Kajian Sludge Biogas Limbah Cair Kelapa Sawit sebagai Sumber Biofertilizer

Abstract

The problem regarding the processing of CPO in oil palm plantations is the liquid waste or POME (Palm Oil Mill Effluent) produced, which has a very dangerous impact on the environment. The management of this waste in the production of biogas is often carried out by anaerobic treatment. However, the inadequate utilization of a biogas sludge is commonly observed, where the high diversity of microbial populations supports soil fertility and plant productivity. This indicates the necessity to study the characteristics of biogas sludge towards field applications, to assist oil palm companies in managing the remaining waste from the anaerobic POME processing. This dissertation contained 2 stages, starting with a pre-study to obtain several chemical characteristics and the number of beneficial bacteria populations to be used as an isolate source. This study was carried out by obtaining a sludge sample from the anaerobic biogas tank of a palm oil mill in South Labuhanbatu Regency, North Sumatra, Indonesia. Using an analytical descriptive method, this process was subsequently accompanied by analyzing the chemical characteristics of the sludge within January-February 2020, as well as the number of beneficial bacteria population, including nitrogen fixing bacteria and phosphate solubilizing bacteria. The results showed that the sludge from the anaerobic tank had a pH of 7.41 which meets quality standards, indicating lower BOD and COD than palm oil effluent. The population of nitrogen fixing bacteria was also more than the phosphate solubilizing bacteria. This indicated that the bacterial population from biogas sludge had the potential for morphological characteristics, biochemical activity, potential testing, and identification of superior isolates. The first research was aimed to (1) obtain the characteristics of superior bacterial isolates from biogas sludge, with the potential to increase available P and the N-total, as well as dissolve P, and (2) molecularly identify superior bacterial isolates from biogas sludge. This study was conducted using a Completely Randomized Design (CRD) with 3 replications at the Soil Biology Laboratory, Agriculture Faculty, University of North Sumatra between March-August 2020. The process began with the isolation, selection, potency testing, as well as the identification of nitrogen fixing and phosphate solubilizing bacteria isolates. This was subsequently accompanied by a synergism test, organic acid measurement, and molecular identification. The results showed that the nitrogen fixing bacteria isolates dominantly had flat elevation, smooth edges, milky white color, gramnegative, round cells, as well as positive in the motility, citrate, and catalase tests, respectively. Meanwhile, the dominant phosphate-solubilizing isolates had flat elevation, smooth edges, milky white color, gram-negative, rod cells, and were positive in the catalase test. The potency test showed that the nitrogen fixing bacteria (N3) isolate had nitrogenase activity, as well as increased the N-total soil of the highest ultisols by 2.2 nmol/h and 62.56%. The results also showed that the phosphate solubilizing bacteria isolate (P7) was able to increase the highest available P-content of the ultisol soil by 36.21%, and also had the highest sequential organic compounds, namely lactic, oxalic, acetic and citric acids. The highest phosphate solubilization index and efficiency were subsequently found in the P1 isolate (medium IPF). In addition, the P7 and P1 isolates had the highest Psolubilization abilities from calcium triphosphate/rock phosphate (4.62 and 2.66 times) and aluminium (1.42 times) sources, compared to the control group. The nitrogen fixing bacteria isolate (N3) and phosphate solubilizing bacteria isolate (P7) from the biogas sludge were related to Bacillus paramycoides and Bacillus cereus, respectively. The second research was aimed to determine the effect of superior bacterial isolates, biogas sludge, as well as their growth interactions and production of upland rice on ultisol soils. This was conducted on a farmer's land at Ikahi Street, Medan Selayang Subdistrict, Medan City, Indonesia, from October 2020 to March 2021, using a randomized block design with two factors on 3 replications. The first factor (Factor I) indicated the use of superior bacterial isolates at a dose of 10 ml/polybag (B0 = no isolates, B1 = N3 nitrogen fixing bacteria isolates, B2 = P7 phosphate solubilizing bacteria isolates, B3 = a combination of isolates N3+P7). However, the second factor (Factor II) was the dose of the biogas sludge (S0= control, S1= 157.5 ml/polybag, S2= 315 ml/polybag, S3= 630 ml/polybag). These parameters were analyzed by variance and DMRT at a 5% level. The results showed that superior isolates (B1-B3) increased canopy dry weight, N-total and P-available soils, N-uptake, the total phosphate-solubilizing and nitrogen-fixing bacteria population, plant growth rate, as well as all production features of upland rice. At a dose of 315-630 ml/polybag, the biogas sludge increased plant height and growth rate, the number of tillers, wet and dry weights of the roots and canopy, RV (root volume), N and P-uptake, the total nitrogen fixing bacteria population, and the panicles on upland rice. The interaction of the nitrogen fixing isolates at a dose of 630 ml/polybag (B1S3) increased the total N-soil and N-bacteria population, as well as the plant growth rates. Therefore, the biogas sludge contained a population of beneficial bacteria, such as the nitrogen fixers and phosphate solubilizers, which increased the total N and P-available acid soils (ultisol), as well as supported the growth and production of upland rice plants.

