Does energy efficiency increase with orchard size? A case study from peach production

The aim of this study was to explain the relationship between orchard size and energy efficiency in the case of peach production carried out by households. The data were obtained from 118 peach orchards that were classified into four groups, including orchards less than 0.5, 0.5–1.0, 1.0–2.0 and larger than 2.0 ha, by using stratified random sampling method. The total energy requirement for peach production on average was 36,284.51 MJ ha^?1. Total energy input use decreases as orchard size increases; however, it is minimal in group III. Fertilizer energy was the largest energy input, followed by diesel oil and pesticides for all groups.     

A comparative study on energy use and cost analysis of potato production under different farming technologies in Hamadan province of Iran

The aim of this study was to determine the amount of input–output energy used in potato production and to make an economic analysis of potato production in Hamadan province, Iran. Data for the production of potatoes were collected from 100 producers by using a face to face questionnaire method. The population investigated was divided into two groups. Group I was consisted of 68 farmers (owner of machinery and high level of farming technology) and Group II of 32 farmers (non-owner of machinery and low level of farming technology). The results revealed that 153071.40 MJ ha⁻¹ energy consumed by Group I and 157151.12 MJ ha⁻¹ energy consumed by Group II. The energy ratio, energy productivity, specific energy, net energy gain and energy intensiveness were calculated. The net energy of potato production in Group I and Group II was 4110.95 MJ ha⁻¹ and −21744.67 MJ ha⁻¹, respectively. Cost analysis showed that total cost of potato production in Groups I and II were 4784.68 and 4172.64 $ ha⁻¹, respectively. The corresponding, benefit to cost ratio from potato production in the surveyed groups were 1.09 and 0.96, respectively. It was concluded that extension activities are needed to improve the efficiency of energy consumption in potato production.     

Determination of energy balance of sugar beet production in Turkey: a case study of Kırklareli Province

This study aimed to make an energy analysis of sugar beet production in K?rklareli Province of Turkey during production season in 2012–2013. In order to determine energy input-output of sugar beet, the surveys were performed in 48 sugar beet farms, selected by using Neyman method, located in K?rklareli Province. The data were collected by face-to-face questionnaires and observations. The energy input and output were calculated as 34,201.75 and as 285,600 MJ ha^?1, respectively, in sugar beet production. Energy inputs consist of 41.97 % chemical fertilizer’s energy, 21.16 % diesel fuel energy, 11.97 % irrigation, 11.96 % electricity energy, 6.47 % human labour energy, 5.53 % machinery energy, 0.61 % seed energy and 0.33 % chemical energy. Energy usage efficiency, energy productivity, specific energy and net energy in sugar beet production were calculated as 8.35, 1.98 kg MJ^?1, 0.50 MJ kg^?1 and 251,398.25 MJ ha^?1, respectively.     

An analysis of energy use and relation between energy inputs and yield,costs and income of garlic production in Iran

This paper studies the energy balance between the input and the output per unit area for garlic in Hamedan province of Iran. In this study, data were collected by administering a questionnaire in face-to-face interviews. Results showed that the highest share of energy consumption belongs to chemical fertilizers (41.7%) followed by diesel (13.94%). The results indicated that a total energy input of 40307.89 MJ ha^?1 was consumed for garlic production. The energy productivity and net energy value were estimated as 0.416 kg MJ^?1 and ?13477.82 MJ ha^?1, respectively. The ratio of energy outputs to energy inputs was approximately 0.66. Results indicated that direct, indirect, renewable and non-renewable energies were (28.14%), (71.85%), (36.73%) and (63.26%), respectively. Highest shares of expenses were found to be 45% and 19% for human labor and hired machineries, respectively. Cost analysis revealed that total cost of production for 1 ha garlic production was around 6969.11$. Accordingly, the benefit-cost ratio was estimated as 1.36. Using Cobb-Douglas model, energy function was estimated with the coefficient of determination, R² of (80%), and expenses function was estimated with coefficient of determination, R² of (83%).     

Hybrid (solar and wind) energy system for Al Hallaniyat Island electrification

Wind–PV–diesel hybrid power generation system technology is a promising energy option since it provides opportunities for developed and developing countries to harness naturally available, inexhaustible and pollution-less resources. The aim of this study is to assess the techno-economic feasibility of utilizing a hybrid wind–PV–diesel power system to meet the load of Al Hallaniyat Island. Hybrid Optimization Model for Electric Renewables software has been employed to carry out the present study. The simulation results indicate that the cost of generating energy (COE) is $0.222 kWh^?1 for a hybrid system composed of a 70 kW PV system, 60 kW wind turbine and batteries together with a 324.8 kW diesel system. Moreover, using the same system but without batteries will increase the COE to $0.225 kWh^?1, the fuel consumption, the excess energy and the total operating hours for the diesel generators. The PV–wind hybrid option is techno-economically viable for rural electrification.     

