The major biomass components in municipal solid waste (MSW) are food waste and paper, and thus biological (2.15.1 and 2) or thermal processes (2.15.3 and 5) are used to recover energy from the biomass fraction.

2.15.1 Methane recovery in landfills

In landfills containing organic waste, anaerobic biodegradation of biomass produces methane gas because oxygen diffused from the atmosphere is consumed near the landfill surface. Landfill gas can damage nearby plant growth and even cause neighboring buildings to explode. Therefore, gas control methods including flaring have been implemented since the 1960s. In large-scale landfills, vertical wells are installed to pump out the gas, which is used on-site for power generation or sold as fuel. Average gas recovery rates range from 120 to 150 m3/ton of dry MSW, equivalent to a heating value of 2500 MJ/ton (the methane concentration of landfill
gas is around 55%). Since the late 1990s, many American studies have investigated “bioreactor landfill,” in which moisture content is controlled to maximize biodegradation. Bioreactors also increase the rate of gas generation and consequently the rate of energy recovery.

In contrast, landfill gas is not recovered in Japan for two reasons: landfills contain little organic content due to the common practice of incineration, and landfills are aerated through the use of a semi-aerobic landfill structure, in which natural convection is allowed to form an aerobic zone around leachate collection pipes below the landfill. The Chuo-Botahei landfill in Tokyo Bay does recover methane, but its annual power generation (averaged over 20 years) is 3000 MWh, enough power for only 850 households.

The pyrolysis liquid can not be mixed with the transportation fuel, and any improvement is required. There is tar trouble, but the know-how to operate the rector is not opened. To get liquid at high yield, rapid heating and cooling are needed, and heat loss and recovery is an important issue. Merit and demerit should be considered.

Further information

Miura, M. in “Biomass Handbook”, Japan Institute of Energy Ed., Ohm-sha, 2002, pp. 106-115 (in Japanese)

Miura, M.; Kaga, H.; Sakurai, A.; Takahashi, K. Rapid pyrolysis of wood block by microwave heating, J. Anal. Appl. Pyrolysis, 71, 187-199 (2004)

Lactic acid bacteria produce a lot of lactic acid from several types of sugars. They are gram-positive rod-type or spherical bacteria which can grow under an anaerobic condition. They show no mobility and negative in a catalatic reaction. They form no spores. They use only sugars as an energy source to yield lactic acid, and convert more than 50% of the consumed sugars. There are the following four groups in the bacterial species to satisfy the above-mentioned conditions: Lactobacillus, Leuconostoc, Pediococcus, and Streptococcus. Lactic acid bacteria can grow with higher growth rates and produce lactic acid with higher productivities. Since they request a lot of nutrients including amino acids and vitamins, the composition of the fermentation broth is not simple. We can classify lactic acid fermentation into two groups, homo-lactic acid fermentation and hetero-lactic acid fermentation. In the homo fermentation two moles of lactic acid and two moles of ATP can be produced from one mole of mono-saccharides with almost 100% of the lactic yield. On the other hand, in the hetero fermentation, lactic acid and other compounds are produced; it is classified into two groups: 1) one yielding lactic acid, ethanol and carbon dioxide. 2) one yielding one mole of lactic acid and

1.5 moles of acetic acid from one mol of mono-saccharides. Lactic acid bacteria possess both D type and L type or either D type or L type of lactate-dehydrogenases. Thus D-lactic acid and (or) L-lactic acid can be produced by the bacteria. Most of lactic acid bacteria has enzymes

which racemize the produced lactic acid, affecting the chiral quality of lactic acid. Lactobacillus

rhamnosus can produce only L-lactic acid with almost 100% of the optical purity, which is used as a raw material for the poly-lactate production.

Energy models that are used for policy study about energy and environment were developed as following orders. First, energy models that focus on specific energy technologies that are gigantic technologies to need long-term development plan and huge cost such as nuclear technologies.

Since latter half of 1980’s when global warming is important topic, energy models that include overall energy systems and CO2 emission have been developed. The first energy model that focused on policy study about global warming is Edmonds-Reilly model developed in the United States that is a simulation type model. ETA-MACRO and DICE model developed in the United States are typical optimization model that evaluate global energy, economy, and environment. In addition, GLUE model developed in Japan is a typical model that evaluates global bioenergy supply potential considering land use competitions and overall biomass flows.

7.12.1 Governmental policy

Project No 177/2007/QD-TTg (Nov. 20, 2007) of Gov. for development of biofuels to 2015 and line of vision to 2025 and Gov. Strategy No 1855/QD-TTg (Dec. 27, 2007) for development of National Energy to 2020 and line of vision to 2050. The government approves a new and renewable energy as 3, 5 and 11% to 2010, 2020 and 2050 respectively. There are no duties for biomass introduction. Ministry of Industry and Trade; Ministry of Science and Technology; Ministry of Agriculture and Rural Development; Ministry of Natural Resources anfd Environment.