Permasalahan yang ditimbulkan saat pengolahan CPO pada perkebunan kelapa sawit menghasilkan limbah cair atau Palm Oil Mill Effluent (POME) dan dampaknya sangat berbahaya pada lingkungan. Pengelolaan POME dapat dilakukan dengan pengolahan secara anaerobik dalam memproduksi biogas, namun terdapat sludge biogas yang belum dimanfaatkan dengan baik. Tingginya keanekaragaman populasi mikroba dari sludge biogas yang mendukung kesuburan tanah maupun produktivitas tanaman. Oleh karena itu diperlukan beberapa penelitian karakteristik sludge biogas sampai diaplikasikan ke lapangan untuk membantu perusahaan kelapa sawit dalam mengelola sisa limbah dari pengolahan POME secara anaerobik. Penelitian disertasi ini terdiri dari 2 tahap, yang diawali dengan pra-penelitian dengan tujuan untuk memperoleh beberapa karakteristik kimia dan jumlah populasi bakteri yang menguntungkan dari sludge biogas limbah cair kelapa sawit yang dapat digunakan sebagai sumber isolat. Penelitian ini dilaksanakan dengan mengambil sampel sludge biogas dari tangki anaerob biogas pabrik kelapa sawit di Kabupaten Labuhanbatu Selatan, Sumatera Utara kemudian dianalisis karakteristik kimia dan jumlah populasi bakteri menguntungkan (penambat nitrogen dan pelarut fosfat) pada Januari-Februari 2020. Penelitian ini menggunakan metode deksriptif analitik. Hasil menunjukkan bahwa sludge biogas dari tangki anaerob biogas pabrik kelapa sawit memiliki pH 7,41 (memenuhi standar mutu), BOD dan COD lebih rendah dibandingkan dari limbah cair kelapa sawit. Diperoleh jumlah populasi bakteri penambat nitrogen lebih banyak dibandingkan populasi bakteri pelarut fosfat. Hasil ini menjadi dasar bahwa populasi bakteri dari sludge biogas berpotensi untuk pengujian karakteristik morfologi, aktivitas biokimia dan uji potensi serta identifikasi jenis isolat bakteri unggul. Penelitian Tahap Pertama dengan tujuan (1) memperoleh karakteristik isolat bakteri unggul dari sludge biogas yang potensial meningkatkan N-total, melarutkan P dan meningkatkan P-tersedia, (2) mengidentifikasi isolat bakteri unggul dari sludge biogas secara molekuler. Penelitian ini dilakukan di Laboratorium Biologi Tanah, Fakultas Pertanian, Universitas Sumatera Utara menggunakan Rancangan Acak Lengkap (RAL) dengan 3 ulangan. Penelitian ini diawali dengan isolasi, seleksi, dan uji potensi, serta identifikasi isolat bakteri penambat nitrogen dan pelarut fosfat, uji sinergisme, pengukuran asam organik dan identifikasi secara molekuler. Penelitian ini dilakukan pada Maret sampai Agustus 2020. Hasil karakteristik morfologi isolat bakteri penambat nitrogen pada sludge biogas dominan memiliki elevasi datar, tepian licin, warna putih susu, gram negatif, sel bulat serta positif pada uji motilitas, sitrat, dan katalase, sedangkan isolat bakteri pelarut fosfat dominan memiliki elevasi datar, tepian licin, warna putih susu, gram negatif, sel