There are many kinds of biomass, which may be classified into woody type, agricultural one, food residual one, domestic waste one, biomass produced overseas and others.

1.

Woody biomass includes waste wood from lumber mill, scrap wood derived from destructed building structures, thinned wood derived from mountain forest management and others.

2.

Agricultural biomass includes "hulls", "straws" derived from rice/wheat production and others.

3.

Food residual biomass includes dregs left after making of juice, coffee and tea as well as sludge and wastes discharged from food processing plants and others.

4.

Domestic waste biomass includes kitchen garbage, discarded plastic products, sewage sludge and others. (MSW : Municipal Solid Waste)

5.

Typical biomass from overseas includes dregs from palm oil mill and Jatropha oil mill.

Is there anything good expected from utilization of biomass? As for biomass, there is an idea of "carbon neutral". This idea is based on the concept that combustion of biomass generates CO₂ whereas growing trees absorb this CO₂, and so its concentration in atmospheric air does not increase, thus securing its zero emission. Amount of biomass can be increased by means of forestation and so biomass can be called one of the important renewable energy resources.

In past days kitchen garbage was incinerated merely for disposal, while in recent days the heat produced by burning of garbage has been utilized to generate electricity. Such utilization system is very important for Japan poor in natural resources.

Biomass secures "carbon neutral".

As distinct from utilization of fossil fuel, there are several problems raised in utilization of "carbon neutral" biomass. For instance, "It is not easy to use biomass as it is.", "What kind of biomass should be used?" and so on.

"It is not easy to use biomass as it is."

1.

Biomass contains much water and so is hardly flammable.

2.

Biomass is voluminous and so not easily transportable.

3.

Biomass has low calorific value and so energy obtainable is there little.

4.

Biomass in nature is distributed sparsely in wide region and so it is hard to collect it in large quantity.

"What kind of biomass should be used?"

There is an important order of priority for utilization of biomass as an energy resource. It is necessary to take care not to compete with its utilization as food stuff and living wares which have been used widely so far. It is important to utilize all garbage and wastes derived from making whatever materials. Based on this viewpoint, CRIEPI takes into consideration the following priority sequence referred to as 5 Fs.

1st F :

Food (Food stuff for human)

2nd F :

Feed (Food for domestic animals)

3rd F :

Fertilizer (Fertilizing materials for vegetables, crops and others)

4th F :

Fiber (Fiber, wooden products as well as wooden furniture such as desks and chairs)

5th F :

Fuel (Fuel materials)

We have been starting to use biomass energy widely in various fields ranging from home living to industries including electric utility industry. CRIEPI, following the above-mentioned viewpoint, has been conducting various R&D activities to use proficiently any hard-to-use biomass.

An example of biomass utilization in coal-fired thermal power station

Leftward photo gives full view of coal-fired thermal power station. Rightward one shows how to carry biomass fuel mixed with coal on belt conveyor.

Large-capacity coal-fired thermal power stations generate electricity at thermal efficiency as high as approx. 40%. In case biomass is used as mixed with conventional fuel (coal) in such stations, they can generate electricity, keeping high efficiency. Thus development of power generation system by firing coal mixed with biomass has been under way. As power stations must fulfill their own important mission to generate electricity stably and supply it also stably, it is necessary in advance to check and confirm any unfavorable influence that might be caused by coal co-firing with biomass. In this regard, CRIEPI, using various kinds of evaluation equipment, has been making preliminary assessments regarding storage safety, grindability, combustibility, environmental impact and so on.

Experimental equipment for combustibility evaluation and environmental impact assessment

Experimental facility simulating real coal-fired thermal power station is used to evaluate various combustion characteristics during coal co-firing with biomass.

Examples of environmental impact assessment during coal co-firing with biomass

Examples of environmental impact characteristics evaluated during coal co-firing with biomass. This experiment proved that biomass mixing rate as much as approx. 10% gives no trouble for co-firing.

A biomass in nature is distributed sparsely in wide region, it is difficult to collect it in large quantity. Besides, medium and small scale plants have large heat loss and are forced to operate generally at low efficiency. In this regard, however, CRIEPI has been conducting R&D activities aiming for realization of high-efficiency power generating system using biomass even in medium and small scale plants. Utilization of various kinds of biomass at the same time may promote expansion of plant scale and also give convenience for their treatment.

1:

Using woody biomass and residues from food processing, CRIEPI carried out demonstration experiments on carbonizing gasification power generation system using gas engine and, as the result, succeeded in achieving power generation efficiency approx. 25%.

2:

Further, CRIEPI carried out demonstration experiments on carbonizing gasification power generation by combining high-temperature dry gas cleaning process (developed by CRIEPI) with MCFC (molten carbonate fuel cell: single cell developed also by CRIEPI). Experimental results proved stable power generation of this system and gave perspective on achieving power generation efficiency approx. 32% in real plant scale.

Results of demonstration experiments on carbonizing gasification power generation

The experimental results made it clear that high-efficiency power generation can be achieved even in medium and small scale plants.