spread the influence of the cities and towns further into the rural sector. Thus, the biomass supply resources were exhausted at ever increasing distances from the urban centres. The size of the market in Mogadishu resulted in its ability to absorb rising prices allowing low efficiencies in conversion of fuelwood to charcoal (often less than 15% by weight); the resulting high costs could be paid for through the gains in energy density of charcoal thereby facilitating longer transport distances compared to wood. Charcoal contains twice as much energy per tonne as wood, and is more convenient to package, hence over distances greater than 100 km the energy lost through conversion to charcoal is compensated for by its lower transportation costs per GJ. {Robinson, 1989). These factors expand the radius to which forests and woodlands can be exploited for urban energy provision. This analysis holds true in many other countries where natural vegetation can be regarded as a free feedstock for charcoal production.
In addition, whilst the exploitation of woodlands around Mogadishu was supposed to be carefully controlled (only trees above 15 cm dbh of certain species should be cut) monitoring was superficial, if it existed at all; the wood was therefore regarded as virtually "free". However, the rural populations nearby the woodland source (of the charcoal) noticed that when the selection criteria for suitable trees to be cut was not being followed, resupply was not ensured and degradation inevitably followed. Improper harvesting practices render such land areas prone to severe degradation as a result of loss of vegetative cover leading to soil erosion. Since the costs of restoring the land to its former productivities (if possible) are not met by the charcoal producers, they can simply afford to move to new sources of wood.
Thus, whilst regulations are an important tool in the control of such industries, they can be rendered meaningless without proper monitoring and institutional backup. (section 6, policies)
The need for an economically competitive, indigenous and sustainable supply of liquid fuel for transportation has resulted in a number of biomass to ethanol projects in developing countries. Most of these projects have been based on sugarcane as the source of biomass. Sugarcane is the world's most photosynthetically efficient agronomic crop, utilising about 2-3% of the energy in the incident radiation for biomass production. Sugarcane is also associated with high levels of by-product formation e.g. bagasse, molasses, stillage. Much of the by-product is either suitable for processing into higher value products (such as animal feed) or for use as energy (thermal, electricity).
This multi-product potential, including the ability to upgrade previously unwanted waste products into useful commodities such as electricity and animal feed, has resulted in renewed interest from international development funding organisations. For example, the Global Environment Facility is now funding two major projects involving the utilisation and optimisation of sugarcane for energy. It is presently providing funds for a Brazilian project (1992 US$ 30 million) for the production of electricity from both sugarcane and wood residues, and a Mauritian project (1992, US$ 3.3 million) to optimise the use of bagasse for electricity production (see Electricity section).
The potential of cane to produce products tailored to a changing market has been explored by Smith {1992}. Based on recent Puerto Rican data he suggests that the concept of a cane mill which produces ethanol, sugar, animal feed, fibre and recycles refuse would be economically viable. Such a plant would be theoretically able to provide an internal rate of return of 8.7% and a simple payback of less 7½ years, based on a plant life of 30 years in Puerto Rico. Instead of using bagasse residues solely for the production of steam, the majority of the energy required is derived from processed MSW. MSW disposers pay a significant tipping fee; once sorted, however, it could provide revenue from sales of scrap and energy from the combustible fraction. Whilst only 26% of sales are projected to be derived from ethanol, sensitivity analysis suggests that the wide range of products produced (ethanol, feed, fibre and scrap) make this type of plant relatively immune to inflation. {Smith, 1992}
Brazil has been producing ethanol for use as a fuel since 1903. However, after the introduction of government incentives under the 1975 "Proalcool" programme, ethanol has become a significant energy source (4% of total energy consumption). Ethanol is produced as a petrol substitute for the transport sector where it accounted for 18% of fuel consumption by 1987, with annual production now reaching 12 billion litres. It is sold as either a 22% ethanol (0.4% moisture):gasoline blend (Gasohol) for use in unmodified internal combustion engines, or as neat hydrated ethanol (4.5% moisture) for dedicated ethanol cars and light vans. In 1989, there were 4.2 million cars running on neat ethanol and about 5 million on gasohol. This programme has been successful at reducing Brazil's foreign exchange burden from imported liquid fuels. The share of the total energy market occupied by gasoline has dropped from 12% in 1973 to 4% in 1987 and is now equalled by ethanol (substituting for about 250,000 bbl oil/day). Total savings in oil imports between 1976 and 1987 are estimated at $12.48 billion whilst the total investment in the programme was only $6.97 billion. Presently ethanol costs about 18.5 US c/1 with a high value of 23 c/1 and low of 17 c/1 (approx. US $ 7.9 per GJ). At these prices ethanol (as gasohol) would compete economically with crude oil priced at US$ 24/bbl (1992 US$). {Goldemberg et al., 1992}
Despite such an apparent lack of economic competitiveness, continued gains in productivity and efficiency have meant that subsidies and price controls are now regarded as detrimental to the viability of the private ethanol production companies and car manufacturers {Goldemberg, 1992}. Furthermore, straightforward economic analysis fails to account for the secondary benefits arising from this programme, such as indigenous employment, wealth generation and reduced atmospheric pollution in the cities.
