Table 2.4.1 gives the data for moisture content, organic matter content, ash content, and heating value of representative types of biomass.

atmospheric pressure.

** Ash content is determined from the weight of residue (metal oxides) left after heating at about 800°C.

Moisture content differs considerably depending on the kind of biomass, for example, 3% in paper and 98% in sludge. With most biomass types, water content exceeding two-thirds makes the available heat negative (-). Therefore, even if the heating value of the biomass itself is high, if it has a high moisture content in its natural state, it is not suitable for combustion. For example, water hyacinth and sewage sludge have high heating values, when they are dried, but moisture content is about 95% at the sampling, and they are unsuitable for combustion actually.

Total organic matter is left when the ash content subtract from total dry matter. Because the value of ash as energy is zero, a large amount of organic matter means a higher heating value, which is desirable as an energy source. Additionally, organic substances have different heating values depending on the kinds and ratios of their constituent elements (see 2.3 Biomass Composition). Table 2.4.2 presents the elemental analysis results and heating values of representative biomass types and other organic fuels. Because biomass contains more oxygen and less carbon and hydrogen than coal or petroleum, it has a lower heating value per unit weight. Woody and herbaceous biomass types have carbon contents of 45%-50% and hydrogen contents of 5%-6%, giving them an H:C molar ratio of about 2, with little variation. This is because they are affected by their composition, the main components of which are cellulose and lignin.

Table 2.13.1 shows the amount of standard excretion for major livestock types. The amount of feces and urine excreted from each type of livestock is calculated under the conditions of standard feed conditions according to animal type and body weight. Generally, cow manure has a high carbon content (C/N ratio: ratio of carbon and nitrogen contents), but there are many organic materials that are relatively difficult to degrade, and poultry manure includes high concentrations of nutrient chemicals, such as nitrogen, phosphorus and potassium, and also contains many types of organic matters that are relatively easy to decompose. The category “waste” in slaughterhouse residue includes substances that are not suitable as foods (inedible visceral, bone, fat, blood, skin, and feathers.

In order to convert solid biomass into inflammable gas, a substance to promote the chemical reaction is necessary. This substance is called the gasification agent, and mainly air (N2, O2), oxygen (O2), H2O, or CO2 are applied as an appropriate mixture. Air (only O2 reacts) and O2 generate heat by oxidation, and increased O2 decreases the effective amount of inflammable gas.

Hydrogen-producing bacteria are classified into 2 types by the difference in reaction enzymes. One is bacteria with hydrogenase, and the other with nitrogenase.

Hydrogenase: 2H+ + X2- —— H2 + X (5.4.1)

Nitrogenase: 2H+ + 2e — + 4ATP —► H2 + 4ADP + Pi (5.4.2)

X: electron carrier, Pi: inorganic phosphate

As shown in above reactions, hydrogenase catalyzes a reversible reaction of evolution and uptake of hydrogen. On the other hand, the reaction by nitrogenase needs energy (ATP). In anaerobic fermentation, the reaction by hydrogenase is mainly investigated. Representative

CeHiaOe + 2H2O -► 2CH3COOH + 2CO2 + 4H2 AGO’ = -184 kJ (5.4.3)

C6H12O6 -► CH3CH2CH2COOH + 2CO2 + 2H2 AGO’ = -257 kJ (5.4.4)

Figure 5.4.1 shows the pathway of hydrogen fermentation. Hydrogen is formed from hydrogenase via both NADH and ferredoxin, via only ferredoxin, or via formate-lyase. In hydrogen fermentation, hydrogen is produced from oxidative decomposition of organic substrates. Therefore, hydrogen fermentation is utilized as treatment of wastes and waste water. In such cases, the following treatment such as methane fermentation or activated sludge method is needed, since hydrogen fermentation accompanies the production of organic acids. The reaction rate of hydrogen fermentation is fast compared with methane fermentation. It may be promising pre-treatment method of methane fermentation.

Fig.5.4.1. Pathway of hydrogen fermentation

Production of bioenergy is expected to improve domestic energy security. On the other hand, there are opportunities for developing countries to get foreign currency by exporting bioenergy. Here describes the commitment to bioenergy production by the Thai government briefly.

