Table 5.3 provides an overview of mechanical properties of various biomasses. The mechanical properties of the fibre types from different sources and origin clearly show why the large variation of mechanical properties of biomass becomes a crucial concern when it comes to commercial utilization. The large variability of tensile properties is also a drawback for all natural products which is influenced by species, fibre structure and environmental conditions during plant growth. The structural parameters that have been reported by different methods have influences on the tensile properties of plant fibres—chemical composition, cellulose crystallinity, microfibril angle and stiffness of cell wall materials—and the fibre lumen size as well as the presence of defects (Vincent 2000; Alix et al. 2009).

Figures 8.5 and 8.6 represent the SEM images of untreated and treated fibers. A clear rougher surface with channels is visualized from treated IDL fiber (Fig. 8.7). These void channels help in filling of matrix and thereby bonding among treated fiber and matrix.

The benzoylation treatment on sisal fiber resulted in decrease in diameter, and alkali-soluble fractions like waxy layer and lignin were removed from the fiber (Manikandan Nair et al. 1996). It was further noticed that the benzoylation treatment gives rise to many fine holes on the fiber surface which will enhance mechanical bond between the fiber and matrix.

Woody biomass is used only in integrated gasification combined cycle (IGCC) power plants with CCS (carbon capture and sequestration). As for all other power generation technologies, the electricity production based on bio-energy with carbon capture and sequestration (BECCS) is governed by a Leontief type production func­tion as given below (Rose et al. 2012):

ELbeccs _ тІП {bbeccs Fel, wbio’SbeccsCCSwbio’VbeccsOMbeccs’hbeccskbeccs } (12.1)

where 0(^beccs(1 is an efficiency parameter that determines the amount of biomass which is measured in units of energy as needed to generate 1 kWh of BECCS elec­tricity. The demand of woody biomass is then formulated as:

F:i, wbio = b ELbeccs (12.2)

beccs

CCSwbi0 is the storage capacity needed to sequester CO2 from BECCS. The total amount of carbon dioxide removed and stored depends mainly on the carbon con­tent of woody biomass, denoted by ®wbio, and on the capture rate of power plant, which is denoted with e : CCS = e®wbioFwbio. By using the Eq. 12.2 it can be possibly

shown that = Bbeccs/ernbeccs. Henceforth, we generally omit the technology that

subscript when no ambiguity arises in the process. K measures the BECCS genera­tion capacity in units of power. q as an efficiency parameter which regulates the number of hours of operation of BECCS power plants. Power generation capacity grows in the following way as given below:

K(t +1,n) = (1 -8)K(t, n) + Iel (t, n)/ j (12.3)

where Iel are the investments in BECCS region n at time t, 8 is the depreciation rate of power plants and q> is the investment cost of BECCS generation capacity. Finally, the operation and maintenance costs (OM) are needed to run power plants and their demand is regulated by £ reluctantly.

If any country is a net importer of biomass, the BECCS power plants pay the cost for transporting biomass (TC), which is proportional to distance D from major production regions. The transportation cost is generally paid on the share of imported biomass of total consumption, denoted by у : у = 0 if the region is a net exporter, у = 1 if a region imports 100 % biomass. By denoting the interest rate of the economy with r, the cost of generating 1 unit of electricity with BECCS is thus equal to the equation given below:

where BECCS power generation firms to maximize the profits nEL = PeLEL — C(EL). The optimality conditions require that dC(EL*)/dEL* = pEL. Thus:

Pel — j p,.„ +b gTCD + s C„ (TCCS) + i + 2 (r + S)j (125)

The optimality conditions in the final good sector resembles that the marginal product of electricity is equal to its price. In particular, the optimal power mix depends on the relative convenience of the power technologies, i. e. j. Thus, the fol­lowing condition holds as: (9GY / 9ELbeccs) / (9GY / 9ELj) = pEL^ jpEL "j.