The Zimbabwean Triangle Programme was commissioned in 1980. Construction was carried out entirely in Zimbabwe using indigenous materials wherever possible. The final cost of 1980 US$ 6.4 million, made it one of the cheapest plants of its capacity to be constructed. However, this cost effectiveness was not at the expense of reliability, as it has run with few problems for over a decade. It has a maximum ethanol production capacity of 40 million litres per year with a target blend of 13% (ethanol; gasoline). Whilst originally having been conceived with strategic goals in mind, its performance in foreign exchange savings have been significant and is presently estimated to be reducing foreign exchange spending by over Z$4 million per year {Chadzingwa, 1987}. Furthermore, the alcohol presently costs little more than imported petrol to produce. {Scurlock et al., 1991}
The provision of heat in temperate countries is a major source of domestic energy consumption, and often occurs when power production is most expensive i.e. at night. Even the most efficient thermal power stations produce large amounts of low quality heat which is no longer useful for power generation. The use of this "low quality" heat, which is still of sufficient temperature to supply domestic heating systems, can significantly increase the overall efficiencies of thermal generating systems. In some countries, the development of district-heating supply infrastructure has allowed this "waste" heat to be sold as a commodity to the domestic market providing heat in winter. (see below)
During the 1980's Austria increased the share of primary energy consumption provided by biomass from about 2 or 3% to about 10%. This rapid increase in biomass energy use is predominantly due to the successful promotion of District Heating plants powered by wood chips. The prime political motivation for this scheme continues to be concern about security of energy supplies, the environment and a wish to support the rural economy. It has been greatly facilitated by the decentralised form of government which exits in Austria, and the availability of large quantities of relatively cheap wood residues from forest industries.
The size of the present forest industry is mainly a function of the large areas of natural forests remaining in Austria. Presently, approximately 30% of its land area is forest covered, with individual states such as Steiermark, having an excess of 50%.
There are now over 80 to 90 district heating systems of 1 to 2 MW average capacity (compromising a total of 11,000 installations), producing 100 PJ (1,200 MW total capacity) which represents about 10% of total energy consumption in 1991. This is expected to increase to 25% of total primary energy consumption by the turn of the century. {Howes R., 1992}
The success of this scheme has required both supply and demand side incentives and regulations. Unlike the UK, for example, there are unlikely to be dedicated wood energy plantations in Austria in the near future because of the abundance of existing forestry residues. In particular the banning of practices such as landfill disposal of bark residues by sawmills now means that bark is being sold at 50 to 80 schillings per m3 (approx. 1991 US$ 19-30/t). Sawdust and offcuts are sold at US$ 28 to $ 38/t. Commercial timber is sold at above US$ 40/t.
Supply-side incentives are available through the provision of grants for capital equipment. The Federal government provides 10% of the capital costs and the State government a further 3.3%. In addition, the Department of Agriculture provides an extra capital grant of 40% of the final cost if a scheme is set up by a farmer's group. Thus, incentives may be as high as 50% of total capital costs. On the demand side the government will pay 30% of the heat exchanger costs. Further state grants may be available based on the connection fee (additional to the cost of the heat exchanger), charged in proportion to the heating capacity required by each house8. In general this grant is sufficient to cover the connection fee for the average house (peak demand of 15 KW).
8 Cost of connection is between Schillings 40,000 to 60,000, and thus a 30% grant is equivalent to 1991 US$ 1,100 to 1,700. [Exchange rates are assumed to 20 schillings = 1991 US$ 1.9]
High capital costs for installed equipment (especially pipes) have rendered these schemes relatively insensitive to fuel price, with success a function of overall intensity of use (defined as kWh per km of pipe) and reliability of supply. Subsidies have in effect only reduced payback times from 14 or 15 years to 10 or 11 years. Thus, income received from domestic users covers all the running costs and a slight surplus; hence the long payback times.
The cost of the heat varies, but is in general similar to fossil-fuel (including electrical) heating. It is worth emphasising, however, that in regions where the cost of wood-fired district heating is greater than its alternatives, surveys indicate that people are willing to pay slightly more because they perceive that this money is returned to the local community. It may therefore indirectly benefit the consumer through increasing local wealth and economic activity. {Howes. 1992}
Presently thermal conversion efficiencies of well run modern power stations are between 20-35% fuel to electricity. The maximum efficiencies of thermal conversion facilities (the "Carnot Limit", see chp 4) means that it is physically impossible for thermal technologies to raise their power generating efficiencies above 60%. Thus, many countries are now concentrating on methods of using the low-grade "waste heat" which cannot be turned into a higher value energy carrier. This heat may be ideally suited for space heating or even for the various heat requirements of an associated factory.
2 Sweden's Combined Heat and Power programme.
|
In 1991, biomass provided 25% of the fuel consumed in District Heat and CHP programmes. In total, biomass (including peat, 1%) provided approximately 15% of Sweden's primary energy consumption. {NUTEK, 1992} The CHP programme now provides 142 PJ (39.7 TWh) of energy, of which 93% is consumed as district heat and the rest for electricity. There is now a considerable infrastructure in place, with over 8,000 km of pipes for heat distribution, and 2.4 GW of installed CHP capacity. Having curtailed the nuclear option for environmental and economic reasons, Sweden is pursuing methods to increase its energy production from renewable sources. In particular, it continues to invest large quantities of time and money in woodchip technologies both for present thermal technology, mainly for district heat supplies, and also gasification for CHP production from wood powered gas turbines. |
While the concept is certainly not new, the technologies being applied and developed are innovative. Both Sweden and Denmark now run significant programmes for the use of biomass powered CHP. (box 2 Sweden)
Denmark has a long standing tradition for the use of renewable forms of energy. It is presently best known for its widespread use of wind-generated electricity for supply to the grid. However, since the early 1970's it has also provided incentives for the use of cereal straw for heat and the digestion of animal manure to produce biogas.
The anaerobic digestion of animal manure for the production of biogas has many potential advantages. These range from the safe disposal of manure (presently a costly procedure for farmers due to stringent environmental regulations regarding its disposal) and to the production of electricity and heat.
However, during the 1970's all the digesters were of a technically simple design and based on single farms. This led to problems of maintaining stable conditions in the digester due to their relatively small capacity and low cost. Forty of such small scale digesters have been built but about 30 of them have since been abandoned. Nevertheless, animal manure still represents a significant problem and large potential energy resource.
