Institute of Agricultural Engineering Lithuanian University of Agriculture Dr. Almutas Dravininkas

1. Institute of Agricultural EngineeringLithuanian University of AgricultureDr. Almutas Dravininkas THE USE OF PLANT BIOMASS AND IT’S WASTE PRODUCTS FOR ENERGY PURPOSE IN LITHUANIA

2. ObjectThe objective of the present study is to identify energy potential of plant biomass and it’s waste products utilization for energy purposes in Lithuanian, according to technically validated possibilities for 2010-2020.

3. Results and Discussion Wood fuel Presently one of the major renewable energy sources is wood fuel (wood handling and processing waste and firewood timber). Total energy value of Lithuania-produced wood fuel was 26.2 PJ in 2000. About 1.24 Mm3 of wood fuel is currently used in rural areas. At 7.1 GJ/m3 heat value this amounts to 8.8 PJ. Wood fuel: potential in the nearest decade will be 4-4.5 Mm3. Thus the total non-used wood potential is 2.2-5.7 PJ, of which 1.5 PJ would be attributed to rural areas. At the moment, wood fuel is successfully competing with other types of fuel. Straw fuel Straw is another source of biomass fuel. About 0.5 Mt (million tons) i.e. 12-15 % of the total straw yield can be used for fuel in Lithuania. At straw heat value of 14 GJ/t (15 % moisture content) this amounts to 7 PJ. In order to utilize straw, fuel boilers with a total capacity of around 300 MW must be fitted up or reconstructed. At the moment a few straw-fired boiler houses with a total capacity of 5 MW and low-capacity boilers are operating in Lithuania and as little as 3 %, of targeted straw fuel resources is used. Forest and shrub plantations According the data of the Lithuanian Institute of Forestry, about 50 thousand hectares of the land not used for agricultural production (exploited peat land and gravel quarries) could be used for establishing plantations of fast-growing trees and shrubs for energy purposes. At an average productivity of 10 t/ha dry biomass per year, we could get 0.5 Mt (7 PJ energy value) biomass. Program for increasing forest area in Lithuania was approved in 2002, which envisages that over the 20 years' period 100-120 thousand hectares of the land not used or unfit for agricultural production will be afforested. Short rotation plantations could cover about 40-50 % of this area.

4. Results and Discussion Energetics grasses Experiments set up at the Lithuanian Institute of Agriculture and the Lithuanian Institute of Agricultural Engineering suggest that tall-growing grasses and legumes and topinambours could be grown for energy purposes i.e. for fuel production. At l0 t/ha yield level and 46 thousand cultivation area energy grasses can produce, 0.46 Mt dry biomass (6.4 PJ value). The fact that that conventional agricultural machinery can be used for cultivation, management and handling of these crops makes their production attractive. As it is known, biogas can be produced from plant biomass in anaerobic reactors. Such trials were carried out at the Lithuanian Institute of Agricultural Engineering and at the Lithuanian University of Agriculture. If we allocated a 14 thousand hectare area for this purpose, at 10 t/ha productivity (calculated in dry matter) and biogas output of 500 m3/t we could produce about 70 million m3 of biogas. At a heat value of 22.6 MJ/m3 the total biogas potential from plant biomass would amount to 1.6 PJ. Biogas can be used for the production of electrical energy and heat. At present plant biomass is practically not used for the production of electric energy in Lithuania. Potential of plant biomass utilization for energy purposes is presented in Figure 1.

5. Fig. 1. Potential of plant biomass cultivation and usage for energy in Lithuanian agriculture (the currently used amount is presented in black)

6. Results and Discussion The total potential of plant biomass use for energy needs amounts to 36.4 PJ. Plant biomass specially grown for energy purposes accounts for about 52 % of this potential. Only about 24 % of the total potential are being used at the moment. Around 26 PJ of fuel energy is used in rural areas (for agricultural operations and household use). The potential of renewable energy from plant biomass exceeds the current energy consumption in rural areas by 1.4 times. Thus, cultivation of energy plant biomass can become an alternative business in agriculture. Furthermore, agriculture can become a supplier of renewable energy raw material. Gross amount of energy produced from crops are at the above-indicated productivity levels is presented in Figure 2.

7. Fig. 2. Gross amount of energy produced from 1 ha of energy crops

8. Results and Discussion Waste products – crude glycerol Production of 1 t RME yields 106 kg of crude glycerol. Such product does not meet commercial requirements and either has to be further purified or its possible applications have to be identified. We suggest using crude glycerol in the production of fuel briquettes from sawdust. However, it was necessary to study the composition of its oxide emission, since acrolein, a highly toxic material, can be produced in a high temperature. Glycerol phase from which methanol has been removed should be used in the production of briquettes. Developing technology for sawdust briquette production can solve this problem. A biodiesel (RME) production plant with an annual capacity of 1000 t owned by a farmer A. Blazys (Telsiai district) was fitted with sawdust briquette production facilities following the technology developed by LIAE. The production technology involves the use of RME production waste – crude glycerol (Figure 3).

9. Fig. 3. Technological scheme of sawdust briquette production: 1 – sawdust hopper; 2 – auger conveyor; 3 – valve; 4 – drier; 5 – fan of the burner; 6 – chamber of primary combustion; 7 – chamber of secondary combustion; 8 – chopper; 9 – cyclone; 10 – dust separator; 11 – distribution hopper; 12 – batcher; 13 – oven hopper with level sensor; 14 – auger-batcher; 15 – press batcher; 16 – press; 17 – fan; 18 – ejector

10. Table 1.Technical parameters of the technological line Wood sawdust briquettes were tested according to four parameters: average density, moisture content, ash content and heat capacity. Test results are presented in Table 2.

11. Table 2.Physical parameters of fuel briquettes with 5-10 % glycerol additive

12. Results and Discussion According to set parameters wood sawdust briquettes with glycerol 5- 10 % additive meet DIN 51731- HPI requirements. Also was performed change combustion temperature and amount of nitrous oxides in smoke in relation to crude glycerol amount in fuel mixture. The test results indicated increasing the combustion temperature, when fuel mixture with higher glycerol content is burnt. It was established that the higher content of crude glycerol in fuel mixture, the higher burning temperature is. This is explained by higher calorific value of glycerol. With increasing combustion temperature the amount of nitrous oxides NOx in smoke declines. From the environmental viewpoint, this is a positive phenomenon, since nitrous oxides are attributed to the group of compounds hazardous to human health (Fig. 4).

13. Fig. 4. The content of nitrous oxides NOx (mg/m3) in smoke in relation to crude glycerol content in fuel mixture G (%). Relative rate of blown air V0 = 5 m3/kg

14. Conclusions • Technical potential of renewable energy from plant biomass amounts to approximately 36.4 PJ in therural areas of Lithuania. This exceeds energy and fuel consumption in the ruralareas by about 1.4 times. At present about 24 % of the total technicalpotential is being used. • Cultivationof plant biomass for energy purposes can be an alternative business in rural areas of Lithuania, and agriculture can become a supplier of energy raw material. • The crude glycerol can be utilized in the production of fuel briquettes made from sawdust.