Effects of process,operational and environmental variables on biohydrogen production using palm oil mill effluent (POME)

A batch study for biohydrogen production was conducted using raw palm oil mill effluent (POME) and POME sludge as a feed and inoculum respectively. Response Surface Methodology (RSM) was used to design the experiments. Experiments were conducted at different reaction temperatures (30–50 °C), inoculum size to substrate ratios (I:S) and reaction times (8–24 h). An optimum condition of biohydrogen production was achieved with COD removal efficiency of 21.95% with hydrogen yield of 28.47 ml H₂ g^?1 COD removed. The I:S ratio was 40:60, with reaction temperature of 50 °C at 8 h of reaction time. The study showed that a lower substrate concentration (less than 20 g L^?1) for biohydrogen production using pre-settled POME was achievable, with optimum HRT of 8 h under thermophilic condition (50 °C). This study also found that pre-settled POME is feasible to be used as a substrate for biohydrogen production under thermophilic condition.     

Experimental investigation of solar assisted hydrogen production from water and aluminum

Sustainable production of hydrogen at high capacities and low costs is one the main challenges of hydrogen as a future alternative fuel. In this paper, a new hydrogen production system is designed and fabricated to investigate hydrogen production using aluminum and solar energy. Numerous experiments are performed to evaluate the hydrogen production rate, quantitatively and qualitatively. Moreover, correlations between the total hydrogen production volume over time and other parameters are developed and the energy efficiency and conversion ratio of the system are determined. Also, a method is developed to obtain an optimal and stable hydrogen production rate based on system scale and consumed materials. It is observed that at low temperatures, the hydrogen production volume, efficiency and COP of the system increase at a higher sodium hydroxide molarity. In contrast, at high temperatures the results are vice versa. The maximum hydrogen production volume, hydrogen production rate, reactor COP and system efficiency using 0.5 M NaOH solution containing 3.33 g lit^?1 aluminum at 30 °C are 6119 mL, 420 mL min^?1, 1261 mL H₂ per 1 g of Al, and 16%, respectively.     

Energy-use efficiency and economic analysis of vegetable cropping sequences under greenhouse condition

Under off-seasonality, high-value vegetable cultivation in the greenhouse is more profitable and gaining more acceptances day by day. This study aims to analyze the energy requirement and energy input–output relationship with the economics of vegetable-based cropping sequences viz., tomato nursery–tomato–pepper–onion nursery (CS1), tomato nursery–pepper–soil treatment–cucumber (CS2), tomato nursery–tomato–soil treatment–cucumber (CS3), tomato nursery–cucumber–soil treatment–pepper (CS4), and tomato nursery–tomato–soil treatment–pepper (CS5) in greenhouse conditions of Indian sub-Himalayas. The five sequential treatments were statistically analyzed in randomized block design with four replications. Results reveal that cucumber production required highest input energy (1,059.9 MJ/100 m²) than tomato or pepper. The highest input (3,477.4 MJ/100 m²) and output (4,787.5 MJ/100 m²) energy was observed with CS3. Crop protection (28.9–55.7 %), manures and chemical fertilizers (17.5–33.1 %), and plant stacking, training and pruning (16.3–21.9 %) consumed the bulk of the energy for all cropping sequences. The CS3 with the highest tomato equivalent yield produced the highest net energy (1,310.1 MJ/100 m²), energy productivity (0.63 MJ/100 m²), energy intensiveness (0.297 MJ/100 m²), and benefit/cost ratio (1.82). Energy consumption in the form of indirect (70.6–80.2 %) and non-renewable (83.9–85.7 %) energy was higher than direct and renewable energy, respectively. Considering these, CS3 (tomato nursery–tomato–soil treatment–cucumber) cropping sequence will be a more suitable option for greenhouse cultivation.     

