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In this study, levulinic acid (LA) was produced from rice straw biomass in co-solvent biphasic reactor system consisting of hydrochloric acid and dichloromethane organic solvent. The modified protocol achieved a 15% wt LA yield through the synergistic effect of acid and acidic products (auto-catalysis) and the designed system allowed facile recovery of LA to the organic phase. Further purification of the resulting extractant was achieved through traditional column chromatography, which yielded a high purity LA product while recovering ∼85% wt. Upon charcoal treatment of the resultant fraction generated an industrial grade target molecule of ∼99% purity with ∼95% wt recovery. The system allows the solvent to be easily recovered, in excess of 90%, which was shown to be able to be recycled up to 5 runs without significant loss of final product concentrations. Overall, this system points to a method to significantly reduce manufacturing cost during large-scale LA preparation.

This study highlights how Chinese economic development detrimentally impacted water quality in recent decades and how this has been improved by enormous investment in environmental remediation funded by the Chinese government. To our knowledge, this study is the first to describe the variability of surface water quality in inland waters in China, the affecting drivers behind the changes, and how the government-financed conservation actions have impacted water quality. Water quality was found to be poorest in the North and the Northeast China Plain where there is greater coverage of developed land (cities + cropland), a higher gross domestic product (GDP), and higher population density. There are significant positive relationships between the concentration of the annual mean chemical oxygen demand (COD) and the percentage of developed land use (cities + cropland), GDP, and population density in the individual watersheds (p < 0.001). During the past decade, following Chinese government-financed investments in environmental restoration and reforestation, the water quality of Chinese inland waters has improved markedly, which is particularly evident from the significant and exponentially decreasing GDP-normalized COD and ammonium (NH4+-N) concentrations. It is evident that the increasing GDP in China over the past decade did not occur at the continued expense of its inland water ecosystems. This offers hope for the future, also for other industrializing countries, that with appropriate environmental investments a high GDP can be reached and maintained, while simultaneously preserving inland aquatic ecosystems, particularly through management of sewage discharge.

Abstract Enhancing microalgae biomass productivity through different abiotic and environmental factors optimization is crucial. Design of experimental (DOE) methodology using Taguchi orthogonal array (OA) was studied to evaluate the specific influence of eight important factors (light, pH, temperature, carbon concentration, nitrates, phosphates, magnesium ion concentration and carbon source) on the biomass production using three levels of factor (2 1 × 3 7 ) variation with experimental matrix [L 18 -18 experimental trails]. All the factors were assigned with three levels except light illumination (2 1 ). Substantial influence on biomass productivity is observed with carbon concentration contributing 16.8%, followed by nitrates 12.8% and light 9.3%. Experimental setup eight (Light, pH-8.5, Temperature 25°C, Carbon concentration 10 g/l, nitrates 1.5 g/l, phosphates 0 g/l, magnesium 150 mg/l, Carbon source (glucose)) showed maximum biomass growth (5.26 g/l) and good substrate degradation (63%, COD removal efficiency) contributing to carbohydrate production (257 mg/g biomass) which is further converted to lipids (20% Total lipid and 10% Neutral lipids). Chlorophyll ( a , b ), carbohydrates composition, FAME analysis for lipid percentage were monitored during process operation. Elemental analysis reveals that the carbon to hydrogen and oxygen ratio present in dried algal biomass can be hydrothermally liquefied (HTL) to produce biocrude.

This paper describes anaerobic thermophilic sludge digestion (55 °C) in a continuously stirred tank reactor (CSTR) on a pilot-plant scale (150 L). The experimental protocol was defined to examine the effect of the increase in the organic loading rate on the efficiency of the digester and to report on its steady-state performance. The reactor was subjected to a programme of steady-state operation over a range of solids retention times (SRTs) of 75, 40, 27, 20 and 15 days and organic loading rates (OLR) in the range 0.4–2.2 kg VS/(m3 day). The digester was fed with raw sludge (containing approximately 35 kg/m3 volatile solids (VS)) once daily during the 75-day SRT period, twice daily during the 40-day SRT period and three times a day during the 27-, 20- and 15-day SRT periods. The reactor was initially operated with an organic loading rate of 0.4 kg VS/(m3 day) and an SRT of 75 days. The volatile solids removal efficiency in the reactor was found to be 73%, while the volumetric methane production rate produced in the digester reached 0.02 m3/(m3 day). Over a 338-day operating period, an OLR of 2.2 kg VS/(m3 day) was achieved with 49.1% VS removal efficiency in the pilot sludge digester, at which time the volumetric methane production rate content of biogas produced in the digester reached 0.4 m3/(m3 day). The chemical oxygen demand (COD) mass balance obtained indicated that COD used for methane generation increased when the SRT was decreased or when the influent organic loading rate was increased. This implies that the amount of COD used in the anabolism route decreased with SRT due the microbial population becoming adapted to new operational conditions and more COD being used to generate methane.