batang serta positif pada uji katalase. Uji potensi menunjukkan bahwa isolat bakteri penambat nitrogen (N3) memiliki aktivitas nitrogenase dan dapat meningkatkan N-total tanah ultisol tertinggi masing-masing sebesar 2,2 nmol/jam dan 62,56%. Isolat bakteri pelarut fosfat (P7) dapat meningkatkan kadar P-tersedia tanah ultisol tertinggi sebesar 36,21% dibandingkan kontrol dan memiliki asam-asam organik tertinggi secara berurutan yaitu asam laktat, asam oksalat, asam asetat, dan asam sitrat. Indeks dan efisiensi pelarutan fosfat tertinggi terdapat pada isolat bakteri pelarut fosfat P1 (IPF sedang). Isolat P7 memiliki kemampuan melarutkan P tertinggi dari sumber calsium triphosphate dan batu fosfat (4,62 dan 2,66 kali), sedangkan isolat P1 memiliki kemampuan melarutkan P tertinggi dari sumber aluminium fosfat (1,42 kali) dibandingkan kontrol. Isolat bakteri penambat nitrogen (N3) dan bakteri pelarut fosfat (P7) dari sludge biogas memiliki kekerabatan masing-masing dengan Bacillus paramycoides dan Bacillus cereus. Penelitian Tahap Kedua dengan tujuan mendapatkan pengaruh isolat bakteri unggul, sludge biogas, dan interaksinya terhadap pertumbuhan dan produksi padi gogo pada tanah ultisol. Penelitian ini dilakukan di lahan petani Jl. Ikahi, Kecamatan Medan Selayang, Kota Medan, pada Oktober 2020-Maret 2021. Penelitian ini menggunakan Rancangan Acak Kelompok dengan dua faktor pada 3 ulangan. Faktor I yaitu penggunaan jenis isolat bakteri unggul dosis 10 ml/polybag (B0= tanpa isolat, B1= isolat bakteri penambat nitrogen N3, B2= isolat bakteri pelarut fosfat P7, B3= kombinasi isolat N3+P7). Faktor II yaitu dosis sludge biogas (S0= kontrol, S1= 157,5 ml/polybag, S2= 315 ml/polybag, S3= 630 ml/polybag). Parameter penelitian ini dianalisis dengan sidik ragam dan dilanjutkan DMRT pada taraf 5%. Hasil menunjukkan bahwa isolat bakteri unggul (B1-B3) dapat meningkatkan bobot kering tajuk, N-total dan P-tersedia tanah, serapan N, total populasi bakteri pelarut fosfat dan penambat nitrogen, laju pertumbuhan tanaman, dan semua karakter produksi tanaman padi gogo. Sludge biogas dosis 315-630 ml/polybag dapat meningkatkan tinggi tanaman, jumlah anakan, bobot basah akar dan tajuk, volume akar, bobot kering akar dan tajuk, serapan N dan P, total populasi bakteri penambat nitrogen, laju pertumbuhan tanaman, dan jumlah malai tanaman padi gogo. Interaksi isolat bakteri penambat nitrogen dengan sludge biogas dosis 630 ml/polybag (B1S3) dapat meningkatkan N-total tanah, total populasi bakteri penambat nitrogen, dan laju pertumbuhan tanaman. Berdasarkan tahapan penelitian yang telah dilakukan dapat disimpulkan bahwa sludge biogas terdapat populasi bakteri yang menguntungkan seperti bakteri penambat nitrogen dan pelarut fosfat yang dapat meningkatkan N-total dan Ptersedia tanah masam (ultisol) serta mendukung pertumbuhan dan produksi tanaman padi gogo.