The components of lignocellulosic fibers include water soluble substances, hemicelluloses, cellulose, pectin, lignin, and waxes. Cellulose is a semicrystalline polysaccharide, the large amount of hydroxyl group in cellulose gives natural fibers

the hydrophilic character; when used to the hydrophobic matrix, the result is an incompatibility (poor adhesion) between matrix and fibers and poor resistance to moisture absorption (Yang et al. 2007). The strength of the interface adhesion (fiber/ matrix) depends on the degree of mechanical, chemical and electrostatic bonding, and level of interdiffusion between the matrix and fibers. The compatibility between the two components can be achieved by physical and chemical modification of the fibers and polymer surface, or by use of coupling agents and compatibilizers. Figure 14.4 shows SEM image of fractured surfaces of composite without coupling agent. It can be seen clearly a decohesion zones fiber/matrix. This is a clear indica­tion of the poor adhesion between fibers and the matrix.

Alkali treatment was the standard chemical modification of fibers surface. The fibers are alkali washed using sodium hydroxide to remove amorphous materi­als from the fibers surface such as waxes, pectin, and other non-cellulosic compo­nents. Figure 14.5 shows the FTIR spectrum of hemp fibers, as example, before and after alkali treatment. It was observed in the Fig. 14.5 that a disappearance of the peaks around 1,730 and 1,230 cm-1, which correspond respectively to the carboxylic

ester in pectin and to the C-O stretching in lignin, respectively. The chemical treatment used has eliminated pectin and waxes in the fibers and also it has reduced lignin rates in the fibers surface.

Burhan Ahad, Zafar A. Reshi, Humeera Rasool, Waseem Shahri, and A. R. Yousuf

Contents

17.1 Introduction…………………………………………………………………………………………………… 290

17.2 Jatropha curcas: Occurrence and Morphology……………………………………………………. 291

17.3 Plantation and Ecological Requirements of Jatropha curcas…………………………………… 292

17.3.1 Soil Requirement……………………………………………………………………………….. 292

17.3.2 Climate………………………………………………………………………………………….. 293

17.3.3 Propagation…………………………………………………………………………………….. 293

17.3.4 Irrigation…………………………………………………………………………………………. 293

17.3.5 Fertilization……………………………………………………………………………………… 294

17.3.6 Pruning…………………………………………………………………………………………… 294

17.3.7 Weed Control……………………………………………………………………………………. 294

17.3.8 Harvesting……………………………………………………………………………………….. 295

17.4 Energy Constituents of Jatropha curcas…………………………………………………………… 295

17.4.1 The Fruit…………………………………………………………………………………………. 296

17.4.2 The Shell……………………………………………………………………………………….. 296

17.4.3 Seeds……………………………………………………………………………………………… 296

17.4.4 Seed Oil………………………………………………………………………………………….. 297

17.4.5 Press-Cake……………………………………………………………………………………….. 298

17.4.6 Woody Products……………………………………………………………………………….. 299

17.5 Net Energy Output…………………………………………………………………………………………. 299

17.6 Jatropha curcas and Environmental Concerns……………………………………………………….. 300

17.7 Non-energy Uses of J. curcas………………………………………………………………………….. 301

17.8 Conclusions & Future Endeavor……………………………………………………………………….. 302

References …………………………………………………………………………………………………………….. 303

B. Ahad (*) • Z. A. Reshi • H. Rasool • W. Shahri

Department of Botany, University of Kashmir, Srinagar, Jammu and Kashmir, India e-mail: burhanahad@gmail. com; burhanahad@rediff. com

A. R. Yousuf

Centre for Research and Development, University of Kashmir,

Srinagar, Jammu and Kashmir, India

K. R. Hakeem et al. (eds.), Biomass and Bioenergy: Processing and Properties,

DOI 10.1007/978-3-319-07641-6_17, © Springer International Publishing Switzerland 2014

Abstract Declining reserves of fossil fuels, climate change issues, aim to reduce dependence on fossil fuels and CO2 emissions has inspired global interest in Jatropha curcas L. as an alternate energy biosystem. J. curcas, an underutilized, robust energy plant belonging to family Euphorbiaceae has ability to grow in wastelands and semi­arid areas with low nutrient requirements and produces wood, fruit shells, seed husks, seed oil, and press-cake which are potential sources of renewable energy. J. curcas seed contains 35 % oil which is an eco-friendly renewable energy resource and has properties highly suited for making biodiesel which emits less greenhouse gases (GHG) than fossil diesel fuel and if well exploited can help most of the countries in the world to meet their fuel requirements. However, several issues such as energy versus food, energy and environmental impacts need to be addressed.