The first large-scale biogas plant, Vester Hjermitslev, was constructed by the beginning of 1984 and nine more have since been built. It has a digester capacity of 1,500 m3 (approx. 50 t manure per day) designed to produce 3,500 m3/day biogas; it also included a wind turbine for electricity production. The plant was commissioned and run by a private company consisting entirely of members of the local village, who put up over 2/3 of the construction cost (DKK 12.4 M; 1992 US$ 2 million9). The Danish government provided DKK 4 M. It was built as part of the North Jutland County Council's "village energy project," designed to bring a measure of energy self-sufficiency to its villages by providing electricity and heat.
9 1992 exchange rate of DKK 6.12 to US$ 1.
The plant encountered a series of technical problems which never allowed it to meet its specifications, eventually resulting in its reconstruction in 1989. The costs of the years of development have resulted in the plant's debts becoming unserviceable, but the county council has arranged a moratorium. During the reconstruction extra pre-storage was added to enable the plant to use fish processing sludge. Since reconstruction the plant has increased its gas production substantially and an extra gas-powered generator has been added.
There are now nine more large-scale biogas plants running in Denmark with the latest plants have capitalising on the lessons from the previous plants. "Lemvig," the most recent plant to become operational (May 1992) was constructed in only 8 months. It was commissioned by a farmers co-operative who supply the manure; the plant manufacturers entered into a novel service agreement which makes them responsible for the operation and maintenance of the plant for five years. This contract also guarantees the co-operative a minimum budgeted profit. The total construction cost was DKK 40 M (1992 US$ 6.5 million) of which the government provided DKK 9.5 M ($ 1.5 million). There have been no serious problems in operation since its start-up.
Lemvig is the largest plant built to date (7,600 m3) and is based on the continuous one-step design from a previous plant. It is a thermophilic (55°C) plant, which uses a highly automated wood chip heating process to maintain the temperature of the digester. The biogas is supplied to CHP gas-engines in the nearby town via a 4.5 km low pressure pipeline, developed for land-fill gas systems.
In 1986, the Danish government recognised the potential for centralised biogas production and set up an Action Programme whose task it was to review the potential feasibility of the biogas programme. In June 1991, the Action Programme stated that "it would be possible to establish profitable centralised biogas plants without subsidies from the public purse." It did, however, qualify this remark by stating that economic feasibility would continue to depend on the present governments policy of not taxing biogas, which represents an indirect subsidy.
In 1991, only one plant realised enough income to break-even, whilst five have budgeted sufficient income to break even in 1992. (table 17) In the Action Programme's report the conditions necessary for profitability are stated as: 1) 10 to 25% of easily convertible organic material is added to the manure delivered (the main source is from source-sorted household waste and sewage sludge), 2) there must be a steady/reliable market, and the biogas must not be taxed, and 3) good management is necessary to keep down running costs and maintain high gas production levels.
The Danish government has continued its commitment to the biogas programme through the commissioning of the "follow-up programme," under which six or seven new large-scale plants will be established. It bases its renewed commitment to several factors:
(a) The potential improvements in economic status through continued development, many of which are already being demonstrated.(b) Presently only 2% (0.5 PJ) of the potential biogas production is being utilised (25-30 PJ).
(c) The need for farmers to dispose of their waste products in an environmentally acceptable way.
(d) Possible environmental benefits include: displaced CO2 production from fossil fuel use, thus decreased net CO2 emissions, and decreased methane emissions as this is now burnt in the collected biogas. Also, correctly timed applications of the digested sludge on farmers land, which take advantage of the increased availability of nitrogen in digested manure and increased nutrients from the household waste, results in reduced need for artificial fertilisers. A saving of both economic and energy inputs.
(e) The potential to distribute biogas through the existing natural gas pipeline network, possibly as a mixture (natural gas and biogas), resulting in considerable savings in transport costs, and siting problems with the digesters.
(f) Helps to dispose of household waste.
(g) Stimulus to the rural economy.
In 1987, the Public Utility Regulatory Policy Act (PURPA) was introduced requiring US Electricity Utilities to purchase electricity from other suppliers at the cost they "avoided." The "avoided cost" sets the price the utilities are obliged to buy electricity from independent suppliers. It is calculated as the marginal cost of electricity production from a new conventional power station, i.e. equivalent to the cost (c/kWh) of producing electricity from new coal, gas or oil power stations. PURPA thus forced these utilities to procure electricity from suppliers who have alternative cheaper fuel supplies. The utilities were obliged to buy this electricity regardless of internal economic considerations i.e. even if the most economic way of providing base-load and peak demand was through the use of electricity supplies from other sources, including their own power stations. {Turnbull, 1993} PURPA resulted in an explosion of co-generators who use waste materials and by-products as a cheap source of heat. These by-products are obtained from associated processing plants e.g. saw mills, abattoirs, food processors and paper manufacturers, which then gain an income from a product which they may previously have had to pay to have removed. The scale of electricity production is generally small scale i.e. < 50 MW. The guaranteed price at which the co-generators can sell electricity has made long term economic planning possible, thus making it easier to procure loans and calculate profits.
This Act is largely responsible for the present extent of electricity production from renewable sources; over 9 GW of installed capacity presently exists. In California, it has stimulated the growth of a market in biomass residues providing employment and clean energy. It is now being recognised that the use of these residues can help to reduce the level of US CO2 emissions.
Concern over the present levels of US CO2 emissions have resulted in a number of studies being published detailing possible mitigation strategies. {Trexler, 1991; CAST, 1992; Ranney, 1992a; Wright et al., 1992} These studies have highlighted the potential for renewables in providing low cost (or even negative cost) options for the reduction in net CO2 emissions. One study from the US Environmental Protection Agency suggests that the "US will probably come close to stabilising its CO2 emissions at 1990 levels by the year 2000." This, it is hoped, will mainly occur through increases in energy efficiency, the promotion of which utilities now find more cost effective than the construction of new plants. {Global Climate Change Digest, 1992} The prospects for increasing the production of energy from dedicated renewable sources, in combination with increased efficiency of production and use, seem auspicious both in the USA and elsewhere (see below).
