Masaki Saito

Oita Industrial Research Institute

Takae-nishi 1, Oita

870-1117, Japan

m-saito@oita-ri.go.jp

　

Suguru Ogura, Hisato Fukushi

Takahisa Nagashima

Maritime Disaster Prevention Center

Takadanobaba 1-31-18, Shinjukuku,

Tokyo, 169-0075, Japan

fukushi@mdpc.or.jp

　

Yoshihiko Yamada

Nippon Foundation

Akasaka 1-2-2, Minatoku

Tokyo, 107-8404, Japan

y_yamada@ps.nippon-foundation.or.jp

　

　

I. INTRODUCTION

 Oil sorbent is one of the effective resources for land and marine oil spill responses. In contrast to polypropylene (PP) which has been frequently used in the existing oil sorbent, we developed the practical application of an oil sorbent using sugi (Cryptomeria japonica D. Don) bark¹⁾ as a starting material which is a natural product of which there is an excess supply in Japan so the development of its uses has been in demand. We gave permission to Bungo Yuki Hiryo Inc. (Taketa, Oita), to proceed with patent filing procedures for SBS's commercializataion²⁾.

　

A. R & D of SBS

 There were 3 objectives in this R & D.

 We have tried to make an oil sorbent from sugi bark and test its basic absorbency under dry/wet conditions. The oil absorption function is as efficient as that of the test piece, which is in a state of dryness. Concerning the size of fiber, a tendency is clearly observed that the oil absorbing function improves when the fiber size is larger. Controlling fiber size and the state of dryness made the Sorbency Ratio the highest 13.4 (Bunker A), which is an equivalent absorption of PP products. From the viewpoint of the practicality in the spill site, we suggest about appropriate form for its use in real spills through the water tank experiments. After all, they were improved into commercial products (Fig. 1), which started to be released in 2001 at Japan.

　

　

B. R & D of Biodegradation Disposal

 As the next step, we conducted a study regarding a biodegradation treatment technology in an attempt to propose a non-incineration treatment method for the used organic oil sorbent such as sugi bark which has been greatly requested by users.

 In addition to the concern about 3 items, (1) harmful substances generated during incineration such as dioxin which has attracted recent attention, (2) the resistance to the emission of carbon dioxide which causes global warming, and (3) the generation of incineration heat, an expectation of the biodegradability is a part of the background when requesting a non-incineration treatment. The biodegradability is a characteristic of SBS, which has been emphasized as a product made of 100% natural material.

 In comparison with PP products which have over 90% of the domestic share, the SBS has the following advantages:

 However, in terms of a treatment method, there are no other choices but an incineration method now. Although the SBS generates less heat than the PP products, it is handled in the same way as the PP products from the aspect that it can be safely incinerated under specified conditions.

 Another treatment method besides incineration is the biodegradation. Environmental remediation by the biodegradation (bioremediation) has recently been applied increasingly to contaminated shores due to oil spill accidents, and the conditions and procedures have been discussed actively. The application of a method of spraying a bio formula containing oil decomposing bacteria is questionable when considering the ecosystems around the area. For this reason, the common method is to activate oil-decomposing bacteria which originally live on the polluted shores by fertilization with nitrogen and phosphorus or supplying oxygen by tilling the land surface in order to shorten the time required for decomposition. However, due to the environmental conditions including atmosphere or seawater temperature, it generally requires long time such as several months to years for remediation.

 The biodegradation treatment of oil in a closed space is relatively safe since there is only a small effect on the surrounding ecosystems. Since environmental factors such as temperature and water content can be controlled easily to achieve stable results, it has been applied to a variety of applications including grease traps in kitchen drains. On the other hand, a study on the decomposition of waste vegetable oil in the process of fertilization of livestock feces has been conducted at certain research institutions. Additionally, some institutes researched the microbial decomposition of fuel/diesel oil after compost addition to oil-contaminated soil³⁾⁴⁾.

 We primarily focused on the fact that a part of the heavy oil such as Bunker C, which can be the subject of recovery at many oil spill accidents, and lignin constituting Sugi bark (approximately 52% in the external bark) have relatively similar chemical structures. We reached a concept of a biodegradation treatment for the used SBS after adsorbing oil, utilizing the process of the biodegradation at the bark compost plants where composts are manufactured by fermentation of Sugi bark. In addition to a drastic reduction in the environmental loads by the application of a non-incineration treatment, the product obtained after the decomposition treatment may serve as compost, with the safety that the treatment is carried out in a closed space. If the process is applicable in practice, we expect the establishment of a superior oil recovery system using SBS.

