Cultivation of Jatropha is uncomplicated (Fig. 8.3.2). Jatropha curcas can grow in wastelands/marginal areas and grows almost anywhere, even on gravelly, sandy and saline soils. It can thrive on the poorest stony soil and grow in the crevices of rocks without competing with annual food crops, thus filling an ecological niche. Complete germination is achieved within 9 days. Adding manure during the germination has negative effects during that phase, but is favourable if applied after germination is achieved. However, it is usually multiplied by cuttings, because this gives faster results than multi-plication by seeds. The flowers only develop terminally, so a good ramification (plants presenting many branches) produces the greatest amount of fruits. Another productivity factor

is the ratio between female and male flowers within an inflorescence (usually about 1 female to 10 male flowers — more female flowers mean more fruits).

Jatropha curcas can grow at annual rainfall of 300 — 2,380 mm, with the optimum rain fall on 625 mm/year. The best time to start planting is in dry season or before the rainy season, with the annual average temperature is 20 — 28oC.

Waste biomass includes wastes and residues discharged from our living. Quantity of this production is now referred to as “waste biomass production”. Waste biomass has a variety of uses, not only for energy but also for feed or fertilizer. On the other hand, biomass currently not being utilized but convertible to energy is referred to as "energy potential of biomass."

In this section, a method of estimating the quantity of resource will be shown, referring to waste biomass generated in association to production in agriculture, forestry, and livestock industry

(a) Amount of waste biomass production

It is necessary to know the waste biomass production to estimate current stock of waste biomass, but it is difficult to know the amount of waste biomass production in each country and region of the world. Therefore, the waste biomass production is often estimated typically by assuming ratio of waste production relative to the biomass resources production. An example of the parameters for the estimation of waste biomass production is shown in Table 2.2.1 Note that these parameters are generalized on the global basis, and that it is desirable to set parameters adapted to each region, in a study of a limited region.

Fig. 2.2.1 shows the current stock of waste biomass estimated using the above parameters by the following procedure;

• Amounts of production of agricultural waste and forestry waste were estimated by adjusting agricultural (2000) and forestry (1999) productions using statistics of the FAO, multiplied by ratio of waste production.

• Amount of production of livestock waste was estimated by determining the number of head of livestock (2000), and using amount of dung per head.

• The current stock of biomass was estimated based on waste biomass production multiplied by a coefficient of energy conversion.

The current stock (annual value) of waste biomass was estimated as approximately 43 EJ for livestock biomass, approximately 48 EJ for agricultural biomass, and approximately 37 EJ for forestry biomass, totals approximately 128 EJ. Approximately 22 EJ of dung of cattle accounts for the largest part of resources, which is followed by an approximately 20 EJ of log residue.

Rice Wheat Maize Roots and tubers

Sugar cane residue (tops and leaves).

Bagasse

Cattle

Swine

Ponltry

Horses

Buffaloes

Camels

Goats

Sheep

Industrial logs Fuel logs Wood waste

(b) Energy potential of waste biomass

Part of current stock of waste biomass has already been used for other applications, so that it may supposedly be difficult to efficiently recover the complete mass, and to reuse it as an energy source, even if it is reserved unused. For example, some of rice straw is used as feed for livestock at present. It may be almost impossible to collect dung of cattle in pasture, and it is not always possible to completely collect dung of cattle even if they are fed as being tried. Whenever current stock of biomass quantity is estimated, it is necessary to consider such availability, so that energy potential of the waste biomass is given as a portion actually available as an energy source out of the entire current stock. Ratios of availability proposed by Hall et al. are shown in Table 2.2.2.

Energy potential of waste biomass estimated using ratio of availability is shown in Fig. 2.2.2. The largest portion of the energy potential of waste biomass (annual value) is contributed by forestry waste biomass, which accounts for approximately 22 EJ on the worldwide basis. Especially, log residue accounts for approximately 15 EJ, which is about two-thirds of the waste forestry biomass, and accounts for as much as approximately 36% of the total biomass resources. There is approximately 15 EJ of agricultural waste biomass on the worldwide basis. The individual items of the agricultural biomass in concern exist to as much as 1.5-3.5 EJ on the average. On the other hand, livestock biomass is about 5.4 EJ on the worldwide basis, where the largest contribution is approximately 2.8 EJ of cattle dung.