Hydrogen evolution in microbial electrolysis cells treating landfill leachate: Dynamics of anodic biofilm

This study investigates the potential opportunities of hydrogen evolution treating landfill leachate in a set of two microbial electrolysis cells (MEC-1 and 2) under 30 °C and 17 ± 3 °C temperatures, respectively. The system achieved a projected current density of 1000–1200 mA m^?2 (MEC-1) and 530–755 mA m^?2 (MEC-2) coupled with low cost hydrogen production rate of 0.148 L La^?1 d^?1 (MEC-1) and 0.04 L La^?1 d^?1 (MEC-2) at an applied voltage of 1.0 V. Current generation led to a maximum COD oxidation of 73 ± 8% (MEC-1) and 65 ± 7% (MEC-2) with ≥100% energy recovery. The system also exhibited a high hydrogen recovery (66–95%), pure hydrogen yield (98%) and tremendous working stability during two months of operation. Electroactive microbes such as Pseudomonadaceae, Geobacteraceae and Comamonadaceae were found in anodophilic biofim, along with Rhodospirillaceae and Rhodocyclaceae, which could be involved in hydrogen production. These results demonstrated an energy-efficient approach for hydrogen production coupled with pollutants removal.     

Synergistic effect of TiF3@ graphene on the hydrogen storage properties of Mg–Al alloy

Mg–Al alloy was prepared by sintering and mechanical alloying, and the effects of graphene (Gp), TiF₃ and Gp/titanium (III) fluoride (TiF₃) on the hydrogen storage properties of the Mg–Al alloy were studied. The results show that Gp and TiF₃ could improve the hydrogen storage properties of Mg–Al alloy. In particular, Gp and TiF₃ showed good synergistic effect for enhancing the hydrogen storage properties of Mg–Al alloy. For example, when 1.0 wt% of H₂ was absorbed/desorbed, the hydrogen adsorption/desorption temperature of the Mg–Al alloy and Mg–Al-M (M = Gp, TiF₃, and TiF₃@Gp) composites were 241/343 °C, 185/310 °C, 229/292 °C and 159/280 °C, respectively. For the Mg–Al alloy, the apparent activation energy was 176.5 kJ mol^?1, and it decreased to 139.8 kJ mol^?1, 171.6 kJ mol^?1, and 94.3 kJ mol^?1, with the addition of Gp, TiF₃ and TiF₃@Gp composites, respectively. Evidently, the comprehensive hydrogen storage properties of Mg–Al alloy were improved remarkably under the synergistic effect of Gp and TiF₃.     

Hydrogen production by a low-cost electrolyzer developed through the combination of alkaline water electrolysis and solar energy use

Electrolysis is a relatively simple process for obtaining hydrogen and can be combined with use of renewable energy sources, such as solar photovoltaic energy, for clean, sustainable gas production. This study designed a cylindrical electrolytic cell made of acrylic and 304 stainless steel electrodes to produce hydrogen. The electrolyte used was sodium hydroxide (NaOH 2–5 mol L^?1), and the direct current voltages applied were 2.0, 2.7, and 3.4 V. The maximum hydrogen production was achieved with 5.0 mol L^?1 NaOH and 3.4 V electric voltage. The system was connected to a photovoltaic panel of 20 W and exposed to solar radiation from 10 a.m. to 2 p.m. Approximately 2 L of hydrogen was produced within a period, and an average irradiance of 800.0 W m^?2 ± 60 W m^?2 was achieved. The system was stable throughout the tests.     

An analysis of energy use and relation between energy inputs and yield in tangerine production

The objective of this study is to determine energy balance between inputs and output for tangerine production in Mazandaran province, one of the most important citrus production centers in Iran. Data is collected by administering a questionnaire in face-to-face interviews. The results show that the highest share of energy was utilized by application of chemical fertilizers and chemicals. Average yield and energy consumption are calculated as 26862.5 kg ha^?1 and 62260.9 MJ ha^?1, respectively. The energy productivity and net energy value are estimated as 0.43 kg MJ^?1 and ?8201.4 MJ ha^?1, respectively. The ratio of energy outputs to energy inputs is approximately 0.87. In addition, the Cobb–Douglas production function is applied to estimate the econometric relationship among different forms of energy consumption. The findings suggest that tangerine producers must optimize their use of indirect and non-renewable energy resources; they apply an excess use of some energy inputs, resulting in an inverse effect on yield as well as imposing risks to natural resources and human health.     

