The usual method that is used for the interpretation of DRIS index is the ordering of the values of the indices, the ordering is more limiting disabilities by the most limiting excess.

By this method of ordering of the index establish that the lowest DRIS index and negative has been considered the most limiting, the second lowest, the second most limiting disability and until the most limiting excess, which would have the DRIS index greater and positive (Walworth & Sumner 1987; Bataglia & Santos, 1990). These criteria have been used both to evaluate the accuracy of the method (Jones, 1981) and for nutritional surveys, when there is the DRIS as a tool for identifying classes of farms and the distribution of nutritional status (Beaufils, 1973; Eymar et al., 2001; Hundal et al., 2005, Silva et al., 2009; Sema et al., 2010).

Total power generation capacity in BiH is around 4 GW, 2 GW of which are hydropower plants (HPP), 600 MW lignite-fired plants, and the rest coal-fired units. There are 17 district heating (DH) systems operating in BiH. Solid fuels account for nearly 41% of total heat production [15]. It is estimated that around 180 MWth of DH systems operate with brown coal and lignite [5]

Both literature and experts opinion suggests that cofiring 5 — 10% biomass feedstock with fossil fuel (on a weight basis) require relatively minor changes to the technology that is already in place, such as fuel feed systems, storage facilities, emissions controls etc and hence relatively low capital investment. Higher proportions of biomass fuel require more profound technical issues to be addressed and therefore higher investment. Power generation and district heating plant is typically at an advanced age and is unlikely to merit substantial investment, therefore it was considered that the most likely approach would be to co-fire at lower percentages.

Waste wood, forest and industrial residues as well as agriculture residues such as prunings and straw could be used for co-firing although wood chips are the preferable fuel. Forest residues, as estimated by the study, accounts for 3,07 PJ or 380.000 tonnes. If 50% of this could be used for co-firing this would result in the production of 149 ‘green’ GWh within existing solid fuel power facilities [5]). Coal-fired boilers in the government sector could be co-fired or fully fired on biomass fuel. It could especially be realized within government sectors (schools, health organizations etc.) in rural areas of Bosnia and Herzegovina.

Another route to obtain more energy from oil palm plantations is the more efficient use of oil palm biomass other than the palm oil. There are no detailed statistics for oil palm dry matter production. Such statistics are only compiled for palm oil, palm kernel and fresh fruit bunches (FFB). Rough extrapolations, however, can be made based on estimates of the ratio of palm oil to other dry matter. For each kg of palm oil roughly another 4 kg of dry biomass are produced; approximately a third of which is found in FFB derived wastes and the other two thirds is represented by trunk and frond material [27,30,44]. On an energy basis, the palm oil represents roughly a third of the biomass yield, as it has roughly twice the heating value of the other oil palm dry matter, which therefore amounts to approximately 2 kg on a palm oil equivalent basis. Based on 2005 production, around 30 million metric tonnes of oil equivalent of non palm oil dry biomass matter were available for energy production from Malaysian palm oil plantations, or in other words approximately half of 2004 total primary energy demand. Only a small fraction of this potential was used, and that vary inefficiently. Open burning is still too common and responsible for substantial air pollution problems in South East Asia, indicating that other solutions urgently need to be found. Some of the biomass is used for mulching and as fertiliser, though this use is limited by labour and logistical limitations and concerns about encouraging oil palm pests [45].

Generally, oil palm mills generate a numbers of oil palm wastes. The oil palm wastes contribute about RM6379 million of energy annually [46]. However, there is much to be done to optimise the utilization of oil palm wastes for cogeneration in Malaysia. Various studies conducted in Malaysia have indicated that the used of biomass as a source of energy is one of the most promising ways of effectively using the residues. Some of the commercial projects and research activities are include treatment of palm oil mill effluent [47,48], pyrolysis of oil palm shell [49], chars from oil palm waste [50], solid biofuels from biowastes [51], briquetting of palm fibre and shell [36], palm oil effluent as a source of bioenergy [52] ethanol fermentation from oil palm trunk [53] and converting oil palm trunks and cocoa wood to liquid fuels [37]. In the following sections, potential uses of oil palm wastes are presented.

