Dendromass potential in Bulgaria

Biomass residues are among the main sources of renewable energy. These residues can easily be transformed into fuels for industry. Some of the most quickly developing technologies for wood processing are the ones that produce briquettes and pellets – products that result from pressing of biomass residues. Appropriate wood residues for briquette and pellet production are the following:

• From logging – brushwood, branches, bark, dry fallen wood-pulp, etc.
• From wood processing industries – sawdust, wood chips, bark, shavings, bits, etc.
• From pulp and paper industry – chips, bark, waste paper;
• From agriculture – straw, maize (stem and corn-cob), sunflower (stem and cob), branches from gardens, vineyards, tobaccos (stems), etc.

The biomass use for heating and CHP may have substantial contribution for the increased share of RES in the country energy balance. On the other hand, the biomass potential and the opportunities for its efficient utilization are still not popular.

Forestry enterprises have available very large quantities of biomass resources that can be converted into energy. The total forest area in Bulgaria in 2003 was 4 mil. hectares (according to the Ministry of Agriculture and Forests), which is 35% of the country area. The total wood stock is 526 mil.m3 and the average stock per hectare is 155 m3. The total annual increase is 13.4 mil.m3 and the increase per hectare is 4.03 m3.

The residues that result from logging and wood processing are classified in categories, depending on the sequence of their “production”, usage, physical and mechanical properties, size, weight, etc. Depending on the thickness, the residues are classified in 2 groups – below 3 cm and 3-10 cm. Those below 3 cm are mostly small branches and brushwood and they remain unused. Those in the range 3- 10 cm are used either as fire-wood, or as production materials in both wood processing and pulp & paper industries. These residues are also suitable for briquette and pellet production.

The structure of the broad-leaved and coniferous wood is important for determining the technologies for production, transportation, and use of the residues. On average, this structure is the following:

Table 6: The structure of the broad-leaved and coniferous wood