When the food products market is limited and much of agricultural land is not utilized (the Latvian case at present), then agriculture must be directed to the production of new alternative products. The land may be used for technical cultures to obtain non-food products including biofuels for the domestic market to diminish imports. Biofuel is part of bioenergy, obtained from renewable sources. Bioenergy is stored in the material produced by photosynthesis, or as a by-product of waste (including organic waste). Biomass resources comprise conventional forestry and wood processing by-products, agricultural and energy crops including oil plants, and wastes. 
 
National bioenergy programmes, coordinated by the International Energy Agency (IEA), exist in many countries. Today, 3÷ (5% of the total energy consumption in the EC is covered by bioenergy. The increase of bioenergy use in the EC is planned to reach 12÷ (15% during the next decade. 
 
The EC has analyzed the potential bioenergy production and use in Europe. In accordance with this information, the ratio of energy output/input is an important factor in selection of a raw material for energy carrier production. Sugar beet, potatoe and wheat have output/input ratios of 1.63, 1.04 and 1.14, respectively, for ethanol production. In Central Europe, the average yield of sugar beet in 1998 was 48,740 kg/hectare, with a sugar content of 16 %. Tops and leaves had a yield of 38,990 kg/hectare. The anhydrous ethanol yield from 7795 kg of beet juice was 3775 kg (4755 l). Calculations show that, if about 10 %  of the arable land in the EC is used for the production of ethanol for fuel from sugar beet, then this would supply all of the farm machinery with fuel. Wheat grain and straw yields are 5420 kg/hectare and 7050 kg/hectare, respectively. The anhydrous ethanol yield from this amount of grain is 1642 kg (2081 l). Production costs of bioethanol from wheat, sugar beet, potatoe and corn are 0.095, 0.22, 0.50, and 0.163 ECU/litre, respectively. Wheat is more attractive for ethanol production in Europe due to the technologies involved (reduced energy consumption and simplified machinery as compared with the sugar industry). Similar analyses have been discussed during the 10th European Conference and Technology Exhibition held on 8-11 June 1998 in Wurcburg. 
 
It should be mentioned that the competitiveness of biofuel with fossil fuel is currently possible only due to tax subsidies. This clearly indicates the experience of Brazil [Gregg D.J., 1998] and USA. 
 
Environmentally  friendly technologies, the wasteless use of raw  materials and recirculation of water are the general principles of future technologies. Agriculture and industry must be integrated as environmentally friendly complexes. Any number of processes can be included in the complex to produce target products in accordance with principles of a closed or a semiclosed biotechnological system. 
 
General principles of a semiclosed integrated biotechnological system for processing of agricultural raw materials are as follows: 

• Production of non-food products from agricultural raw materials by using wasteless technologies with minimum energy consumption.
• Optimized use of soil for biomass production with minimum use of mineral fertilizers and chemicals.
• Maximum use of biological processes as opposed to chemical ones.
• Utilization of wastes, preferably using methane fermentation to obtain biogas as a local energy source and to recover the  liquid fraction with minerals for soil improvement.
• Environmentally friendly technologies, including utilization of CO₂ from fermentation.

The transition period to the market economy in Latvia after the restoration of independence has caused some disbalance in agriculture and the national industry. 50-60% of energy resources including transport fuel is covered by import. 
 
The area of the agricultural land in Latvia is 2.57 million hectares, and the arable land occupies 1.6 million hectares. About 15% of the arable land can be used for rape cultivation to obtain up to 200,000 metric tons rape-seed oil per year. Grain, potatoe and sugar beet can be used for bioethanol production. From 1931 to 1940 the motor fuel ‘’Latols’’ with an ethanol content of 30 to 50 % had been produced. Today, three ethanol factories with a total annual capacity of 11 million litres of ethanol operate in Latvia. The consumption of gasoline in 2000 will be about 700,000 tons. 
 
The biofuel concept has been accepted by the Latvian Government. A working group at the Ministry of Agriculture is developing a programme of biofuel production and use in Latvia within 2000 - 2010. Ethanol, rape oil and biogas will be the main components of biofuel in Latvia. 
 
The concept envisages ethanol additives of 5% to gasoline. This means that 35,000 t of ethanol will be used as a fuel additive. The cost of the ethanol obtained from grain is about 0.60-0.70 USD per 1 l. 
 
An annual output of biodiesel (REE or RME) for agriculture will make up 58,000 t to substitute 40% of diesel. An estimated cost of REE and RME is 0.56 USD/l and 0.42 USD/l, respectively, in the case of  the optimum version when all by-products are realized. 
 
