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CLOSE THIS BOOKApplication of Biomass Energy Technologies (HABITAT, 1993, 168 p.)

Application of Biomass Energy Technologies (HABITAT, 1993, 168 p.)


A. Introduction

Alcohols can be used as a liquid fuel in internal combustion engines either on their own or blended with petroleum. Therefore, they have the potential to change and/or enhance the supply and use of fuel (especially for transport) in many parts of the world. There are many widely-available raw materials from which alcohol can be made, using already improved and demonstrated existing technologies. Alcohols have favourable combustion characteristics, namely clean burning and high octane-rated performance. Internal combustion engines optimized for operation on alcohol fuels are 20 per cent more energy-efficient than when operated on gasoline (Johansson et al, 1992), and an engine designed specifically to run on ethanol can be 30 per cent more efficient (EPA, 1990). Furthermore, there are numerous environmental advantages, particularly with regard to lead, CO2, SO2, particulates, hydrocarbons and CO emissions.

Global interest in ethanol fuels has increased considerably over the last decade despite the fall in oil prices after 1981. In developing countries interest in alcohol fuels has been mainly due to low sugar prices in the international market, and also for strategic reasons. In the industrialized countries, a major reason is increasing environmental concern, and also the possibility of solving some wider socio-economic problems, such as agricultural land use and food surpluses. As the value of bioethanol is increasingly being recognized, more and more policies to support development and implementation of ethanol as a fuel are being introduced. A number of countries have pioneered both large-scale and small-scale ethanol fuel programmes. In the United States, the current fuel ethanol production capacity is over 4.6 billion litres and there are plans to increase this capacity by more than 2.3 billion litres. Worldwide, fermentation capacity for fuel ethanol has increased eight-fold since 1977 to about 20 billion litres per year in 1989 (Rosillo-Calle, 1990).

Latin America, dominated by Brazil, is the world's largest production region of bioethanol. Countries such as Brazil and Argentina already produce large amounts, and there are many other countries such as Bolivia, Costa Rica, Honduras and Paraguay, among others, which are seriously considering the bioethanol option (Rosillo-Calle, 1990). Alcohol fuels have also been aggressively pursued in a number of African countries currently producing sugar - Kenya, Malawi, South Africa and Zimbabwe. Others with great potential include Mauritius, Swaziland and Zambia. Some countries have modernized their sugar industry and have low production costs. Many of these countries are landlocked which means that it is not feasible to sell molasses as a by-product on the world market, while oil imports are also very expensive and subject to disruption. The major objectives of these programmes are: diversification of the sugarcane industry, displacement of energy imports and better resource use, and, indirectly, better environmental management. These conditions, combined with relatively low total demand for liquid transport fuels, make ethanol fuel attractive (Hall and Rosillo-Calle, 1991).

The production of ethanol by fermentation involves four major steps: (a) the growth, harvest and delivery of raw material to an alcohol plant; (b) the pre-treatment or conversion of the raw material to a substrate suitable for fermentation to ethanol; (c) fermentation of the substrate to alcohol, and purification by distillation; and (d) treatment of the fermentation residue to reduce pollution and to recover by-products. Fermentation technology and efficiency has improved rapidly in the past decade and is undergoing a series of technical innovations aimed at using new alternative materials and reducing costs (Yasuhisa, 1989). Technological advances will have, however, less of an impact overall on market growth than the availability and costs of feedstock and the cost-competing liquid fuel options.

The many and varied raw materials for bioethanol production can be conveniently classified into three types: (a) sugar from sugarcane, sugar beet and fruit, which may be converted to ethanol directly; (b) starches from grain and root crops, which must first be hydrolysed to fermentable sugars by the action of enzymes; and (c) cellulose from wood, agricultural wastes etc., which must be converted to sugars using either acid or enzymatic hydrolysis. These new systems are, however, at the demonstration stage and are still considered uneconomic. Of major interest are sugarcane, maize, wood, cassava and sorghum and to a lesser extent grains and Jerusalem artichoke. Ethanol is also produced from lactose from waste whey; for example in Ireland to produce potable alcohol and also in New Zealand to produce fuel ethanol. A problem still to be overcome is seasonability of crops, which means that quite often an alternative energy source must be found to keep a plant operating all-year round.