In the US, Hall et al {1990} estimated that advanced wood gasifier-based electricity production could be economically competitive with advanced coal gasifier-powered electricity plants. Much of the wood could theoretically be supplied from Short Rotation Woody Coppice (SRWC) on the 139 Mha of economically marginal and environmentally sensitive crop, pasture and under-stocked forest lands held by private owners other than the forest industry. Furthermore, this would have the effect of offsetting up to 56% of present US CO2 emissions at negative cost. When compared with estimates for carbon sequestration, costing between US$ 20 and 40/tC by US forest plantations, or flue-gas CO2 removal from coal-fired steam electricity plants (estimated for the Netherlands) of about US$ 120/tC, biomass substitution options look highly competitive. It should be noted that biomass feedstock costs are strongly correlated with growth rates (estimated by Moulton and Richards {1990} in the US to be 2.7 tC/ha/yr. above ground productivity or 5.3 tC/ha/yr. if roots and soil carbon production is included); if the productivity is halved then biomass feedstock costs are roughly doubled.
Historically, Brazil has relied on the development of large-scale hydro-electric projects to supply its increasing demand for energy. Electricity demand has grown at about 5% per year throughout the 1980's. In 1990, hydro electricity supplied about 96% of total electricity use (226,377 GWh). It thus satisfied the stated governmental aim of avoiding excessive reliance on imported fossil fuels. However, the most favourable sites have now been used. Further expansion of the hydro capacity seems limited due to increasing social and environmental costs and also physical and economic factors. For example, installation costs have ranged between 1988 US$ 100 and 2,700 per kWh and electricity production costs 1988 0.3 to 3.3 USc/kWh. Future costs are likely to be higher, ranging from US$ 1,000 to 3,200 per kW for installation, and from 1.8 to 7.8 c/kWh for production costs. {Carpentieri et al., 1992}
There are also problems with the sheer size of the capital costs of such large scale dams. For example, the Itaipu dam was budgeted at $3.5 billion in 1975, but at final completion it is expected to cost US$ 21 billion, excluding interest payments. {Lenssen, 1992} Such problems have played a significant role in Brazil's continuing struggle with size of its foreign debt and the associated problems.
When compared to the likely costs of future hydro-electric schemes, the relatively low production costs and the smaller incremental nature of the installation costs, future biomass energy projects seem highly competitive and desirable, (see below)
Wood-based electricity. Under the conditions in Northeast Brazil, total life-cycle costs for fuelwood plantations are estimated to rise particularly sharply at productivities of less than 8 odt ha-1 yr.-1 (17 m3/ha). The average weighted cost (weighted by BCR distribution)10 is US$ 1.36 ±0.20 GJ-1 and falls to US$ 1.09 ±0.12 GJ-1 for the highest productivity zone, BCR I. The cost rises to $3.71 ± 0.89 GJ-1 for the worst zone, BCR V (fig. 5)11. At these costs, plantation-derived electricity could be extremely competitive with oil at present world traded prices12.
10 In assessing the potential land areas available for forestry, Carpentieri has analyzed the Northeast region in detail, breaking it down into Bioclimatic regions (BCR's), using soil and rainfall, annual average temperature, water deficit and altitude parameters. Being sensitive to possible land-use conflicts, only land which is not at present being utilised for settlements and which is unsuitable for agriculture has been targeted. This land has been divided into five Bioclimatic regions (analogous to the FAO's Agroecological zones), each of which is estimated to be capable of supporting average productivities of 44, 33, 28, 15 and 6 m3 ha-1 yr-1 for BCR's I through to V, respectively. The parameter most closely correlating to productivity was rainfall, and this was used as the dominant BCR allocation criterion.11 The weighted average productivity for the NE was 26.6 m3/ha/yr. All costs are calculated using a 10% discount rate, wood transported 85 km at 0.39 c/GJ/km and a plantation life time of 30 years.
Most of the cost variation is due to differences in potential land costs.
12 The price of crude oil is presently (Nov. 1992) about US$ 3.5/GJ @ $20/barrel and 42 GJ/t (LHV).
The costs which are related to a given amount of energy generated can be shown graphically in the form of "supply curves." Such supply curves show the quantity of wood which can be produced up to a given cost and are valuable in providing data for a realistic economic comparison with alternative fuel sources (fig. 5b). For example, the Carpentieri et al. {1992} analysis predicts that over 86% of the potential wood production would be produced at an average cost of less than $1.35 per GJ, less than half the cost of oil.
The total potential energy production of this scheme, if all the available land were to be planted and expected productivities achieved, is 12.6 EJ yr.-1. Thus, there is considerable potential to meet future energy demand when compared to Brazil's total 1990 energy consumption of about 8.1 EJ {AEB91, 1992). Clearly a very large potential for such a biomass-based industry exists. Even if only a small portion of the total were to be realised, large amounts of energy could be produced.
One of the main advantages of modern conversion facilities are the relatively small scales at which electricity production would be possible. The biomass can therefore be converted to electricity obviating the need for excessive biomass transport costs. 30 MW is envisaged as the largest practical size of a power generating unit which can be economically supplied by plantations (due to restrictive transport costs at greater distances). Approximately 12,000 ha of plantation would be required for each 30 MW unit. For economic reasons, these units will only be commissioned as demand requires, minimising capital costs (cf. large-scale hydroelectric plants.) Importantly, this modular approach also provides the chance to rectify technical problems before large capital investments have been made. Plantation biomass-to-electricity programmes would therefore allow energy planners to follow the electricity demand curve more closely, thus reducing costs resulting from periodic over supply- periods of oversupply are inevitable after the commissioning of each large-scale hydro plant.
Another benefit resulting from the requirement for large numbers of generating units is an increase in supply reliability. Increased reliability is due to the relative size differential between the production capacity of one plant and total production; thus the lack of one or two plants due to failure, will have relatively little effect on total production.
