Acceleration of Decomposition Process by Lignocellulolytic Bacteria and Its Effect on the Physical and Engineering Properties of Kalimantan Fibrous Peat

Abstract

Peat is an organic soil which has very low bearing capacity and very high compressibility; its organic content is higher than 75%. Peat is classified into two categories, amorphous granular peat and fibrous peat (fiber content > 20%). Fibrous peat has higher bearing capacity compared to the amorphous one due to its fiber content. When the fiber undergoes decomposition, however, its bearing capacity drops, and bigger compression takes place. For this reason, decomposition process of fibrous peat has to be accelerated before the construction starts in order to prevent the change of its properties. In this study, lignocellulolytic bacteria was used to accelerate the fiber decomposition. The results show that 10% of bacteria with 28 days of curing period had the optimum results. The fiber content decreased from 50% to 36.67% in 28 days of curing period. The coarse and medium sizes of fiber decreased 5.13% and 22.03%, respectively; but the fine fiber increased 27.16% because of the change of coarse and medium fiber. Its unit weight and specific gravity decreased 6.83% and 7.89%, respectively. The peat compression increased 22.95% compared to the initial one; but the internal friction angle decreased 27.29%.

Bacteria Pseudomonas taiwanensis as a decomposing agent of peat fiber

“…According to ASTM D-4427-07, peat with a fiber content of 61,14% is classified as " moderate fibrous peat" or "hemic peat". This is in line with the results of previous studies which state that the peat of Bereng Bengkel Village, Palangkaraya is classified as moderate fiber peat or hemic peat (Ma'ruf et al, 2022;Prativi et al, 2018;Yogyanta et al, 2019;Yulianto et al, 2022). This can also be proven based on visual soil observations, where the soil has clearly visible fibers, a soft and moist texture, and a blackish brown color, as shown in Figure 7.…”

“…As mentioned earlier in previous studies the results of peat fiber decomposition obtained were not too significant because it used more than one type of decomposer bacteria (Prativi et al, 2018;Yogyanta et al, 2019), so in the current study only one type of bacteria was used to accelerate the process of peat fiber decomposition through the bioaugmentation method, which is the bacterium Pseudomonas taiwanensis proposed by Zulaika et al (2022). This bacterium was chosen as the bioaugmentation agent in this study because it has a very high decomposition ability (Zulaika et al, 2022), and can survive in a very extreme peat environment (He et al, 2018).…”

“…The variation in the addition of bacteria to the samples can be seen in Table 1. The determination of the variation of bacteria addition is based on the results of a literature review in previous studies (Prativi et al, 2018;Yogyanta et al, 2019). The samples were then observed and tested every 7, 14, and 28 days to see the effect of the addition of Pseudomonas taiwanensis bacteria on the decomposition of peat fibers at various curing times.…”

“…Efforts to accelerate the decomposition process of peat fibers in Indonesia are still very limited. Based on the results of the literature, it was found that there were only two related studies that accelerated peat fiber decomposition through the bioaugmentation method (Prativi et al, 2018;Yogyanta et al, 2019). Bioaugmentation is the process of adding microorganisms such as bacteria, fungi, or algae into an environment to increase the degradation or decomposition of certain pollutants (Medaura et al, 2021).…”

“…Bioaugmentation is the process of adding microorganisms such as bacteria, fungi, or algae into an environment to increase the degradation or decomposition of certain pollutants (Medaura et al, 2021). However, in the research (Prativi et al, 2018;Yogyanta et al, 2019) there was a misconception that was thought to be the cause of the lack of maximum acceleration of the peat fiber decomposition process so that the geotechnical properties of fibrous peat did not experience a significant increase. The misconception is the addition of more than one species of microbial decomposer to the fibrous peat, resulting in competition between microbial species for nutrients (Bauer et al, 2018;Hibbing et al, 2010).…”