Keywords Jatropha curcas • Fossil fuel • Global warming • Alternate energy

17.1 Introduction

Global energy reserves and their use have been and still are most debated and researched issues worldwide for a long time. Globally there is rapid multiplication of energy demand as a result of greater than ever increasing population and develop­ment rate. Patently current global trends of energy supply and consumption are economically, socially, and environmentally unsustainable which has stimulated the necessity of finding alternatives. Recognition of the facts that fossil-fuel-based can hardly sustain the same outsize share which once they occupied in global energy consumption and that growing green house gas (GHG) emissions from their use are driving climate change and impacting global warming have focused world attention on the need to reduce fossil fuel dependence and stimulated the necessity to look for alternatives. The depletion of fossil fuels reserves has reached to such an extent that they are unlikely going to fulfill future needs (Dowlatabadi 2006) and also wide spread awareness about harmful impacts their use have on environment can no longer be neglected (IPCC 2007). In order to deal with the world energy crisis, both in developing and developed countries, reduction in energy consumption and search for alternatives to fossil fuels are gaining serious attention (FAO 2008) so that affordable, reliable, low-carbon efficient, and environmentally benevolent energy supply system can be secured. As such switching to such renewable energy has been provoked which can reduce global warming and curb current trends (IEA 2006). There are several renewable alternative energy sources to fossil fuels such as wind, sun, water, nuclear and biomass. The pursuit for alternate energy source, poses momentous question that which choice could alleviate successfully current fossil energy crisis and allied climatic problems importantly global warming mitigation, and improve life quality globally. Numerous solutions which may vary according to regional peculiarities taking into account economic, environmental, and social spheres, seem available nowadays to countenance worldwide energy hunger, with­out compromising the health of the planet.

Biofuels as renewable energy substitutes to fossil fuels have attracted great atten­tion worldwide because of their production ease, environmental benefits and sus­tainable supply advantages (Jingura et al. 2010) . Over 14 % of world’s energy demand is catered by biomass resources (McKendry 2002; Demirba§ and Demirba§ 2003). For many years now, biofuels have been a theme of lot of claims. FAO has classified biofuels into two groups; First-generation and Second-generation biofu­els. Those biofuels which are mainly derived from food crops, including starch and sugar based bioethanol and oilseed are termed as First-generation biofuels (Pramanik 2003; Bozbas 2008); while biofuels derived from non-food crop forestry and agri­cultural products are termed as second-generation biofuels (FAO 2008, Jinguara et al. 2010). On one hand, biofuels from both from first and second generation pro­vide an option to reduce dependence on fossil fuel and combat adverse climate change, but directly or indirectly at the same time can affect food security. The main concerns which looms with fuels coming from food crops is that apart from compe­tition for land, soil nutrients and water, they can goad increase in food price. Also repeated monoculture can lead to biodiversity loss, reduction in soil resources that are of vital importance as well as water use efficiency, which at present is the con­cern in non-industrialized countries, where for introduction and cultivation of bio­energy plantations, demand for large land area is increasing (Demirba§ and Demirba§ 2003; Daey Ouwens et al. 2007; von Braun and Meinzen-Dick 2009).

As far as second-generation biofuels are concerned, their use seems difficult owing to lack of technology knowledge (FAO 2008). Though second-generation biofuels represent a viable option to tone down fossil fuel dependence, reduce global warming, and also might not affect food availability; the selection of the fuel crop, their competition for land, mineral resources and water, and its management in the cultivation and processing steps are the major concerns. Moreover less effi­ciency or usefulness of some bioenergy crops have rendered their use controversial while some others call for more research before being used as an energy feedstock.

Fortunately, some shrubs and spermophytic trees offer an option to be utilized as biofuels. With no competing food uses, this characteristic turns attention to Jatropha curcas, as one of the potential renewable energy source, which thrives in subtropical and tropical climates across the world (Martin and Mayeux 1985; Jones and Miller 1991; Openshaw 2000, Daey Ouwens et al. 2007; Achten et al. 2008). Since without detoxification, Jatropha oil cannot be used for nutritional purposes, its use becomes more attractive as energy source.

Lignocellulose is a class of biomass that consists of three major compounds: cellu­lose, hemicellulose, and lignin. Lignocellulose is the most abundant renewable bio­mass; its annual production has been estimated in 1 x 1010 MT worldwide (Sanchez and Cardona 2008). Inside the lignocellulose complex, cellulose is a major struc­tural component of cell walls, and it provides mechanical strength and chemical stability to plants; cellulose is found in both the crystalline and the noncrystalline structure and resistant to hydrolysis.

