Heating values of biomass types shown in Tables 2.4.1 and 2.4.2 were all measured. Attempts are being made to estimate heating value by calculating it from information such as the values obtained by elemental analyses of the materials. A number of equations have been proposed, one of which is given here.

High heating value (HHV) [MJ/dry-kg] = 0.4571 (%C dry standard) — 2.70

Table 2.4.3 compares the heating values calculated with this equation and those obtained by measurement. Except for sludge, biosolids, the results coincide closely.

Based on the data shown in Table 2.13.1, the annual production of livestock waste in Japan was calculated to be 60.7 million tons of feces and 27.7 million tons of urine (Table 2.13.2). Livestock waste in Japan contains 670 thousand tons of nitrogen and 108 thousand tons of phosphorus. Those amounts are very large considering that the amounts of nitrogen and phosphorus used as chemical fertilizer in Japan are 480 thousand tons and 250 thousand tons, respectively. Statistics for the total amount of slaughterhouse residue are not available, but the quantity (about 1.5 million tons) is less than 2% of the total amount of animal waste.

2.13.2 General treatment and usage of animal waste

Dr. Haga (National Agriculture and Food Research Organization) summarized the main systems used for treatment of major livestock waste in Japan (Fig. 2.13.1). According to the results of an investigation by the Agricultural Production Bureau of the Livestock Industry Department, solid parts of manure were just piled or operated by a simple composting process and liquid parts of manure were stored and used on their own fields as fertilizer in most dairy cattle and beef cattle farms. In the case of pig breeding, composting with a forced aeration system was the main method used for processing of solid parts and wastewater purification systems were used on most farms for treatment of liquid parts. Moreover, after drying treatment, layer and broiler manure is sold and used in other farms in many cases. Generally, dairy and beef cattle farmers have their own land for cultivation but pig and poultry farmers do not. This is thought to be the major reason for the differences in livestock waste treatments. The slaughterhouse residue and other by-products of meat processing are treated by a process called “rendering”, and most of them are used as edible fat and oil, feed, or an industrial source.

2.13.3 Animal waste value and total amount in the world

To calculating the value of livestock waste as resources, consideration should be given to its value as 1) a source of plant nutrition (nitrogen, phosphorus, etc.), 2) a source of organic compounds with favorable effects on crop growth and 3) a source of energy. Because of the differences in breeding conditions, it is difficult to accurately calculate the amount of nutrients such as nitrogen and phosphorus in manure of all livestock throughout the world. Based on FAO statistics, total amount of nutrients in manure of all livestock in the world is estimated to be about 140-150 times greater than those in Japan.

Fundamental gasification processes are as follows:

(a) Evaporation of surface moisture

Surface moisture evaporates from the raw material at the water boiling point (depends on pressure). Inner moisture remains when the raw material is large.

(b) Evaporation of inherent moisture

Following surface moisture evaporation, inherent moisture evaporates at 110-120°C.

(c) Volatilization

Thermal decomposition of biomass begins at 200-300C, and CO, CO2, H2 and H2O are vaporized as gas. Thermal decomposition is a heat generating reaction which is a characteristic phenomenon of biomass CJdmOP).

(d) Volatilization and gasification reaction

The temperature is raised further during volatilization, and the volatile matter of the lightweight hydrocarbons (CxHy where x and y are integers of at least 1; a low value of x indicates lightness and a high value of xindicates heaviness) is transformed into heavy CxHy with a high boiling point. Subsequently, the CxHy reacts with the gasifying agent for conversion to lightweight molecule clean gas, although tar and soot can form when diffusion of the gasifying agent is slow and the CxHy condenses.

(e) Char gasification

Following volatilization of the volatile content in the raw material biomass, the fixed carbon and ash become char, and the char is heated to the surrounding temperature. The subsequent reaction with the gasifying agent transforms the carbon into CO and CO2. However, in cases where the gasifying agent contains excess steam and the surrounding temperature is over 750C, a wet gas reaction occurs (C+H2O ( CO+H2) producing gas composed mainly of CO, CO2 and H2.