Sugarcane is the world's largest source of fermentation ethanol. It is one of the most photosynthetic efficient plants - about 2.5 per cent photosynthetic efficiency on an annual basis under optimum agricultural conditions. A further advantage is that bagasse, a by-product of sugarcane production, can be used as a convenient on-site electricity source. The tops and leaves of the cane plant can also be used for electricity production. An efficient ethanol distillery using sugarcane by-products can therefore be energy self-sufficient and also generate a surplus of electricity, in addition to CO2 for industrial use, animal feeds and a range of chemical-based products. The production of ethanol by enzymatic or acid hydrolysis of bagasse could allow off-season production of ethanol with very little new equipment

Methanol which can be obtained from biomass and coal, but which is currently produced from natural gas, has only been used as fuel for fleet demonstration and racing purposes and, thus, will not be considered here. In addition, there is a growing consensus that methanol does not have all the environmental benefits that are commonly sought for oxygenates and which can be fulfilled by ethanol (NAS, 1983).

B. Brazil

Brazil first used ethanol as a transport fuel in 1903, and now has the world's largest bioethanol programme. Since the creation of the National Alcohol Programme (ProAlcool) in 1975, Brazil has produced over 90 billion litres of ethanol from sugarcane. The installed capacity in 1988 was over 16 billion litres distributed over 661 projects (Anon, 1989). In 1989, over 12 billion litres of ethanol replaced about 200,000 barrels of imported oil a day and almost 5 million automobiles now run on pure bioethanol and a further 9 million run on a 20 to 22 per cent blend of alcohol and gasoline (Hall et al, 1992a) (the production of cars powered by pure gasoline was stopped in 1979). From 1976 to 1987 the total investment in ProAlcool reached $6,970,000 million and the total savings equivalent in imported gasoline was $12,480,000 million (Anon, 1989; Lima, 1989).

Table 5 shows sugarcane, sugar, and alcohol production as well as sales of alcohol-powered cars in Brazil from 1976/77 to 1990. Sugarcane production has increased from about 88 million tons in the 1976/77 harvest to 241 Mt in 1988/89, while alcohol production has increased from about 660 million litres to 12.3 billion litres during the same period (Mazzone, 1989). The planted area of sugarcane increased from 1,540,000 ha in 1972 to 2,820,000 ha in 1982 and 4.31 million ha in 1987 (IBGE, 1989). In the 1983/84 harvest, 47 per cent of the total amount of sugarcane crushed was used for ethanol production, and in 1987/88 the proportion reached 61 per cent (Rosillo-Calle et al, 1991). In 1978, only 0.3 per cent of vehicles sold in the domestic market ran on ethanol but by 1985 this figure has reached % per cent However, by 1990 this was down to an estimated 50 per cent due to difficulties in alcohol supply and retail prices (Mazzone, 1989).

Apart from ProAlcool's main objective of reducing oil imports, other broad objectives of the programme were to protect the sugarcane plantation industry, to increase the utilization of domestic renewable-energy resources, to develop the alcohol capital goods-sector and process technology for the production and utilization of industrial alcohols, and to achieve greater socio-economic and regional equality through the expansion of cultivable lands for alcohol production and the generation of employment Although ProAlcool was planned centrally, alcohol is produced entirely by the private sector in a decentralized manner.

Table 5. Sugarcane, sugar, and alcohol


Sugarcane (Mt)

Sugar (Mt)

Ethanol ((10X9) litres)

Alcohol operated cars (percentage)b







































































Sources: Compiled from Mazzone, 1989


a The years correspond to a twelve-month period from 1979 through 1990.
b Percentage of alcohol-powered cars manufactured in a year.
c Estimated

Achievement of these objectives involved an intricate and politically difficult combination of technology and economic policy in the agricultural and industrial sectors. The Government established several support mechanisms: agreeing that the State-owned oil company, Petrobras, would purchase a guaranteed amount of ethanol; providing financial incentives such as low interest rates and $US2.0 billion in loans to ethanol producers; establishing a price policy to ensure an effective remuneration to alcohol producers; encouraging consumers by selling ethanol at 59 per cent of the price of gasoline (the price of ethanol is now 75 per cent of the price of gasoline, and hence there is almost no subsidy in ethanol (Goldemberg et al, 1992)); public investment in agricultural research; and incentives for alcohol production and utilization technology, and for private innovation and investment. In the Centre-South region of Brazil, it is no longer considered necessary to provide economic incentives to producers and end-users. The combination of these factors, together with the introduction of new equipment, increases in productivity and the number of new plantations, has given a continued boost to alcohol production.