Abstract A process engineering strategy was developed for cultivation of high density biomass of Chlorella sp. FC2 with improved productivity under photoautotrophic condition. The process engineering strategy involved a combinatorial approach of: (i) optimization of CO2 concentration in the inlet gas stream & aeration rate; (ii) growth kinetic driven feeding recipe for limiting nutrients; and (iii) dynamic increase in light intensity. The strategy was tested by growing the cells on laboratory grade BG11 medium. With an attempt to reduce the cultivation cost, the growth performance of the organism was then evaluated on commercial grade BG11 medium. Finally, hydrothermal liquefaction was carried out for direct conversion of microalgal slurry into bio-crude oil. Cultivation on laboratory grade BG11 medium resulted in biomass titer and overall productivity of 8.41 g L−1 and 575.9 mg L−1 day−1 respectively. Significant improvement in biomass titer (13.23 g L−1) and overall productivity (731.6 mg L−1 day−1) was observed when grown on commercial grade BG11 medium. Higher fraction of hydrocarbon in the bio-crude oil depicted better oil quality. Thermal gravimetric analysis revealed that maximum distillate fraction lies within the boiling point range of 200–300 °C which is suitable for conversion into diesel oil, jet fuel, and fuel for stoves.

Abstract Algae have been considered as a promising biodiesel feedstock. One of the major factors affecting large-scale algae technology application is poor wintering cultivation performance. In this study, an integrated approach is investigated combining freshwater microalgae Chlorella zofingiensis wintering cultivation in pilot-scale photobioreactors with artificial wastewater treatment. Mixotrophic culture with the addition of acetic acid (pH-regulation group) and autotrophic culture (control group) were designed, and the characteristics of algal growth, lipid and biodiesel production, and nitrogen and phosphate removal were examined. The results showed that, by using acetic acid three times per day to regulate pH at between 6.8 and 7.2, the total nitrogen (TN) and total phosphate (TP) removal could be increased from 45.2% to 73.5% and from 92.2% to 100%, respectively. Higher biomass productivity of 66.94 mg L−1 day−1 with specific growth rate of 0.260 day−1 was achieved in the pH-regulation group. The lipid content was much higher when using acetic acid to regulate pH, and the relative lipid productivity reached 37.48 mg L−1 day−1. The biodiesel yield in the pH-regulated group was 19.44% of dry weight, with 16–18 carbons as the most abundant composition for fatty acid methyl esters. The findings of the study prove that pH adjustment using acetic acid is efficient in cultivating C. zofingiensis in wastewater in winter for biodiesel production and nutrient reduction.

Abstract Small hydropower projects (SHPs), though generally considered more environmentally benign and socially acceptable as compared to large projects, yet their overall sustainability is under suspicion in the Himalayan regions. Almost all SHPs in this region are being developed as run of the river mode which generally causes less/no submergence and quite less displacement of people as compared to large reservoir based hydropower production mode. However, in the absence of proper planning and monitoring mechanism, these projects are causing implacable tunnelling of hills, choking of streams, conversion of streams into dry ditches and long term socio-environmental impacts. This paper presents a SHP development study from hydro rich Beas river basin of Himachal Pradesh, a state nestled in western Himalayan region of India. In depth field studies, focus group discussions with the project affected people and interaction with project proponents of five SHPs in this region suggest that sustainability issues with respect to SHPs are not small vis-a-vis size of their installed capacity. There is an urgent need to take steps to include SHPs having an installed capacity of above 10 MW into the ambit of environment clearance process which is absent in many countries of the world at present.

AbstractAgricultural organic wastes (AOW) have the potential to provide bioenergy particularly found in biogas by anaerobic digestion (AD). In this study, the biogas production (BP) of AOW was obtained by batch AD with anaerobic digesters (500 mL) at 35°C incubator. The results showed that BP values in terms of volatile solids (VS) from rice husk, rice straw, flower residues, fruit and vegetable residues, wasted oyster shell residue (WOSR), fishery residues, livestock and poultry manures, livestock and poultry slaughter wastes (LPSW), and eight equally mixed wastes (EEMW) were 84.03, 193.36, 153.32, 76.27, 150.48, 63.26, 169.63, 615.74, and 172.83 mL/g VS, respectively. LPSW showed the highest μm of 16.99 mL/g VS‐d, the highest BP of 615.74 mL/g VS and the highest bioconversion efficiency of 65.98% compared to the other organic wastes. BP from the most AOW in Taiwan by AD was estimated to be 768,567,753 (743,522,223, excluding WOSR) m3/year. The annual BP of 768,567,753 m3/year of the eight total major AOW by AD was lower (∼20.11%) than 961,989,781 m3/year of the EEMW by anaerobic co‐digestion. Result also showed that modified Gompertz equation was suitable to describe BP accumulation and BP rate.

Abstract It is usual to extract hot water from a storage tank, using displacement by cold water from the mains; this causes the temperature of the outgoing hot water to decrease with time. In order to alleviate this undesirable feature a number of tanks in series may be employed. In this communication the effect of number of tanks on the outlet temperature of hot water, has been analytically investigated; it has been assumed that the only heat exchange, taking place in the tanks is on account of flow of water. The considerations in this analysis are similar to those made by Rabinovich and Fert [1] and Rabinovich [2], for a system of tanks in a solar collector loop without any outflow of water. Thus the analysis is best applicable when hot water is extracted at a fast rate, so that the gain or loss of heat by other mechanisms is negligible, compared to that due to the flow of water. The analysis should also be applicable to shallow solar ponds, Sodha et al. [3], and built in storage water heaters, Sodha et al. [4].