Sugarcane Electricity. The global energy content of potentially harvestable sugarcane residues is calculated to be 7.7 EJ {Williams & Larson, 1992}. Production of cash crops can be highly intensive in many developing countries, resulting in the production of significant amounts of residues. The energy content of these-residues can equal or even exceed commercial energy consumption e.g. Mauritius, Belize. Residues therefore represent a large potential energy resource, (table 9)
The energy potential of sugarcane residues was also considered by Carpentieri et al. (1993) for the Northeast region of Brazil since the sugarcane residue resource is already available and essentially free. There are, however, sometimes opportunity costs associated with the bagasse resource since a part of it may already used as animal feed, paper making and fertiliser. Where conflict of use may exist, the relative benefits of the different types of use must be assessed.
In comparison with the potential for tree plantation biomass the size of the bagasse resource is relatively small. However, when compared to the present energy consumption of the Northeast Brazil (1.1 EJ), the bagasse resource could still provide an estimated 174 PJ yr.-1 (16% of present energy consumption). The main importance of the sugarcane residues is their availability for collection and electricity production.
Energy production from bagasse is well characterised since the quantity, energy content and moisture content of bagasse produced per tonne of crushed cane varies little from site to site {Alexander, 1985}. Thus gains in the amount of useful energy produced from bagasse is likely to come from increases in conversion efficiency and biomass productivity. More recently, more attention has been given to the energy potential of the tops and leaves, the so called "barbojo." The efficient of use of this barbojo may be able to significantly increase energy production from cane. {Hall et al., 1992; Carpentieri et al., 1992; Williams and Larson, 1992; Howe and Sreesangkom, 1990; Tugwell et al., 1988.}
Economic analysis shows that the conversion of sugarcane residues into electricity can be very competitive with alternative fuel sources. When factors such as transport, storage, drying and processing are accounted for residue-based electricity remains competitive, (table 11) The cost of using stored tops and leaves as an energy feedstock varies from 0.95-2.21 $/GJ, whilst bagasse is in the range 0.28-1.68 $/GJ. The variation between the costs for bagasse and barbojo arises because the barbojo is assumed to be collected and transported to the mills off-season, whilst the bagasse is a by-product of the sugar production. The bagasse is thus effectively transported free when the fresh cane stems are brought to the mills during harvest, whilst the barbojo requires separate collection and transport costs. The potential competitiveness of this indigenous source of fuel can be seen when compared to the fossil-fuel alternatives, i.e. fuel oil, 1985 US$ 2.45-7.50 per GJ and coal, (imported and indigenous) US$ 1985 1.43-4.22 per GJ.
A similar study for Jamaica concluded that potential (present value) savings of US$ 270 M could be achieved if sugarcane residue-fired BIG/STIG were to replace state-of-the-art coal-fired CEST technology. Furthermore, if existing oil-fired plants were replaced, savings of up to US$ 300 million per annum might be feasible. {Tugwell, 1988}
The perceived developmental advantages of widespread access to electricity have been translated from public demand into the political imperative that every village and farm in India should be connected to the national grid. To a large extent this has been achieved with over 80% of the 550,000 villages now grid connected. However, connection has required the construction of many thousands of km's of transmission lines at a cost of US$ 800 to 1,200 km-1 {Ravindranath, 1993}. Furthermore, during the 1980's, oil imports cost India US$ 36.8 billion, the equivalent to one third of all foreign exchange earnings, or 87% of its new debt. When the capital cost of the imported electricity generation equipment was included in this analysis, the total expense for energy amounted to more than 80% of foreign exchange earnings between 1980 and 1986. {Lenssen, 1992}
In addition, many of the villages connected to the grid only require small amounts of power and can also be distant from the power station. This combination of low loads and long transmission distances has led to a number of problems: i) high transmission & distribution losses, with a national average of about 22.4%, ii) low and fluctuating voltages (often below 180 V (estimated 20% of time) despite a nominal voltage of 220 V), iii) high operation & maintenance costs, iv) erratic supply and poor maintenance (power cuts are common), and v) the external costs of centralised power production including: CO2, SO2, particulate emissions, no provision of local employment or wealth generation. {Ravindranath, 1993}
The production of electricity in India is a significant contributor to Indian greenhouse gas emissions. Coal combustion accounts for 60% of total CO2 emissions, with 70% of electricity production being coal-derived. Presently, the provision of electricity to villages consumes one quarter of total production. Electricity generation is responsible for a significant fraction of total Indian CO2 emissions even at today's low levels of per capita electricity consumption (i.e. 61 kWh/yr.). {Ravindranath, 1993}
There are therefore several imperatives for the adoption of widespread decentralised systems for power generation. In addition to overcoming the above problems, such schemes should reduce the subsidies burden presently shouldered by the national government. {Reddy and Goldemberg, 1990} However, electricity production is expected to grow at 10% per year into the next decade. In fact, the constraint on growth is on the supply-side, with actual demand estimated to be much higher. {Grubb, 1990}
The adoption of decentralised power generation systems which use indigenous energy sources has been proposed as an environmentally, economically and socially beneficial model for the development of India's rural villages.{Ravindranath, 1993} Furthermore, all the lighting and power needs of India's rural villages could be met on only 16 Mha of land; a small area when compared to the estimated 100 Mha of degraded land potentially available for tree planting. Ravindranath (1993), has further estimated "that biomass conservation programmes such as biogas and improved cook stoves could provide more than 95 Mt of woody biomass. If gasified, this biomass could provide energy in excess of the total rural energy requirements." Thus, theoretically, no extra land would be needed.
The whole-hearted adoption of such small-scale systems (5 to 20 kW) by the villagers themselves will only be achieved if such systems can address their multiple needs at lower overall costs and more conveniently than present traditional methods. Such needs include the provision of water (primarily for drinking and then for irrigation), light (domestic and street) and shaft power for milling, with cooking considered a low priority.
