• Energy Research

Pyrolysis-gas chromatographic mass spectrometry (Py-GC/MS) was used to determine the yield and chemical composition of the pyrolysis products of Schizochytrium limacinum. The pyrolysis was carried out by varying the temperature from 300 °C to 800 °C. It was found that the main decomposition temperature of Schizochytrium limacinum was 428.16 °C, at which up to 66.5% of the mass was lost. A further 18.7% mass loss then occurred in a relatively slow pace until 760.2 °C due to complete decomposition of the ash content of Schizochytrium limacinum. The pyrolysis of Schizochytrium limacinum at 700 °C produced the maximum yield (67.7%) of pyrolysis products compared to 61.2% at 400 °C. While pollutants released at 700 °C (12.3%) was much higher than that of 400 °C (2.1%). Higher temperature will lead to more pollutant (nitrogen compounds and PAHs) release, which is harmful to the environment. Considering the reasonably high yield and minimum release of pollutants, a lower pyrolysis temperature (400 °C) was found to be optimum for producing biofuel from Schizochytrium limacinum.

Anaerobic digestion wastewater (ADW), which contains large amount of nitrogen and phosphorus, particularly high concentration of ammonium, might lead to severely environmental pollution. A new unicellular green microalgae species from a wetland at the Olympic Forest Park, Beijing, China was screened based on its growth rates and nutrients removal capability under ADW. Results of 18s rDNA and ITS1 analysis indicated that this strain have a close relationship with Desmodesmus sp., named as EJ9-6. Desmodesmus sp. EJ9-6 could remove 100% NH4-N (68.691mg/L), TP (4.565mg/L) and PO4-P (4.053mg/L), and 75.50% TN (84.236mg/L) at 10.0% ADW, which the highest biomass production was 0.412g/L after 14d cultivation. Maximum nutrients removal was observed at 10.0% ADW with daily removal rates of TN, NH4-N, TP and PO4-P at 4.542, 5.284, 0.326 and 0.290mg/L/d, respectively.

The toxic emissions from coal combustion associated with domestic winter heating requirements are an important public health issue. Waste cooking oil (WCO) holds promise as a means of reducing pollutant emissions thereby improving human health with the co-benefit of decreasing climate-forcing gas emissions by avoiding the combustion of mineral coal. With an annual production of ~2.17 Mt of WCO in Northern China, it could be used to meet the winter heating demand of ~3.25 million rural households, offsetting ~9.83 Mt of raw coal consumption. Through the adoption of coal-to-WCO shift in rural regions of 15 provinces, approximately 15.0%, 15.6%, 15.9% and 13.7%, respectively of CO, PM2.5, SO2 and NOX emissions would be eliminated. It is estimated that such a change would remove the respective contributions of these pollutants to the premature deaths of respectively, 63,400, 29,300, 173,00 and 31,300 rural residents. Such a positive health impact on the labor cohort would reduce the loss of labor supply and work time, as well as producing billions of RMB in economic benefits. WCO-based heating technology has the same effect on the reduction of GWC100 value as other modern energy carriers while also being cheaper and sustainable, long term. Reducing household emissions by substituting raw coal with green energy is a vital strategy to support pathways for sustainable environment design. The results of this work for the coal-to-WCO shift can reinforce the support for coal phase-out in China.

The whole process of biofuel production from Desmodesmus sp. EJ 8-10 cultivated in anaerobic digested wastewater (ADW) under the optimal temperature was evaluated by using the method of Life Cycle Assessment (LCA). The energy efficiency and environment emissions were under considerable for the corresponding parametric study. The functional unit was 1 kg microalgae. It was concluded that the harvest stage was responsible for the main energy consumption during the microalgal whole pyrolysis process. The energy conversion efficiency of the whole process was larger than 1, which indicated that the process was profitable. The environmental impact of the whole process was 1165.67 mPET2000, among which the primary impact on the environment was eutrophication that accounts for 57.36%, followed by photochemical ozone synthesis (22.56%), acidification (17.36%); and global warming (2.73%), respectively. Keywords: microalgae, fast pyrolysis, life cycle assessment (LCA), anaerobic digested wastewater (ADW), biofuel production DOI: 10.25165/j.ijabe.20201301.4178 Citation: Li G, Lu Z T, Zhang J, Li H, Zhou Y G, Zayan A M I, et al. Life cycle assessment of biofuel production from microalgae cultivated in anaerobic digested wastewater. Int J Agric & Biol Eng, 2020; 13(1): 241–246.

