4.4.1 What is carbonization?

Carbonization is the method or technology to obtain charcoal as the main product by heating such solid biomass as wood, bark, bamboo, rice husks, etc. at 400-600°C in the almost or complete absence of air or oxygen. It can afford tar, pyroligneous acid, and combustible gases as by-products. In case of discrimination from ‘dry distillation’ aiming at the recovery and utilization of liquid products, ‘charcoal making’ is used as the terminology. Carbonization customarily means charcoal making, although it is the general term including dry distillation.

4.4.2 Characteristics of carbonization

Carbonization is a classical energy conversion means of biomass, similarly to combustion. While the main objective is increase in the calorific value of the solid product charcoal, it has two sides of liquefaction and gasification. As liquefaction means corresponding to ordinary pyrolysis (see Chapter 4.3), commercial operation was early examined together with high pressure (direct) process (Chapter 4.6). However, the obtained tar (oil) was in a low yield (< 30%) with poor quality (high viscosity, high oxygen content, low heating value, low pH, etc.), so that the process was given up after the appearance of rapid pyrolysis (Chapter 4.3) yielding a
large quantity of oil. As gasification means (Chapter 4.2), it is inferior to current processes in the production of combustible components, due to lower reaction temperature. In the utilization of product gas for generation, a considerable amount of tar must be removed. Nevertheless, carbonization that has industrial advantages of inexpensive apparatus and easy operation is still important for cheaply producing solid fuels with high heating value. The features making a certain proportion of organic carbon stably fixed and the features making the volume of municipal wastes, garbage, sewage sludge, cow dung, etc. effectively reduced contributes to the control of CO2 emission and serves as a practical measure to dispose of various wastes, respectively.

Glucose is a major substrate for lactic acid fermentation, which is usually obtained by hydrolysis of starch. Starch is now obtained from crops. However, we sometimes worry about competition between energy or materials and food, as claimed in the ethanol production from biomass resources. Thus soft cellulosic biomass like rice husk which has been currently not used is expected for biomass resources. Anyhow such unused biomass has less quality and that is why it has not yet been used. Then some conditions must be considered for its utilization in fermentation. First, constant and stable supply of the biomass is required. Next, sugars should be obtained easily with energy as least as possible. Of course, more effective and sophisticated technology for the fermentation is needed, and moreover, it is also important to solve the issues accompanied by transportation and storage of biomass in terms of energy, cost, etc.

DNE21 model is an optimization model that was developed for assessment of technologies that mitigate global warming. DNE21 model is based on the NE21 (New Earth 21) model that was developed for numerical analysis of "New Earth Plan" announced in 1990 by Japanese government. DNE21 is dynamic model that minimizes inter-temporal energy systems cost in the world. In the model the world is divided into 10 regions and global energy systems till 2100 are analyzed. In the model bioenergy conversion technologies are analyzed in detail.

6.7.2 GLUE model

GLUE model is the abbreviation of global land use and energy model and was developed in Japan. The model that is a simulation model is a typical model that evaluates bioenergy supply potential in present and in the future. In the model, biomass demand is calculated by data of biomass demand per capita and population. Biomass supply potential is calculated by data of arable land area and arable land productivity. In the model the biomass demand and the biomass supply potential are compared and the surplus arable land and the energy crop supply potential produced on the surplus arable land are calculated. In addition, the model evaluates supply potential of biomass residues discharged from processes of biomass flows such as production, processing, consumption, disposal, and recycling.

The recent version of GLUE model is an optimization type and evaluates not only bioenergy supply potential but also biomass utilization technologies.

Bioethanol

Feedstock: Casava, molasses, rice Production: 76.63 ML in 2006.

Biodiesel

Feedstock: waste cooking oil; Basa fish oil; rubber oil; Jatrofa Prodution: R&D project"

Biofuel introduction has not been made, but by plan of Gov. to 2021 will be 100,000 t of E5 and 50,000 t of B5 available on the market

7.12.3 Energy crops

Amount of production and utilization of energy crops are none, but in the future, introduction of 2 ethanol factories using cassava, each productivity of 100 ML/year (1 factory produces 50ML/year using molasses and sugarcane) is planned.