(f) Char residue

The reaction rate of the wet gas reaction is slow, and char residue can easily form. The formation of tar, soot and char tends to reduce efficiency, as well causing equipment trouble.

4.2.3 Characteristics of gasification product gas

Gasification generally adopts the direct gasification method with partial combustion of raw material to raise the temperature. Raw materials are mainly wood chips and corn stalks. Most gasification furnaces use normal pressure and a direct gasification process. To keep the reaction temperature at 800°C and above for direct gasification, air, oxygen and steam (as appropriate) are required for the gasification agent. For this purpose, approximately 1/3 of the oxygen required for complete combustion (known as the oxygen ratio) is supplied, with partial combustion (partial oxidation) causing gasification. The calorific value of product gas depends on the percentage of inflammable gas (CO, H2, CdH) contained. Generally, gas can be divided into low calorie gas (4-12 MJ/m3), medium calorie gas (12-28 MJ/m3) and high calorie gas (above 28 MJ/m3). For the most part, direct gasification of biomass yields low calorie gas. Fig.

4.2.1 presents composition of the product gas from rice straw when steam and oxygen is employed as gasifying agent. The ratio between the calorific content of the biomass and that of the product gas (at room temperature) is called cold gas efficiency.

4.2.4 Gasification equipment and a practical example

Here is shown a fixed bed gasifier, based on the combustion or gasification of solid fuel, and featuring a comparatively simple structure and low equipment cost. Fig. 4.2.2 shows a concept diagram of the gasifier. Wood chips of about 2.5-5 cm are generally used as the raw material. They are supplied from the upper feed port, and layered in the furnace. The gasifying agent (air, oxygen, steam or a mixture thereof) is supplied from the bottom in a rising flow (some systems

use a descending flow). The gasification reaction proceeds from the bottom towards the top. From the bottom upward, individual layers are formed due to the changes accompanying gasification of the raw material, in the order of ash, char, volatilized and decomposed material, and product. The product gas is obtained at the top.

Further information

Kawamoto, H. in “Baiomasu, Enerugi, Kankyo”, Saka, S. Ed., IPC, 2001, pp.240-244 (in Japanese)

Sakai, M. in “Baiomasu, Enerugi, Kankyo”, Saka, S. Ed., IPC, 2001, pp.409-421 (in Japanese)

Takeno, K. in “Baiomasu Enerugi Riyono Saishin Gijutsu”, Yukawa, H. Ed. CMC, 2001, pp.59-78 (in Japanese)

Sakai, M. “Baiomasuga Hiraku 21 Seiki Enerugi”, Morikita Shuppan (1998) (in Japanese)

Yokoyama, S. “Baiomasu Enerugi Saizensen”, Morikita Shuppan, 2001, pp.87-95 (in Japanese)

4.2 Pyrolysis

4.3.1 What is pyrolysis?

Biomass is consisted mainly of carbon, hydrogen and oxygen. The photosynthesis and pyrolysis can be simply described as the following formulas,

Heat (500 ~ 600 °C)

Pyrolysis: "(CeH12O6)m ——- ► (H2+CO+CH4+.. .+C5H12)|+(H2O+.. .+CH3OH+CH3COOH+.. ,)+C

Biomass Gas Liquid Char

(4.3.1)

Light

Photosynthesis: m(6CO2+6№O)———— ► -(C6H12O6)m + 6mO2| (4.3.2)

Carbon dioxide & water Biomass Oxygen

The main chemical components of biomass are cellulose, hemicellulose and lignin. Fig. 4.3.1 shows the composition changing during pyrolysis.

The cellulose, hemicellulose and lignin are decomposed with temperature increase. Solid residue is char in the yield of 10 to 25%.