In order to achieve a more significant application of biomass in BiH, first of all, it is necessary to carry out the following research:

• defining target areas in BiH where detailed research of economically and ecologically sustainable use of biomass should be performed,

• quantification of different flows of non-used biomass in target areas,

• estimation of biomass costs as a fuel in the future and a comparative analysis with the costs of other fuels,

• identification of the possibility for suitable, financially competitive solutions of biomass application,

• identification of the most suitable technologies, investment methods and incentive measures for selected solutions of biomass application,

• identification of obstacles in legislation and regulations that influence the selection of technologies for biomass application in the target areas in a most efficient way,

• identification of institutional obstacles for accepting the most efficient solutions for the construction of a biomass-fueled system for production of thermal and/or electrical energy

Implementation of the above mentioned steps would clearly show the real economical and ecological potential and solutions for the application of biomass-fueled facilities in the target areas in BiH, and it would help the competent authorities to plan the construction of such facilities. The identified activities greatly depend on the agriculture and forestry development strategy and the ministry of energy should plan and implement them together with the competent ministries for these areas [6].

Despite the high dependence of Bosnia and Herzegovina’s rural population on biomass energy and the apparent large biomass energy resources, information related to the biomass energy sector is difficult to find and is frequently out of date. Modern biomass energy systems are virtually unknown, and consequently, there is a significant need for technical assistance that will benefit the sector as a whole. This should run parallel to targeted activities to develop specific biomass energy markets. Technical assistance, in the first instance, is required to deal with:

— Information on resource availability: scepticism about the availability of biomass for fuel was frequently expressed, and this manifested itself in a belief that biomass energy is something to be discouraged. Clear and unambiguous information about fuel availability (going well beyond the estimates based on production that have been used in this report) are needed;

— Awareness on options and benefits: knowledge of the options and benefits for biomass energy appears to be severely limited, and there is a need for targeted awareness raising (through, for example, study tours and training courses) and for information dissemination, including promotion campaigns and the like. This is closely tied to a need to training, human and institutional capacity building on supply, energy and heat generation, and demand.

Progress in these areas of technical assistance would provide the basis upon which further assistance could build. Assuming that a case can indeed be made for biomass energy (that sufficient bio-resources are available and cost effective technical options could be adopted), technical assistance would be required in a number of related areas including:

— Legal and contractual issues (standard biomass fuel supply contracts for example);

— Tariff adjustment, including issues related to installed capacity payments;

— Policy issues (including biomass based electricity in energy policy/plan), and the development of more coherent energy strategies for rural / remote areas;

— Government, NGO and private sector institutional requirements to support a modern biomass energy market

— Project financing and project development.

Technical assistance should go hand in hand with one or two targeted demonstration projects, characterized by relatively low risk, and with sufficient potential for the development of a viable market.

Since relevant data appears to be held by a wide variety of government, NGO and private sector stakeholders, in some cases with unhelpful competition, an institutional structure which is transparent and non-partisan is needed to make available basic and common information as envisioned through sector-wide technical assistance.

8. Conclusions

In contrast to many other energy technologies biomass and bioenergy production is connected to many policy areas, such as climate, energy, agriculture and waste policies, which means that definition of bioenergy policy requires more wider and inter sector approach in order to achieve sustainability of the whole system, An adequate policy concept is a key factor in the establishment of the sustainable bioenergy systems in any country. The availability and use of biomass resources are often intertwined with various major sectors of the economy: agriculture, forestry, food processing, building materials, traffic, etc, but from the other, positive side, this gives bioenergy many opportunities to generate multiple benefits apart from energy generation

It is obvious that only integral approach in establishment of biomass conversion systems, bioenergy and biofuels from biomass can find place on a market and became competetive to fossil fuels.. Bioenergy projects must be economically viable for the different actors in the value chain. Biomass used for energy purposes must be able to compete with other uses of the biomass, and at the same time the energy produced from biomass must be as cheap as or cheaper than energy produced from competing energy systems. Bosnia and Herzegovina is a country with significant potential in different biomass resources, and it is obviously that biomass and bioenergy in a forthcoming period can play more important role in the economy of the country. In order to achieve sustainable system of biomass use and exploitation, it is necessary to define an adequate policy and legal framework which leads to that goal. .