1. Improved sugarcane yields

Between 1977 and 1985, sugarcane yields per hectare increased by 16 per cent and yield of alcohol per ton of cane increased by 23 per cent (Goldemberg et al, 1992) with alcohol productivity increasing from 2660 litres/ha to 3800 litres/ha (Mazzone, 1989). Cane productivity stood at 62.6 tons/ha in 1988 (Carpentieri, 1991). New varieties of sugarcane have been developed in order to gain greater productivity on poor soils, in consideration of the need to expand sugarcane growth without interfering with traditional food production. Intercropping and rotation cropping technologies developed by Brazilian sugar research laboratories have also made it possible for sugar plantations to increase food production. The Brazilian Government has undertaken a major effort to promote the improvement of cane-production technology, e.g., through the establishment of cane prices based on sucrose content rather than on weight, efficient management of sugarcane plantations and pest control, among other devices.

2. Industrial development

The ProAlcool programme has accelerated the pace of technological development and reduced costs within agriculture and other industries. Brazil has developed a modem and efficient agribusiness capable of competing with any of its counterparts abroad. The alcohol industry is now among Brazil's largest industrial sectors, and Brazilian firms export alcohol technology to many countries. Brazilian distillery manufacturers have been so successful in producing efficient hardware that the distilleries were frequently found to perform at up to 30 per cent above their rated capacity. In a number of distilleries, small additional investments have increased production still further to 50 per cent above nominal capacity (Weiss, 1990).

Another industry which has expanded greatly due to the creation of ProAlcool is the ethanol chemistry sector. Installed capacity for ethanol utilization in the chemical industry rose from 60,105 tons in 1976 to 336,980 tons in 1984. From 1975 to 1985 the ethanol-based chemical sector consumed a total of nearly 2.2 billion litres of ethanol, i.e., about 3.5 per cent of the annual alcohol production (Rosillo-Calle, 1986). Ethanol-based chemical plants are more suitable for many developing countries than petrochemical plants because they are smaller in scale, require less investment, can be set up in agricultural areas, and use raw materials which can be produced locally.

3. Social development

Until recently the Government's main objectives had been economic growth, with relatively little emphasis on social development. However, rural job creation has been credited as a major benefit of ProAlcool because alcohol production in Brazil is highly labour-intensive. Some 700,000 direct jobs with perhaps three to four times this number of indirect jobs have been created, although it is unclear how many of these jobs are new ones. The investment to generate one job in the ethanol industry varies between $12,000 and $22,000, about 20 times less than in the chemical industry for example (Goldemberg et al, 1992).

4. Environmental impacts

Environmental pollution by the ProAlcool programme has been a cause of serious concern, particularly in the early days. The environmental impact of alcohol production can be considerable because large amounts of stillage are produced and often escape into waterways. For each litre of ethanol produced the distilleries produce 10 to 14 litres of effluent with high biochemical oxygen demand (BOD) stillage. In the later stages of the programme serious efforts were made to overcome these environmental problems, and today a number of alternative technological solutions are available or are being developed, e.g., decreasing effluent volume using the Biostil process and turning stillage into fertilizer, animal feed, biogas etc. These have sharply reduced the level of pollution and in Sao Paulo. The use of stillage as a fertilizer in sugarcane fields has increased productivity by 20-30 per cent (Rosillo-Calle, 1986). Tougher environmental regulations have also reduced pollution considerably.

5. Economics

Despite many studies carried out on nearly all aspects of the programme, there is still considerable disagreement with regard to the economics of ethanol production in Brazil. This is because the production cost of ethanol and its economic value to the consumer and to the country depend on many tangible and intangible factors making the costs very site-specific and variable even from day to day. For example, production costs depend on the location, design and management of the installation, and on whether the facility is an autonomous distillery in a cane plantation dedicated to alcohol production, or a distillery annexed to a plantation primarily engaged in production of sugar for export. The economic value of ethanol produced, on the other hand, depends primarily on the world prices of crude oil and sugar, and also on whether the ethanol is used in anhydrous form for blending with gasoline, or used in hydrous form in 100 per cent alcohol-powered cars.