According to Rajabapaiah et al. (1992) small scale decentralised systems in India could theoretically be both more cost effective than present centralised power production and less environmentally damaging. In fact, such systems could be beneficial to the environment in terms of decreases in the emissions of pollutants (including greenhouse gases) and in the rehabilitation of degraded lands if they were planted with energy forests.
The demonstration of three such schemes by the Centre for the Application of Science to Rural Areas (ASTRA), of the Indian Institute of Science in Bangalore, has shown the feasibility of such an approach. The projects are based in three villages in Karnataka state South India, namely, Pura, Ungra and Hosahalli villages.
The Pura village (population of 209) scheme was initially conceived as a biogas-for-cooking project requiring the collection and use of most of the villages cattle dung production. {Rajabapaiah et al., 1992} Surplus gas would then be utilised for electricity production, mainly for lighting. However, problems with inadequate incentives for dung collection resulted is less gas production than planned. Initially insufficient gas was produced to cook all the villagers' meals and thus the villagers became disinterested in the project. Thereafter, the implementation of community-based management with a transparent decision making process altered the project's priorities. The provision of cooking gas was demoted in favour of the supply of clean water and, at the same time, fair returns for dung provision were allocated. The Pura village project now recuperates its operation and maintenance costs and is fully accepted and welcomed by the village as a whole.
This Pura village project demonstrates that local initiatives can be successful if they are adaptable and can take a longer term view over the provision of social and economic benefits.
Hosahalli, a nearby village, has demonstrated the feasibility of electricity production from the gasification of fuelwood for lighting, water-pumping, milling and for irrigation (future). Hosahalli is analyzed in more detail below.
Hosahalli: This is a small, non-electrified village of 42 households and a population of just over 200. As with Pura village, detailed discussions were undertaken between ASTRA and the villagers before the initiation of the scheme. The main aim of the project was to demonstrate the feasibility of small-scale energy plantations for the provision of sufficient wood to sustainably supply a 5 kW wood-gasifier. This wood-gas is then used in a diesel-engine as a substitute for diesel. The engine is connected to a 5 kWe alternator which generates 3-phase (nominally 220 V) electricity to supply specified village energy services. The project funded the hardware, and initially aimed for the operation and maintenance of the system to be "self funding. This is presently the case, and there are good prospects that developmental work, both hardware and social, will lead to full economic profitability and a reasonable payback period.
The project is being implemented in 5 phases:
I) growing 2 ha energy forest to provide a sustainable wood supply. The installation of the wood gasifier/diesel engine and generating system.II) Electrification: the provision of lighting to all households (1x40 W fluorescent and 1x25 W incandescent bulbs) + 9 street lights.
Ill) Installation of a water pump and tanks for drinking water.
IV) Installation of a flour mill. (5 kW electrical).
V) Provision of water pumping for irrigation. (10 pumps x 3.7 kWe/pump x 300 hr/yr./pump for flood irrigation).
The engine is modified to run on both diesel and wood-gas, however, starting requires the use of the diesel-only mode until the gasifier reaches operating temperature. Once the gasifier is operating the wood-gas produced completely displaces the need for diesel. An overall diesel displacement of 67% has been achieved when compared to the diesel saved if the engine were running on diesel alone. Presently a saving of 42 litres of diesel a month is being achieved. A diesel substitution level of over 85% is possible if the gasifier is run for longer periods which would have significant economic benefits.
Electricity for lighting has been supplied for 3 to 4 hours daily since September 1988, drinking water since September 1990 and the flour mill (2 hours daily) has been in operation since March 1992. This has been achieved with a reliability in the supply of power of 95%- a remarkable level of reliability when the consistently high voltage level provided is taken into account, in contrast to the erratic supply and fluctuating voltage of the central electricity grid. In addition to the provision of these services, two men have been employed full-time to cut and supply wood from the energy forest and to maintain the gasifier and engine; more recently a woman has volunteered to be trained in running the equipment.
A proper comparative economic analysis is made difficult because of the high level of subsidies given to centralised grid electricity. However, according to Ravindranath and Mukunda (1990), at the level of operation for lighting only (4 hr/day) the wood gasification system would only be economic, in terms of covering its running costs, if electricity is priced at Rs. 3.5 per kWh (14 USc/kWh). However, if the gasification system operates beyond 5 hr/day, the unit cost of energy becomes cheaper than the diesel-only system. For comparison, the current subsidised price of grid-based electricity is Rs. 0.65 (equivalent to about 3 USc/kWh). {Ravindranath, 1993}
An important aspect of this project is that the villagers are prepared to pay over twice as much for their electricity (approx. Rs. 1.3/kWh (5 USc)) because: i) the supply is reliable, ii) provision of ancillary benefits (clean drinking water, flour mill, etc.), iii) quality of supply (never below 180 V) and iv) emergence of self reliance (the formation of village management committee). This emergence of self reliance for the decentralised and small-scale, provision of energy also plays an important role in the other two projects being implemented by ASTRA in Pura and Ungra.
At the present rate of diesel-substitution (42 I/month), the monetary savings are equivalent to Rs. 2,520/yr. (US$ 101/yr.). This is the equivalent to a payback period of 9.5 years including the additional cost of the energy forest, gasification equipment and modification of the diesel engine, (table 15) However, the other benefits listed above, or the revenue from lighting, paid by each household (Rs. 10/household/month) is not accounted for and would reduce the payback period. A general increase in energy demand in combination with a demand for more powerful lights is resulting in the gasifier being run for longer periods of time and therefore should result in decreasing running costs per kWh.
One concern voiced by the villagers was the amount of land which had to be devoted to the growth of wood for the gasifier. The eventual planting of 2 ha with 6 different species has resulted in an average annual yield of 6.9 dry t/ha/yr. compared with a total use of only 10.2 t over the 32 month period (3.8 t/ha/yr.). The productivity of this land is therefore considered more than sufficient to meet present and future demand. The excess wood can be used by the villagers or sold.