Energy inputs – yield relationship and cost analysis of kiwifruit production in Iran

This study examines energy consumption of inputs and output used in kiwifruit production, and to find relationship between energy inputs and yield in Mazandaran, Iran. For this purpose, the data were collected from 86 kiwifruit orchards which were selected based on random sampling method. The results indicated that total energy inputs were 30285.62 MJ ha^?1. About 47% of this was generated by total fertilizer including farmyard manure, 28% from diesel fuel and machinery. About 70% of the total energy inputs used in kiwifruit production was indirect while only about 30% was direct. Econometric estimation results revealed that energy inputs of human labour, water for irrigation, total fertilizer and machinery contributed significantly to the yield. The impact of human labour energy (0.17) was found the highest among the other inputs in kiwifruit production. The results also showed that direct, indirect and renewable and non-renewable, energy forms had a positive impact on output level. Cost analysis showed that total cost of kiwifruit production was obtained as 6063.81 $ ha^?1. The productivity (4.05 kg $^?1) was obtained by dividing kiwifruit yield by total production cost.     

Photo-oxidation of liquid sulphur by iron (iii) salt

One of the applications of solar energy is the photo-thermochemical production of fuel, particularly hydrogen. In this regard photo-oxidations/reductions are important processes and may provide a route to harnessing solar energy. Liquid sulphur absorbs in the visible region (400–500 nm). The absorption of light in this region will produce excited sulphur and hence can take part in the photo-oxidation/reduction process. The photo-oxidation of liquid sulphur by Fe(III) salt (anhydrous ferric chloride) at 150 ± 5°C was studied in both the presence and absence of visible light. It was found that liquid sulphur was photo-oxidized by Fe³⁺ which itself was reduced to Fe²⁺. The overall rate constants for photo-thermochemical and pure thermochemical reactions were found to be 5–3 × 10^?6 M^?1 s^?1 and 2–8 × 10^?6 M^?1 s^?1, respectively. A mechanism for the photo-thermochemical reaction is proposed.     

Assessment of the adequacy of different Mediterranean waste biomass types for fermentative hydrogen production and the particular advantage of carob (Ceratonia siliqua L.) pulp

The conversion of agro-industrial byproducts, residues and microalgae, which are representative or adapted to the Mediterranean climate, to hydrogen (H₂) by C. butyricum was compared. Five biomass types were selected: brewery’s spent grain (BSG), corn cobs (CC), carob pulp (CP), Spirogyra sp. (SP) and wheat straw (WS). The biomasses were delignified and/or saccharified, except for CP which was simply submitted to aqueous extraction, to obtain fermentable solutions with 56.2–168.4 g total sugars L^?1. In small-scale comparative assays, the H₂ production from SP, WS, CC, BSG and CP reached 37.3, 82.6, 126.5, 175.7 and 215.8 mL (g biomass)^?1, respectively. The best fermentable substrate (CP) was tested in a pH-controlled batch fermentation. The H₂ production rate was 204 mL (L h)^?1 and a cumulative value of 3.9 L H₂ L^?1 was achieved, corresponding to a H₂ production yield of 70.0 mL (g biomass)^?1 or 1.6 mol (mol of glucose equivalents)^?1_. The experimental data were used to foresight a potential energy generation of 2.4 GWh per year in Portugal, from the use of CP as substrate for H₂ production.     

Optimization of furfural production from millet husk using response surface methodology

Biomass has been recognized as a viable source for energy and bio-based chemicals. This study reported furfural production from millet husk via simultaneous hydrolysis and dehydration processes. Effect of reaction variables such as temperature (120–200°C), resident time (15–45 min), and acid concentration (5–10%) was studied using central composite design. Furfural yield (71.55%) was achieved at 184°C, 39 min, and 9% acid concentration. FT-IR spectrum of the produced furfural showed absorption at 1,697 and 2,880 cm^?1 indicating a conjugated carbonyl functional group and aldehydic hydrogen. The results revealed that millet husk could be a potential substrate for furfural production.     

Continuous production of biohydrogen from oil palm empty fruit bunch hydrolysate in tubular photobioreactors

Production of hydrogen by the photosynthetic bacterium Rhodobacter sphaeroides was compared in continuously operated tubular photobioreactors illuminated by natural outdoor sunlight (0.15–66 klux; diurnal cycle) and constant indoor artificial light (10 klux; tungsten lamps). In both cases the operating temperature was 35 °C and the organic carbon source was an acid hydrolysate of oil palm empty fruit bunch (EFB), an agroindustrial waste. In the outdoor photobioreactor, under the best production conditions, the daytime feeding rate of the mixed carbon substrate was 48 mL h^?1 and the average pseudo-steady state hydrogen production rate was 36 mL H₂ L^?1 medium h^?1. The cumulative hydrogen production was 430 mL H₂ L^?1 medium. For the indoor photobioreactor fed at the same rate as the outdoor system, the steady state average hydrogen production rate was 43 mL H₂ L^?1 h^?1 and the cumulative hydrogen production was 517 mL H₂ L^?1 medium. Reducing the feed rate to less than 48 mL h^?1, enhanced the biomass concentration, but reduced hydrogen production in both bioreactors. The sunlight-based cumulative hydrogen production was only about 17% less compared to the artificially lit system, but required only 22% of the electrical energy.     