7.12.2 Utilization of biomass

Availability, amount used, and how to use, for each biomass is listed below.

• Livestock waste: availability: Pig dung — 25.7 million tons/year; Cattle dung — 20.2 million tons/year; Buffalo dung — 16.0 million tons/year; Municipal garbage — 6.4 million tons/year, amount used 70-80% (compost; fertilizer; Biogas…

• Food waste: availability not determined (animal feed)

• Paper: consumpition 997,400t/year, amount used 70% (recylce)

• Black liquor: availability not determined, amount used 40% (combustion)

• Sawn wood: 3,414 thous. m3 Lumber-mill residue: amount used 100% (energy use)

• Forestry residue: availability 1,648.5 thousand tons/year, amount used 0%

• Non-edible portions of farming crops: availability: rice straws:76 Mt/year; rice husks 7.6 Mt/years; Bagasse2.5 Mt/year, amount used 20% (compost, animal feed, animal bedding material, electrcity, Mushroom production…); 73,800 tons of used cooking oil; 60,000 tons of “Basa” fish oil (2005) now producing 10,000-tons/year

1.2.3 General scope

For the utilization of biomass, a raw biomaterial is selected among various kinds of biomass by taking into consideration of its utilization purpose, demand and availability. Then, the raw material is converted to new material or energy.

Biomass as bioresource comes mainly from plants and their debris. Animals and microorganisms as well as their organic matters are also important. Many species of plants are useful as biomass. Land biomass mainly consists of herbal biomass from major farm crops, and woody biomass from forest. Many of them are cultivated, converted and utilized for specific purposes. Aquatic biomass from oceans, lakes and rivers can also be cultivated in such a case as kelp. Biomass which is cultivated on farm land or felled from forest for specific purposes is called virgin biomass, whereas the discarded biomaterials in production, conversion and utilization processes are named waste biomass and used for other purposes. For example, bagasse which is the waste of sugarcane processing is used as excellent fuel for the sugar extraction and ethanol distillation processes. Utilization of waste biomass is also important for avoiding the conflict of bioenergy utilization with food and feed. Bagasse is also considered as one of the major raw materials for “the second-generation biofuel”.

Transportation and storage of biomass is not easy because of its bulkiness and degradation. It is, therefore, reasonable to use biomass in the areas where it is produced. For this reason, biomass is used in or nearby regions where biomass supply and demand are balanced. However, when biomass is converted into more transportable form like densified pellet or liquid fuels, it can be utilized in distant regions.

Biomass can be used either as materials or energy. Biomass is utilized as diversified materials such as food, feed,
fiber, feedstock, forest products, fertilizer and fine chemicals. Utilization as energy in the form of biofuels occurs on the final stage and biomass is decomposed into carbon dioxide or methane and emitted in the air. The diversified use can be called ”8F Use” of biomass.

Biomass can be used stepwise like a cascade as its quality is degraded. Fig. 1.3.1. illustrates examples of cascade use of food to feed and then to fertilizer.

Food waste can be treated into good feed. Feed changes into livestock manure which can be fermented into methane. The digested sludge can be used as fertilizer. Forest products such as wood from pulled down houses can be utilized as particleboard or pulp, and as the final step, it can be converted into energy through the combustion of bio-solid fuel.

Recycling is made for paper, fiber, some feedstock and wood products as shown with round-arrows in Fig. 1.3.1. So far as biomass is used as material, its carbon is kept in the material and does not emit any greenhouse effect gas contributing to reduce the ill effect of global warming.

2.9.1 What is oil producing biomass?

Oil producing biomass produces and accumulates fat & oil in its seed or fruit meat. The main component of fat & oil is tri-ester of fatty acid and glycerin. Fat & oil is widely used as food, industrial raw material and bio-diesel production as an alternative for mineral diesel oil.

Examples of oil producing biomass are as follows;

(a) Soybean (Glycine max Merrill)

USA, Brazil, Argentina and China are the main production country. Soybean oil contains oleic acid (20-35%), linoleic acid (50-57%) and linolenic acid (3-8%). It is widely used as edible oil and raw material for paints and varnish as an un-drying oil.

(b) Rape (Brassica campestris L)

Rape is cultivated in wide area from Asia to Europe because it can grow even in the cold district. Main production countries are China, Canada, India, Germany and France. Rape seed oil expressed from rape seed contains oleic acid (55-59%), linoleic acid (21-32%) and linolenic acid (9-15%). It is mainly used as food such as frying oil and salad oil.