At the time of December 2006, the unit price of ethanol was 23.50 baht per liter, which is determined by the Ministry of Energy, Thailand. In Thailand, 6 plants are licensed to produce ethanol fuel from cassava. The production capacity of the 6 plants will be 702 million L/year, demanding 4.13 million ton/year of cassava. Thailand is the largest exporter of cassava in Asia. The average annual production is 20 million ton/year: About 8 million ton for domestic starch consumption; Another 8 million ton (cassava chips) for export; The remaining 4 million ton can be used for ethanol. Therefore, the cassava production for food and that for ethanol are balanced now. Cultivated area of cassava is about 1 million ha. The expansion of agricultural land is prohibited, but farmers can grow a different crop if allowed by the government. In the future, the amount of cassava production for ethanol may increase, while it is often said that bioenergy utilization may be in conflict with food production, eg, the international growing demand for ethanol may threaten the stability of domestic supply of food. Even the cassava production for food and that for ethanol are balanced in Thailand now, the future use of cassava root should be carefully determined. Moreover, the market price of cassava heavily declined before, so financial support by the government to farmers will be

necessary in some instances.

Further information

The Japan Institute of Energy. “Report on the Investigation and Technological Exchange Projects Concerning Sustainable Agriculture and Related Environmental Issues,” Entrusted by the Ministry of Agriculture, Forestry and Fisheries of Japan (Fiscal year of 2006) (2007)

The Royal Thai Government launched a strategy to increase renewable energy share in the energy mix since 2005. This was a cabinet resolution, binding all governmental agencies to harmonize policy direction to achieve the declared policy targets. In response to this policy needs, the Ministry of Energy has set forth the seven strategies for energy sufficiency

development as follows.

1. Establish the independent organization to regulate electricity and natural gas

2. Foster energy security by recourse to His Majesty Sufficiency Initiatives

3. Promote efficient energy usage

4. Promote the development of renewable energy

5. Seek for appropriate pricing structure for energy

6. Establish clean energy development mechanism

7. Encourage private sectors and the public to contribute to policy making process. Targets of Biomass-derived energy :

The target set forth by the government is that Thailand must increase the share of renewable energy in the final energy consumption from 0.5% in 2005 to 8% by 2011 (6,540 ktoe). The target for renewable share in the transportation fuel is 3% for biofuels i. e. bioethanol use must be at leat 3 Million L/day and biodiesel must be 4.0 Million L/day by 2011. A target for biomass-deriveded heat and steam is 4% equivalent to 3940 KTOE by 2011. A share of 1% was set for electricity from renewable resources which is equivalent to 3251 MW by 2011. Due to recent price increase of crude oil, an adjustment of the target has been announced by the government to start implementing E20 gasohol (20% blend of ethanol into gasoline) on January 1st 2008 and B2 (2% blend of biodiesel into biodiesel) has been mandated since February 1st, 2008. This implementation has made Thailand the first country in Asia to fully commercialize both bioethanol and biodiesel blends all over the country.

Duties

The policy targets and implementation milestones are reviewed and adjusted periodically and reported to the government by the National Energy Policy Committee.

1.1 Benefit of Biomass

1.1.1 What is biomass?

Generally biomass is the matter that can be derived directly or indirectly from plant which is utilized as energy or materials in a substantial amount. “Indirectly” refers to the products available via animal husbandry and the food industry. Biomass is called as “phytomass” and is often translated bioresource or bio-derived-resource. The resource base includes hundreds of thousands of plant species, terrestrial and aquatic, various agricultural, forestry and industrial residues and process waste, sewage and animal wastes. Energy crops, which make the large scale energy plantation, will be one of the most promising biomass, though it is not yet commercialized at the present moment. Specifically biomass means wood, Napier grass, rape seed, water hyacinth, giant kelp, chlorella, sawdust, wood chip, rice straw, rice husk, kitchen garbage, pulp sludge, animal dung etc. As plantation type biomass, eucalyptus, hybrid poplar, oil palm, sugar cane, switch grass etc. are included in this category.

