Modeling and sensitivity analysis of energy inputs for apple production in Iran

This study was conducted to determine the energy balance between the energy inputs and yield for apple production in Tehran, Iran. For this purpose the data were collected from 56 apple orchards. The following results were obtained from this study: The total energy input of 42819.25 MJ ha⁻¹ was required for apple production. The share of diesel fuel by 21.88% of the total energy inputs was the highest energy input. This was followed by farmyard manure (17.66%) and electricity (13.09%), respectively. The energy use efficiency, energy productivity, Specific energy, and net energy were found as 1.16, 0.49 kg MJ⁻¹, 2.06 MJ kg⁻¹ and 7038.18 MJ ha⁻¹, respectively. According to the research results, the contribution of direct energy was higher than that of indirect energy; also the share of non-renewable energy was more than that of renewable energy. The results of econometric model estimation revealed that the impact of farmyard manure, water for irrigation, electricity, chemical fertilizer and human labour energy inputs were significantly positive on yield. The results of sensitivity analysis of the energy inputs showed that the MPP value of water for irrigation was the highest, followed by human labour and chemicals energy inputs, respectively.     

An investigation on energy consumption and sensitivity analysis of soybean production farms

The aims of this study were to determine the energy consumption and evaluation of inputs sensitivity for soybean production in Kordkuy county of Iran. The data used in this study were obtained from 32 farmers using a face-to-face questionnaire base of random sampling method. The sensitivity of energy inputs was estimated using the marginal physical productivity (MPP) method and partial regression coefficients on soybean yield. The results indicated that the total input and output energy use was to be 18,026.50 and 71,228.86 MJ ha⁻¹ respectively. With 66.67%, the diesel fuel was the highest within the energy equivalents and followed by chemical fertilizers and water for irrigation with 14.32% and 6.18% respectively. The input-output ratio was found as 4.62 (used efficiency). The share of direct, indirect, renewable and non-renewable was 74%, 26%, 14% and 86% respectively. The econometric model estimation emphasized that the seed was significantly positive on yield. The sensitivity analysis indicated the MPP value of 2.42 for seed, indicates that with an additional use of 1 MJ of seed energy would lead to an increase in yield by 2.42. The impact of direct, indirect and non-renewable energies on yield was significant.     

Energy use patterns and econometric models of major greenhouse vegetable productions in Iran

This paper examines the energy use patterns and energy input-output analysis of major greenhouse vegetable productions in Iran. Data from 43 farmers were obtained using a face-to-face questionnaire method. The majority of farmers in the surveyed region were growing cucumber and tomato. Total input energy was found to be 141493.51 and 131634.19 MJ ha⁻¹ for cucumber and tomato productions, respectively. Among input energy sources, diesel fuel and fertilizers contained highest energy with 54.17-49.02% and 21.64-24.01%, respectively. The energy ratio was found to be 0.69 and 1.48 for cucumber and tomato productions, respectively. Econometric model evaluation showed the impact of human labor for cucumber and chemicals for tomato was significant at 1% levels. Sensitivity analysis indicated that the MPP value of energy inputs were between −5.87 and 7.74. RTS (returns to scale) values for cucumber and tomato yields were found to be 1.29 and 0.76; thus, there prevailed an IRS of cucumber for estimated model. The net return was found positive, as 22651.13 and 78125.08 $ ha⁻¹ for cucumber and tomato, respectively. The benefit-cost ratios from cucumber and tomato productions were calculated to be 1.68 and 3.28, respectively. Among the surveyed greenhouses, the result indicated tomato cultivation was more profitable.     

Energy and economic analysis of rice production under different farm levels in Guilan province of Iran

The study was carried out on energy requirement and energy input–output relationship of rice production in Guilan province of Iran. Data were collected from 105 farmers with face-to-face questionnaire method. The research results revealed rice production consumed a total energy of 39333 MJ ha⁻¹ which fuel energy use was 46% followed by chemical fertilizer (36%), seed (8%) and biocide (6%), respectively. The share of direct, indirect, renewable and non-renewable energies was 49%, 51%, 11% and 89% respectively. The energy use efficiency and energy productivity were found as 1.53, 0.09 kg MJ⁻¹, respectively. The econometric model was developed using Cobb–Douglas type function and results showed that fuel and machinery energy inputs contributed significantly to the yield. The results of sensitivity analysis of the energy inputs showed that the MPP value of fuel was the highest (0.93), followed by machinery (0.23), biocide (0.17) and seed (0.15) energy inputs. Economic analysis indicated that total cost of production was 3156 $ ha⁻¹. Gross and net return were 1642 $ ha⁻¹ and 940 $ ha⁻¹, respectively and the benefit-cost ratio was calculated 1.29. Mainly, large farms (more than 1 ha) had better management and were more successful in energy use and economic performance.     