Estimates for India as a whole, show that the use of degraded land (or edges of fields) around many villages would not only provide more than sufficient area to supply present demand, but would also help to rehabilitate such land. In addition, the potential of this land to becoming a C-sink could be significant, whilst at the same time helping rural development. {Ravindranath, 1992} (see also Land Use section)
If such decentralised systems are to become widespread then the lessons learnt from these studies must be built into future policies aimed at their promotion. ASTRA emphasises that it is crucial to listen to and address the recommendations made by the users, and secondly, the continuing involvement of the community in the organisation and running of the plant is essential.
Similarly, in Hosahalli, community involvement was only secured when phase II was implemented and clean drinking water made available. Thus, both Pura and Hosahalli required a long-term commitment and flexible approach by ASTRA, which have given them the confidence to recommend that decentralised power production systems, based on the experiences from Pura and Hosahalli, be broadened to encompass a "cluster" of villages (of about 100 in total). This would allow the system to be realistically compared with grid electricity. The interconnection of the villages would allow increased reliability and profitability making decentralised power generation more desirable.
Mauritius is a small island (1,865 km2) off the East coast of Africa with a population of just over 1 million. About a quarter of the workforce is currently employed in the agricultural sector. Its primary export crop is sugar, and with the decreasing export value of sugar (and raw commodities in general) the government has been seeking ways to increase the overall value of its sugarcane crop. There is an emerging view of sugarcane as a multi-product crop, able to produce both food (sugar and animal feed) and energy (ethanol, biogas and electricity). Thus sugarcane is increasingly seen as an opportunity for development and not a hinderance.
Cane production in 1990 totalled over 5.5 Mt (fresh stems) but only one third (29%) of the potential excess energy from bagasse is presently being utilised. {Comarmond, 1992} However, whilst gross electricity production from bagasse increased from 27 GWh in 1980 to 71 GWh in 1991, total electricity production doubled from 355 GWh to 737 GWh in the same time period. Consequently, bagasse's share of electricity rose only slightly from 7.5% to 9.6%.
Prior to 1982, 16 of the 19 cane mills sold electricity during the milling season to the Central Electricity Board (CEB). All these mills used inefficient low pressure and temperature back pressure technology. {Comarmond, 1992}. In 1984, 14 of the sugar mills and 1 tea factory supplied 34 GWh of electricity to the grid. {Purmanund et al., 1992} The main purpose of the technology used is to deliver process steam to power the mill and secondly, as a means of bagasse disposal. Even so, a total of 31 GWh of bagasse generated electricity was purchased by the CEB during 1981.
This inefficient technology is only capable of producing 300 kg of steam per tonne of cane (kg/tc), and thus the opportunities presented by newer technology (able to produce 550 to 600 kg/tc) were evident. The newer technologies do however, involved higher capital costs. In 1982, the Medine mill started operating a new 10 MW CEST system to exploit these potential benefits, and during the crushing season exported an additional 10 GW (2,770 kWh) to the CEB.
In 1985, the largest sugar factory in Mauritius, the Flacq United Estate Limited (FUEL) commissioned a modern steam boiler capable of burning both bagasse and coal, sufficient to deliver high temperature and pressure steam to power both the factory and a 24 MW CEST alternator. The dual-fuel ability of the FUEL boiler enables it to burn bagasse during the harvesting season and coal during the off-season. Total electricity production is approximately half (40 GWh) from bagasse and half (40 to 45 GWh) from coal.
All year round electricity production is obviously a more valuable commodity for the CEB than seasonal production. It results in the CEB needing less standby generating equipment to meet demand when seasonal production is not available. The CEB thus pays a premium for such electricity production; 100 c/KWh for permanent electricity production, 45 c/kWh for seasonal, and only 16 c/kWh for intermittent (wind, PV, tidal etc,). The tariffs paid by the CEB, are derived from the "avoided costs" that would be incurred if the demand were to be provided from CEB's own electricity generating plant i.e. specifically the cost of electricity production from a 24 MW diesel powered generating plant. {GEF, 1992} In fact, current forecasts for growth in electricity demand have resulted in the commissioning of 106 MW of new fossil fuel generating capacity; in addition, two future 24 MW bagasse/coal plants have been ordered.
Funding for the two bagasse plants and the enhanced use of the sugar industries by-products is envisaged to cost about US$ 80 million over an eight year period. The funding will be allocated under the Bagasse Energy Development Programme (BEDP) which is a central part of the Mauritian Governments Sugar Energy Development Project (SEDP). Under the SEDP's US$ 55 million financing plan 48% of the funding (US$ 26.6 million) is from foreign sources, of which only US$ 3.3 million is provided by the Global Environment Facility (GEF). {GEF, 1992}
The GEF funding is specifically for technical and staff development (US$ 1.9 million) BEDP co-ordination and for environmental monitoring (US$ 1.4 million). In justifying this funding GEF states that "increased use of sugarcane biomass as energy in Mauritius will have significant environmental benefits." To this end it estimates that CO2 emissions will be reduced, in terms of avoided fossil fuel emissions, from 75,000 t/yr. to between 60,000 and 67,000 t/yr., and at the same time NOx and SOx emissions will be reduced from 4,000 t/yr. to 1,000 t/yr.
The primary aim of the BEDP is to increase cane residue-derived electricity production from the present level of 70 GWh to about 120 GWh. This will exploit about 56% of the total potential from bagasse, but due to increased electricity demand bagasse is only expected to provide about 9% of total electricity production by the year 2000. {Comarmond, 1992}
However, if the full potential of sugarcane residues (bagasse and tops + leaves, and other crop residues) were to be exploited for electricity production, estimates of the potential resource for electricity production are much larger. A crude estimate of the theoretical total potential would be about 3,500 GWh (at 40% conversion efficiency, biomass to electricity) or 2,500 GWh at 30% efficiency. When compared with the CEB forecast of total electricity consumption of 1,678 GWh/yr. {Comarmond, 1992} in the year 2000, bagasse and barbojo represent a significant energy resource.