Fig. 2.2.2. Availability of biomass residue in the world.

Further information

FAO (The Food and Agriculture Organization of the United Nations), FAO Statistical Database, (http://www. fao. org/)

Hall, D. O. et al. (1993), “Biomass for Energy: Supply Prospects”, In: Renewable Energy, Johansson, T. B. eds., pp.594, Washington, Island Press.

World’s bio-energy potential of the agricultural residue in 2000 is shown in Table 2.11.1. These values were estimated based on production of residues multiplied by energy conversion factor, availability factor and so forth (Hall et al., 1993).

Rice residue was found to be as largest as 3.4 EJ, followed by bagasse and wheat residue as much as 3.3 EJ, respectively.

4.1 Combustion

4.1.1 General scope

(a) What is combustion?

Combustion is an exothermic chemical reaction accompanied by large heat generation and luminescence, and is a phenomenon in which the reaction is spontaneously continued by the heat generated by the reaction. When using biomass as fuel, the heat-generating oxidation reaction, where carbon, hydrogen, oxygen, combustible sulfur, and nitrogen contained in biomass react with air or oxygen, is known as combustion, industrially. Combustion process proceeds by gas phase reaction, surface reaction, or both, following processes such as fusion, evaporation, and pyrolysis. In actual combustion reaction, complicated phenomena such as evaporation, mixture, diffusion, convection, heat conduction, radiation, and luminescence advance complexly at a very high velocity. Gas fuel burns directly in gas phase as premix combustion or diffuse combustion. Liquid fuel burns as inflammable gas in gas phase after surface evaporation, which is called evaporation combustion., Heavy oil etc. burns in evaporation combustion but decomposition combustion also proceeds, where decomposing the fuel portion occurs by the produced heat.

(b) Forms of combustion

The combustion forms of direct combustion of biomass, which is in solid form, include evaporation combustion, decomposition combustion, surface combustion, and smoldering combustion. In evaporation combustion, the fuel containing simple component and molecular structure with comparatively low fusing point fuses and evaporates by heating, and reacts with oxygen in gas phase and burns. In decomposition combustion, gas produced from thermal decomposition by heating (H2, CO, CmHn, H2O, and CO2) reacts with oxygen in gas phase, forms flame, and burns. Usually, char remains after these forms of combustion and burns by surface combustion. Surface combustion occurs in the case of the component composed of only carbon containing little volatile portions such as charcoal, and oxygen, CO2, or steam diffuses to pores existing inside or on solid surface of the component, and burns by surface reaction. Smoldering combustion is the thermal decomposition reaction at temperature lower than the ignition temperature of volatile component of the reactive fuels such as wood. If ignition is forced to smoke or temperature exceeds ignition point, flammable combustion occurs. In industrial direct combustion of biomass, decomposition combustion and surface combustion are the main forms of the combustion.

(c) Combustion method

Industrially, combustion surplus air is supplied in addition to the theoretical amount required for biomass combustion. If surplus air rate is too high, it causes decrease in combustion temperature and thermal efficiency. As the combustion method of biomass, grate combustion (fixed grate and moving grate), fluidized bed combustion, rotary hearth furnace combustion, and burner combustion are used. The features of each combustion method are shown in Table 4.1.1.

(d) Application

The combustion of biomass is the simplest use of biomass to obtain heat, and is widely used because experiences of fossil fuel technology can be applied, because generation of NOx, SOx,

HCl, and dioxin is low, which is the advantage of biomass combustion, and because flammability is excellent. Combustion heat is used for power generation and heat production by recovering heat through heat transfer media such as steam and hot water using boilers and heat exchangers. In district heat supply and in energy centers of industrial complexes, cogeneration fueled by waste wood and agricultural waste is widely used. There are many power plants and heat utilization plants regardless of scale using paddy husk, bagasse, waste wood, oil palm waste and poultry chicken droppings, etc. as fuels.

