Biomass Conversion and Biorefinery

Chromium metal ion (Cr(VI)) is a highly mobile species which pollutes the entire biosphere originating from the discharge of point and nonpoint sources. Carcinogenic and mutagenic Cr(VI) is then remediated by adsorption process using a carbonaceous material. Biochars are biomass derived carbonaceous materials which effectively holds water in its micro pores there by facilitating the multiplication of microbial population with wide range of applications. Biochars are employed as adsorbent materials for contaminant removal. In the present work experiments were conducted to investigate the Cr(VI) removal efficiency of corn husk biochar (CHB) from aqueous synthetic K2Cr2O7 solution. However, the discharge of Cr(VI) loaded CHB in environment once again creates challenges in the form of nonpoint source pollution. Hence, it was further planned to add the Cr(VI) adsorbed CHB to soil which might renders the mixture as fuel in soil microbial fuel cell (SMFC) for power generation with Cr(VI) degradation. SMFC is a device which generates electrical power using soil as fuel in presence of pollutant. Soil microbes serve as catalyst, mediators, degraders, and exoelectrogens in SMFC. CHB was prepared by the method of slow pyrolysis at 450 °C. The prepared biochar’s physicochemical properties and water holding capacity (WHC) measurements were done using standard protocols. CHB was then subjected as adsorbent material for Cr(VI) adsorption. The mode of adsorption was characterized by standard isotherm modeling, FTIR, SEM with EDS, and XRD studies. The propagation of secondary pollution after adsorption experimentation is prevented by mixing Cr(VI) loaded CHB with soil and utilized as fuel in SMFC. The study concluded that CHB belonged to class I biochar possessing alkaline nature. Nine percent addition of CHB to soil holds double the amount of water as compared to blank soil benefitting microbes. Cr(VI) was adsorbed onto CHB surface physically and had justification from FTIR, SEM with EDS, and XRD studies. The discharge of Cr(VI) loaded CHB in SMFC generated potential of 320 mV steadily for eight number of days. Thus, the present study explored CHB as adsorbent material for Cr(VI). CHB also possessed the character of holding water effectively in soil facilitating microbial population. Both the properties were thus coined into single roof as fuel in SMFC which delivered power from pollutant and aids in finding a viable solution for the control of primary and secondary pollution.

This research presents an approach for using waste cooking oil as a substrate for the production of polyhydroxyalkanoate (PHA) by Bacillus thermoamylovorans. In addition, PHA was utilised as a feedstock for a biofuel, namely 3-hydroxyalkanoate methyl ester (3HAME). The largest amount of biomass (4.0 ± 0.1 g/L) and the greatest production of PHA [3.5 ± 0.1 g/L, corresponding to 87.5% of cell dry mass (CDM)] were obtained under optimal conditions, with 4% (w/v) waste cooking oil (WCO) used as a carbon source at 45 °C and 150 rpm for 48 h under batch cultivation. The isolated polymer was identified as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] with 85 mol% of 3-hydroxybutyrate (3HB) and 15 mol% of 3-hydroxyvalerate (3HV) using gas chromatography–mass spectrometry (GC–MS). Notably, the properties of the copolymer were similar to the properties of the commercial P(3HB-co-3HV). Moreover, P(3HB-co-3HV) was used as a feedstock for the biofuel. P(3HB-co-3HV) methyl ester, a biofuel, was obtained under optimal conditions, with methanol and 15% (v/v) H2SO4 under a reaction temperature of 65 °C and time of 60 h. The highest yield of 3HAME that was obtained was 74.4%, with 97% methyl ester content. Almost all of the properties of 3HAME pass ASTM and Thailand’s fuel standards.

Through increased interest in the use of macroalgae for biofuel production, the concept of a biorefinery approach has been developed to improve its economic viability. This paper looks at the use of seaweed residue after enzymatic saccharification of the seaweeds Saccharina latissima, Alaria esculenta and Ulva lactuca as a novel feed component for the aquaculture industry. Chemical composition analysis was used to evaluate the impact of enzymatic treatment on the nutritional aspect of seaweed residue. During saccharification, the relative ash and carbohydrate content was reduced, but total nitrogen, total carbon and lipid content increased in all three species. In addition, the saccharification of S. latissima and A. esculenta resulted in the elimination of polyphenols, further enhancing the nutritional value of the residue. The residue supported the survival and growth of bivalve spat and commercially valuable sea urchins over the course of 3-week preliminary trials.

Chicory (Cichorium intybus var. foliosum) roots are an agricultural residue and a low cost feedstock for the production of the platform chemical 5-Hxdroxymethylfurfural (HMF). In a first step, inulin and fructose have to be extracted from the roots. The resulting aqueous extract represents the starting material for the HMF production. In the reaction to HMF, inulin has to be hydrolyzed first to fructose. For this reason, two methods to increase the fructose content in these extracts before the reaction were investigated. This was conducted within the framework of integrating acid hydrolysis into a biorefinery process for HMF production. The first method (one-step process) was acid-assisted extraction to directly hydrolyze inulin in the course of the extraction process. Chicory roots were extracted at 60 and 80 °C at pH 2 and 4 using buffer solutions. The second approach (two-step process) was aqueous extraction at neutral pH followed by nitric acid hydrolysis of the extract at 60 and 80 °C under reduced pH. It was found that in the first approach, the pH of 2 led to a fivefold increase in the fructose content of the extract, resulting from inulin hydrolysis and corresponding to 56% of theoretical fructose yield. For the second approach, it was possible to achieve complete hydrolysis at pH below 2.5 and at 80 °C. Separating extraction and hydrolysis was found to be more suitable in terms of including this process step into a biorefinery concept for HMF production. It was possible to reduce the initial inulin content by 95%.

