The biomass utilization for energetic purposes in Czech Republic.

Strašil Zdeněk

VÚRV Praha-Ruzyně

Currently, agriculture in Czech Republic faces a very important decision. If the Czech Republic agriculture has not been exposed to a danger of high overproduction of food and the resulting liquidation of a part agriculture and the leaving of the agricultural landscape by it’s inhabitants, it is necessary to begin immediately considerable restructuralization under the conditions of effectively utilized agricultural soil. Adapting of agriculture to non-food production will be necessary, this means the production of plant raw materials and the production of bioenergy in less productive areas.

At this time, there is supported, according to the rate of yield’s increase of main crops, inland consumption and situation on the world market in 1998, that there will be about 250 thousands hectares of set-aside soil in Czech Republic, which can be used for non-food production. This soil can be used particularly for the production of bio-fuels (cultivation of rape for the production of bio-diesel, cultivation of cereals and sugar beet for the production of ethanol) and particularly for the cultivation of energetic and industrial plants.

The present energy needs in Czech republic represent annually about 1750 PJ and it is covered from 62,7% by ecologically inconvenient brown coal, form 26% by imported natural gas and oil, from 10,5% by nuclear and water energy and only 0,8% is covered by energy from biomass.

Among the most elaborate technologies for the production of energy from biomass in Czech Republic belongs to the production of bio-diesel from rape-seed oil. Nowadays, there are in operation 23 facilities which produce bio-diesel. The whole annual capacity of these sites is 73 thousand tons of bio-diesel which represent about 78 thousand ha of rape fields. The ecological and economic effectiveness of the production of bio-diesel supposes the utilization of all by-products as well, particularly the rape straw and glycerine.

The combustion of straw, wood, tree bark and agricultural wastes is the most commonly used way of thermal utilization of biomass in Czech Republic. In the substitution of fossil fuels by the biomass it is necessary to solve all tasks as a whole with respect to the local conditions, particularly with regards to the technical problems, economic tasks and matter of organization.

There is produced the complete assortment of devices for the combustion of biofuels in Czech Republic till the 3 MW of heat output, including the energy blocks for the gasification of biomass for the production of heat and electricity of up to 650 kW output. The highest development represents the production of biomass gasification for family houses with the output of 20-30 kW, which were sold in Czech Republic in a number higher than 20 thousand. Further there are produced and installed additional devices for the combustion of biomass in existing fossil fuel furnaces and for the combustion of briquetted straw with the brown coal.

It is possible to expect that after the year 2000 the potential of bio-fuels will represent 10 mil. tons of plant biomass in Czech Republic. Into this amount is included all oil-plant straw, that means 0,9 mil. tons, 25% of the whole harvest of cereal straw, that is 1,6 mil. tons, further more grass and reeds, which represent 0,8 mil.tons, and energy plants grown for direct combustion, which represent 4 mil. tons. It is supposed that the intensive utilization of harvest remains in the 1^st stage of the development of phytoenergetics and the targeted cultivation of energy plants with high yields of energy phytomass in the 2^nd stage.

In further development of phytoenergetics in Czech Republic, more significant cultivation of energy plants with high yields of energy phytomass is counted on. Therefore the research in Czech Republic is aimed at finding out suitable species and varieties of plants for the utilization mentioned above, and improving the cultural practices, in a similar way as in the other countries of EC.

A few years ago, the Research institute of crop production in Prague-Ruzyně, in cooperation with some institutions, started the research of cultivation of untraditional industrial and energy plants. The research is predominantly aimed at looking for suitable species of plants from the point of view of their suitability for industrial and energetic utilization. The research would have to improve their cultivation technologies. At present, we have the results of long-term field experiments from the different ecological localities.

Some results from the research of energy plants

Yields of some plants from different localities which are intended to be used as a energy source are stated in table 1. The plants of genus Sorghum reach high yields of phytomass in Czech Republic, particularly in warmer areas (Ruzyně, Troubsko) with the assumption of rainfall sufficiency. Although the Sorghum is a plant of C₄ type and during the creation of dry matter it saves water, about 6000 ton of water to reach 20 tons of dry matter is necessary. This amount of water correspond to the 600 mm of rainfall. E.g. the Sorghum has reached the high yield of 38,9 tones of phytomass dry matter per hectare at Troubsko in 1996. When about 650 mm of rainfall had fallen in that year. The highest yields of Sorghum phytomass in the marginal areas (Lukavec, Chomutov), although they were favourably influenced by nitrogen fertilization, reached only 30-50% of dry matter yields observed at more fertile and warmer stands. At less fertile stands the efficiency of Sorghum plants is overcome by Secale cereale or Triticale (see tab. 1).

At the stand of Ruzyně, the yields of dry matter of Miscanthus sinensis were 10,59 t.ha^-1 in the 3^rd year after planting. In Troubsko by Brno, where the conditions for the cultivation of Miscanthus are more favourable, dry matter yields has reached 16,7 t.ha^-1 on average during the 3^rd year after planting. At the stand Lukavec, where the temperature conditions are less suitable for the more heat-loving Miscanthus, we have reached 2,0 t.ha^-1 of dry matter yield on average during the 3^rd year after planting.

Further, on the basis of our yield results (see table 1), it^’s evident that in the warmer areas of Czech Republic, the satisfactory yields of phytomass were produced by Sorghum and Reynoutria (during the 3^rd year after planting). In the cooler areas, the higher yields of shoots were produced by Reynoutria, Secale cereale, Triticosecale.

Table 1.: The yields of phytomass dry matter (t.ha^-1 ) of some observed plants for energy use

^x during the 2^nd year after planting

^xx during the 3^rd year after planting

For illustration are in table 2 compared yields of energy from 1 hectare obtained by energy plants with the amount of energy gained by brown coal combustion in the same amount, as the yield of energy plants.

Table 2.: Energetic values of energy crops

^x amount of brown coal in mass identical with energy crop (mean content of energy in coal = 12 MJ.kg^-1)

Advantage of these energy resources is that they are uniformly distributed regularly on the whole state territory. The utilization of wastes and of agricultural land could represent a significant contribution for solving local energetic problems and could play an important role in decreasing the consumption of imported conventional energy resources.