Soybean straw was pretreated with either liquid hot water (LHW) (170-210°C for 3-10 min) or alkaline soaking (4-40 g NaOH/100g dry straw) at room temperature to evaluate the effects on cellulose digestibility. Nearly 100% cellulose was recovered in pretreated solids for both pretreatment methods. For LHW pretreatment, xylan dissolution from the raw material increased with pretreatment temperature and time. Cellulose digestibility was correlated with xylan dissolution. A maximal glucose yield of 70.76%, corresponding to 80% xylan removal, was obtained with soybean straw pretreated at 210°C for 10 min. NaOH soaking at ambient conditions removed xylan up to 46.37% and the subsequent glucose yield of pretreated solids reached up to 64.55%. Our results indicated LHW pretreatment was more effective than NaOH soaking for improving cellulose digestibility of soybean straw.

Although severe air pollution has been recognised to be associated with coal combustion, coal is still the main living energy for domestic purposes because of the living habits and low fuel price. Pollutant emission control incoal combustion is urgently needed in the residential sector. In this study, the combustion performanceand gaseous pollutant emissions of a natural draft stove with cross-draft combustor were determined using Shenmu raw coal under different sieved sizes (8–16 mm, 16–20 mm, 20–25 mm, and 25–50 mm). The results showed that the particle size of coal had different effects on firepower and energy efficiency. The coal fuel with a large particle size (25–50 mm) achieved the highest energy efficiency of 82.0%, while the firepower was limited to 13.4 kW. Reducing particle size was helpful to increase the firepower. Low emission factors of CO, NO and SO2 were found in this combustion system with large size coal fuel and the changes were nonlinear. Moreover, manual operation played an important role in pollutant emissions. The heating phase with steady combustion released fewer gaseous pollutants than the ignition and complex cooking/heating phase. These results can provide support for the research on the matching of stoves and coal fuels to deliver clean combustion performance.

Abstract Biomass is a sustainable and renewable energy source with relatively low pollution emissions. It can be transformed into gaseous, liquid and/or solid biofuels as well as other raw chemical materials and products. Among the biomass conversion technologies, densified solid biofuel is one of the means that is storable and transportable with low heating cost. In order to achieve the target of reducing the amount of carbon dioxide emissions per unit of Gross Domestic Product (GDP) by 40–45% until 2020 as set at the United Nations Framework Convention on Climate Change (UNFCCC), and realize the goal of China׳s 12th Five-year Plan (2011–2015) for the development of biomass energy, given that carbon emissions will peak in 2030 as estimated in 2014 during Asia-Pacific Economic Cooperation Conference, China should vigorously develop densified solid biofuel, so as to sharply minimize the unorganized burning of crop residues. This paper introduces the current status of China׳s densified solid biofuel and the industry in following aspects: (a) the classification of densified solid biofuel; (b) development of densified solid biofuel industry; (c) molding technology of densified solid biofuel; (d) characteristics of densified solid biofuel combustion; (e) the problems faced during molding, handling, transportation and storage; (f) existing Chinese standards for densified solid biofuel and the assessment of densified solid biofuel; and (g) market analysis and perspectives of densified solid biofuel and the industry. Moreover, this study provides a comprehensive overview of the development of China׳s densified solid biofuel and the related industry, proposes some recommendations for further development of the industry for domestic and international biomass energy researchers as well.