Author details

Petar Gvero and Milovan Kotur

University of Banja Luka, Faculty of Mechanical Engineering, Banja Luka, Republic of Srpska,

Bosnia and Herzegovina

Semin Petrovic

IGT — Research and Development Centre of Gas Technology, Sarajevo, Bosnia and Herzegovina

Sasa Papuga

University of Banja Luka, Faculty of Technology, Banja Luka, Republic of Srpska,

Bosnia and Herzegovina

The comparison for sorption capacity of lanthanides by four kinds of sieved Buccinum tenuissimum shell samples is shown in Fig. 9. In this experiment, the initial lanthanides concentration was taken as 100|jg-dm-3. From this figure, it is found that all kinds of sieved samples showed excellent sorption capacity under this experimental condition. However, the sorption capacity in sample (b) (i. e., the main phase is calcite) decreases slightly relative to that of the original material (i. e., (a): the main phase is aragonite) and others. The decrease

of sorption capacity in sample (b) may be attributable to the remarkable decrease (i. e., by a factor of less than one eighth) of specific surface area of the biomass.

Prieto et al. [36] pointed that the sorption capacity of calcite is considerably lower than that of aragonite for Cd. In case of lanthanides, similar tendency of sorption capacity were suggested from our work.

Looking from the time prospective, bioenergy interest has been greatly stimulated by the fuel price rises in the late 2000s. Bioenergy is seen as a way to protect against the rising fossil fuel prices, furthermore, biomass can act as a carbon sink and as a substitute for fossil fuels, due to that biomass is seen as one of the mechanisms mitigating climate changes.

Regarding definitions of biomass potentials, there are international practice and standards for that. Estimations can vary according to the calculation methodology and the assumptions made (e. g. land use patterns for food production, agricultural management systems, wood demand evolution, production technologies used, natural forest growth etc). In terms of biomass potentials, the following potential types are often discussed: theoretical, technical, economic, implementation potential and environmentally sustainable potential.

According to data from 1990, forests and forest land in BiH encompass an area of approximately 2,709.800 ha, which is around 53% of the territory of the country. Arable land accounts for 1,4 million ha and permanent meadows and pastures for 0,6 million ha [1,2]. Despite the fact that some 41% of the country comprises agriculture land, Bosnia and Herzegovina is relatively poor in agriculture resources, since some two thirds of the country is mountainous / hilly. Land is cultivated with various field crops, such as cereals, industrial crops, vegetables and fodder crops, represented just one quarter of the total agricultural land in 2008. On the contrary, meadows and pastures covered 49% of the agricultural land, while a significant part of the arable fields remained fallow or uncultivated during the same year. Finally, permanent crops, such as orchards and vineyards, covered 4% of the agricultural land or 86.000 ha [5]. The structure of agricultural sector is characterized by small family farms which to a large extent produce for home consumption. Over 50% of agriculture holdings are estimated to be less than 2 ha. State firms are much larger but are either operating under severe constraints or inoperable due to the incomplete process of privatization. As far as forest land is concerned, public forest land amounts to 73% in RS and 83% in FBiH of the total forest land, while the rest is private [5].

Regarding to the country distribution of biomass potentials, field crop residues are mostly found (70%) in the Republic of Srpska, while livestock manure, mostly cow and chicken manure, in the Federation of Bosnia and Herzegovina. Forest based biomass distribution between the two entities is quite balanced.

Different types of biomass have been analyzed, taking into consideration their theoretical and technical potential:

• Forest based biomass includes fuel wood, forest residues and wood industry residues.

• Agricultural biomass includes field crops, arboricultural residues, livestock and agro­industrial residues.

• Energy crops in this work are defined as crops specifically bred and cultivated for energy production either by direct conversion to heat and electricity or by production of bio-fuels (solid, gaseous or liquid).

• Municipal solid waste (MSW) refers to waste collected by or on behalf of municipalities.

NDVI values were calculated from multispectral images by means of Erdas Imagine software. The obtained results were processed with Statgrafic and Statistica software using elementary statistical characteristics, analysis of variance (ANOVA) and correlation analysis.

2. Results and discussion

2.1. Vegetation period

The correlation values (Table 3 and 4) confirmed the possibility to compensate for higher stand density by available sources, which is in accordance with the law of final constant yield [43]. Its validity was later confirmed for tillering cereals by several authors [26,44,45,]. Source availability during vegetative growth and development makes plant density less important. What becomes more important is the number of tillers per plant and their performance. The increasing autonomy of tillers changes the character of cereal stand. Population of plants is gradually changing to metapopulation of tillers and in compensation relationships increases the importance of intra-plant competition [46,1,2]. Thus the relatively high correlations between stand height and production parameters, observed during tillering, can be explained, which is in accordance with our previous results [47].