Further information

Fujii, S. in “Baiomasu Enerugino Riyo, Kenchiku, Toshi Enerugi Sisutemuno Shingijutsu", Kuuki Chowa Eisei Kogakkai Ed., 2007, pp.212-218 (in Japanese)

Mizutani, Y. in "Nensho Kogaku", 3ed., Morikita Shuppan, 2002, pp.169-181 (in Japanese)

Hemicellulose fraction is degraded into sugars composed of mainly pentose and some hexoses through first dilute sulfuric acid (0.5-1.0%) treatment at 150-180oC, and at about 1 MPa (10 atm). Residual fraction containing cellulose and lignin is again treated with similar concentration of the dilute acid at 230-250oC and at 3-5 MPa (30-50 atm) to produce glucose. Sugar yield in first and secondary treatments are reported to be about 90%, and 50-60%, respectively. In the ethanol plant of “Bioethanol Japan Kansai” (Osaka, Japan), which has been operated since January, 2007, sugar solution only from hemicellulose fraction of wood is reported to be converted to ethanol through fermentation by genetically modified E. coli.

In the United States, research groups including NREL have been challenging to improve cellulase activity for industrial use in dilute sulfuric acid process. Their target is, reportedly, to start production of bioethanol from biomass like corn stover in 2013.

Further information

9th Alcohol Handbook, Japan Alcohol Association Ed., Gihodo Shuppan Co. Ltd, 1997 Elander, R. T.; Putsche, V/ L/, in Handbook on Bioethanol, Wyman, C. E. Ed., Taylor & Francis Pub. 1996, pp329-350

Saiki, T. in Biomass Handbook, Japan Institute of Energy Ed., Ohm-sha, 2002, pp 157-165, (in Japanese)

Saiki, T.; Karaki, I.; Roy, K.,in CIGR Handbook of Agricultural Engineering, Vol. V Energy and Biomass Engineering, Kitani, O. Ed., American Society of Agricultural Engineers, 1999, pp139-164 Saiki, T., in Bioethanol Production Technology, Japan Alcohol Association Ed., Kogyochosakai 2007, pp75-101. (in Japanese)

Yamada, T., in Bioethanol Production Technology, Japan Alcohol Association Ed., Kogyochosakai 2007,

Bioenergy resource consists of raw material, plantation bioenergy, and residue biomass (discharge during biomass conversion and consumption process). When raw material such as wood and food are converted into bioenergy, opportunity cost is incurred. Environment cost is estimated based on impacts on local land use change, biodiversity and aspects. Biomass residue can be negative when appropriate waste management of biomass is implemented.

Bioenergy resource cost can be expressed by the following equation: [bioenergy resource cost] = [supply cost] + [opportunity cost] + [environment cost] — [disposal cost]

Modern wood fuel and wooden chip have higher cost due to their good quality as material and opportunity cost. Cereal residues also have higher cost due to transportation and stock. Plantation cost is essentially high. Residue bioenergy can be available at negative cost due to waste management.

The Malaysian population has been increasing at a rate of 2.4 % per annum or about 600,000 per annum since 1994. With this population growth, the MSW generation also increases, which makes MSW management crucial. Currently, the MSW is managed mainly through landfill. However, due to rapid development and lack of new space for it, the big cities and islands are considering incineration to tackle this problem.

Fig. 7.8.1. Pie Chart of Typical Malaysian MSW Composition.