(c) Palm Tree (Elaeis guineenis Jacq)

Main production countries are Malaysia and Indonesia. Palm tree has the highest oil productivity in oil producing biomass because palm fruits can be harvested several times in a year. Palm oil expressed from palm fruit contains saturated fatty acid such as palmitic acid (35-38%) and Stearic acid (3-7%), and it is used not only in food industry but also in detergent industry.

3.1 Firewood

3.1.1 General scope

Firewood is a classic energy source, and is still important household energy source in many developing countries. In the latter half of the 20th century, firewood was deprived of many uses by petroleum, but firewood production occupies more than half of the harvested wood, and firewood covers 14% of the world energy consumption, and 36% of the energy consumption in the developing countries.

However, in some regions, the amount of wood is decreasing with the increasing population, and they have to travel far to get firewood. They have troubles even for getting firewood for cooking. In Asian countries, most of the forestry wood has difficulties in use, due to the troubles encountered for transporting wood from the forest of high slope area.

For the left side of Fig.1, which is the supply side of firewood from raw wood to the furnace, what matters now is not the amount of the resource, but the energy and cost for the transporting the wood from the forest. When external energy supply for this transportation *e and energy available from the product firewood E have the relationship I*e > E,

this system fails to be a net energy producing system. This aspect is also very important for the case where chipping or palletizing is made so that the fuel is easily handled at the furnace.

*e transportation, etc. p^[E] ^cooker or heating

Raw wood————————————- > stove————— > [flue gas]

*e drying, cutting, etc. *—- dash]

Fig.3.1.1. Material — and energy-flow around stove in firewood system
*e ^energy supply from outside, E ^useful energy

For the right side of Fig. 3.1.1, which is the user of the firewood, what matters is the low energy efficiency of the old heating devices similar to traditional kitchen stoves.

In addition, hygiene of the indoor air is to be considered when small stoves are used that often accompanies with incomplete combustion. The problems of soot, carbon monoxide (CO), tar, Non-methane volatile organic matter (NMVOC), and polyaromatic hydrocarbons (PAH, carcinogen) are pointed out.

Ash content of the firewood is lower than that of coal by one order, but ash removal is important from the view point of mass balance, although it usually does not cause a serious problem. Ash of wood has high content of potassium, which is an important fertilizer, and return of ash to the forest is essential for the sustainability of the system.

Herbaceous plants have higher ash content than wood by 5-20 times, and ash treatment is a large problem for production of artificial firewood from straw, husk, and bagasse.

Heating values of plant is about 20GJ/t-dry for various woody biomass (half of heating value of oil), and mostly decided by its water content. Woody biomass is not suitable for transportation of long distance due to its bulkiness. This is why utilization of firewood near the forest is insisted.

Fundamentally, hydrothermal liquefaction is pyrolysis, and therefore degradation and polymerization occur. Simple reaction scheme is shown in Fig. 4.6.2. At first step, biomass can be degraded into water-dissolved materials. Then the water-dissolved materials are

polymerized to form oil. When reaction is prolonged, the formed oil is polymerized into char.

4.6.3 Product oil from hydrothermal liquefaction

Properties of obtained oil by liquefaction are shown in Table 4.6.1. The reaction was conducted without reducing gas, such as hydrogen and carbon monoxide, and with alkali catalyst for wood and without catalyst for sewage sludge. The obtained oil has oxygen content of around 20 wt%, and therefore, its higher heating value is lower than that (around 42 MJ/kg) of heavy oil from petroleum. In addition, its viscosity is very high.

The obtained oil from wood has much amount of acid fraction, and it can corrode and polymerize during storage.

On the other hand, the obtained oil from sewage sludge has nitrogen originated from protein, and NOx treatment is needed at its combustion.

As chemical fraction, pyridine derivative, pyrazine derivative, and amid compounds are detected. If they can be separate, they might be used as chemicals.

6.1 Fundamentals of LCA

6.1.1 Outline of life cycle assessment

Life Cycle Assessment (LCA) address the environmental impact of the target product or service throughout their life cycles; so called “from the cradle to the grave”, and measures the amounts of resources consumption and the emissions of all the stages from raw material acquisition through production, use, end-of-life treatment and final disposal (inventory analysis), then evaluating the impact based on the results of the inventory analysis (impact assessment).

International standard (ISO-14040) provides “Principles and framework” of LCA. ISO-14040 defins LCA as “LCA is one of the techniques being developed to better understand and address the impacts from products, both manufactured and consumed, including possible impacts associated

with”. ISO-14040 also clearly shows the four phases for conducting LCA: “Goal and scope definition”, “Inventory analysis”, “Impact assessment”, and “Interpretation” (Fig. 6.1.1).