The biogas produced from agricultural and industrial wastes, municipal wastewater treatment plants and landfills can be used to supply the local energy and will eliminate the major  environmental problems. Several methane fermentation installations, such as the Wastewater Treatment Plant in Riga, a manure treatment plant at a swine farm in Ogre and installations at two dairy factories, are currently in operation in Latvia. A potential annual output of methane from biogas by fermentation of animal manure is estimated to reach 6 million GJ. In the near future, the landfills around Riga (Getliði, for example) can be  equipped by biogas gathering facilities. The implementation of the bioethanol programme in Latvia depends on advances in agrotechnology, modernization of ethanol production and  the taxation policy. 
 

Prospective ethanol technologies 

Wheat, triticale and sugar beet are recommended as basic raw materials for ethanol production in Latvia during the next decade. 
 
To obtain ethanol from starch substrates by fermentation with yeast, the following processes are carried out: 

• enzymatic conversion of starch into sugars by liquefaction, using (alpha-amylase and subsequent saccharification by (beta-amylase and/or glucoamylase; thermostable (alpha-amylase is recommended)

• fermentation by the Saccharomyces cerevisiae yeast. Lignocellulose is a prospective raw material for ethanol production. The process of obtaining fermentable sugars by chemical and enzymatic hydrolysis of lignocellulotic raw materials had been intensively investigated. The Riga Hydrolysis Method, using concentrated sulfuric acid, was developed by the Institute of Wood Chemistry, Latvian Academy of Sciences. Furfural production from pentose solutions during the continuous dehydration process was investigated by N. Vedernikov et al.,  and the new  technology for furfural, ethanol and acetic acid production from lignocellulotic materials was  evaluated. 32 kg of acetic acid, 115 kg of furfural, 202 l of ethanol, 120 kg of carbon dioxide and 310 kg of fuel granules (on the lignin basis) can be obtained from 1000 kg of straw. Pentose-containing substrate fermentation and a two-stage weak acid hydrolysis of wood products, the CASH process, have been developed to obtain ethanol. The National Renewable Energy Laboratory (USA) suggests that the fermentation of both xylose and glucose in a combined process can produce ethanol at a cost of 0.32 USD per litre that is considerably lower than that projected previously, in contrast to 0.60 USD in the case of conventional ethanol production from corn. These calculations were made, taking into account the recent experimental results with the genetically engineered Zymomonas mobilis that produces ethanol from xylose and glucose. The Zymomonas mobilis metabolism and biotechnology have been  investigated in many laboratories, and Professor Doelle is one of the leaders. Experiments with Z. mobilis  have been carried out  at the Institute of Microbiology of the Latvian Academy of Sciences, since 1983. As compared with yeast,  Zymomonas mobilis  is more resistant to sugars and ethanol; the substrate utilization is 2 to 3 times faster; the ethanol yield is higher. Levan and ethanol production in sucrose medium has been investigated in detail, including energy metabolism, physiology, and osmotolerance.

  Rape oil methyl-ester (RME) or ethyl-ester (REE) have a  good potential as a  replacement of diesel fuel. RME can effectively eliminate injection problems in direct-injected diesel engines. The fuel properties of RME are  similar to those of diesel fuel. Approximately 1000 kg of RME (biodiesel) can be obtained from 3000 kg of rape seed.  The mass flow diagram for the production of rape seed oil and RME shows that  1 hectare can yield 3180 kg of rape seed and 5470 kg of rape straw. From this amount of rape seeds, 1285 kg of RME can be obtained using 139 kg  of methanol for transesterification. The associated by-products are: 1848 kg of rape seed meal as a feed protein source, 53 kg of phosphatides and 133 kg of glycerol. This process has a very favourable energy output/input ratio of 3.47. Rape oil is one of the best fuels from renewable agricultural resources. Biotechnological methods can be used to convert rape straw into ethanol or biogas, increasing the ergy output/input ratio from 3.47 to 5.43. 
 
Glycerol is a raw material for the chemical industry. Honey can also provide an increased saving in biodiesel production. 

Methane fermentation 

Methane fermentation is a well investigated process. The Institute of Microbiology and Biotechnology  (Latvia) investigated  methane fermentation of animal manure with additives of herbage juices and straw in both laboratory and  pilot-scale  studies. Methanogenesis was significantly increased in the thermophilic regime (53-550C), compared  with the mesophilic  (35-400) one. In the thermophilic regime, the inactivation of the pathogenic microflora, helminths and weed seeds as well as  biodegradation of  pesticides were stimulated. However,  mesophilic methane fermentation proved to be energetically more attractive. To increase the methane yield from pig manure, herbage juice or straw additives were recommended. Methanogenesis can be stimulated using special surfaces (fibres) in bioreactors for immobilization of bacterial cells. The herbage juice can be fermented in a separate fermenter, prior to methane fermentation for conversion of components to acids and  coagulation of  the juice protein for animal feed. 

