KINETIKA PEMBUATAN BIOGAS DARI SUBSTRAT KULIT KOPI DENGAN MIKROORGANISME KOTORAN SAPI DAN RUMEN

Sumber daya minyak dan gas alam dunia yang berasal dari energi fosil semakin berkurang. Sehingga pengembangan penelitian sumber energi alternatif semakin sering dilakukan, salah satunya adalah produksi biogas. Bahan baku alternatif yang potensial untuk menghasilkan gas metana adalah limbah kulit kopi. Kulit kopi dipilih karena merupakan limbah yang banyak dihasilkan dari proses pengolahan biji kopi. Kopi sendiri merupakan komuditas unggulan di Indonesia. Akan tetapi produksi metana dari limbah kulit kopi masih banyak mengalami kendala karena kandungan zat kimia beracun seperti tanin, kafein, dan polifenol yang dapat menghambat produksi biogas yang diinginkan. Oleh karena itu, dilakukan pretreatment dengan menggunakan kotoran luwak (Paradoxurus hermaphroditus) untuk menghilangkan zat kimia beracun tersebut. Penelitian ini bertujuan Mengetahui kinetika pembentukan biogas dari kulit kopi (dengan pretreatment dan tanpa pretreatment feses luwak) menggunakan tambahan kotoran sapi dan campuran cairan rumen + kotoran sapi, serta membandingkan kinetika pembentukan biogas dari substrat kulit kopi dan jerami padi. Beberapa fungsi dari perhitungan kinetika antara lain untuk mengetahui variabel mana yang laju pertumbuhannya lebih cepat, dapat digunakan untuk parameter perhitungan desain pada digester, dan untuk scale up dari digester skala laboratorium ke skala pilot plane. Tahap pertama dalam penelitian adalah persiapan alat dan bahan antara lain kulit kopi, kotoran luwak, cairan rumen dan kotoran sapi. Kemudian tahap kedua melakukan pretreatment terhadap kulit kopi menggunakan kotoran luwak. Tahap selanjutnya yaitu melakukan fermentasi anaerobik selama 40 hari dengan suhu mesofilik (30–40oC) dan pH dijaga 6,8-7,2 pada volume kerja reaktor sebesar 12 liter. Terdapat enam reaktor yang masing-masing berisi mikroorganisme cairan rumen (R), kotoran sapi (KS) dan campuran keduanya yang kemudian dibandingkan dengan hasil pretreatment. Kemudian membandingkan laju pembentukan biogas antara substrat kulit kopi dengan jerami padi. Adapun parameter yang diukur antara lain penurunan kandungan inhibitor, Chemical Oxygen Demand (COD), Total Solid (TS), Volatile Solid (VS), biogas (CH4, dan CO2) dan nilai kalor pembakaran (heating value). ================================================================================================== Resources of oil and natural gas which are derived from fossil energy are wane more and more. So the research development of alternative energy sources are increasingly being conducted, one of the research of alternative energy are the production of biogas. Potential alternative raw materials to produce methane gas is the waste of coffee skin. Skin (epicarp and mesocarp) coffee been a lot of waste that is produced from the processing of coffee beans. Coffee itself is an excellent commodity in Indonesia. However, methane production from waste of coffee skin is still much problems because of the content of toxic chemicals such as tannins, caffeine and polyphenols which can inhibit the production of biogas as desired. Therefore, doing pretreatment to remove toxic chemicals are either mechanically (size reduction), thermal (solar radiation) and biological mixed with the addition of rumen microorganisms, cow dung and feses of civet (Paradoxurus hermaphroditus). This study is purposed to knowing the kinetics of the formation of biogas from coffee skin (with and without pretreatment civet feces) additional uses cow dung and rumen fluid + cow dung, and to compare the kinetics of the formation of biogas from coffee skin and rice straw substrate. Some functions of calculation of the kinetics are to determine which variable rate will grows faster, it can be used for the calculation of the parameters on the digester’s design, and to scale up from laboratory scale to digester pilot plane scale. The first step in this research is the preparation of tools and materials include coffee skin, civet droppings, rumen fluid and cow dung. Then the second step is doing pretreatment for the coffee skin by using civet droppings The next step is, doing anaerobic fermentation for 40 days at mesophilic temperature (30-40oC) and the pH is maintained from 6.8 to 7.2 on a reactor working volume of 3.6 liters. There are six reactors which each contain different microorganisms, cow dung (KS) and a mixture of both (KS-CR) and then compared with the results of reactor which is using coffee skin pretreatment. Then comparing the rate of the formation of biogas between the substrate coffee skin with rice straw. The measured parameters include inhibitor compound decrease, Chemical Oxygen Demand (COD), Total Solid (TS), Volatile Solid (VS), and biogas (CH4, and CO2) This study results that pretreatment with a liquid civet droppings can reduce the inhibitor compound in the substrate of pretreatment coffee skin and produces methane concentrations higher than those without pretreatment in each reactor