According to Oxford English Dictionary, it was in 1934 that the term ”biomass” appeared first in the literature. In Journal of Marine Biology Association, Russian scientist Bogorov used biomass as nomenclature. He measured the weight of marine plankton (Calanus finmarchicus) after drying which he collected in order to investigate the seasonal growth change of plankton. He named this dried plankton biomass.

Biomass is very various and the classification will be reviewed in 2.(1). Biomass specifically means agricultural wastes such as rice straw and rice husk, forestry wastes such as sawdust and saw mill dust, MSW, excrement, animal dung, kitchen garbage, sewage sludge, etc. In the category of plantation type, biomass includes wood such as eucalyptus, hybrid poplar, palm tree, sugar cane, switch grass, kelp etc.

Biomass is renewable resource and the energy derived from biomass is called renewable energy. However, biomass is designated as new energy in Japan and this naming is a legal term peculiar to our country. Law concerning promotion of the use of new energy was enforced in April of 1997. Though biomass was not approved as one of new energies at this moment,

biomass was legally approved when the law was amended in January of 2002.

According to the Law, power generation by photovoltaics, wind energy, fuel cell, wastes, and biomass as well as thermal use of waste are designated as new energy. Legally new energy is provided by the law what should be the production, generation, and utilization of petroleum alternatives, what is insufficiently infiltrated by the economic restriction, and what is specially prescribed in order to promote the use of new energy by the government ordinance. In foreign countries, biomass is usually called and designated as one of renewable energies.

Many studies have suggested that biomass-derived energy will provide a greater share of the overall energy supply as the price of fossil fuels increase over the next several decades. The use of biomass a source of energy is very attractive, since it can be a zero net CO2 energy source, and therefore does not contribute to increased greenhouse gas emission. It is carbon neutrality of biomass, which is precisely described in 1.(2). The combustion of biomass energy results in the emission of CO2, however, since nearly all of the carbon in the fuel is converted to CO2, just as it is during the consumption of fossil fuels. The zero net CO2 argument relies on the assumption that new trees, or other plants, will be replanted to the extent that they will fix any CO2 released during the consumption of biomass energy. This may well be true for the properly managed energy plantations, but is not likely to pertain in many developing countries where most of the biomass energy is obtained from forests which are not being replanted, at least not to the same degree that they are being harvested.

The widespread expansion of biomass energy use may result in significant concerns about availability of land, which may otherwise be used for food production, or other commercial use such as timber production. Recent reports showed that a wide range of estimates of future biomass energy potential, ranging from the current level of approximately 42 EJ to nearly 350 EJ close to the current level of total energy production by the year 2100. Consequently, it is desired that biomass energy should be wisely utilized in accordance with the food or valuable material production as well as environmental preservation.

Biomass is quite various and different in its chemical property, physical property, moisture content, mechanical strength etc. and the conversion technologies to materials and energy are also diversified. Researches which make it possible to develop cost effective and environmentally friendly conversion technologies have been done to reduce the dependence on fossil fuels, to suppress CO2 emission, and to activate rural economies.

(a) What is switchgrass?

Switchgrass (Panicum virgatum L.) is a perennial tropical grass (C4 species) native to the Great Plains of the USA. The indigenous people of the region saw and called prairies consisting of switchgrass “Ocean of grass”. The plant height is ca. 90-150 cm, the leaf blade length is 15-45 cm, the width is 0.6-1.3 cm, with

short rhizomes. Switchgrass exhibits adaptation to Fig. 2.7.1. Switchgrass Trial

relatively wet and fertile soils and is also tolerant of (USDA AR^ El Ren° OK UBA,

courtesy of Dr. B. Venuto)

both drought and flooding conditions. Annual dry matter yields are ca. 15 t/ha (Some data exhibit nearly 30 t/ha) and as with most forage species, its nutritious value lessens after the flowering. Seed yield is ca. 230 kg/ha from broadcasted stands and ca. 690 kg/ha from row-seeded stands. The 1,000-seed weight ranges 1.07-1.22 g.

