BioEnergy Research

Hydrolysis can be considered as the bottleneck for biofuel production from microalgae due to the recalcitrance of this type of biomass. Thermochemical pretreatment is an effective and widely used process to solubilize different types of biomass. Nevertheless, the variability of the cell wall composition, among different microalgae species, hinders the development of a suitable pretreatment. In this work, the most relevant factors for thermochemical pretreatment to solubilize organic matter from microalgal biomass (Scenedesmus obtusiusculus) were analyzed and identified. The aim was to obtain hydrolysates, rich in soluble organic matter, that allow attaining higher hydrogen and methane yields than with raw microalgae, using a factorial design to identify the significant factors of the thermochemical pretreatment. The results showed that temperature (100 °C) and HCl concentration (3%) were the most significant factors to achieve carbohydrates solubilization close to 100%. Further, reaction time (1.7 h) and biomass concentration (30 g total solids/L) were also important to achieve up to 60% chemical oxygen demand (COD) solubilization. Overall, the microalgal hydrolysates produced 48 NmL H2/g VS and 296 NmL CH4/g VS, which is 1.7- and 1.3-fold higher hydrogen and methane yields, respectively, than raw microalgae. These results are meaningful because high soluble carbohydrates and COD would allow the application of high organic loading rates in continuous reactors for biofuel production using renewable biomass such as microalgae.

The present study is to understand the impact of process conditions on the quality attributes of wheat oat, barley, and canola straw briquettes. Analysis of variance indicated that briquette moisture content and initial density immediately after compaction and final density after 2 weeks of storage are strong functions of feedstock moisture content and compression pressure, whereas durability rating is influenced by die temperature and feedstock moisture content. Briquettes produced at a low feedstock moisture content of 9 % (w.b.) yielded maximum densities >700 kg/m3 for wheat, oat, canola, and barley straws. Lower feedstock moisture content of <10 % (w.b.) and higher die temperatures >110 °C and compression pressure >10 MPa minimized the briquette moisture content and maximized densities and durability rating based on surface plots observations. Optimal process conditions indicated that a low feedstock moisture content of about 9 % (w.b.), high die temperature of 120–130 °C, medium-to-large hammer mill screen sizes of about 24 to 31.75 mm, and low to high compression pressures of 7.5 to 12.5 MPa minimized briquette moisture content to <8 % (w.b.) and maximized density to >700 kg/m3. Durability rating >90 % is achievable at higher die temperatures of >123 °C, lower to medium feedstock moisture contents of 9 to 12 % (w.b.), low to high compression pressures of 7.5 to 12.5 MPa, and large hammer mill screen size of 31.75 mm, except for canola where a lower compression pressure of 7.5 to 8.5 MPa and a smaller hammer mill screen size of 19 mm for oat maximized the durability rating values.

Self-sufficiency in energy requirement is critical to the success of any developing economy. Apart from the search for alternatives, there is a need to achieve energy independence, directing much focus on biofuels. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. Oil was extracted from the seeds of Blighia unijugata and Luffa cylindrica, subjected to chemical characterization and biodiesel production. The oil yield from the seed of B. unijugata was 50.82 ± 1.20% while that of L. cylindrica was 39.10 ± 0.20%. The biodiesel produced had ester content above 98%. The flash point of the biodiesel from B. unijugata and L. cylindrica was above 120°C while the phosphorus content was also below 1 ppm in both cases. The oxidative stability of B. unijugata was 44.30 ± 0.30 h, while that of L. cylindrica was lower than this value due to its high unsaturation. The copper strip corrosion value of the biodiesel was also found to be 1A. This study showed that the high free fatty acid content of B. unijugata and L. cylindrica seed oil can be reduced in a one-step pretreatment of esterification reaction using H2SO4 as catalyst thus reducing the problem of soap formation encountered when using oil with high free fatty acid for the production of biodiesel.

The original version of this article unfortunately contained incorrect data in Fig. 2 caption.

Powdered activated carbon-treated lignocellulosic syrup prepared from energy cane bagasse was evaluated as a potential feedstock in the production of fumaric acid by Rhizopus oryzae ATCC® 20344™. Energy cane bagasse was pretreated with dilute ammonia and enzymatically hydrolyzed with commercially available enzymes, Cellic® CTec2 and HTec2. The collected hydrolysate samples were subjected to powdered activated carbon adsorption for the removal of non-sugar compounds (i.e., organic acids, furaldehydes, total phenolic compounds) and concentrated to a final 65°Bx syrup (mostly xylose and glucose sugars). The use of lignocellulosic syrup, the effect of nitrogen source, medium additives, and initial pH in the seed culture medium on fungal morphology were investigated. The carbon to nitrogen (C/N) ratio in the acid production medium was also optimized for maximum yields in fumaric acid production. Optimum seed culture medium conditions (2.0 g/L urea, 3.0 pH) produced the desired compact, smooth, and uniform fungal pellets. Optimum acid production medium conditions (400 C/N ratio, 0.2 g/L urea) resulted in a fumaric acid production of 34.20 g/L, with a yield of 0.43 g/g and a productivity of 0.24 g/L/h. These results were comparable to those observed with the control medium (pure glucose and xylose). The present study demonstrated that lignocellulosic syrup processed from dilute ammonia pretreated energy cane bagasse has potential as a renewable carbon source for fumaric acid fermentation by Rhizopus oryzae ATCC® 20344™.