Two types of relationships can be observed among shoots in the stand: relationships among plants which are more or less random, and intra-plant relationships which are controlled by the hierarchic structure of plants [18,26]. Reactions of plants in a stand to certain conditions are performed in the changes of intra-plant relationships which are then reflected in tiller variability. The structural conception [9], therefore, should not be only used for dividing yield to its components, which is difficult to interpret, but also for the assessment of intra­plant relationships which reflect plant adaptation to specific conditions [26, 48]. It is evident from the results that plant weight is increasing with increased N supply. In contrast, increased plant density reduces increase in their weight and variability.

It was possible to compensate low plant density by N fertilization. The effect of N fertilization on production parameters appears in spring barley as early as at the tillering stage due to earlier N application (prior to seeding or at the third leaf stage). At BBCH 31, the effect of N fertilization was obvious in both crops.

The results confirmed that the production potential is established by the amount of the above-ground biomass per area unit and its structural composition is being formed during the vegetative period. Regarding the possibilities to innovate the canopy management using its spectral characteristics and remote sensing, it is important to answer the question whether the information on the amount of the above-ground biomass per area unit or on the number of plants and tillers is more important at the tillering stage. The answer is a controversial requirement to create the largest possible amount of biomass of productive tillers using the smallest possible density of plants [49]. Thus the conditions for optimum plant growth and development within the stand are defined (inter- and intra-plant competition should arise as late as possible) as well as for sufficient tillering and formation of strong adventitious root system, which provide plants with nutrients and water at subsequent growth stages. This is also confirmed by practical experience showing that less dense stands can be managed better than over-dense ones. From this stand point, even distribution of plants (optimum size and shape of nutritive area) providing the least local variability at crop canopy and thus even distribution of competition relations is important for an effective canopy management [50].

Current practice requires rapid and effective methods for stand assessment — The conventional canopy management is very laborious. Regarding a large number of tillers per assessed area (usually 0-25 m2) and needed number of replications, it is practically impossible to carry out their accurate identification in plants as described by Rawson [24] or Klepper et al- [51]- Based on the obtained results, the following parameters should be considered by canopy management during the vegetative period:

— density of plants after emergence,

— tillering intensity, variability of plant size and stand height during tillering,

— tiller size or number of strong tillers, their uniformity at the beginning of stem elongation,

— the amount of total above-ground biomass per unit area of a stand-

The interpretation of DRIS index for the nutrient application potential response, was originated by Wadt (1996). This method of interpretation consists on grouping five categories of nutrient application potential response (NAPR), by comparing the rates of each nutrient DRIS with the nutrient balance index average (NBIa), which is the arithmetic average of the module of all DRIS index. The NBIa was chosen to be a value that reflects the average of the deviations of each dual ratio relative to the reference value (Wadt, 1996), as seen in Table 2.

The nutrient status of "highest deficiency" represents the situation where there is greater likelihood of positive response with the addition of the nutrient to soil. This positive response should be represented by higher crop yields, or by improving the quality of the agricultural product into a commercially desired degree. In turn, the status of "deficiency" also indicates that it is likely to increase in crop yield with the application of the nutrient, however, this probability is lower than the nutrient with the highest degree of deficiency ("highest deficiency") (Wadt, 1996).

The status "balanced" means that no crop response is expected in relation to the application of the nutrient in soil, there would be no response or a response of the crop "null". The nutrient status of "highest excess" represents the situation where the application of the nutrient may result in negative response on the crop yield, decreased productivity. Finally, the status of "excess" indicates that the addition of nutrients in soil may also result in negative response of the crop and its yield, but that this effect on yield can be controlled by higher nutrient excess (Wadt, 1996).

As recommended by Wadt (1996) the central concept for the addition of the nutrient to soil by the nutrient application potential response is that this increase should be considered as an adjustment in the fertilizer to soil. For example, when it is sure that the nutrient is in a

status of balance and adds it to the crop, it will not result in improved yield, yet, it does not mean that this nutrient should be excluded from the fertilizer recommendation, but that should be kept at fertilization at the same dosages that had been used.