Another independent estimate of the total theoretical energy potential from crop, forest and dung residues, based on 1984 data, is of 4,007.3 GWh (14.4 PJ).13{Purmanund et al., 1992} The energy value of cane tops & leaves (roughly equivalent to bagasse in weight) was not included in this study as it is presently either used as animal feed or left on the field to act as a mulch. However, the study did include the potential alcohol production from molasses (8% of the total energy derived from cane). If half the tops and leaves from the sugarcane were to be used, the total potential energy from residues would rise to about 5,833 GWh.14 Using the efficiencies assumed (see footnote 13) for conversion to electricity residue-based energy could produce approximately 1,400 GWh of electricity or virtually the total Mauritian electricity production forecast for the year 2000. {Comarmond, 1992}
13 If the Purmanund et al. {1992} estimate for conversion efficiencies is used, which assumes a boiler efficiency of 70% and a thermal conversion efficiency (heat to electricity) of 35%, then an electricity production potential of 982 GWh is estimated.14 It is estimated that in Puerto Rico 30 to 50% of the tops and leaves should be left on the field. {GEF, 1992}
Estimates of potential energy production from sugarcane residues, such as those cited above, do not attempt to estimate the likely effects of optimised strategies for both energy and food production. It is estimated that large potential gains in both sugar and fibre production could be achieved from sugar cane if breeding programmes concentrated on total biomass production and not simply increasing the sugar concentration in the stem. {Alexander, 1985} If likely increases in the efficiencies of conversion of biomass to useful energy (i.e. electricity) are accounted for i.e. the use of biomass gasification and gas turbine technologies (BIG/STIG) much larger potentials are estimated. For example, Williams and Larson (1992) estimate that by 2027, the electricity potential from cane in Mauritius could be 29 times (14,300 GWh) Mauritius's total 1987 electricity production (490 GWh). This figure is based on the assumption that cane production grows at 3.1% per year and that BIG/ISTIG technology is used with a conversion efficiency (biomass to electricity) of 38%.15 {Williams & Larson, 1992} It is interesting to note that the installed cost in 1989 US$/kWe for BIG/ISTIG is estimated to be between $ 870 and $ 1,380 which is lower than the present installed cost of CEST at US$ 1,520 per kW.
15 Biomass Integrated Gasifier/Intercooled Steam Injected Gas Turbine (BIG/ISTIG) technology is a derivative of BIG/STIG technology (section 4, Energy Conversion) and is used for the co-generation of process steam and electricity. BIG/ISTIG conversion efficiencies (biomass to electricity) are estimated at about 8% higher than BIG/STIG (30% efficient); however, commercialisation is expected to take longer.
If rural communities are to prosper as a country develops then secure and financially beneficial rural employment must be a central theme. The history of agricultural development is often characterised by the reduction in man hours per tonne of produce harvested. The fall in manpower required in agriculture has accentuated, or is a direct cause of urban drift so exacerbating urban unemployment and related problems.
One trait of agriculture is the seasonably of the employment. In developing countries where the bulk of the harvest is often carried out manually this requirement for large numbers of temporary jobs during the harvesting season is regarded as socially damaging. Whilst the quality of the work may be poor it does at least provide some form of income where there might not otherwise be any. It should therefore not be the aim of any investment programme to destroy this important opportunity for income. Rather the aim should be to secure those jobs throughout the year in the most economically efficient way, possibly by providing alternative employment during the off-season.
The Carpentieri et al. (1992) study of biomass electricity in NE Brazil provided a detailed analysis of the manpower requirements for both the tree plantation and sugarcane biomass energy sectors. The sugarcane industry of the Northeast presently employs labour at the rate of 19.8 jobs per km2 for on-season work and only 2.7 jobs per km for off-season (permanent) employment. If in the future labour was to be employed to bale and collect the tops & leaves which would be done off-season (an essential activity if enough energy is to be produced from sugarcane residues), then the on-season requirement for jobs would hardly change at 19.6 jobs km-2 but the off-season requirement would rise to 23.7 jobs km-2 At present only about 36,000 people are employed permanently by the sugarcane industry of the Northeast; however, if the industry became a combined sugar and energy production system the theoretical total number of permanent jobs is estimated to be more than 326,000. The seasonal requirement (harvesting period only) would fall from 272,600 to 55,800 people, with all the present seasonal jobs being absorbed into the extra permanent vacancies.
The tree plantation industry is much less labour intensive with an average requirement of 2.7 jobs km2. Approximately 12% of these jobs are needed for research and administration. In analysing the potential plantation requirements to supply the additional electricity demand for the period 2000-2015, 32,454 jobs would be needed. This represents 9 % of the ultimate potential total if all the area identified as "free for forestry" in the Northeast were eventually to be planted for electricity production.
In the agro-ethanol industry, job quality is also comparable or higher to many of the main large-scale employers in Brazil. It is estimated that the ethanol industry in Brazil has generated 700,000 jobs with a relatively low seasonal component compared to other agricultural employment. Job security and wages are important for workers in this industry; they receive higher wages on average than 80% of the agricultural sector, 50% of the service sector and 40% of those in industry. {Goldemberg et al., 1992}
One of the most important developmental comparisons is the investment cost per job created. For the biomass energy industries envisaged above, this lies between $15,000 and $100,000 per job, with costs in the ethanol agro-industry between $12,000 and $22,000. Such job creation costs compare with the average employment costs in industrial projects in the Northeast at $40,000 per job created, in the petro-chemical industry of about $800,000 per job, and for hydro power over $106 per job. Lower job creation costs are one of the most significant benefits of biomass energy. {Carpentieri et al., 1992; Goldemberg et al., 1992}.