(b) Advantages of switchgrass as a raw material for biofuel production

In the USA, Switchgrass has attracted the interest as a raw material for bioethanol production through cellulosic fermentation. The dry matter yield, however, is mostly similar to or less than some temperate and tropical forage grasses, it will not be very useful to use this grass for biofuel production in Japan. For example, if ca. 16t/ha of hay is harvested and 300 L of ethanol is produced from 1 t of hay, based on the price of raw materials, the cost of producing 1 gallon of ethanol from switchgrass is estimated at 0.51-0.89 USD, which is lower than the cost of 0.7-1.21 USD utilizing corn. This report suggests that the potential conversion of ca. 33 million ha of pasture, typically consisting of poorer soils and utilized for the production of a low quality hay crop for horses, to corn would lead to dramatic increases in soil erosion. If, however, switchgrass is sown to this area, ca. 520 million tons of hay can be produced and bypass the soil erosion problem caused by an annual corn crop. This point is very important for the USA, which maintains vast pasturelands and has a need to establish a cultivation system of perennial forage grasses, such as switchgrass, for biofuel production.

Once switchgrass pastures are established, a low-input, sustainable cultivation system for biofuel production may be practical. This system would be similar to the system in Japan that utilizes Miscanthus for a similar purpose. One deficit of the species is its seed dormancy. Seedlings germinate irradically and more than 1 year may be required to achieve a full stand.

(c) Cultivar of Switchgrass

Some cultivars developed in the USA are explained below.

(1) Alamo

Soil Conservation Service (SCS) and Texas Agriculture Experiment Station (AES) selected from collection in Texas, and released in 1978. It is a “lowland type”, flowers 1 or 2 month later than cv. Blackwell, taller, wider leaves with medium saline tolerance and high productivity. It grows well on all soil types with 630 mm or more annual precipitation, from Iowa to Florida.

(2) Blackwell

The SCS in Kansas developed this cultivar from single plant collected in Blackwell, OK and released it in 1944. It is an “upland type” of medium height with rather large stems, good in seedling vigor, high in forage production, and grows well on wide range of soil types with 500 mm or more annual precipitation in Kansas, Oklahoma, southern Nebraska and north Texas.

(3) Cave-In-The-Rock

The SCS and Missouri AES developed from the collections of Cave-in-the-Rock, IL and released in 1973. It is a “lowland type” with high seedling vigor, resistance to lodging and diseases. It is tolerant to flooding and drought and grows well in Iowa, Kansas, and Missouri.

(4) Dacotah

The SCS and Northern Great Plains Research Laboratory selected 10 plants from collections of North Dakota and released the cultivar in 1989. It flowers 27 days earlier than cv. Forestburg, 45 days earlier than cv. Blackwell and cv. Pathfinder. It is shorter in height and exhibits high drought tolerance. It grows well in North Dakota, Minnesota, and Montana.

(5) Forestburg

The SCS in North Dakota and Northern Great Plains Research Laboratory developed this cultivar from collections obtained near Forestburg, ND and released in 1987. It has superior winter hardiness and persistence, seed production ability, and is of earlier maturity than other cultivars. Forage production at northern latitude exceeds that of cv. Dacotha, cv. Nebraska 28. It grows well in Montana, North and South Dakota, and Minnesota.

(6) Kanlow

The Kansas AES developed this cultivar from collections in Oklahoma and released in 1963. It is a tall and productive “lowland type”, especially adapt to lowlands where excess water problems occur; it also performs well on upland sites where soils are not too thin or dry.

(7) Pathfinder

The Nebraska AES originally released this cultivar as “Type-F” from a polycross and progeny test of collections in 1967. It is a late-flowering “highland type”, winter-hardy, vigorous, leafy, and resistant to rust and drought. It grows well in Nebraska and adjacent areas.