7.12.4 Successful examples

40,000 family-size biogas digesters (1-50 m3) had been installed. Development of new technology for biofuel production from agricultural residue is under way.

There are many conversion technologies available for changing the quality of biomass to match its utilization purposes. They are physical, chemical and biological techniques. Fig. 1.3.2 illustrates typical conversion technologies.

Physical conversion includes milling, grinding and steam explosion to decompose the biomass structure for increasing its surface areas to accelerate chemical, thermal or biological processes. It also covers separation, extraction, distillation etc. for obtaining useful ingredients of biomass as well as densification, drying or moisture control for making biomass more suitable for transportation and storage. Physical conversion technologies are also often used for the pretreatment to accelerate the main processes.

Chemical conversion includes hydrolysis, partial oxidation, combustion, carbonization, pyrolysis, hydrothermal reactions for decomposing biomass, and also synthesis, polymerization, hydrogenation for constructing new molecules or reforming biomass. Generation of electrons in oxidation process of biomass can be used for fuel cells to generate electricity.

Biological conversion is mainly composed of fermentation processes such as ethanol fermentation, methane fermentation, acetone-butanol fermentation, hydrogen fermentation, and enzymatic treatments which will play more important role to bring the second-generation bioethanol on the practical stage. Application of photosynthesis and photolysis processes will be important to improve biomass systems.

Combustion heat of biomass is converted to mechanical power by means of such heat cycles as Otto cycle (for gasoline engine), Diesel cycle (Diesel engine),

Rankine cycle (steam engine), Brayton cycle (gas turbine) and others.

Electric generator with electromagnetic induction is used to convert mechanical power into electricity.

Such pretreatments as separation, extraction, milling, grinding, moisture regulation etc. are often performed before the main conversion processes. Fig. 1.3.2 illustrates so-call-ed a magic box in which biomass is put on the bottom and converted by using various techniques to match its utilization purpose.

Evaluation of the conversion processes is done in terms of product quality, energy efficiency, yield and system economy.

Planning of conversion and utilization system should take the following items into consideration: fluctuation of biomass supply, means and cost of transportation & storage, managing organization and rules which are in harmony with the relevant regulations, as well as the economy of the total system.

For the fat & oil isolation from seed/fruit expression process or solvent extraction process is applied.

(a) Expression process

Used for high oil content seed such as rapeseed by rough crashing by roll mill, flaking, heating at 75-850C and expression by expeller.

(b) Solvent extraction process

Applied for low oil content seed such as soybean by extraction with hexane.

2.9.2 Production volume of oil producing biomass

World oil seed and fat & oil production (2005/06) are summarized in the following table. Production volume of palm fruit was calculated by the palm oil production volume and oil content in palm fruit.

2.9.3 Bio-diesel fuel

Fatty acid methyl ester produced by the trans-esterification of fat & oil with methanol has the similar physical properties as mineral diesel oil in terms of heating value, viscosity, cetane number etc,. and it is used as bio-diesel fuel (Diesel oil alternatives).

As raw materials for bio-diesel production, rapeseed oil in EU, soybean oil in USA and palm oil in Asia are mainly used. In EU nation’s, bio-diesel has been spreading since 2002 and its consumption reached to 4 million ton in 2005.

The potential of firewood supply is discussed here. According to FAO (Food and Agriculture Organization), forest area of the world is 39,500 km2 (3.95 Gha) and decreasing gradually (-0.2%/year). Although the primary growth rate of forest is estimated to be more than 5.1 km3/year (5.1 billion m3/year), annual lumber production is as small as 1.6 km3/year (1.6 billion m3/year) for industrial use, and 1.8 km3/year (1.8 billion m3/year) for fuel use. Even if forestry area is constant, artificial forest with high growth rate is increasing gradually, and supply increase with mild development of economy can be met.

For lumber production, production of forest residue and thinning wood is accompanied with. If proper development is made for transportation of these biomass, supply potential largely increases. However, transportation from steep mountain that is often found in Japan and Asian countries leads to very large value of *e-1 in Fig. 3.1.2, and the woody biomass cannot be effectively utilized. The value of *e-1 is expected to increase with distance proportionally, and increase with the slope with the exponent value of 2 to 3, but has not been studied in detail. The bulk density largely affects the transportability. Packing factor is 1/4-1/3 for twigs, 1/2 at maximum for chip, and 0.6 for pellets.

