4.2.1 Definition

The process to convert biomass solid raw material into fuel gas or chemical feedstock gas (syngas) is called gasification or thermochemical gasification.

4.2.2 Classification of gasification method

Gasification methods are classified according to combinations of conditional factors shown in Table 4.2.1..

Acetone-butanol fermentation was industrialized for supply of raw materials of smokeless powder and fighter planes. Presently, acetone and butanol are synthesized in petroleum industry. Biofuels, renewable gasoline or diesel additives are now paid much attention throughout the world. Butanol can be added to both gasoline and diesel fuels and has more affinity for gasoline than ethanol. Therefore, butanol will be promising biofuel.

Further information

Crabbe, E.; N-Hipolito, C.; Kobayashi, G.; Sonomoto, K.; Ishizaki, A., Biodiesel production from crude palm oil and evaluation of butanal extraction and feel properties, Process Biochim., 37, 65-71 (2001) Ishizaki, A.; Michiwaki S.; Crabbe, E.; Kobayashi, G.; Sonomoto, K.; Yoshino, S., Extractive acetone-butanol-ethanol fermentation using methylated crude palm oil as extractant in batch culture of Clostridium saccharoperbutyl acetonicum N1-4 (ATCC13564), J. Biosci, Bioeng., 87, 352-356 (1999)

Lee, T M.; Ishizaki, A.; Yoshino, S.; Furukawa, K., Production of aceton, butanol and ethanol from palm oil waste by N1-4, Biotechnol. Letters, 17, 649-654(1995)

6.5.1 Standard of living

Since agriculture is of much importance for the economies under development, it is desirable that sustainable agriculture leads to improvement of farmers’ standard of living as well as their income. In this section, a small-scale biomethanation plant in a rural area of Thailand is taken up as an example. A small farm gave animal manure as feedstock for anaerobic digestion. Manure from 5 cows was feedstock. Product biogas was used for cooking. It was expected to be sufficient for 3-times cooking for 1 hour for a daily basis. In this sense, the small-scale biomethanation is desirable since the farmers can use the cattle manure in their own farm, and the product gas can be used for their own purpose. Utilization of the fermentation residue as fertilizer resulted in the recycling, reducing the amount of chemical fertilizer. It is usual for the Thai farmers to use chemical fertilizer that is not sustainable, and the product compost from this biomethanation plant is helpful to switch to sustainable agriculture. As a result, the plant achieved the local recycling of cattle manure as energy (biogas) and material (compost). Another good aspect of this biomethanation plant was the increase in farmers’ hygiene. The number of flies reduced after introduction of the plant.

The plant investigated in 2006 was the only one under operation, and other two were under
construction (Fig. 6.5.1). The reason for this should be the farmers’ ignorance on this technology. During the discussion with Thai people, it was pointed out that education of people is important. In the rural area of Thailand, the literacy rate is not high. Actually, the investigated plant was a demonstration one fully supported by the local government to show neighbors the effectiveness of the biomethanation plant. In this sense, it is important to supply proper information on this technology to the farmers.

What is important for the biomass utilization for farmers to be effective is the accessibility of the biomass plant or biomass collecting site from farmers. Even if farmers possess or produce biomass feedstock, it is nothing if they do not have access to the sites where it can be made use of.

The government will continue to promote the use of alternative energy in the transport sector particularly biofuels (i. e cocobiodiesel or cocomethyl esther, fuel ethanol and jatropha carcus.)

The President has signed into law RA 9367 or the Biofuels Law that mandates the use of biodiesel and bioethanol nationwide.

At present, biodiesel is already being used nationwide at 1% of the total volume of diesel sold.

This is in accordance with the provision of the Law that, three months after the approval of the Act, a minimum of 1% biodiesel by volume shall be blended into all diesel engine fuels sold in the country. The country has 211.3 million liters per year capacity from 5 accredited biodiesel producers.

Biodiesel requirement in 2007 is 41 million liters at 1% blend. 100% compliance nationwide. Targets:

Within two years from the effectivity of the Act, the Philippine Department of Energy, may mandate a total of 2% blend depending on the results of the study by the national Board created under the Act. Provided that the ethanol and biodiesel blends conform to Philippine National Standard. Two years from the effectivity of the Act, at least 5% bioethanol by volume of the total volume of gasoline fuel sold and distributed by each and every oil company in the country. Within four years from the effectivity of the Act, the Philippine Department of Energy, may mandate a mimimum of 10% blend depending on the results of the study by the national Board created under the Act.