Experimental studies on the catalytic behavior of alloy and core-shell supported Co-Ni bimetallic nano-catalysts for hydrogen generation by hydrolysis of sodium borohydride

Monometallic (Co) and bimetallic (Co-Ni and Co-Cu) oxides catalysts supported on the almond based activated carbon (AC) were prepared by the heterogeneous deposition-precipitation method. The activity of these catalysts was evaluated as a function of reaction temperature, NaOH, and NaBH₄ concentration. Several analysis methods including XRD, XPS, FTIR, TEM, FESEM, ICP-OES, and BET were applied to characterize the structure of prepared samples. Well-dispersed supported bimetallic nano-catalysts with the size of particles below 20 nm were formed by using nickel and copper oxides as a promoter which was confirmed by XRD and TEM techniques. Surface composition of alloy and core-shell cobalt-nickel oxides catalysts was analyzed by ICP-OES which was in a good agreement with nominal content during catalyst preparation. The performance of bimetallic cobalt-nickel oxides catalysts indicated the synergic effect between cobalt and nickel in comparison with monometallic and bimetallic cobalt-copper samples for hydrogen production. Maximum hydrogen generation rate was measured for the supported core-shell catalyst as named Ni1/Co3/AC. The reaction rate increased with increasing the temperature of the alkaline solution as a significant parameter while other operating conditions were kept constant. The optimal values for NaOH and NaBH₄ content were calculated to be 10 wt % for both variables at 30 °C. Hydrogen production rates were calculated to be 252.0, 310.8 and 658.8 mL min^?1.g^?1 by applying Co3/Ni1/AC, Co3-Ni1/AC (alloy) and Ni1/Co3/AC at 30 °C in 5 wt % NaBH₄ and 5 wt % NaOH solutions, respectively. Obtained activation energy (50 kJ mol^?1) illustrated that the suitable catalysts were synthesized for hydrogen generation. The experimental study showed that the hydrolysis of NaBH₄ was a zero-order type reaction with the respect to the sodium borohydride concentration. A semi empirical kinetic model was derived at the various temperatures and NaOH concentrations.     

Enhancement of fermentative hydrogen production by Thermotoga maritima through hyperthermophilic anaerobic co-digestion of fruit-vegetable and fish wastes

In this work, different proportions of model fruit and vegetable wastes (MFVW) and acid hydrolyzed fish wastes (AHFW) were used for hydrogen production in a minimum culture medium based on seawater. Experiments were performed in pH-controlled Stirred Tank Reactor (STR) with or without the addition of nitrogen and sulfur sources. The total H₂ production and the maximum hydrogen productivity of T. maritima in the culture medium, containing MFVW and AHFW (45 mmol L^?1 carbohydrates) at a C/N ratio of 12, were 132 mmol L^?1 and 15 mmol h^?1 L^?1, respectively. However, tripling the concentration of carbohydrates to reach a C/N ratio of 22, has increased two times the maximum H₂ productivity (28 mmol h^?1 L^?1) due to the improvement in nutrient balance. The cumulative H₂ production was 285 mmol L^?1, yielding a potential energy generation of 0.1210³ MJ ton^?1 wastes, which could be an interesting alternative for energy recovery.     

Economical analysis and relation between energy inputs and yield of greenhouse cucumber production in Iran

This paper studies the energy balance between the input and the output per unit area for greenhouse cucumber production. For this purpose, the data on 43 cucumber production greenhouses in the Tehran province, Iran, were collected and analyzed. The results indicated that a total energy input of 148836.76 MJ ha⁻¹ was consumed for cucumber production. Diesel fuel (with 41.94%) and chemical fertilizers (with 19.69%) were amongst the highest energy inputs for cucumber production. The energy productivity was estimated as 0.80 kg MJ⁻¹. The ratio of energy output to energy input was approximately 0.64. Results indicate 10.93% and 89.07% of total energy input was in renewable and non-renewable forms, respectively. The regression results revealed that the contribution of energy inputs on crop yield (except for fertilizers and seeds energies) was significant. The human labour energy had the highest impact (0.35) among the other inputs in greenhouse cucumber production. Econometric analysis indicated that the total cost of production for one hectare of cucumber production was around 33425.70 $. Accordingly, the benefit–cost ratio was estimated as 2.58.