The Effect of Biomass-Water Ratio on Bio-crude Oil Production from Botryococcus braunii using Hydrothermal Liquefaction Process

Abstract

The increasing demand of energy in Indonesia has led to the urgency to conduct research and development in renewable energy. Biomass is one of the largest renewable energy sources in Indonesia. For biomass to energy conversion, hydrothermal liquefaction (HTL) has been considered as one of the potential methods where biomass is processed using subcritical water to produce bio-oil, aqueous phase, gas, and solid product. In this research, the effect of biomass-water ratio on hydrothermal liquefaction (HTL) process of microalgae Botryococcus braunii has been investigated. The HTL was conducted using biomass/water ratio 1:10, 1:20 and 1:30 with various holding time for each ratio. The product was bio-crude oil with similar characteristics to crude oil. Experimental results showed that biomass-water ratio affected the distribution of bio-crude oil yields. For biomass-water ratio of 1:10 and 1:20, it was found that bio-crude oil yields reached a maximum at 20 minutes, while the highest bio-crude oil yield of 4% was obtained at biomass-water ratio of 1:10. On the other hand, with biomass-water ratio of 1:30, bio-crude oil yield was continuously increasing with holding time until it reached the maximum yield of 4% at 40 minutes of holding time. The aforementioned results indicated that the highest bio-crude oil yield was obtained using biomass-water ratio 1:10 and 20 minutes of HTL processing time. A B S T R A KPeruraian anaerobik merupakan salah satu bidang riset yang sangat menarik perhatian dalam era krisis energi. Biogas tidak hanya menyediakan energi alternatif, tetapi juga dapat mencegah pencemaran akibat limbah organik. Limbah lemak susu adalah substrat yang potensial untuk proses peruraian anaerobik karena memiliki potensi biogas teoritis yang tinggi akibat kandungan lemaknya yang tinggi. Namun, peruraian anaerobik dari limbah organik dengan kandungan lemak yang tinggi memiliki tantangan tersendiri. Hambatan utama dalam peruraian anaerobik dari limbah lemak susu adalah kecenderungan untuk membentuk lapisan padatan yang tidak larut dan mengapung di bagian atas fase cair. Fenomena ini menghambat akses bakteri hidrolisis terhadap substrat. Saponifikasi adalah salah satu cara untuk meningkatkan kelarutan lapisan padatan tersebut, sehingga meningkatkan ketersediaan substrat untuk bakteri. Saponifikasi akan mengubah kandungan lemak menjadi sabun yang memiliki gugus fungsi polar maupun non-polar. Gugus fungsi yang bersifat polar akan meningkatkan kelarutan substrat dalam air. Studi ini mengevaluasi pengaruh dari berbagai dosis larutan basa yang ditambahkan sebagai reaktan selama perlakuan awal saponifikasi terhadap peruraian anaerobik limbah lemak susu. Kinetika proses peruraian anaerobik dianalisis dengan menggunakan model matematika. Variasi dosis yang diamati pengaruhnya untuk perlakuan awal saponifikasi adalah 0,04 mol basa/g sCOD; 0,02 mol basa/g sCOD; dan nol (tanpa perlakuan awal saponifikasi). Dari penelitian ini, terbukti bahwa saponifikasi berhasil meningkatkan kelarutan limbah lemak susu dan juga ditunjukkan oleh nilai konstanta hidrolisis (kH) 0,00782/hari lebih tinggi dua puluh kali lipat dibandingkan dengan nilai kH 0,00032/hari pada reaktor tanpa saponifikasi. Akan tetapi, penelitian ini juga mengindikasikan bahwa bakteri asidogenik bawaan substrat terhambat kinerjanya oleh paparan pH yang tinggi selama perlakuan awal saponifikasi berlangsung sehingga hasil gas metan yang diperoleh lebih rendah daripada reaktor kontrol.

Production of Bio-Crude Oil from Microalgae <i>Chlorella </i>sp<i>.</i> Using Hydrothermal Liquefaction Process

“…It was observed that alcohol was the main constituent of the bio-crude oil. The other results conducted by Adhisatrio & Pradana [8] and Prasakti [9] showed hydrocarbon as dominant functional group. However, the alcohol content was still in medium-high value.…”

Application of Analytic Hierarchy Process in the Selection of Botryococcus braunii Cultivation Technology for Bio-crude Oil Production

“…The yield of bio-crude oil from the HTL process on the microalgae biomass of B. braunii from previous results varied from 4.04 wt% [2] to 58 wt% [27,28] and 68 wt% [29]. This study used a yield value of 58 wt% to calculate the produced bio-crude oil, however, it was reported that the high heating value in the bio-crude oil was 48 MJ/k [27,28].…”

“…Bio-crude oil is the application of biofuel as alternative energy and is a blackish compound containing various hydrocarbons similar to petroleum-based on its straightchain hydrocarbon content [2]. In its production, processes such as cleaning, hydrotreating, and hydrocracking are required to remove oxygen and heavy compounds to produce a drop in biofuel [3,4].…”

Catalytic Hydrothermal Liquefaction of Brachychiton populneus Biomass for the Production of High-Value Bio-Crude

“…Among them, hydrothermal liquefaction (HTL) is one of the most effective technologies, able to efficiently convert several biomass types, such as rice straw [2], peanut shell [3], oak wood [4] sugar beet pulp [5] and microalga [6,7], into more valuable liquid bio-crude. Furthermore, the process is carried out at a medium temperature (250-400 • C) and under high pressure (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), using water as a solvent [8]. The influence of several process variables, such as temperature [9], residence time [10], catalyst activity [11] and water-biomass ratio [12], on the product yields has been widely investigated in literature in order to find the optimal conditions.…”

“…Furthermore, the process is carried out at a medium temperature (250-400 • C) and under high pressure (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), using water as a solvent [8]. The influence of several process variables, such as temperature [9], residence time [10], catalyst activity [11] and water-biomass ratio [12], on the product yields has been widely investigated in literature in order to find the optimal conditions. Generally, during HTL, wet biomass reacts with water, producing numerous compounds that are mainly distributed into four phases: a liquid bio-crude, an aqueous phase rich in organic soluble compounds, a gas phase and a solid residue.…”