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.     

Optimization of energy consumption for soybean production using Data Envelopment Analysis (DEA) approach

In this study a non-parametric method of Data Envelopment Analysis (DEA) is used to estimate the energy efficiencies of soybean producers based on eight energy inputs including human labor, diesel fuel, machinery, fertilizers, chemicals, water for irrigation, electricity and seed energy and single output of grain yield. The study also helps to rank efficient and inefficient farmers and to identify optimal energy requirement and wasteful uses of energy. Data were collected using face-to-face surveys from 94 farms in Golestan province which is the most important center of soybean production in Iran. Based on the results, average yield and energy consumption for soybean production were 3233.15 kg ha⁻¹ and 35372.23 MJ ha⁻¹, respectively. Also, the results of DEA application showed that, the technical, pure technical and scale efficiencies of farmers were 0.853, 0.919 and 0.926, respectively. Moreover, energy saving target ratio for soybean production was calculated as 20.12%, indicating that by following the recommendations resulted from this study, about 7116.84 MJ ha⁻¹ of total input energy could be saved while holding the constant level of soybean yield. Also, electrical energy had the highest share (78.08%) from total saving energy, followed by fertilizers (10.46%) and diesel fuel (6.18%) energy inputs.     

Study on energy efficiency in corn production of Iran

The aims of this study are determining the energy use, qualitative analyzing of energy flow and also investigating energy efficiency by Data Envelopment Analysis (DEA) in corn production of Iran during a seven years period. Results indicated that the average of total energy input increased from 40.98 GJ ha⁻¹ in 2001 to 63.64 GJ ha⁻¹ in the year of 2007. Similarly, the average of total output energy rose from 89.03 to 107.54 GJ ha⁻¹ in the same years, respectively. Also the results showed that average energy use efficiency, energy productivity, specific energy and net energy gain in the studied period was 2.59, 0.17 kg MJ⁻¹, 7.24 MJ kg⁻¹ and 51.34 GJ ha⁻¹, respectively. DEA considered the yield (kg ha⁻¹) as output and three major energy inputs; fertilizers, diesel fuel and machinery as input of 10 provinces in each year. Findings revealed that average energy efficiency score was 90.26%. There is impermanent trend in growth of energy efficiency in corn production of Iran, which needed to further analysis in future studies to realize relevant fluctuations in corn farming.     

Energy use pattern and sensitivity analysis of energy inputs and input costs for pear production in Iran

The purposes of this study were to determine energy use pattern and investigate the relationships between energy inputs and yield, cost inputs and income for pear production in the Tehran province of Iran. In this study, data were collected by administering a questionnaire in face-to-face interviews in the production year of 2009/2010. This article presents a comprehensive picture of the current status of energy consumption and some energy indices like energy ratio, energy productivity, specific energy, net energy and energy intensiveness. Results showed that the total energy input of 172,608.43 MJ ha⁻¹ was required for pear production. Among input energy sources, electricity energy with share of 78% of total input energy had the highest share. The energy use efficiency and energy productivity were found as 0.51 and 0.27 kg MJ⁻¹, respectively. To investigate the relationships between energy inputs and yield, cost inputs and income, Cobb–Douglas production function was selected as the best function. Sensitivity analysis of energy and cost inputs was carried out using the marginal physical productivity (MPP) technique. Economic analysis of pear production was carried out and total cost of pear production was obtained as 11,936.97 $ h⁻¹. Also the benefit to cost ratio was calculated as 3.11.     