For extraction of nitrogen in the soil, the extractants that have been used do not show a good correlation between the contents extracted by plants with the growth of plants or amount absorbed, and the fertilizer recommendations arising from fertilization of tables that are constructed by means of average curves response generated under field conditions, with data from multiple trials and different locations. Thus, it is expected that the diagnostic system allows adjustments to the amount of each nutrient to be applied, and the interpretation of DRIS index for the nutrient application potential response a useful tool for this purpose.

The nutritional diagnosis would be a complementary tool for the recommendation of the nutritional need of crops, however, it is not feasible to take off the use of soil analysis, because it is essential to check the evolution of soil fertility, and ability to supply nutrients (Wadt, 1996).

The use of nutrient application potential response (NAPR) for interpreting the DRIS index is well seen in Brazil, where, Wadt (1996), Dias et al. (2011), Serra et al. (2010a, b) and Serra (2011) (Figure 2) used to interpret the DRIS index in assessing the nutritional status of the cotton crop, Dias et al. (2011) used the NAPR in the cupuagu crop (Theobroma grandiflorum).

JONES (1981)

Figure 2. Percentage of plots diagnosed with the method of interpretation of DRIS index named nutrient application potential response (NAPR) (Wadt, 1996): (n) Negative response, with a higher probability; (nz) Negative response, with a low probability; (z) Nula response; (pz) Positive response, with low probability; (p) Positive response, with higher probability. (1) norms with all dual ratio; (2) norms with F value; (3) norms with r value (Serra, 2011).

Technical potential for forest residues reaches 3,07 PJ or 380.000 tones per year. If the remaining 50% (from the abovementioned co-firing scenario) could supply medium scale CHP installations the total installed capacity would be around 21 MWe and annual output would be 149 GWh and 213 GWh of electricity and heat respectively (SYNENERGY, 2010).

6.1.1. Decentralised bio-gas units

The available livestock manure derived bio-gas can be utilized in small to medium bio-gas CHP units installed near the breeding farms. Nearly 18 MW of such installations may be fuelled by the 1,30 PJ of available bio-gas. These units could produce 126 GWh of electricity [5].

POME is the effluent from the final stages of palm oil production in the mill. It is a colloidal suspension containing 95-96% water, 0.6-0.7% oil and 4-5% total solids including 2-4% suspended solids [54]. Most palm oil mills and refineries have their own treatment systems for POME, which due to its high organic content is easily amenable to biodegradation. The treatment system usually consists of anaerobic and aerobic ponds. However, because of silting and short circuiting many do not reach discharge standards to water courses. This situation can be significantly improved by introducing enclosed anaerobic digestion systems which reduce the biological oxygen demand (BOD) of the effluent and capture methane, one of the more potent greenhouse gases. The energy in the methane can then be recovered, either as a supplementary boiler fuel, or in a biogas engine generator. For each tonne of crude palm oil (CPO) produced, about an average of 0.9-1.5m3 POME is generated. The biological oxygen demand (BOD), chemical oxygen demand, oil and grease, total solids and suspended solids of POME ranges from 25000 to 35000 mg/L, 53630 mg/L, 8370 mg/L, 43635 mg/L and 19020 mg/L respectively [55]. Therefore, this had created environmental problem because the palm oil mill industry in Malaysia produces the largest pollution load into the rivers throughout the country [56]. However, POME contains high concentrations of protein, nitrogenous compounds, carbohydrate, lipids and minerals that could be converted into useful material using microbial process [57,58]. As example, bio-gas can be produced by processing POME through anaerobic treating system. Anaerobic digestion is a series of processes in which microorganism break down biodegradable material in the absence of oxygen. About 400m3 of bio-gas produced from 100 tonnes of POME, of which this amount of POME had been released during processing of 20 tonnes of fresh fruit bunches [59-61].

Currently, fertilizers is also derived from POME and used in the farms and vegetation areas [62]. It is also found that the gas composition contained hydrogen (66-68%) and carbon dioxide (32-34%) that can be produced from POME using anaerobic micro flora and this generated gas is free from methane [63]. At present, a renewable energy power plant developer in Malaysia, known as Bumibiopower is in the progress of setting up a plant from methane extraction and power generation using POME near Pantai Remis at the west coast of Peninsular Malaysia. A closed anaerobic system is installed to produce and collect consistently high quality of methane-rich biogas from POME. The installation of a generator of size between 1 and 1.5 MW is also included in this project [64].