The costs of ethanol were declining at an annual rate of 4 per cent between 1979 and 1988 due to major efforts to improve the productivity and economics of sugarcane agriculture and ethanol production (Goldemberg et al, 1992). The costs of ethanol production could be further reduced if sugarcane residues, mainly bagasse, were to be fully utilized as has been shown by Ogden et al, (1990). With sale credits from the residues, it would be possible to produce hydrous ethanol at a net cost of less than $0.15/litre, making it competitive with gasoline even at the low early-1990 oil prices. Using the biomass gasifier/intercooled steam-injected gas turbine (BIG/STIG) systems for electricity generation from bagasse, they calculated that simultaneously with producing cost- competitive ethanol, the electricity cost would be less than $0.045/kWh. If the milling season is shortened to 133 days to make greater use of the barbojo (tops and leaves) the economics become even more favourable. Such developments could have significant implications for the overall economics of ethanol production.

Several economic analyses exist for Brazilian alcohol production. Zabel (1990) estimated that the average cost of ethanol was $0.20 litre in Sao Paulo State and that this could be reduced by 17 per cent by the year 2000 to $0.16 litre. Reddy and Goldemberg (1990) calculated that the cost of ethanol produced in Sao Paulo was about $0.185 per litre; and that at this price, ethanol could compete successfully with imported oil. Goldemberg et al (1992) estimate that an overall cost reduction of about 23 per cent could be achieved in a few years just by using existing technology. Borges and Campos (1990) calculated that ProAlcool is economically feasible with both basic and high petroleum prices but in the low-petroleum-price scenario their analysis indicates that it would be more economical to use gasoline instead of ethanol.

The total gains per annum of ProAlcool were estimated to be equivalent to $7.2 billion and $2.5 billion in the high and basic petroleum price scenarios, while in the low-petroleum-price scenario there would be an estimated loss of about $700 million.

In 1989, ProAlcool received severe economic criticism, with many voices calling for its reduction or even total dismantling (Seroa-da-Motta, 1989). The main reason was the sharp drop in oil prices and me steady growth in Brazil's domestic petroleum production, e.g., about 212 million barrels in 1988 at an estimated cost of $20 per barrel versus an “estimated cost” of alcohol of $45 per barrel according to Young (1989). With the current relatively low oil prices (about $19-20 per barrel, May, 1993) and increased domestic oil production, the economics of alcohol production are unfavourable on a microeconomic basis.

The situation was exacerbated due to a shortage of alcohol fuel. In 1988, the Government was forced to import 200 M litres of alcohol to fill the fuel-ethanol shortage which continued in 1989 and 1990, resulting in a drastic reduction in sales of alcohol cars. Although a drought in the north-east was blamed for the shortfall, part of the crisis stemmed from bureaucratic and technocratic shortcomings. For example, fuel consumption was greatly stimulated when prices were frozen by the Summer Plan (a Federal economic anti-inflation programme launched in January 1989) and by the stagnation of alcohol prices, both of which discouraged the distillers from producing more alcohol. Government policies of maintaining low alcohol prices relative to the cost of gasoline were not accompanied by sufficient incentives to expand the production of alcohol, while depressing the price to hold down inflation destabilized the industry further. This led to the Government raising prices in 1991. Further, in 1989, sugar prices surged in (he international market making it more profitable to sell sugar than to produce alcohol. Meanwhile, farmers had been shifting from cane to other more profitable export commodities so sugar production was down. This illustrates the vulnerability of the programme to short-term market fluctuations (Hall et al, 1992a; Goldemberg et al, 1992).

Many of the problems with ProAlcool are blamed by the industry on two institutions: the Institute of Sugar and Alcohol (IAA), which in June 1989 finally lost its 56-year monopoly over the country's sugar industry; and Petrobras, the State oil monopoly. The first was blamed for creating a price production stalemate by not correctly evaluating price levels for sugarcane and alcohol, and the second, for its long-standing opposition to the alcohol programme, e.g., payment delay tactics to distillers which, in an economy with very high inflation rates, results in large financial losses to the alcohol producers (Mazzone, 1989). Petrobras' opposition to ProAlcool stemmed from the fear of losing its monopoly of liquid-fuel supply and also because the company made large investments in fluid catalytic crackers (large refining installations that convert residual fuel oil into lighter distillates, especially gasoline) which increased the proportion of gasoline obtained from oil and resulted in large surpluses of gasoline.

6. Future implications

The recent economic problems have decreased the overriding importance of ethanol as a liquid-fuel substitute although supply interruptions and energy security are still of great concern to Brazil. Some policy changes were contemplated including a reduction in the alcohol content in gasoline from 22 per cent to 18 per cent, a decrease in the retail differential between gasoline and alcohol from 40 per cent to 25 per cent, and a proposed reduction in the manufacture of alcohol-powered cars to between 30 to 50 per cent of all new vehicles. These last two measures posed the greatest long-term threat to the future of ProAlcool. It is likely that the trend to lower use of ethanol-fuelled cars will continue, considering present low oil prices and the Government's attempt to reduce subsidies for ethanol production.