Optimization of energy consumption and input costs for apple production in Iran using data envelopment analysis

In this study a non-parametric method of data envelopment analysis (DEA) was applied to analyze the efficiency of farmers, discriminate efficient farmers from inefficient ones and to identify wasteful uses of energy in order to optimize the energy inputs for apple production in Tehran province, Iran. From this study the following results were obtained: from the total of 56 farmers, considered for the analysis, 34% and 54% were found to be technically and pure technically efficient, respectively. The technical, pure technical and scale efficiency scores of farmers were 0.7857, 0.8982 and 0.8666, respectively. Optimum energy requirement was found to be 37993.15 MJ ha⁻¹; indicating that 11.29% of total energy input could be saved if the recommendations of this study are followed. From total energy saving, the contribution of electrical energy was the highest; it followed by chemicals energy inputs; implying that there was a great scope for saving energy inputs by improving the use pattern of these inputs. The results of economical analysis showed that the total costs of production could decreased from 8227.70 to 7570.01 $ ha⁻¹; also the benefit to cost ratio and productivity improved from 1.24 to 1.34 and 2.52 to 2.74, respectively.     

An economic analysis and energy use in stake-tomato production in Tokat province of Turkey

The aim of this study is to determine the input–output energy consumption and to make a cost analysis of intermediate type stake-tomato grown in open field in Tokat province of Turkey. The data used in the study were obtained from 98 local tomato growers using a questionnaire. The farms were chosen by random sampling method. The results showed that the amount of energy consumed in stake-tomato production was 96 957.36 MJ ha⁻¹. About 42% of this was generated by diesel oil and 38% from fertilizers and machinery. The input–output ratio was 0.80 and energy productivity was found to be 1.00 kg MJ ha⁻¹. About 76% of the total energy inputs used in stake-tomato production was non-renewable while only about 22% was renewable. These findings reveal that intensive input use in stake-tomato production, especially chemical fertilizers, gives a high tomato yield but also raises some problems like environmental pollution and global warming. Thus, new policies, emphasizing energy consumption without degradation of national resources, should be designed for such farms.     

Fossil energy usage for the production of baby leaves

The cultivation of fresh-cut crops is shifting from traditional systems in open fields to soilless cropping systems in greenhouses. As a result, the energy requirements of crop cultivation are increasing rapidly. In this study, we analysed the economic and energetic performance of four baby leaf species (lettuce, rocket, spinach, and lamb’s lettuce) cultivated in a greenhouse under floating system. Four indicators were calculated, namely fossil energy input per unit area (EnIa: sum of the direct and indirect energy input per m² per cycle), fossil energy input per unit product (EnIp: ratio of EnIa to fresh product mass per m² per cycle), economic efficiency (EE: ratio of the gross income per m² per cycle to the EnIa), and gross margin (GM: the difference between the gross income and the variable costs per m² per cycle). In general, the EnIas obtained in this study were high (10.2-31.6 MJ m⁻² cycle⁻¹). Lettuce provided the lowest EnIp (3.0 MJ kg⁻¹), and the highest EEs were attained under low nutrient conditions (0.81 and 0.48 € MJ⁻¹ for lamb’s lettuce and lettuce, respectively). The GM of lettuce (on average 1.85 € m⁻²) and lamb’s lettuce (1.67 € m⁻²) were high. However, the consumption of fossil energy by baby leaves cultivated under soilless conditions in a greenhouse can be reduced by adopting precise nutrient management practices.     

Net energy balance of small-scale on-farm biodiesel production from canola and soybean

One necessary criterion for a biofuel to be a sustainable alternative to the petroleum fuels it displaces is a positive net energy balance. This study estimated the net energy ratio (NER), net energy balance (NEB), and net energy yield (NEY) of small-scale on-farm production of canola [Brassica napus (L.)] and soybean [Glycine max (L.)] biodiesel in the upper Midwest. Direct and embodied energy inputs based on well-defined system boundaries and contemporary data were used to estimate the energy requirement of crop production, oil extraction, and biofuel processing. The NER of canola biodiesel was 1.78 compared with 2.05 for soybean biodiesel. Canola biodiesel had a NEB of 0.66 MJ MJ⁻¹ of biofuel compared with 0.81 MJ MJ⁻¹ for soybean biodiesel. The NEY of soybean biodiesel was 10,951 MJ ha⁻¹, less than canola biodiesel which had a NEY of 11,353 MJ ha⁻¹. Use of soybean as a biodiesel feedstock was more energetically efficient than canola primarily due to reduced nitrogen fertilizer requirement. In terms of energetic productivity, canola was a more productive biodiesel feedstock than soybean due to its higher oil content. A best-case scenario based on optimal feedstock yields, reduced fertilizer input, and advanced biofuel processing equipment suggested that potential gains in energetic efficiency was greater for canola than soybean. According to our results, small-scale on-farm biodiesel production using canola and soybean can be an energetically efficient way to produce energy for on-farm use.     