Raw Material Requirement:

For bioethanol, supply of feedstock is initially from sugar based ethanol. With 880,000 liters per day committed capacity from various plants. Other feedstocks considered are sweet sorghum and cassava. For biodiesel, is currently from coconut oil or CME but Jatropha is also being considered.

Current feedstock yield: sugarcane has 23.98 million metric tons, corn has 5.25 million metric tons, and cassava 1.64 million metric tons. Coconut oil production is 1.4 billion liters per year (80% for export and 20% for local use).

Biodiesel requirement : 85 million liters in 2008, 229 million liters in 2010 and 277

million liters per year in 2015.

Further information

Banzon, J. A. and J. R. Velasco, Coconut: production and Utilization, 1982 Philippine Energy Plan 2005-2014 (2006 Update)

Elauria, Jessie C., Policy and Actual Biomass Status in the Philippines. Paper presented during the Biomass Asia Workshop held in Japan

Elauria, J. C., M. L.Y. Castro, M. M. Elauria, S. C. Bhattacharya and P. Abdul Salam (2005). Assessment of Sustainable Energy Potential of Non-Plantation Biomass Resources in the Philippines. Volume 29. September 2005. pp. 191-198.

Growth rates of plants are regulated by the photosynthetic ability and a multitude of environmental factors. Grasses are classified into C3 species and C4 species based on their unique photosynthetic pathway. It is important to note the anatomical differences in leaf and bundle sheath cells that occur between C3 and C4 grasses. Typically, the optimum light intensity for C4 species is ca. 50,000-60,000 lux and is twice that for C3 species (15,000-30,000 lux). The highest photosynthetic efficiency of the C4 species generally reaches at high temperature and high light intensity which is characteristics of tropical regions. The C4 species, however, cannot maintain their high photosynthetic efficiency under low light intensity and low temperature. Table2.7.1 shows that napiergrass recorded a yield of 85 t/ha/year and the yield of sugarcane is 64 t/ha/year, with a mean of 232 kg/ha/day, and 176 t/ha/day, respectively. The yield of sugarcane and guineagrass in subtropical regions is 50 t/ha (140 kg/ha/day) and that of some tropical grasses is 25-30 t/ha (50-80 kg/ha/day). Since forage grasses generally exhibit rapid regrowth and persistency, they are utilized for low-input and sustainable biomass production. As one example, “Natsuyutaka” guineagrass has attained 40 t/ha (all are dry matter weight in the report) on a seven-year average in subtropical Ishigaki Island, Okinawa. In temperate regions, winter-hardy tropical grasses such as bermudagrass and bahiagrass produce 20-30 t/ha/year (50-80 kg/ha/day) but go dormant in winter. On the other hand, temperate grasses produces 15-26 t/ha/year (40-70 kg/ha/day) but go dormant in summer. A primary advantage in utilizing perennial C3 or C4 grasses for biomass production is that less maintenance is required and stands can persist for 5-10 years producing stable amount of biomass following stand establishment.

In the annual C4 species, such as maize, exhibiting superior seedling vigor following germination can produce a rangeing, respectively from 13-34 t/ha to 132-260 kg/ha/day in 5 months. These yields are comparable to that of perennial napiergrass. These data suggest that the highest yield in tropical regions is achieved in the summer of temperate regions by using these C4 crops. Although rice is C3 plants, it can compete with C4 species and produce high amount of biomass in temperate regions. However, winter cereals, such as wheat, annual forages, can produce lower yields per day, but can be cultivated during the winter month.

2.16.1 Black liquor

Black liquor, a mixture of organic wastes, is made from a wood as a by-product during the production of chemical pulp. And it’s routinely burned as a liquid fuel in a recovery boiler in a pulp mill. Approximately 1.5 tones of black liquor are produced in the manufacture of 1 tone of pulp. Generally, a calorimetric heat value of black liquor is 12.6 MJ/kg and its energy is mainly used for pulp and paper making process.

2.16.2 Process of black liquor generation

There are a number of different processes which can be used for separating of the wood fibers. And their produced pulp is mainly divided into 2 types. One is mechanical pulp which is manufactured by a grinding process. The other is chemical pulp which is manufactured by a cooking process where the cellulose fibers are cooked out from the wood. Black liquor is produced during the cooking process. In this chapter, details of black liquor generation are described in terms of the kraft process so that the kraft process is nowadays the main stream for pulping (Fig. 2.16.1).

Wood, the raw material of paper, is composed by wood fibers which consist of cellulose, hemicellulose, and lignin which is an integral part between the fibers. The ratio of cellulose, hemicellulose and lignin is approximately 55: 20: 25.