Brazil's alcohol programme crisis has many international as well as domestic implications. Abandoning ProAlcool, or even down-playing it, could mean a great increase in Brazil's capacity to produce sugar which could have serious implications for the world sugar trade. It was ProAlcool in part, that pushed international sugar prices upward in the 1980s after a decade of slump. A new export policy would flood the international sugar market, which would have serious economic consequences for the cane-growing developing countries which are already calculated to be losing $7 billion in sugar export earnings annually as a result of trade barriers in industrialized countries (Durning and Brough, 1991).

However, ProAlcool is an outstanding technical success that has achieved many of its aims, its physical targets were achieved on time and its costs were below initial estimates. It has enabled the sugar and alcohol industries to develop their own technological expertise along with greatly increased capacity (Rosillo-Calle, 1990). It has increased energy independence, made significant foreign-exchange savings, provided the basis for technological developments in both production and end-use, and created jobs. Overall, Brazil's success with implementing large-scale ethanol production and utilization has been due to a combination of factors which include: government support and clear policy for ethanol production; economic and financial incentives; direct involvement of the private sector, technological capability of the ethanol production sector, long historical experience with production and use of ethanol; cooperation between Government, sugarcane producers and the automobile industry; an adequate labour force; a plentiful, low-priced sugarcane crop with a suitable climate and abundant agricultural land; and a well established and developed sugarcane industry which resulted in low investment costs in setting up new distilleries. In the specific case of ethanol-fuelled vehicles, the following factors were influential: government incentives (e.g., lower taxes and cheaper credit); security of supply and nationalistic motivation; and consistent price policy which favoured the alcohol-powered car (Hall et al, 1991a; Goldemberg et al, 1992).

The Brazilian experience with ProAlcool shows the inherent difficulty of long-term energy planning. As Weiss (1990) points out

“on the positive side, Brazilian energy planners enjoy a substantial buffer against any possible future energy shortage, an advantage the rest of the world may some day come to envy. But as things now stand, the ProAlcool Program appears today to be an expensive and impossible-to-cancel insurance policy against an unlikely contingency”.

C. Zimbabwe

Zimbabwe is an example of a relatively small country which has begun to tackle its energy import problem while fostering its own agro-industrial base. An independent and secure source of liquid fuel was seen as a sensible strategy because of Zimbabwe's geographical position, its politically vulnerable situation and foreign-exchange limitations, and for other economic considerations.

The consumption of liquid fuel in Zimbabwe is relatively modest (but crucial to the running of a modern economy), with diesel now accounting for 55 per cent and gasoline 32 per cent (the remainder being kerosene) of the country's total liquid fuel consumption. Zimbabwe's current annual consumption of motor gasoline is about 1,850,000 barrels. Zimbabwe has no oil resources and all petroleum products must be imported, accounting for nearly $120 million per annum on average in recent years (Steinglass et al, 1988) which amounted to 18 per cent of the country's foreign-exchange earnings in 1984. Because of its landlocked position Zimbabwe had to import petroleum fuels by means of a pipeline from Mozambique, or by road and rail through South Africa. Both means of import are subject to disruption.

Zimbabwe pioneered the production in Africa of fuel ethanol for blending with gasoline in 1980. Initially a 15-per cent alcohol/gasoline mix was used, but due to increased consumption, the blend is now about 12 per cent alcohol. This is the only fuel available in Zimbabwe for vehicles powered by spark-ignition engines (Scurlock et al, 1991). Annually, production of 40 million litres has been possible since 1983, although this has recently been severely constrained by the drought Plans for a 35 million litres per year expansion have been finalized, but the expansion depends on the availability of water. Production costs in 1988 were approximately $0.75 per gallon (Steinglass et al, 1988) which at least break even with landed gasoline imports when compared with local molasses prices of approximately $25/ton.

Zimbabwe's sugar industry consists of two private sugar companies, Hippo Valley Estates Ltd and Triangle Ltd, both located in the south-east low-veld of the country. Together they operate two of the world's most efficient irrigated sugarcane estates and factories. Until recent droughts, each grew and processed approximately 2 million tons of cane per year. Zimbabwe was exporting some 240,000 tons of sugar in 1986 which constituted the country's ninth largest foreign-exchange earner.