4.3.2 Characteristics of pyrolysis

During pyrolysis, moisture evaporates at first (- 110°C), and then hemicellulose is decomposed (200- 260°C), followed by cellulose (240-340 °C) and lignin (280-500 °C). When temperature reaches 500°C, the reactions of pyrolysis are almost finished. Therefore, at the heating rate of 10°C/s, the pyrolysis finishes in 1 min, while it finishes in 5 s at 100°C/s. Higher heating rate results in the more rapid generation of vapor product, increasing pressure, shorter residence time of vapor product in the reactor, and higher liquid yield; named fast pyrolysis or flash pyrolysis. Dynamotive (Canada) and BTG (Netherlands) have developed fast pyrolysis reactors, which show high liquid yield of 60 to 80%. Since heat conductance of wood is 0.12-0.42 W/(m K), which is around 1/1000 of copper, heat transfer is important for fast pyrolysis, and the milling to small particles is required.

4.3.3 Reactors at laboratory scale

Thermobalance is most commonly used at laboratory for the fundamental study. Very small amount of sample, around a few mg to 10s mg, is heated up from room temperature to the desired temperature at the desired heating rate to measure the weight changing. However, it is difficult to recover the products.

A few g to 10s g of sample is used at laboratory scale rector to recover the products. Sand bath or molten salt bath are used as the heater for the batch type reactor. Infrared rays heater is usually used for the continuous reactor. At these reactors, mass balance and product analysis are studied.

Since hydrogen fermentation accompanies organic acids production, it is needed to consider total system combined subsequent treatment methods such as methane fermentation. In hydrogen fermentation, 4 mol of hydrogen is theoretically produced from 1 mol of glucose (Eq. (5.4.3)). When subsequently formed acetate is utilized for methane fermentation and converted to methane, the reaction is shown as follows:

2CH3COOH — 2CH4 + 2CO2 (5.4.5)

C6H12O6 + 2H2O ^ ЗСО2 + 4H2 + 2CH4 (5.4.6)

The sum of high heat value of these products is 2.924 MJ (2,924 kJ). On the other hand, in only methane fermentation, the reaction is shown as follows:

C6H12O6 -► ЗСО2 + 3CH4 (5.4.7)

High heat value of the product from Eq. (5.4.7) is 2.671 MJ (2,671 kJ). It is obvious from these results that the energy yield of hydrogen-methane fermentation increases 10% compared with that of only methane fermentation.

6.6.1 Biodiversity (An example of a palm-oil production)

(a) The summary of a palm-oil production

About biomass utilization, the palm oil production gives an urgent serious to biodiversity in Malaysia and Indonesia, now.

Malaysia and Indonesia account for about 85% of the palm oil production in the world. In Malaysia, a large scale plantation began to be suddenly developed in 1960’s. An Indonesian government put out the policy said becoming the world’s largest production country of palm oil, and production including the construction of a large scale plantation was begun in 1980’s. From 1990 to 2002, the oil palm plantation areas increase about twice in Malaysia and more than 3 times in Indonesia.

As the development of the oil palm plantation, very large land need for the operation of oil mill (the scale of Southeastern Asian typical plantations is 10,000-25,000 ha), and there are a lot of things that the forest is destroyed in creation. About 87% of the deforestation in Malaysia from 1985 to 2000 is considered to be the oil palm plantation development, and it is said by Indonesia that at least 70% of the plantation cleared a forest. Furthermore, the oil palm plantations are developed more and more around the buffer zone such as the national parks, and the biological important area.

(b) Palm oil production and biodiversity

The palm oil plantations are overlapped the low land in tropical rain forests where hold the highest biodiversity on the earth, as it were, located the “Hot Spot” where is "the area that is on the verge of the destruction though to hold the high biodiversity on the earth scale". This area is a little habitation area of the orangutan, Sumatra tiger, Borneo elephant, rhinoceros,

Malaysian tapir and so on. Development of the oil palm plantations is the biggest menace for the rare tropical rain forests in Southeast Asia.