The process to extract lignin from a wood chip by means of decomposition and dissolubilization is called cooking process. In the kraft process, Na2S and NaOH are added as a chemical to cook and the mixture is heated to 140 — 170oC and it keeps several hours. Although it’s important not to damage to the cellulose and the hemicellulose fibers during the process, indeed, a part of the cellulose and most of the hemicellulose fibers are decomposed and dissolved. Generally, the half of the organic materials in the wood turns to pulp and the other turns to black liquor.

Paper Making Process

Fig. 2.16.1. The main stream for pulping.

Black liquor contains decomposed and dissolved lignin, hemicellulose, and Na and S. After the cooking process, the concentration of black liquor is usually 15 to 20%. Then the liquor is concentrated to approximately 70 to 75%. Finally, it’s burned in a boiler called recovery boiler. As for a hard wood chip, 1 tone of the pulp turns to 1.5 tons of black liquor. Generally, a calorimetric heat value of black liquor is 12.6 mJ/kg.

During the process, melted Na and S which were contained in the liquor are extracted and then dissolved into hot water. After that, they’re reproduced to Na2S and NaOH in the causticizing process, and then used in the cooking process again. On the other hand, separated wood fibers turn to pulp through the washing process and the bleaching process. Finally, they’re used as a raw material of paper.

Hydrothermal gasification is treatment of biomass in hot compressed water, usually above 350oC and above 20 MPa to obtain combustible gas. Figure 4.5.1 shows phase diagram of water, where gas-liquid equilibrium line starts from the triple point and ends at the critical point. Hydrothermal condition is located around the critical point. When both temperature and pressure is higher than critical temperature and critical pressure, respectively, the state is called supercritical water, and gasification in supercritical water is called “supercritical water gasification”. This hot compressed water enjoys high reactivity, and when biomass is placed in this water, it is gasified by hydrolysis and pyrolysis reactions.

2.5.2 What is silage?

Silage is now the most commonly preserved cattle and sheep feed in many countries. It is produced by the controlled fermentation of crops with high moisture. Silage is a fermented and stored process which ensilages with forage crops and grasses in a silo (Fig. 5.6.1). The types of silo in which the farmer may choose to ferment their crop are greatly varied. For convenience, commercial silos can be classified into the main categories: stack or clamp without retaining walls, tower, bunker, vacuum, plastic sausage and roll bale. Compared with the hay, the feed intake, digestibility and nutritive value of silage are excellent. Silage can be made of many other by-products of field crops and food, and other materials.

2.5.3 Silage making

Silage originated in ancient Egypt. The silage research on the fermentation mechanism has been made rapid progress in the 20th century. Silage can be prepared from forage crops and grasses at the optimum stage of growth with suitable moisture content, about 50% to 70%. The forage material is collected, chopped into about 10- to 20-mm lengths and packed into silo. Current mechanical forage harvesters are used to collect and chop the forage material, and deposit it in trucks or wagons. These forage harvesters can either be tractor-drawn or self-propelled. Harvesters blow the silage into the wagon via a chute at the rear or a side of the machine. The inoculants of LAB were used for high quality silage making (Fig. 5.6.2).

7.2.1 Amount of biomass resources in Korea

Major biomass resources available in Korea are organic wastes and the agricultural and forest residues. The potential and recoverable amounts of biomass for energy utilization are summarized in Table 7.2.1. According to the data in Table 7.2.1, the total amount of biomass resources available in Korea is about 80 million ton, only 30% of the potential biomass resources are currently utilized for energy production.

Up to now, most of biomass utilization in Taiwan is wastes and residues. The noticeable items are listed below:

• There are 24 municipal solid waste incinerators equipped with power generation facilities, and total capacity is 528.8 MW.

• There are installed capacity of power generators utilizing biogas generated from 4 large landfills and some middle to small scale pig farms.

• There are also some power plants using industrial and agricultural wastes, including bagasse, paper mill waste, plastic waste, rice hull and RDF-5 (Refuse Derived Fuel) etc. The total capacity of these plants is around 67.5 MW.

In addition, the enforcement of recycling used frying oil was started in September, 2007 for enterprise. Household is also encouraged. The potential biodiesel product from used frying oil is estimated to be around 80,000 kL/year.

In the near future, 80 km2 (8,000 ha) of rested cultivating farm is planned to cultivate energy crops. The potential of farmland for cultivating energy crops could be 5,000 km2 (500,000 ha).

If seaweed could be cultivated around 100 km2 (10,000 ha) of seashore, the potential product of 150-300 dam3 (150,000-300,000 kL) biodiesel is expected.