One of the effective methods of processing lignocellulosic biomass is pyrolysis, which allows processing it into the liquid product, regardless of the composition of the feedstock. The liquid product obtained as a result of fast pyrolysis (bio-oil) is gaining popularity worldwide as replacing fossil fuels. In the process of processing pyrolysis condensates for fuel and chemical products, wastewater (wood vinegar) is formed, containing organic acids, furans, and phenols. In a large-scale forest chemical production, this waste is formed in large quantities, and its storage or incineration is extremely expensive. Discharge into centralized sewer systems of this drain is impossible due to its high toxicity and mutagenic effect. In this regard, the purpose of this study is to use a set of methods for cleaning WW for further discharge into centralized sewer systems. On the basis of the analysis carried out, a set of methods was proposed as the main methods for the purification of wood pyrolysis by means of sequential purification stages in the form of adsorption with biochar, oxidation with ozone and hydrogen peroxide, and ultrafiltration of the effluent. A high efficiency of 94% in the course of preliminary tests was achieved by the oxidation method under the conditions of the Fenton reaction due to its greater compliance with the conditions relative to other methods, the acidic environment, and the presence of oxidizing substances in the treated wastewater.

Environmental pollution and the depletion of fossil fuels have created a growing interest in the world community for renewable energy. Large-scale production of liquid biofuels is supported by governments. Iran is a developing country that supplies its energy needs from fossil fuels. However, clean energy must be used to prevent environmental pollution and ensure food security. In this study, with a case study of Golestan province as one of the leading provinces in the field of agriculture, the existing capacities in this country have been studied. The results showed that 58,945.95 tons of biodiesel and 527.55 million liters of bioethanol can be produced annually in this province. By creating suitable grounds for the production of this fuel, solving technological problems and the support of the people and the government of this province, it is able to supply 2% of the fuel of the country’s gasoline engines. Also, the produced biodiesel can supply approximately 13% of the province’s diesel. Reports indicate that it has the largest share in the production of liquid biofuels in the agricultural waste sector.

In order to enhance the adsorption capacity of activated carbon (AC) from cocoa pod husk (CPH) and reuse the solution after the acid-leaching of CPH as a liquid fertilizer, CPH was first leached by acid and then used as a precursor (CPH-A) for preparing ACs by physical activation at a temperature range of 650–850 °C in this work. Based on the proximate analysis, mineral compositions, thermogravimetric analysis, and thermochemical properties, the differences between CPH and CPH-A were investigated. The chemical and pore properties of the resulting ACs were further studied. The results show that the pretreatment of CPH with hydrochloric acid led to removal of over 90% of the ash content in the CPH, mainly composed of potassium minerals. The Brunauer-Emmet-Teller (BET) surface area of the AC derived from CPH-A at 650 °C is 355.8 m2/g, significantly larger than that (i.e., 1.1 m2/g) of the AC derived from CPH. The higher activation temperature (e.g., 900 °C) is beneficial to the pore development of the resulting AC (e.g., BET surface area ˃ 1300 m2/g). In addition, the carbon (C) and sulfur (S) contents of the resulting ACs indicate an increasing trend as the temperature increased from 650 to 850 °C, but a decreasing trend in the hydrogen (H), nitrogen (N), and oxygen (O) contents.

Pearl millet bran is an underutilized by-product of millet with great potential in the food processing industries due to its dietary profile. The dietary fiber extraction from pearl millet bran could be valued approach for utilization of waste with commercial feasibility at the industrial scale. To overcome the disadvantages of conventional techniques, green techniques like ultrasonication might be effective in terms of shorter duration of time and less consumption of solvent, increasing the extraction yield of dietary fiber. In present study, comparative analysis of different green techniques (enzyme-assisted extraction, ultrasound-assisted extraction, microwave-assisted extraction, ultrasound-assisted enzyme extraction, and microwave-assisted enzyme extraction) for extraction of dietary fiber concentrate from pearl millet bran was investigated and microstructural and functional properties using ultrasound-assisted enzymatic extraction were studied. The ultrasound treatment combined with enzymatic extraction at amplitude (35%), temperature (50 °C) and liquid to solid ratio (40:1) after treatment time (10 min) resulted the highest extraction yield (78.8 %, w/w) of total dietary fiber obtained from pearl millet bran. SEM images showed the significant effect of ultrasound-assisted enzymatic treatment on extracted dietary fiber. The dietary fiber from the pearl millet bran possesses good water holding capacity (4.04 g/g and 3.04 g/g) and oil holding capacity (5.33 g/g and 2.42 g/g). The results indicated that pearl millet bran contains a substantial amount of dietary fiber that could be utilized for the preparation of functional food products.