It’s said 80-100% of mammal, reptiles and birds disappear as developing the plantations in the tropical forest. According to the investigation of Miura et al., more than 400 kinds of wild animals were found out in a natural forest or second growth, but the plantations after cut down all forest and cultivating only palm oil, less than 10 kinds were found.(see below)

Nature forest Second growth fringe of forest

oil palm plantation

0 100 200 300 400 500 600 700 800 900

Fig. 6.6.1. Comparison of the appearance frequency of the wild animal used an automatic imager (in Malaysia)

(c) Other impacts due to the palm oil production

In Indonesia, though the control to the illegal felling is strengthened, the authorities permit easer to fell to develop the oil palm plantation. Some are considered to fake the authorities to get permissions of illegal felling. Furthermore, at the time of development, field firing is frequently illegal and as the result peat layer is fired. Then the very large area is disappeared and there is bad influence for the ecosystem. And CO2 is produced at two billions tons per year that exceeds Japan’s emission. This is a big cause of the climate change.

In addition described above, development of the oil palm plantations bring the injustice of local people impacts on economy, culture and social instability such as indigenous people depending on the forest as well as biological diversity disappearance. After the operation of the plantations started, there are problems of the pollutions of soil and river by pesticide and chemical fertilizer, soil erosion, such as the labor problems low wages, pesticide damage, child labor, illegal workers, water pollution by waste fluid and residual substance or methane outbreak and so on.

At the end of 2007 more than 4000 service stations distribute E10 gasohol all over the country and all stations distribute B2 as mandated by the government. B5 biodiesel blend is now available in more than 3000 stations. Bioethanol used in December was 600 KL/day in average. Biodiesel used was 150 KL/day in for low-blend of 2-5% before the mandatory period. After the mandate of blending 2% biodiesel in all highspeed diesel, the use of biodiesel jumped to above 1 million l./day level in February 2008. Renewable eletricity production reached 2057 MWe and biomass-based heat and steam was 1840 KTOE in 2007.

Amount of biofuel production

Biodiesel Production is about 1,150 KL/day; production capacity is 2,185 KL/day. Bioethanol Production is 700 KL/day (Feb.2008) and the production capacity is 1,150 KL/day.

Situation of biofuel introduction

Biofuel introduction is now accelerating in Thailand. Bioethanol-blended gasoline (E10) is now reaching 6 ML/day out of 20 ML/day of total gasoline consumption and the bioethanol blends(E10) gained a market share of 23% of all gasoline use at the end of 2007. Biodiesel-blended diesel is now 3 ML/day out of 50 ML/day total diesel consumption in December 2007. The consumption figure for Feb. 2008, the market for B5 was 5ML/day of the total diesel market of 50 ML/day, the rest of the fuels were B2 blended as mandated by the government.

1.2.1 General scope

Biomass resource can be utilized substantially in endless number of times, on the basic rail of carbon circulation by photosynthetic process. On the other hand, a fossil resource is limited to a transitory use in principle. Additionally the irreversal emission of CO2 caused by fossil combustion gives serious influence on global climate (Fig. 1.2.1). R.= resource.

r<—————- plant———- <———— 1

[Biomass R.]^(use)^CO2(————— »Atmospheric CO2)

[Fossil R.]^(use)^CO2(———— ^Atmospheric CO2)^ CO2 accumulation/air

Fig. 1.2.1. Comparison of biomass and fossil system on Carbon cycling.

But the words “renewable” and “sustainable” are not always same meaning. The recycling power of plants is founded on a very delicate base of ecosystem.

The conditions for the bio-system are, maintaining the balance of harvest vs. growing speed, and the environment protection of the farming land. If not, long term sustainability of the biomass system will be fading out.