Tillage effects on energy use for corn silage in Mediterranean Coastal of Turkey

One of the main concepts of tillage should be to create the most appropriate soil conditions by taking into consideration energy use efficiency because it allows financial savings, fossil resources preservation and environment pollution decrease. Therefore, the study was perform to evaluate the effects of different tillage systems on energy use, the energy output/input ratios and profitability for silage corn (Zea mays L) production. The tillage systems were consisted of conventional tillage without stubble (CT), minimum tillage (MT), band tillage (BT), ridge tillage (RT) and no-tillage (NT).The effects of tillage were found to be statistically on energy parameters. The highest energy use efficiency (8.78), energy productivity (2.12 kg MJ⁻¹), and energy profitability (7.78) were in MT while the lowest in NT. But, the highest energy intensiveness was in NT (24.83 MJ EUR⁻¹). Indirect energy, non-renewable energy and commercial energy shares were higher for all the systems. More renewable energy was used in NT than the other treatments. The highest benefit/cost ratio and productivity were in the MT (2.13), and followed by NT (2.07). For this reason, conservation tillage treatments (i.e. MT and NT) should be supported for the energy and profitability sustainability of corn silage agriculture.     

Evaluation of annual bioenergy crops in the boreal zone for biogas and ethanol production

Three annual plant species, maize, hemp and faba bean were tested for suitability as dedicated biomass crops in Boreal conditions. Biomass yields were 10-15 t ha^-1. The crops were analyzed for their composition and tested as raw materials for conversion to methane and to fermentable sugars. The methane yield was 379 ± 16 Ndm³ kg⁻¹ VS⁻¹ from maize, 387 ± 20 Ndm³ kg⁻¹ VS⁻¹ from faba bean and 239 ± 9 Ndm³ kg⁻¹ VS⁻¹ from hemp. Based on the yield per hectare, maize proved to be the most potential raw material source for methane production. Analogous to methane production, maize was the most productive raw material also in standard hydrolysis tests, with a conversion yield of about 80% of the theoretical sugars. Based on the amount of carbohydrates, the highest theoretical yield per hectare was obtained with hemp. However, considering all parameters, including the need for weeding and fertilizers, all three crops studied proved to be attractive options for cultivation in boreal conditions as well as being used as energy crops in boreal climate.     

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.     

Mesophilic fermentative hydrogen production from sago starch-processing wastewater using enriched mixed cultures

Biohydrogen (bioH₂) production from starch-containing wastewater is an energy intensive process as it involves thermophilic temperatures for hydrolysis prior to dark fermentation. Here we report a low energy consumption bioH₂ production process with sago starch powder and wastewater at 30 °C using enriched anaerobic mixed cultures. The effect of various inoculum pretreatment methods like heat (80 °C, 2 h), acid (pH 4, 2.5 N HCl, 24 h) and chemical (0.2 g L⁻¹ bromoethanesulphonic acid, 24 h) on bioH₂ production from starch powder (1% w/v) showed highest yield (323.4 mL g⁻¹ starch) in heat-treatment and peak production rate (144.5 mL L⁻¹ h⁻¹) in acid-treatment. Acetate (1.07 g L⁻¹) and butyrate (1.21 g L⁻¹) were major soluble metabolites of heat-treatment. Heat-treated inoculum was used to develop mixed cultures on sago starch (1% w/v) in minimal medium with 0.1% peptone-yeast extract (PY) at initial pH 7 and 30 °C. The effect of sago starch concentration, pH, inoculum size and nutrients (PY and Fe ions) on batch bioH₂ production showed 0.5% substrate, pH 7, 10% inoculum size and 0.1% PY as the best H₂ yielding conditions. Peak H₂ yield and production rate were 412.6 mL g⁻¹ starch and 78.6 mL L⁻¹ h⁻¹, respectively at the optimal conditions. Batch experiment results using sago-processing wastewater under similar conditions showed bioH₂ yield of 126.5 mL g⁻¹ COD and 456 mL g⁻¹ starch. The net energy was calculated to be +2.97 kJ g⁻¹ COD and +0.57 kJ g⁻¹ COD for sago starch powder and wastewater, respectively. Finally, the estimated net energy value of +2.85 × 10¹³ kJ from worldwide sago-processing wastewater production indicates that this wastewater can serve as a promising feedstock for bioH₂ production with low energy input.     

