Two large categories of field agricultural residues can be defined: field crop residues and arboricultural residues. Field crop residuals are the residues that remain in the field after the crops are harvested. Depending upon the crop, the harvesting method and other parameters, field agricultural residues may include various plant part such as stems, branches, leaves, chaff, pits, etc. varying in composition, moisture and energy potential. Arboricultural residues are the residues that remain in the field after farming activities performed during the cultivation of perennial crops (pruning vineyards and trees).

Total quantities of residues were estimated using recent statistical data for the production area for each crop as well as specific coefficients indicating the ratio of residues production to cultivated area.

For each crop i cultivated in region j, the annual energy theoretical potential Erescropi, j is calculated by SYNENERGY Project, based on the following formula [5]:

Erescropi, j,= n, Ai, j,Hi,

ri country specific residue production per cultivated area [t/ha]

Ar, j, cultivated area of crop i in region j [ha]

Hi country specific lower heating value of residue [GJ/t]

Data for crops production and harvested area in 2008 were obtained from the official statistical publications on the entity and state level. The coefficients used to estimate the quantities and the energy potential of agricultural field residues derived from local experts’ estimations and references.

The estimation of the quantities of agricultural residues available for energy production is based on the degree of availability which is different for each crop, varies from year to year and depends on several factors such as:

• the harvesting method,

• the moisture content,

• the demand of agricultural residues for non-energy purposes (cereal straw, for example, is used for animal feeding, animal bedding, etc.),

• the need for some residues to remain on the soil to maintain the level of nutrients (sustainability reasons).

The availability factor for arable crop residues is estimated to be 30%. The same factor for arboricultural residues is estimated to be 80%, mainly due to technical difficulties in collection. Based on these factors, it is estimated that 527.765 t of field crop and
arboricultural residues could be annually exploited for energy purposes (reference year of analysis 2008). This is equivalent to 7,47 PJ or 3,24 % of the total primary energy supply in 2008, which means that crop residues could contribute significantly to the energy supply of Bosnia and Herzegovina. Almost 90% of this potential comes from field crop residues, while arboricultural residues contribute the remainder.

Figures 1 and 2 present the technical potential of the most significant crop residues. Maize residues are the most abundant source of biomass contributing 75% to the field crop residues potential or 68% to the total crop residues potential. Wheat residues share in the field crop residues potential is also significant (17%), while barley, oilseeds, rye and oats residues contribute to a lesser extent. The major part of arboricultural residues comes from plum and apple tree prunings (73%). Other sources of arboricultural residues that should be taken into account are vineyards, pears, cherries, sour cherries and peaches prunings.

□ Maize

□ Wheat

□ Barley

□ Rye

□ Oats

□
Oilseeds

Plums Apples Vineyards Pears Cherries/ Peaches Other

Sourcherries

The crop residues potential in RS is more than twice that in FBiH and Brcko district and amounts to 5,20 PJ. In RS almost 90% of the potential comes from cereals, while this
percentage is somewhat lower in FBiH (83%), where the contribution of arboricultural residues is higher (16%). Oilseed field residues have a minor contribution (1-2%) in both entities.

In the Federation of Bosnia and Herzegovina, 53% of the crop residues potential is found in the cantons of Tuzla (FBiH-K3) and Una-Sana (FBiH-K1). Another 30% of the potential is found in the cantons of Posavina (FBiH-K2) and Zenica-Doboj (FBiH-K4) as well as in the Brcko District.