2.8.1 General scope of sugar and starch crops

Starch and sugar can be fermented to biofuel such as ethanol, but fibrous saccharides such as cellulose and hemicellulose in the residual waste cannot easily be hydrolized to fermentable carbohydrates such as glucose.

Primary starch crops are rice (Oryza sativa and Oryza glaberrima), potato (Solanum tuberosum L.), sweet potato (Ipomoea batatas (L.) Lam.), corn (maize; Zea mays L.), wheat (Triticum L.), barley (Hordeum spontaneum C. Koch (wild-type two-rowed barley); H. vulgare L. (six-rowed barley); H. distichum L. (two-rowed barley)), cassava (bitter cassava, cassava, manioc, manihot, sweet-potato tree, tapioca, tapioca plant, yuca; Manihot esculenta Crantz),
and sago palm (Metroxylon sagu Rottb.). As primary sugar crops, sugar cane (Saccharum officinarum L.) and sugar beet (Beta vulgaris var. altissima) are widely known.

Yields of three primary cereals (corn, wheat, and rice) are increasing up to 725, 6.33, and

6.6 million tons, respectively, with a sum of 1,963 million tons, which is about 86% of total cereal production of 22.74 million tons (2004), being realized by novel cultivars and development of cultivation technology (Fig. 2.8.1). However, due to limitations of the conventional technologies, further extension of cultivation area will require novel technology such as genetic modification to cold-, drought-, or halo-resistant cultivars. Production of sugar cane has been increasing up to 1,332 million tons (2004), while that of sugar beet has been around 200 million tons (Fig. 2.8.2). Total production of sugar and starch crops (4,572 million tons (2004)) contributes to the high nutritional intake (2,808 kcal/capita/day (2003)) for 6,370 million population in the world (2004). However, around 800 million people, mainly in population explosion area of Asia and Africa, are still suffering from starvation. Therefore, it should be morally criticized if the crops would be further used as “non-food” energy crops. We have to increase the amount of the foodstuffs by increasing the cultivation area and crop yields with novel technology such as genetic modification, while promoting cultivation of energy crops and developing new technology to convert crop wastes to biofuel.

800

0

(ref. FAOSTAT: http://www. faostat. fao. org/default. aspx)

Baggase is the fibrous solid waste produced after stalks of sugarcane are crushed to extract sugar juice in the sugar mill. Typically, about 25-30% of sugar cane production is baggase, contributing to about 10.9-22.3 Tg/year (Mt/year) from the sugarcane production of 43.5-74.3 Tg/year (Mt/year) over the period between 1998 and 2007 in Thailand. Currently, almost all of baggase from the sugar mills in Thailand are used up as biomass fuel to generate energy partially for the sugar processing within the mills, leaving negligible amount for other applications. As shown below, more than half of grid biomass power plant in 2007 uses baggase as the fuel.

Since 1994, there are 37 SPPs (Small Power Producers) and VSPPs (Very Small Power

Producers) operating on baggase with installed capacity over 780 MW with almost 300 MW of which are sold back to the grid. The recent rapid increase in the baggase power plants are due to governmental strong support on electricity generation.

Furthermore, baggase can only be used to produce other value-added products like biodegradable food container (as shown below) and particle board. The baggase residue & ash from power plants can also be compressed to make a construction brick that weighs 3.2 kg/brick, sustains 80-90 kg/cm2 load and costs only 4 Baht/brick (compared to typical construction brick of 5.8 kg, 70 kg/cm2 strength and 8 Baht/brick cost).

The product gas is automatically separated from liquid phase when the reactor effluent is cooled down to the room temperature. Tar free gas is available, which is a benefit over usual thermochemical gasification of biomass. The main component is hydrogen, carbon dioxide, and methane. Due to the water-shift gas reaction the yield of carbon monoxide is negligible. The high temperature, low pressure, and dilute feedstock favors high hydrogen content. The heating value of the product gas depends on reaction condition, and usually varies from 12 to 18 MJ/m3-N.