Energy inputs and crop yield relationship in greenhouse tomato production

This study examines energy use patterns and the relationship between energy inputs and yield for greenhouse tomato production in Antalya province of Turkey. The data used in this study were based on cross-sectional data collected from growers by using a face to face survey. The results revealed that diesel (34.35%), fertilizer (27.59%), electricity (16.01%), chemicals (10.19%) and human power (8.64%) consumed the bulk of energy. In the surveyed farms, average yield and energy consumption were calculated as around 160000 kg/ha and 106716.2 MJ/ha, respectively. The results also showed that output–input, specific energy and energy productivity were 1.2, 12380.3 MJ/t and 0.09 kg/MJ, respectively. The results implied that small size farms were more efficient than large ones in terms of output–input ratio. An econometric model was developed to estimate the impact of energy inputs on yield. Therefore, tomato yield, an endogenous variable was assumed to be a function of exogenous variables; fertilizer, chemicals, machinery, human, water for irrigation and seed energy. The empirical results indicated that all exogenous variables except seed energy were found statistically significant and contributed to yield. Among all statistically significant exogenous variables, human, fertilizer, water, chemicals and machinery were ranked in terms of elasticities. These results indicate that the Turkish greenhouse industry heavily depends on fossil fuels.     

Comparison of energy of tillage systems in wheat production

Reducing tillage practices results in lower energy consumption as well as soil erosion protection, structural damage control, and a reduction in time and energy required for seedbed preparation. This research was conducted at the Dryland Agricultural Research Institute in Maragheh region of Iran to determine the amount of input energy for different tillage systems. The study was planned as a completely randomized block design with five tillage systems in four replications. The tillage treatments were: moldboard plow+roller+drill (T1); chisel+roller+drill (T2); cyclo-tiller+roller+drill (T3); sweep+roller+drill (T4); and no-till (T5). Wheat yield parameters and energy indices (net energy gain, energy productivity) were recorded. There were significant differences (1% probability level) among the treatments in terms of energy indices and for wheat yield and biomass values. It was found that T3 had the highest yield and biomass and T1 had the lowest. There were also significant differences (1% probability level) among tillage systems for the energy indices. T1 had the lowest energy productivity and energy ratios and T3 had the highest. The least energy consumed for wheat produced was 8.8 MJ kg⁻¹ for T5 and the most was 11.8 MJ kg⁻¹ for T1. Energy consumed for tillage using T1 was 32.5% of the total energy and using T5 was found to be 19% of total energy. It was concluded that T3 was the most efficient overall in the region studied.     

Biomass and energy yield of industrial hemp grown for biogas and solid fuel

This study examined the energy yield of hemp (Cannabis sativa L.) cultivated for energy purposes under cold climate conditions in Northern Europe. Split-plot field trials were carried out over three consecutive years to investigate different nitrogen fertilisation regimes. Dry matter yield per hectare, moisture content, hydrogen content and heating value were determined at roughly monthly intervals from July until the following spring every season. The energy yield was calculated and adjusted for a fair comparison with those of other energy crops commonly grown in the study region.Two harvest periods for optimal energy yield have been determined; harvest in September to October, when the hemp is used for biogas production, yielded 14.4 Mg ha⁻¹ and 296 GJ ha⁻¹; harvest in February to April, when the hemp is used as a solid fuel, yielded 9.9 Mg ha⁻¹ and 246 GJ ha⁻¹. For biogas production, the adjusted biomass energy yield of hemp was similar to that of maize and sugar beet and 24 and 14% greater than that of lucerne and clover-grass ley, respectively. As a solid fuel, the adjusted biomass energy yield of hemp was 120% higher than that of wheat straw and similar to that of reed canary grass. Annual variations in dry matter yield depending on weather conditions and sowing dates exceeded variations due to nitrogen fertilisation.Hemp is suitable as an energy crop in cold climate regions of Northern Europe, as it has similar or often higher energy yields than other common energy crops grown in these regions.