Any estimates of cost must consider the volatility of the international sugar and oil prices, supply problems and transport difficulties. Alcohol production in Zimbabwe reduces the amount of sugar available for export, and so reduces foreign-exchange earnings. The sugar commodity market is notoriously prone to price fluctuations. In 1973 a ton of sugar could buy 76.6 barrels of oil but, only 2.8 and 9.5 barrels in 1984 and 1990, respectively. However, about half of Triangle's annual sugar production of 200,000 tons goes to the relatively unlucrative home market, and most of the rest is exported to the European Community under special trade agreements at around $450 per ton. Any remaining sugar has to be sold on the world market. Zimbabwe's sugar has to be transported through South Africa for export, which reduces the price obtained by around $100 per tonne. Scurlock et al (1991) discuss these economic factors in some detail.

At November 1989 sugar and oil prices, ethanol costs fractionally more than imported gasoline, but when the strategic advantage gained from greater liquid-fuel self-sufficiency is taken into consideration, the balance is firmly in favour of home alcohol production. In August 1990 the price of gasoline was increased by about 50 per cent due to the Gulf War and world sugar prices dropped by 40 per cent between 1989 and 1991. Now oil prices have fallen again and sugar prices have risen due to failing crops in the drought. This demonstrates the vulnerability of ethanol production to political factors and commodity prices.

Serious consideration is being given to the possibility of expanding both sugar and ethanol production. The area of land which would be needed to grow cane to provide enough alcohol to replace all imported gasoline and meet domestic sugar needs (but with none for export) is about 52,000 ha. This is less than double the total area now planted with sugar cane, and represents only 0.2 per cent of available agricultural land in Zimbabwe. An alcohol programme that would power all Zimbabwe's cars with pure alcohol would not, therefore, necessarily compete for land with food crops. However, water for irrigation is the key problem.

An integrated long-term plan has been drawn up allowing a flexible approach to changing variables. The expansion plan involves five phases, the first of which started with the opening of the Mushwe Dam in 1991 that would allow an extra 3000 ha of cane to be planted; the capacity of the ethanol plant could be extended to 50 million litres/year provided there is no appreciable increase in the demand for sugar. The second phase is also dependant upon the construction of the Tokwe-Mukorsi Dam (currently at the planning stage) which will substantially increase the water supply and allow for a significant increase in the sugar-growing area and eventually in ethanol production.

1. The Triangle Plant

The ethanol plant at Triangle is an example of a biomass-to-energy system which has operated successfully for almost a decade. In November 1978, Triangle Ltd., a company involved in producing sugar and cotton, received permission to build a distillery at Triangle in south-east Zimbabwe. Triangle farms 13,000 ha of irrigated sugarcane plantations, yielding, on average, 115 tons of cane (fresh weight) per ha. The production of alcohol began in March 1980. The plant was designed to produce 120,000 litres ethanol per day, with, on average, 1 ton of sugarcane giving 125 kg of sugar and 7.5 litres of alcohol.

With a realistic 96 per cent time efficiency, and operating the distillery for 24 hours per day 50 weeks of the year, production can reach 40 million litres per year. After nine years of operating experience, the expected output was regularly achieved, or even exceeded as in 1986, when the plant produced 41.6 million litres of alcohol. However, the need to supply the increasing demand for domestic sugar can limit the output of ethanol when the cane harvest is low. Also, drought in 1987 reduced the output of ethanol to 37.4 million litres, and similar production levels were forecast for subsequent years for the same reason. In 1992, the droughts were severe and cane productivity fell to only 2 t/ha resulting in the loss of 3000 jobs in the agricultural sector (Nature Special, 1992). Since the cane will have to be replanted, and it takes a year to grow, there will not be a significant crop in 1993 either.

The plant was financed mainly by local capital (one strict government condition was that foreign capital had to be recouped within six months by savings in foreign exchange) and home-based technology was required rather than sophisticated equipment from abroad, whenever possible. All decisions concerning the construction of the plant were made locally. The plant was locally planned with local control over its running. There was considerable cooperation between the various parties involved with very few external constraints and the industry was able to select low-cost technology closely tailored to the industry's needs. By using this approach, Zimbabwe was able to build the plant at a capital cost of $6.4 million (at 1980 prices) - the lowest capital cost per litre for any ethanol plant in the world.

