PENGENDALIAN PELEPASAN NITROGEN DENGAN COATING ZEOLITE PADA CONTROLLED-RELEASE FERTILIZER (CRF) DARI SLUDGE BIODIGESTER

Henry Jonathan, Wiratni, S.T., M.T., Ph.D.; Himawan Tri Bayu Murti Petrus, D.Eng.

2014 | Tesis | S2 Teknik Kimia

Kebutuhan pupuk semakin meningkat, tetapi efisiensi penyerapan nutriennya tergolong rendah, termasuk nitrogen. Controlled-Release Fertilizer (CRF) digunakan sebagai metode untuk mengontrol pelepasan nitrogen total dari pupuk organik granul. CRF terdiri dari inti, yang terbuat dari 2 jenis biodigester sludge, yaitu fiine dan bulk sludge (FS dan BS), dan coating yang terbuat dari zeolite dan sludge dengan 4 variasi komposisi massa (10:0, 9:1, 8:2, 7:3). Uji lepas nitrogen total dilakukan dengan menempatkan pupuk CRF dalam sebuah pot berisi tanah dan disiram setiap hari dengan 50 mL air. Leachate yang tertampung dianalisis kadar nitrogen totalnya dengan metode spektrofotometri dan kadar nitrogen awal dalam CRF dianalisis dengan metode N-Kjedahl. Hasil yang didapat menunjukkan variasi fine sludge (FS) 9:1 memberikan nilai pelepasan nitrogen terkecil yaitu 1,527%. Berdasarkan nilai difusivitas di core (D1) dan di coating (D2) menunjukkan nilai D1 lebih besar dari nilai D2 untuk seluruh variasi CRF, yang berarti proses difusi keseluruhan diatur oleh proses difusi dalam coating. Semakin kecil nilai D2 maka pelepasan nitrogen akan semakin kecil, seperti pada FS 9:1. Hasil penelitian juga menunjukkan bahwa tidak ada pengaruh dari perbedaan jenis sludge yang digunakan sebagai inti terhadap nilai difusivitas nitrogen dalam inti, dengan nilai D1 berkisar antara 3,4 x10-8 cm2/s sampai 4,2x10- 8 cm2/s. Untuk nilai D2, berkisar antara 9,64x10-9 cm2/s sampai 3,01x10-8 cm2/s dengan nilai untuk FS lebih kecil dari BS untuk setiap variasi, memperlihatkan hubungan antara jenis sludge dengan nilai difusivitas yang didapat. Dalam simulasi selama 900 hari untuk pelepasan nitrogen dengan nilai difusivitas terhitung, CRF FS bertahan sampai 600 hari sebelum habis kandungan nitrogennya, sedangkan CRF BS dan urea bertahan sampai 400 dan 100 hari. CRF ini dapat meningkatkan performa urea tentang ketahanan nitrogen dalam granul.

Nowadays, fertilizer need is increasing across the world, but the nutrient use efficiency is still in low grade. Controlled-Release Fertilizer (CRF) was used as a method to control total nitrogen release from organic granular fertilizer. CRF is composed by a core made from 2 (two) kinds of biodigester sludge, which are fine(FS) and bulk sludge(BS), and a coating made from a mixture of zeolite and sludge with 4 (four) variations of mass composition (10:0, 9:1, 8:2, 7:3). Total nitrogen release test was conducted by putting CRF in a pot containing soil and was poured daily by 50 mL of water. Leachate from each pot was analyzed with spectrophotometry methode, meanwhile the initial mass percent of nitrogen was analyzed by N-Kjedahl methode. The results showed that FS 9:1 gave the smallest percent of nitrogen release from the CRF, which was 1.527%. Based on the value of the difusivity in core (D1) and in coating (D2), the value of D1 was bigger than D2 for all the variation of CRF, which meant the overall difusion process in the CRF was controlled by the difusion process in the coating. The smaller value of D2, the smaller mass percent of nitrogen release, as seen in FS 9:1. The results also showed that there was no relation between the kind of sludge with the difusivity in the core (D1), the value of D1 was ranged between 3.4 x10-8 cm2/s to 4.2x10-8 cm2/s. For the difusivity in coating (D2), the value ranged from 9.64x10-9 cm2/s to 3.01x10-8 cm2/s, and the diffusivity mean value for CRF FS is lower than CRF BS for all variation. These values means that there is a relation between sludge size with the value of diffusivity in coating. In a 900 days simulation for nitrogen release using the calculated diffusivity, it is shown that CRF FS have a nitrogen storability around 600 days before depleting. CRF BS and urea can keep the nitrogen around 400 and 100 days, respectively. It is shown that CRF can increase the urea performance regarding nitrogen release and storabilty.

Kata Kunci : CRF, coating, difusivitas