(8) Shelter

The SCS in New York developed this cultivar from collections made in West Virginia and it was released 1986. The cultivar exhibits thicker stems and fewer leaves than the other cultivars with the exception of cv. Kanlow. It is taller and flowers earlier by 7-10 days than cv. Blackwell but exhibits less seedling vigor during the 1st year of establishment. It grows well in a wide region ranging from the East Coast to Arkansas in the central USA.

(9) Trail Blazer

Nebraska AES developed this cultivar from collections made in Nebraska and Kansas and released in 1984. It is a “highland type” exhibiting both higher forage value and yield, flowers

at the same time of cv. Blackwell. It grows well in central Great Plains and eastern states. Additional released cultivars not described are: cv. Sunburst, cv. Caddo, cv. Summer etc.

Further information

Long, S. P. et al. (eds.): Primary productivity of grass ecosystems of the biosphere, 1-267,Chapman & Hall (1992)

Nakagawa, H.: Development and cultivation of forage grasses and crops for clean bio-methanol production to keep gobal environment, Farming Japan Vol. 35-2:22-31(2001)

Nakagawa H. and Momonoki T.: Yield and persistence of guineagrass and rhodesgrass cultivars on subtropical Ishigaki Island, Grassland Science, Vol. 46, pp. 234-241 (2000)

Sakai, M., and Nakagawa H.: A new biofuel towards 21st century, The Chemical Daily Co. Ltd., (in Japanese), pp. 1-197

Burnhart, S., Management guide for the production of switchgrass for biomass fuel in Southern Iowa, http://www. extension. iastate. edu/Publications/PM1710.pdf, (2003)

Nakagawa, H., Forage crops in tropics, Association for International Cooperation of Agriculture and Forestry, Tokyo (in Japanese) (1998)

United States Department of Agriculture, Grass varieties in the United States, CRC Press, Boca Raton. (1995)

Vogel, P. K., Energy production from forages (or American Agriculture — back to the future), Journal of Soil and Water Conservation, Vol. 51, No. 2, 137-139. (1996)

2.17.1 Potential of food processing waste

In this chapter, the example of Thailand is given to show the utilization of food processing waste. As one of the agricultural based countries, food industry sector plays an important role in Thai economy and also is worth a great fraction of Thai export value each year. The processing of food and its related commodity often involves thermal, mechanical and chemical treatment, which reluctantly poses environmental problems on proper treatment of the food processing waste. Broadly, food processing waste can be categorized into two types, according to its physical states, namely solid and liquid wastes. Solid waste varies from empty oil palm bunches, baggase, rice straw/stubble/husk, waste from cassava starch factory and corncob. On the other hands, liquid waste mainly comes from any food processing that involves washing, cleaning, extracting with water or any other solvents.

Conventionally, solid wastes have often been thrown back into the boiler in order to generate steam for the plant processing itself or power generation. With biomass technology like gasification, solid wastes find higher efficiency conversion to energy than simply uncontrolled burning. On the other hand, since liquid wastes are regulated for environmental concern, processing plants are required to install wasted water treatment system. Often such system is of an anaerobic digestion technology, from which biogas can also be produced and used as energy source in the plants.

From the Ministry of Energy evaluation back in 2000, the first nine industries of high potential for biogas production are of cassava, sugar, palm oil, canned seafood, frozen product, slaughterhouse, canned pineapple, carbonated soda and liquor, respectively. Recent investigation on the wasted water from cassava, sugar, oil palm, canned pineapple and ethanol plants to assess the biogas potential was conducted by TRF (http://www. trf. or. th). The results are shown in Table 2.17.1. Cassava plant has the highest potential to produce biogas, more than twice the runner-up ethanol plant. Some reasons for seemingly low potential of biogas production in certain industries are the better management of waste water treatment system and also better by-product utilization.

For the ideal process as shown in Fig. 4.5-2, the energy efficiency of hydrothermal gasification is unity.

This is to be noted since misunderstanding that energy efficiency of hydrothermal gasification is low due to the large amount of heat required to attain hydrothermal condition. When heat recovery is properly made, a high energy efficiency is possible.

Energy efficiencies higher than 70% including electricity and heat loss at the heat exchangers have been shown by a detail process calculation.