After considering a number of options, it was decided to build a standard batch-type fermentation plant. This process requires that tanks are emptied and sterilized after each fermentation, but the plant can be operated by existing staff at the sugar mill. The design was produced by foreign consultants, but the construction was carried out in Zimbabwe by a local project team. Instead of importing distillery components, the locally-available fabrication structure was exploited. The consultants provided technical assistance where necessary, but a remarkable 60 per cent of the plant was fabricated and constructed in Zimbabwe. Only specialist items such as plate heat exchangers, an air blower and instrumentation were imported. To ensure high standards, local welders were given special training. Few problems have been experienced so far; only the fermentation tanks have shown abnormal corrosion.

The sugar mill is capable of producing cane juice and molasses of varying purities and concentrations to suit the needs of both the sugar factory and the distillery. The ethanol plant was also designed to operate on a variety of feedstocks using different grades of molasses, cane juice, or even raw sugar itself. This flexibility means that the plant is fully integrated with the rest of the sugar production process and can respond rapidly to changes. Thus the fermentable sugar content, for example, of molasses entering the plant can be adjusted at the expense of sugar production, depending on relative market prices, in order to maximize the return on total investment in both sugar and ethanol production. Triangle also buys in cane from 150 local growers (small farmers and private companies) and molasses to supplement its own supplies.

The mill is powered from “free” sugarcane bagasse during the seven-month cane-crushing season, and coal for the remaining five months. The Triangle ethanol plant enjoys an advantage over the typical annex molasses-to-ethanol plants built in other locations, which can operate only during the harvest season. During the off-season at Triangle, it is more economical to generate electricity from coal-fired boilers than to purchase electricity from the grid to operate irrigation pumps. The ethanol plant thus serves as a condenser for the electrical turbines, thereby operating on what would otherwise be waste steam. This enables the plant to have an energy output:input ratio of 1.94 (Scurlock et al, 1992). This system permits year-round ethanol production (330 days average), reducing investment, operating costs and seasonal inventory accumulation costs. These factors also make it economically feasible to operate on purchased molasses during the off-season (Steinglass et al, 1988).

Triangle has overcome the stillage disposal problem by diluting the waste up to 200-fold with irrigation water. After cooling in ponds, the water-plus-stillage is applied as fertilizer to around 7500 ha, about half of the sugarcane plantation. Although returning stillage to the land increases crop yields by 7 per cent, care has to be taken not to damage the soil's nutrient balance. Therefore, stillage disposal at Triangle has become a carefully monitored recycling of nutrients. The stillage-rich irrigation water at present provides all the necessary phosphates, and an excess of potassium. The total value of potassium as fertilizer in Triangle's stillage is estimated at $1.1 million each year. Alternative methods of making use of stillage and wastes are also being investigated. One practical method of disposal, for example, is to use the liquid “wastes” to generate more energy by concentrating and then burning for heat and power generation. Alternatively, stillage could be anaerobically digested to make biogas.

Scurlock et al (1991) has recently completed an analysis of the plant Unfortunately there is no detailed breakdown of costs due to security reasons. Over the first three years of operation, the ethanol production cost was around $0.35 to 0.40 per litre, compared with a “landed” cost of gasoline in Harare of $0.50 per litre. Ethanol therefore cost 11 to 27 per cent more than gasoline in terms of energy content only, but this was paid for entirely in domestic currency once the initial foreign-exchange investment had been recouped. The entire production of ethanol has been sold to the State-controlled National Oil Corporation of Zimbabwe. Gasoline and ethanol prices, as well as profit margins for gasoline wholesalers and retailers, are fixed by the Government.

Zimbabwe has proved that a relatively small country can diversify its agro-industry, to become less dependent on the perturbations of the external oil and commodities markets. The country has now gained considerable experience in the building of fermentation and biotechnological industries. Zimbabwe has pioneered the production of fuel ethanol in Africa, and provided valuable experience for other countries wishing to diversify their sugar industry to include fuel production. It sets an example of technological initiative to increase biomass-energy use and achieve some degree of energy independence. From the outset Zimbabwe has maintained both local and national involvement in decision-making at all levels. It offers an example of good use of relatively simple technology and local infrastructure and political commitment. The very survival of this project till now demonstrates that it has fulfilled the important criterion of involvement with local security, industry and agriculture. Indeed, local motivation seems to underpin every aspect of biomass energy at Triangle (Scurlock et al, 1991).