　

II. EXPERIMENTS

　

A. Field Preliminary Experiments

 In an attempt to seek the possibility of the present concept, the following simple preliminary experiments were conducted.

1）Experimental Methods

 A bark compost material containing active microorganisms in the process of fermentation (one year after combining Sugi bark, cow feces and water content) was piled in an amount of about 5m³ on a concrete foundation and the used SBS as a sample was placed on the top. Subsequently, the bark compost material was piled in an amount of about 3m³ on the top of the sample and the interior of an experimental chamber was determined such that a sufficient temperature environment (60 to 70℃) for fermentation can be maintained. The sample used was a mat-shaped (45cm x 45cm) commercial product (about 200g/sheet) of SBS containing Sugi bark and perlite in a cotton unwoven fabric. 200g of Bunker A (light oil), Bunker C (heavy oil) and motor oil were adsorbed respectively (Fig. 2). Another set of the same samples was also set at a location slightly away from the experimental location.

 The experiment was conducted at Bungo Yuki Hiryo Inc.

　

2）Results

 After an 8-week period, the bark compost material covering the samples was removed and the samples were examined. In Set 1 as shown in Table 1 and Fig. 3, the amounts of residual oil were reduced to levels that could no longer be detected by the naked eyes in all kinds of oils. On the other hand, in Set 2, the presence of oil was detected in all kinds of oils, indicated a significantly slow progress.

 The conditions applied to these two sets were almost the same except that the location of the bark compost material (a small mountain shape) containing the samples was in a slightly shaded area.

 Although it was assumed that a decomposition treatment could proceed at a relatively high speed if all favorable conditions are available, the speed was assumed to slow down significantly if any of the conditions are missing.

　

　

　

　

 We assumed that it is desirable to perform an experiment using equipment having a large-sized fermentation tank with a stirring device to disperse sufficient oxygen supply and to be able to control temperature and moisture contents as such that stable data can be obtained. The next experiment was conducted in a commercial high-temperature aerobic fermentation equipment (industrial garbage disposal equipment).

　

1）Experimental Methods

 It is desirable that the high-temperature aerobic fermentation equipment for this experiment has;

 We used 4 same machines, garbage disposal equipment (Toshiba GO-S20A, Fig. 4), in which the samples were placed and controlled under the same condition (Table 2). Samples consisted of a bark compost material in the process of fermentation (Bungo Yuki Hiryo Inc., 1 year after the beginning) and Bunker C.

 In tank No.1(Fig. 5), oil content was 5000ppm, in tank No.2, oil content was 10000ppm, and in tank No.3, there was no oil as the control. Additionally, we put the same sample as No.1 into 105℃ atmosphere for 24 hours in order to kill the microbes, which was called "No.4".

 The moisture contents of samples were analyzed once a week and kept at about 50-60% by adding the water (0.7-2kg). Samples were collected from more than 10 locations in each tank using spatula, they were analyzed by gravimetric method using carbon tetrachloride extraction (analyzed by Sumika Analysis Inc.).

 As the machines we used did not show the sufficient performance in keeping temperature, the water tank was held outside the equipment. The experiment was executed Nov.11, 2002 to Jan. 6, 2003.

　

　

2）Result and Discussion

 Showing at Fig. 6, there seemed be no significant inclination in the data of oil content in any samples. The reasons were possibly related to:

 In sampling mentioned (1), the spatula may picks up "oil ball" or "compost ball" because viscous oil like bunker C is not easily inclined to be distributed uniformly. It is necessary to check the margin caused by instability of distribution and sampling. Table 2 and Fig. 6 show the difference between theoretical data and real analysis data of oil content at the beginning. It suggests the problem in this sampling method.

 The temperature of fermentation tank was about 50℃ through the experiment even using the outer hot bath, much lower than 70℃, usual temperature of fermentation in bark composting factory. However it may mean the low activities of microbes, Table 3 shows the more number of microbes than usual garbage disposal equipment. This issue would be concluded after further experiments and discussions. Although there may be a way to keep the tanks' temperature at 70℃ using some items, the microbes phase necessarily would not be same as the case in natural rising up in usual fermentation.

　

　

 Additionally, as this equipment stirs the compost only for 2 minute every 30-90 minutes, which may not be sufficient for bark compost fermentation, the possibility is pointed out that the aerobic microbes in it do not always aerobic activities. The small scale such as 4 kg of the equipment inclines to cause the lack of stability of fermentation, which may not be a good environment for microbial activities.

 Table 3 shows that there was almost same number of microbes in No.4 after 8 weeks as other samples, despite of the sterilization (mentioned (3)). All the apparatuses were placed in one atmosphere that may allow the air including microbes to come in through the ventilation.