Biodegradasi anaerobik biomassa tanaman laut dan produksi biogas dalam digester skala mini-pilot

Abstract

Marine vegetation anaerobic biodegradation and biogas production in a mini-pilot digester

This paper describes the productivity of biogas from anaerobic biodegradation of macroalgae Ulva lactuca and Padina sp. Marine biomasses especially macroalgae contain less lignin, thus the anaerobic biodegradability of these biomasses was higher than terrestrial biomass. Banana stem waste was used as comparison for the feedstock. Initial inoculums were prepared from cow manure and water. The inoculums and substrates were fed into a mini-pilot digester, operating semi-continuously. Volume of biogas was measured daily while methane content was measured every 3 days using gas chromatograph. Biogas productivity from the mini-pilot digester for feedstock Padina sp., U. lactuca, and banana stem waste was 5.22, 4.88, and 3.06 L respectively, after 28 days operation, with methane content 64.85, 49.90, and 34.76 %-v/v, respectively. The study also shows that lignin content in Padina sp., U. lactuca, and banana stem waste were 5.12,  1.54, and 7.17 %-w respectively. In general, macroalgae have less lignin content and thus produce higher anaerobic biodegradability. The study shows that compounds in microalgae are more biodegradable and more hydrosoluble. Moreover, the experimental results also showed that gross heating value (HHV) of biogas from feedstock of Padina sp. was quite close to that of biogas from cow manure.

Keywords: Macroalgae, Ulva lactuca, Padina sp., biogas, HHV

Abstrak 

Biomassa tanaman laut, khususnya makroalga, memiliki kadar lignin rendah sehingga biodegradabilitas anaerobiknya  lebih tinggi dibandingkan tanaman darat. Dalam penelitian ini, biodegradabilitas anaerobik makroalga Ulva lactuca dan Padina sp. dari perairan Indonesia ditentukan berdasarkan produktivitas biogas, yang terutama diukur dari kadar metana yang dihasilkan. Peralatan berskala mini-pilot dirancang dan dirakit untuk mengukur perolehan biogas dari biomassa tanaman laut tersebut. Inokulum awal diperoleh dari campuran kotoran sapi dengan air. Biomassa basah dan air dicampur dan dihaluskan untuk memperoleh suspensi substrat. Inokulum dan suspensi substrat diumpankan ke dalam digester skala mini-pilot berkapasitas 5 L yang beroperasi secara semikontinu. Volume biogas diukur setiap hari sedangkan kadar metana diukur setiap 3 hari dengan kromatografi gas. Batang pisang digunakan sebagai biomassa pembanding. Produktivitas biogas yang dihasilkan dari Padina sp., U. lactuca, serta batang pisang berturut-turut yaitu 5,22, 4,88, dan 3,06 L, dengan kadar metana sebesar 64,85, 49,90, dan 34,76 %-v/v. Kadar lignin pada biomassa berturut-turut sebesar 5,12, 1,54, dan 7,17 %-b. Secara umum, makroalga memiliki kadar lignin relatif rendah sehingga biodegradabilitas anaerobiknya tinggi. Biodegradabilitas anaerobik paling tinggi dari Padina sp. juga disebabkan tingginya kadar senyawa yang dapat larut dalam air dan terhidrolisis.   Nilai kalor kasar (HHV) biogas Padina sp. mendekati biogas kotoran sapi.

Kata kunci: makroalga, Ulva lactuca, Padina sp., biogas, HHV