D. Malawi

Malawi is entirely dependent upon an agricultural economy for its export earnings. A major reason for embarking on the production of fuel ethanol has been the continuous deterioration of the regional transport system and the uneasy security situation with regard to Mozambique, both of which have caused frequent petrol shortages. Malawi commenced its bioethanol programme in 1982 utilizing ethanol from a distillery located at Dwangwa sugar mill with a capacity to produce 10 million litres/yr. The Ethco (Ethanol Company Ltd) produces ethanol from molasses and raw sugar efficiently and profitably. Ethco has also provided the driving force for the exploration of wider applications of ethanol as neat fuel, diesel fuel substitute and illumination fuel for paraffin lamps. It has sought to expand the options for feedstock with work on cassava and wood chips.

Ethco currently produces ethanol to supply a national blend of 15 per cent (v/v) ethanol which could be increased to 20 per cent. A production of 20 million litres/yr could be achieved with minimal capital investment by operating the present fermentation/distillation plant all year round. A further option under consideration is the construction of a second plant near the Sucoma estate whose by-product molasses are of little or no opportunity value. The potential exists to double ethanol production immediately and, in the longer term, to produce sufficient to displace the country's entire gasoline imports. The annual demand is approximately 60 million litres of gasoline and 80 million litres of diesel oil (Moncrieff and Walker, 1988). If extended applications of neat ethanol, being tested in a small fleet of government Land Rovers (approximately 1500) indicate that only a modest substitution of diesel fuels in transport and agriculture can be achieved, even then, Malawi could displace as much as 10 to 20 million litres of imported petroleum with ethanol in the medium term.

In terms of feedstock for new ethanol production in Malawi, a report (Steinglass et al, 1988) estimates that surplus molasses and the sugar sold at world market prices would be the cheapest feedstocks and would yield approximately twice the current amount of ethanol produced. Beyond this level alternative feedstocks would have to be considered if the ethanol market expands sufficiently.

E. Kenya

In the 1970s, the combination of high oil prices, the large fluctuations of world molasses prices and sharp a rise in transport costs enabled the creation of the economic and political conditions to set up a bioethanol programme in Kenya. This programme was plagued with difficulties from the start. Initially, the idea was to set up two ethanol plants using sugarcane molasses - the Madhvani and the Muhoroni plants. The Madhvani plant was never completed due to a number of techno-economic and political reasons. The plant was too costly and sophisticated and took little advantage of the local conditions. Due to lack of access to information and untied finance, the choice of technology in the international market was severely constrained and the resulting technology chosen was very sophisticated and capital intensive. Unlike the KCJ woodstove programme, government involvement in the joint project had a negative impact and distorted the economics, which was further complicated by the absence of a clear and cohesive long term government policy on ethanol production (Rosillo-Calle et al 1991).

The second smaller plant integrated into an existing sugar refinery was, however, successfully constructed (the Muhoroni plant inland from Kisumu). The Muhoroni plant was completed in 1983. It is an integrated sugar-ethanol plant which also produces 4 tons of baker's yeast per day. At the current capacity of 60,000 litres day, it produces all of Kenya's ethanol using sugarcane molasses. This is blended at 10 per cent with gasoline. At present the plant operates at 75 per cent of its capacity.

F. Thailand

Thailand produced about 20 million tons of cassava in 1988. A typical Thai tapioca starch factory discharges approximately 15-23 m3 wastewater per ton of starch. The COD (chemical oxygen demand) of the wastewater is high and is in the range of 15,000 to 45,000 mg/l which can be a serious pollution problem. In the early 1980s there was a strong interest in producing ethanol from cassava and in 1983, a pilot plant was set up with a capacity of 1500 litres of ethanol per day to study the feasibility of ethanol from tapioca starch. The plant yield was in the range of 185-200 litres ethanol per ton of fresh cassava, and the production cost of ethanol (99.5 per cent v/v) was estimated to be about $0.48/litre (at 1987 prices), including factory operation and depreciation costs (Thomas, 1990).

However, in spite of the technical success of the project, it seems unlikely that fuel ethanol will be produced from cassava, at least in the near future, with the prevailing oil prices. Instead biogas from wastewater treatment looks more promising and efforts are being made to this end. Laboratory and pilot plant studies have shown that it is technically and economically possible to produce biogas from the wastewater in a fixed-bed reactor. The pay-back period of the anaerobic digester system is estimated to be less than three years for a factory producing 70-80 tons of starch per day (Tanticharoen, 1990). The biogas produced from wastewater is estimated to be able to save $11,860 per month (at 1988 prices) in factory fuel costs.