Hemicellulose is a copolymer of different C5 and C6 sugars that also exist in the plant cell wall. Important aspects of the structure and composition of hemicellulose are the lack of crystalline structure, mainly due to the highly branched structure, and the presence of acetyl groups connected to the polymer chain (Kirk-Otmer 2001a, b). Hemicellulose is positioned both between the micro — and the macrofibrils of cellulose.

Lignin is a complex polymer and is the binding of the matrix in which cellulose and hemicellulose are embedded. Considering that cellulose is the main material of the plant cell walls, most of the lignin is found in the interfibrous area, whereas a smaller part can also be located on the cell surface (Kirk-Otmer 2001a, b).

Apart from the three basic chemical compounds that lignocellulose consists of water and inorganic component are also present in the complex. Among inorganic contents, ash is one of the largest constituent. Ash typically comprises of calcium, potassium, magnesium, manganese, and sodium oxides, and lesser amount of other oxides of iron, aluminum, etc.

The cellulosic ethanol feedstock can be broadly categorized into agriculture residue, waste product, woody biomass, and energy crops. The composition of lignocellu — lose highly depends on its source. The composition of lignocellulose encountered in the most common sources of biomass is summarized in Table 20.1.

Bioethanol production from this feedstock could be attractive for disposal of these residues. Importantly, lignocellulosic feedstock does not interfere with food security. Moreover, bioethanol is very important for both rural and urban areas in terms of energy security reasons, environmental concern, employment opportunities, agricultural development, foreign exchange saving, socioeconomic issues, etc.

Since different lignocellulosic biomass have different physicochemical charac­teristics, it is necessary to adopt suitable pretreatment technologies based on the lignocellulosic biomass properties of each raw material.

Unlike isotropic materials, the functional requirements can affect the design of components made of composites. And because natural fibers play a critical role in achieving the desired specific requirements of the composites as engineered materi­als and because the incorporation of these fibers in matrix polymers have been found helpful in determining the properties of the final composites, the appropriate selection of the reinforcement and the polymer as well as other technical aspects should be fairly executed and optimized. That is, several criteria affect the final desired characteristics of the natural fiber composites to be suitable for particular application. These criteria were classified into levels by AL-Oqla and Sapuan (Al-Oqla and Sapuan 2014) to be as:

1. The Natural Fiber Level: where different properties regarding natural fibers have to be concerned.

2. Matrix Level: where different properties regarding the polymer matrix have to be concerned.

3. The Composite Level: where different properties regarding the composite itself have to be concerned. That is, the characteristics of the final composites are not necessarily being exactly similar to any of these for fibers or matrix.

4. The General Performance Level: where different properties regarding the com­posite performance have to be taken into account such as mechanical properties, weather resistance, bio stability, life cycle, etc.

5. The Specific Performance Level: where particular requirements regarding a specific desired function and application should be considered. For instance, for automotive applications: composites’ weight, thermal and acoustic insulation properties, occupational health and safety properties have to be considered. An illustrative diagram of the suggested levels is shown in Fig. 1.14.

The classified criteria that affect the proper selection of the natural fiber compos­ites are shown in Tables 1.6 and 1.7 . According to these criteria, it was approved that date palm fibers are one of the most potential and available fiber types that can be utilized to form attractive natural fiber composites for different applications par­ticularly in the automotive industry (Al-Oqla and Sapuan 2014).

Fig. 1.14 Levels of factors that affect the proper selection NFC materials. From Al-Oqla and Sapuan(2014)

Natural

Fiber

Composites

Selection

Although abaca fibers are obtained from the petioles of abaca leaves, its harvesting is not simple. It requires a set of highly laborious activities involving several opera­tions that range from separation of primary sheaths from secondary ones to extrac­tion and to pre-processing of the fiber (to obtain raw fiber) for various industrial applications. The main operations involved in its extraction include:

1. Tuxying

2. Stripping

3. Drying

The tuxying operation involves the separation of primary sheaths from secondary ones. In this process, the petiole’s outer layer (fiber-bearing layer) is removed in the form of strips or tuxies, which are then freed at one end and pulled off. The stripping operation or cleaning operation involves the scraping of the pulpy material from outer fibrous layer of the petiole for extracting the fiber strands. The stripping is done either by hand or by use of machines. In the Philippines, generally hand-stripping is

practiced while in Central America (Costa Rica), machine-decortication is being done in which the stalks are cut into 0.6-2 m long strips followed by their crushing and scraping inside the machines to yield fibers. In the drying operation, the extracted raw fibers are dried by hanging them in the sun (sun-drying) or by advanced mechan­ical drying as employed in Central America. After drying of the raw fiber, it is then graded on the basis of fiber quality. The excellent or high-quality fibers are separated from the rest and are combed to detangle and removal of other impurities. Moreover, the further processing of the extracted fibers depends on their quality-related param­eters and hence different grades are utilized for different set of industrial activities.

The quality of abaca fiber is determined by many parameters like extraction pro­cedure, strength, fiber length, color, and texture. Based on the cleaning or stripping process the abaca fiber has been classified into various grades as given in Table 3.2. In addition to these mentioned grades, the dried thin strips (5 mm or 1/8th inch wide) of abaca leaf sheaths is called “Lupis” and the outermost light brown covering of the abaca stalk (petiole) is called “Bacbac.” The different grades of abaca fibers are then put into various industrial or other uses as listed in the Table 3.3.

About 200 varieties of abaca are known to exist in Philippines of which only a few varieties are cultivated on a large scale, e. g., Bongolanon, tangongon, and Maguindanao. However, the new and better varieties are being introduced and recommended for abaca cultivation, which includes Inosa, Laylay, and Minenonga

(Lomerio and Oloteo 2000; FIDA 2009). It has been reported that the immature (8-10 month old) stalks of abaca variety “Inosa” provide an excellent material for paper and pulp industry due to their desirable properties like low lignin/ash and high a-cellulose/holocellulose/hemicelluloses content (Moreno and Protacio 2012). Moreover, the hybrid varieties particularly Canarahon x Korokotohan (1841-series) has been found to be quite promising in terms of yield and fiber quality (Moreno 2001). The important characteristics of abaca varieties (“Inosa,” “Laylay” and “Minenonga”) recommended for cultivation in Philippines are listed in Table 3.4.

In addition to the above mentioned varieties, NARC (National Abaca Research Centre, Philippines) have identified and selected five new accessions for fibercraft industry and about seven accessions for paper and pulp industry. Some of which include NARC-MIO, NARC-M107, NARC-159, NARC-M168, and NARC-M179. These accessions have been selected as promising ones due to their high fiber- yielding ability, long fiber length, appropriate texture, uniform fiber strand, and higher tensile strength. Moreover, the accessions selected for pulp and paper indus­try were found to have higher flexibility, strong folding strength, and higher resis­tance to mechanical damage like tearing (qualities required for production of high-quality paper, i. e., thin, strong, and highly porous paper). As far as the chemi­cal composition of the selected accessions is concerned, they have been found to contain higher cellulosic content (holocellulose (83.02-86.90 %), a-cellulose (52.50-64.21 %), and hemicellulose (16.23-26.20 %)) and lower ash content (0.84-1.72 %) (Moreno et al. 2005).

6.3.1 Spinning Property

Kapok fiber is known as the soft gold in plants for its finest and lightest quality, highest hollowness, and most warm nature. Due to their wide lumen filled with air, their smooth surface, and low strength, kapok fibers are considered unfit for textile fabrics in the early years (Fengel and Wenzkowski 1986). With the development of technology, the spinning of 100 % kapok fibers beyond lap formation stage is not possible, but kapok yarn property and weavability could be improved through sizing or blended spinning (Yang and Jin 2008). To resolve the problem of pure kapok yarn such as low strength, much hairiness, poor wear resistance, and difficult to weave, sizing experiment of 27.8 tex pure kapok yarns was carried out in order to improve yarn performance and meet the requirements of weaving. According to the charac­teristics of kapok yarns, a mixed size composed of acid-modified starch and poly(vinyl alcohol) (PVA) was selected to size kapok yarns. The results show that low solid content helps size penetration and facilitates yarn strength and elongation improvement (Yang 2010). Furthermore, the spinning of kapok fiber blended with cotton fiber is largely successful. With an increase in kapok content in the blend, the yarn regularity and tenacity decrease, while the yarn extensibility increases. It is considered that kapok fiber can be blended with cotton for spinning yarn, but the content of kapok fiber should not be more than 50 %, or the blended yarn property and weaving processing will be effected (Dauda and Kolawole 2003 ; Yang et al. 2013). Also, the total cost of production of the yarns decreases significantly as the kapok content increases in the blend.