Further information

Norasikin A. Ludin, Mazlina Hashim, M. Azwan Bakri. Country Report — Workshop on Information for the Commercialisation of Renewables in ASEAN (ICRA). 25 — 27 August 2004 Biomass Resource Inventory Report, BioGen Project Pusat Tenaga Malaysia National Renewable Energy Laboratory, The U. S. Department of Energy BioGen News — Issue 2, November 2004 Economic Planning Unit, Eighth Malaysia Plan (2001 — 2005)

CDM Energy Secretariat, Pusat Tenaga Malaysia: www. ptm. org. my/CDM_website/

The use of woody biomass energy has grown in importance as part of the efforts to reduce dependence on non-renewable energy sources such as fossil fuels. Though woody biomass release carbon into atmosphere when it is burned to produce energy, replanted trees absorb the same amount of carbon from atmosphere into the forest ecosystem through photosynthesis which is in proportion to the growth rate of tree species. The growth rate is depended on temperature, precipitation, soil characteristics and other environmental factors. In general the growth rate is low in boreal zone and high in tropical zone respectively. Fast growing species such as eucalyptus (Eucalyplus), poplar and Acasia manngium in Southeast Asia capture from 5 to 15 ton carbon per hector annually. Whereas Sugi (Cryptomeria japonica), one of representative plantation species in Japan, captures carbon from 2 to 3.5 ton per hector annually.

The growth of forest biomass shows high rate in the early stage and fall down with getting mature. Table 2.6.1 expresses how man-made forest stores carbon in their biomass. Hardwood forests located close to rural communities in Japan used to be the main source to provide fuel wood. Table 2.6.2 shows annual increment of these forests. If we focus on only quantity and do not care timber quality, it is reasonable to adopt cutting rotation at the maximum annual increment which is generally younger than regular timber harvesting rotation.

MSW produces a heating value about one-third that of coal heat, and can burn at temperatures as high as 1000°C. When the combustion gas is cooled to between 200 and 300°C by gas control equipment, energy can be recovered by a boiler system. While even small-scale incinerators commonly reuse waste heat for heating and hot water supply, large-scale facilities can use high-temperature steam for power generation. In 2005, more than 60% of MSW incinerators reused hot water, and 20% generated power.

However, on average, MSW incinerators have a power generation efficiency of only 10%, much lower than coal power plants. They cannot be highly efficient because steam temperatures must remain low to prevent corrosion at temperatures of 320°C or higher; economic incentives are also low due to the low price of generated electricity and the high cost involved in generating power.

An incinerator of the 600 ton/day class can provide central heating service for 1000 to 1500 households. However, this is usually impossible because MSW incinerators are generally located far from residential areas. To increase energy efficiency, waste management systems should be incorporated into city planning.

Carbonization reactions are basically the same as pyrolytic reactions in an inert gas like nitrogen. For wood, after most water is evaporated at below 200°C, three main constituents of cellulose, hemicellulose, and lignin are decomposed to produce liquid fraction and gaseous fraction, consisting mainly of CO and CO2, at 200-500°C, thereby occurring a rapid weight decrease. In this region, each wood constituents undergo dehydration and depolymerization to repeat intermolecular and intramolecular fission and re-bonding, and the resulting low molecular weight fragments are cracked into liquid and gaseous products, whereas high molecular weight fragments formed by condensation are charred together with non-decomposed portion. Although the weight loss becomes smaller at above 500°C, polycondensed aromatic carbon increases with the evolution of H2 to reach about 80% C in char up to 700°C. By further increasing the temperature, the polycondensed carbon structure develops to increase the content of C without prompt production of H2. The overall scheme of carbonization is represented in Fig. 4.4.1. This signifies that product distribution depends on both steps of the decomposition of ‘melt’ resulted from wood constituents into gas, liquid, and solid fractions (first stage) and subsequent decomposition of the liquid fraction (second stage), and the ratio of rate constants for first stage to that for second stage. The distribution is also influenced by moisture and size of feed, heating rate, operating temperature, etc.

The latter three are particularly important, and the yield of liquid (tar) is increased with decreasing the size and increasing the rate.

Higher temperature makes the yield of charcoal lower and that of tar higher at below 500°C. Pressure is likewise important, and the yield of tar becomes higher at the lower value.