 Semiclosed integrated biotechnological system 

A  Latvian interdisciplinary programme, entitled TPF (Transformation of Products of Photosynthesis), was established in 1976. The  goal of the programme was to obtain protein feed and silage from green biomasses (alfalfa, clover), and biogas from agricultural wastes and manure. An experimental leaf protein and biogas production plant was installed at the farm ‘’Uzvara’’ and run for many years. A semiclosed wasteless biotechnological system for green biomass processing was demonstrated to be effective under normal conditions. Today, non-food products production from agricultural raw materials is more important as compared with feed protein production in conditions of the market economy in Latvia. 
 
Sugar beet yields the maximum amount of fermentable sugars from a given land area, while cereals allow to extend the production time. Alfalfa is an excellent protein producer and can enrich soil with nitrogen. Rape is a good raw material for biodiesel production.These crops are good candidates as the raw material for biofuel products production in Latvia. 
 
An example of biofuel production, using a semiclosed biotechnological system, is demonstrated in Fig 1. We suggest that the integrated biosystem developed in Latvia is appropriate to the socio-economic system strategy declaraded by the Da Silva’s [Da Silva et.al., 1992] and  H.W. Doelle’s reports at this Internet Conference. 
 Despite the weak economic parameters of biofuel production in Latvia, the draft of the proposed national programme provides a potential impetus to a sustainable development of agriculture and protection of environment. 

Note: to shorten the present report, our own publications are referred to. The worldwide literature was analysed when planning the initial experiments. 
 

M.Bekers, J.Shvinka, L.Pankova, M.Laivenieks, I.Mezhbarde. 1990. A simultaneous sucrose bioconversion into ethanol and levan by Zymomonas mobilis. Appl. Biochemistry and Biotechnology,  24/25, pp. 265-274; Proc. of Eleventh Symp. on Biotechnology for Fuels and Chemicals, 8-12 May, 1989, Colorado Springs. 

M.Bekers. 1995. Biofuel production as a component of closed biotechnological system. Proc. Latvian Acad. Sci., 9/10,  pp. 113-120. 

M.Bekers. Non-food production in closed biosystems. In: Proc. of Intern. Symposium ‘’Environmental Biotechnology’’, Part II, 21-23 April, 1997, Oostende, Belgium, pp. 319-321. 

M.Bekers, P.Jansons, U.Viesturs, G.Telysheva. Biofuels from renewable sources: the Latvian case. In: Book of Abstr. of the European Congress on Renewable Energy, 5-7 May, 1997, Athens, Greece, p. 127. 

M.Bekers, U.Viesturs, G.Telysheva, E.Gudriniece, V.Gulbis, A.Shkele. 1997. Prospectives of biofuel production from renewable sources. In: Proc. of the World Energy Council Baltic Regional Forum "Energy Strategies in the Baltic States: from Support to Business", Vol. 1,  pp. 181-196. 

M.Bekers, U.Viesturs, E.Gudriniece, G.Telysheva, J.Zandersons, G.Bremers. 1998. The Biofuel Programme in Latvia: experimental background and implementation issues. In: Proc. of the Intern. Conference ‘’Biomass for Energy and Industry’’, W� rzburg, Germany, pp. 1271-1274. 

E.J.DaSilva, C. Ratledge, A.Sasson. 1992. Biotechnology: Economic and Social Aspects. Cambridge University Press. 

D.J.Gregg. Historical perspectives on Brazil's sugar-cane - to - ethanol industry. IEA Bioenergy Newsletter, No. 2, May 1998, pp. 6-11. 

J.Laukevics, M.Bekers, A.Danilevics, E.Kaminska, A.Lisovska, D.Upite, A.Vigants. 1996. Suitability of some sorts of grain for ethanol fermentation in Latvia. Proc. Latvian Acad. Sci., Vol. 50, No. 3, pp. 137-139. 

R.Linde, M.Bekers, I.Vina, H.Kaminska, D.Upìte, R.Scherbaka. 1998. Ethanol and fructose from sugar beet. In: Proc. of the Intern. Conference ‘’Biomass for Energy and Industry’’, Würzburg, Germany, pp. 464-467. 

U.Viesturs, G.Telysheva, G.Dobele, T.Dizhbite. 1995. Energy production from biomass: world experience. Proc. of the Latvian Acad. Sci., 9/10, pp. 97-112. 

U.Viesturs et al. 1997. Certain new biotechnology processes and the equipment for their implementation - fermentor mixing and operation mode effects on efficiency. Prikl. Biokhim. Mikrobiol., Vol. 33, No. 3, pp. 243-256.