The trend of carbon sequesteration is observed when straw of sugarcane in not burned and merely left on the ground. In the management of straw, experiments were conducted in Australia; the content of carbon in the soil was found to be 20 % higher when depth was considered to be 0-0.1 m. This was studied, 2 years after the green cane management beginning, in unburned areas and compared with the burned areas (Wood 1991). In a long-term experiment of nearly 55 years, burned sugarcane and unburned sugarcane in the southeastern part of Brazil were com­pared, and carbon concentration of 22.34 g kg-1 in the cane with straw maintenance and nearly 13.13 g kg-1 in burned cane in 0.2 m soil depth was reported (Canellas et al. 2003).

Razafimbelo et al. (2006) explained that the increase in soil stocks of carbon in the 0-0.1 m layer after six years of management of green cane is almost 15 %, compared to the management with burned cane. A study was conducted in Australia’s adjacent burned areas in 1996 which revealed that for 4 years there was no change in the carbon stocks. Compared to that, a steady increase in carbon concentration was observed in unburned plots (Vallis et al. 1996). Another experiment conducted in the southeastern part of Brazil reported that in 12 years, due to maintenance of straw on the field, an average of 0.32 mg ha-1a-1 was accumulated in the first 0.2 m depth of an Oxisol. During the first 4 years increase from 1.2 to 1.9 mg ha-1a-1 was reported for the 0-0.4 m layer. After 8 years of up-gradation to mechanical harvest along with crop maintenance on the fields, nearly a 30 % increase in carbon stocks was signified (Galdos and Cerri 2009). The conclusion drawn from these observa­tions deduced the results that since the adoption of proper green cane management system, potential increase in soil stocks for carbon can be expected. In the related experiments conducted in Australia and Brazil, involving the measurement of car­bon concentration in burned and unburned areas, there was no significant difference in the given treatments after 12 months (Blair et al. 1998). An analysis on the man­agement and carbon concentration in Australia described that higher concentration in soil carbon was observed to be higher in areas of green cane after 4-6 years. As far as areas that have been recently converted to this management are concerned, no significant increase in carbon concentration has been observed for 1-2 years (Robertson 2003).

In a long-term experiment carried out in South Africa for 60 years, it was noted that between burned and unburned areas, carbon concentration in the 0-0.1 m layer of soil was higher in the latter but no marked difference was observed in the 0.1-0.2 and 0.2-0.3 m layers (Graham et al. 2001). Carbon stock in these areas was as high as 70 mg ha-1 in the first 0.2 m (Six et al. 2002). In Brazil, a review related to litter impact on soil was conducted which involved the evaluation from 12 sites. The estimate showed a mean annual rate of carbon accumulation of 1.5 mg ha_1 a-1 (Cerri et al. 2011). From the above findings, a conclusion can be drawn that the system of sugarcane harvest without burning accumulates stores more carbon in the soil when compared with the system which involves burning. But this accumulation is variable and dependent upon the texture of the soil, for instance, rate of mean annual carbon accumulation was approx. three times greater than the sandy soil (Leal et al. 2013).

The soil texture and carbon stock and concentration correlation is well estab­lished, especially considering clay content and clay along with slit content (Silver et al. 2000; Hao and Kravchenko 2007). Climatic conditions also impart an effect on the soil carbon accumulation (Blair et al. 1998). Other than that, nitrogen fertil­izer management (Graham et al. 2001) and the level of soil disturbance during the replanting operation have also been shown to aid in this accumulation. It has been noted that soils have a finite capacity to act as a carbon sink. This leads to the reach­ing equilibrium with respect to the management (Six et al. 2002). When carbon stock experiment was carried out with corn cultivation and corn stover, the amount of soil carbon stocks varied depending on the system that was used (Wilhelm et al.

2007) . Above all, sugarcane ground maintenance tends to increase carbon stocks in mid and/or long terms. However, when carrying out experiment for understand­ing the optimal straw amount for carbon stock maintaining or increasing pur­poses, conditions such as local soil, climate, and crop management need to be taken into account.