An auto-controlled climate system was used to study how a boreal bioenergy crop (reed canary grass, Phalaris arundinacea L., hereafter RCG) responded to a warming climate and elevated CO2. Over one growing season (April–September of 2009), RCG from young and old cultivations (3 years [3-year] and 10 years [10-year]) was grown in closed chambers under ambient conditions (CON), elevated CO2 (EC, approximately 700 μmol mol−1), elevated temperature (ET, ambient + approximately 3 °C) and elevated temperature and CO2 (ETC). The treatments were replicated four times. Throughout the growing season, the above-ground (leaf and stem biomass) and below-ground biomasses were measured six times, representing various developmental stages (early stages: the first three stages, and late stages: the last three stages). Compared to the growth observed under CON, EC enhanced RCG biomass growth over the whole growing season (p < 0.05), whereas ET increased RCG biomass growth in early stages but decreased growth in late stages, regardless of the cultivation age. However, the negative effect of ET later in the growing season was partially mitigated by CO2 enrichment. Compared to CON plants, the final total biomass was 18 % higher for 3-year plants and 8 % higher for 10-year plants grown under EC. In comparison, for 3-year and 10-year plants, the biomass was 5 and 3 % lower under ET and 7 and 4 % greater under ETC, respectively. Under EC, the below-ground growth contributed more to the total biomass growth compared to the above-ground portion. The opposite situation was observed under ET and ETC. The climate-related changes in biomass growth were smaller in the old cultivation than in the young cultivation due to the lower net assimilation rate and lower specific leaf area in the old cultivation plants.

Bài báo này báo cáo một phân tích dấu chân carbon trong việc sản xuất điện sinh học từ phân bò thu được từ các hệ thống chăn nuôi tập trung ở khu vực Trung Tây Brasil. Các phân tích được thực hiện bằng cách áp dụng hai kịch bản nguồn năng lượng khác nhau: Sc1—sử dụng năng lượng bên ngoài trong một nhà máy tiêu hóa kị khí (AD); và Sc2—tuần hoàn một phần năng lượng được tạo ra trong một nhà máy đồng phát điện (CHP), với hai phương pháp tiếp cận (phân bổ và mở rộng hệ thống) để chia sẻ tác động giữa các sản phẩm và đồng sản phẩm thu được trong chu trình. Ngoài ra, việc sản xuất điện từ phân đã được so sánh với việc sản xuất từ khí tự nhiên (hệ thống tham chiếu). Các emisi khí nhà kính (GHG) đã được tính toán bằng cách sử dụng dữ liệu từ Hướng dẫn của Hội đồng Liên Chính phủ về Biến đổi Khí hậu và phần mềm SimaPro. Sc2 là kịch bản tốt nhất, vì tuần hoàn năng lượng từ hệ thống này làm giảm lượng khí thải từ nhà máy AD tới 83,61%. Cả hai kịch bản với mở rộng hệ thống đều trình bày lượng khí thải ≈4,5 lần lớn hơn so với khi áp dụng phân bổ, vì phân bổ phân chia lượng khí thải giữa các sản phẩm thu được, loại bỏ trách nhiệm của chuỗi sản xuất đối với các đồng sản phẩm được tạo ra. Quản lý phân bò chịu trách nhiệm cho hơn 65% lượng khí thải trong cả hai kịch bản, khiến lượng khí thải trong cả hai kịch bản cao hơn so với hệ thống tham chiếu. Cần cải thiện logistics phân phối các sản phẩm của nhà máy AD-CHP ở khu vực Trung Tây, vì việc sản xuất năng lượng sinh học có thể giảm thiểu khí thải GHG từ hoạt động chăn nuôi bằng cách chuyển đổi chi phí chất thải từ phân thành lợi nhuận, và sản xuất các sản phẩm có giá trị năng lượng và thị trường, nhằm làm cho quy trình hiệu quả và thân thiện với môi trường hơn.

Rice husk is a prospective bio-oil feedstock due to its plentiful supply, but its unfavorable characteristics like high moisture content, high ash content, and low energy density tend to jeopardize both the yield and quality of bio-oil produced by fast pyrolysis. Lately, various pretreatments, namely, washing, torrefaction (dry and wet), and their combined pretreatments, have been researched on rice husk with the aim of improving its unfavorable characteristics for bio-oil production. However, the influences of different pretreatments on pretreated rice husk and the subsequent bio-oil produced have not been compared. Hence, this review paper presents an overview of rice husk as a bio-oil feedstock and its pretreatment methods for bio-oil production via fast pyrolysis. Particular emphasis is placed on the rice husk characteristics and their impacts on the bio-oil production via fast pyrolysis, as well as the different types of rice husk pretreatment and their influences on the characteristics of pretreated rice husk, product yields of fast pyrolysis, and the composition and physical properties of the bio-oil produced. A comparison of the physicochemical properties of rice husk- and other biomass-based bio-oil alongside those of petroleum fuel oil is also outlined. Major challenges and future prospects towards the utilization of rice husk as a bio-oil feedstock and the integration of rice husk pretreatment with fast pyrolysis for large-scale applications are also discussed.