*e-1 transp. *e-2 transp. p—>[E]

Raw wood—————— — village————————— — stove

*e-3 gathering, | *e-4 drying, *e — 5 cutting |

Factory——— processing————

Fig.3.1.2. Material — and energy-flow before stove in firewood system *eR *e 2^ *e 3— :energy supply from outside,

An experiment was made by a Japanese NPO to transport woody biomass from high-slope land forest to the foothills using a slider as shown in Fig. 3.1.3. Successful result was obtained for the thin wood, for the slope of around 20o. This system requires no mechanical power, and applicable to the sloped region.

To convert raw wood to firewood, it is cut into the length of less than 50 cm, because of the furnace dimension. The improve the easiness of burning, change its form to have an aspect ratio of 10-20 by cutting into pieces so that surface area is increased. These requirement is troublesome, and recently, artificial firewood produced by pelletizing the crashed wood into a form of cylinder with empty core is developed (Ex: Ogaraito, See Chap. 3.2 Pelletizing). Order is given for some forms of woody biomass fuel in terms of high specific surface area and improvement in handling as follows, but higher treatment requires higher consumption of the process energy (*e-4^ *e-5) and results in higher cost.

Raw wood > fire wood > chips, briquette > pellet Water content of firewood is 50% for raw material, and 15-30% for air-dried firewood. Both are combustible, but latent heat of water (2.26 MJ/kg-water) is lost. Generally, when water content exceeds 2/3, the fire gets extinguished because the remaining heat is not sufficient to achieve the flame temperature. Drying of firewood consumes process energy, but part of which can be partly recovered by the increase in the heat of combustion.

The energy yield (= calorie in the obtained oil / calorie in the feedstock biomass) is around 70%. As for energy efficiency of hydrothermal liquefaction process, the effective calorie of the obtained oil almost balances or is surplus a little with the required heating energy of feedstock biomass from room temperature to reaction temperature. The moisture content affects it strongly, and at below around 85% of moisture content, it is calculated that the process can
produce energy.

In this phase, the practitioner of LCA defines the product system to be studied and clarifies the goal. For instance, assume that an "influence for global warming of a refrigerator" is defined as the evaluation target. According to the goal, LCA practitioner decides the emissions to be measured and the boundary to be evaluated. The target to be studied in LCA is originally "a function" of the product. For example, it is a function to "cool a thing in the storage" if it is "a refrigerator". Therefore, the same "function” such as same volume, same durability year is to be set when different models of refrigerator are compared. Moreover, when conducting LCA, it is difficult to cover everything in the process related to the target product or service. The process, whose contribution level is low in comparison with the goal of LCA, is excluded from a study (cut-off). A so-called cut-off criteria is used to decide to be excluded from the process. There is no general rule to cut-off because an important process can be different if the goal of study is different. It is fundamental that scope is consistent with the goal of the LCA.

In the 7th 5-year plan (1996—2000^) included activation of agriculture to improve self-supply rate of various agricultural product, but the rate stays only 20%, making biofuel development very difficult.

The plan proceeds study to improve the culturing technology and production system that fits the natural condition of the country so that food demand increasing year by year should be met. It proceeded introduction of new technologies such as water cultivation, and extending of agricultural area. For proceeding water cultivation, half of the expense needed for the tools and fertilizer were supported. The Ministry of Agriculture approved new land-developing zone in 2000. They are for production of vegetables (50 ha), fruits (500 ha), and livestock (100 ha).

The effort to improve self-supply rate of food is taking its effect. In 2004, production of eggs exceeded 100 million eggs/year, and chickens exceeded 13 million, achieving almost 100% of self-supply rate. (Note most of the feed is imported.) However, self-supply rate of other food is still low: tropical vegetables 53%, milk 13%, beef 3.85, goat 3%, other crops 2%, rice 1%. The agriculture has to be much more developed.