Net Energy Output Research Articles

Evaluacija potencijala energije vetra u indijskoj državi Tamil Nadu korišćenjem analize kretanja brzine vetra

An accurate estimate of wind resource assessment is essential for the identification of potential site for wind farm development. The hourly average wind speed measured at 50 m above ground level over a period of 39 years (1980-2018) from 25 locations in Tamil Nadu, India have been used in this study. The annual and seasonal wind speed trends are analyzed using linear and Mann-Kendall statistical methods. The annual energy yield, and net capacity factor are obtained for the chosen wind turbine with 2 Mega Watt rated power. As per the linear trend analysis, Chennai and Kanchipuram possess a significantly decreasing trend, while Nagercoil, Thoothukudi, and Tirunelveli show an increasing trend. Mann-Kendall trend analysis shows that cities located in the southern peninsula and in the vicinity of the coastal regions have significant potential for wind energy development. Moreover, a majority of the cities show an increasing trend in the autumn season due to the influence of the retreating monsoons which is accompanied with heavy winds. The mean wind follows an oscillating pattern throughout the year at all the locations. Based on the net annual energy output, Nagercoil, Thoothukudi and Nagapattinam are found to be the most suitable locations for wind power deployment in Tamil Nadu, followed by Cuddalore, Kumbakonam, Thanjavur and Tirunelveli.

Assessment and optimization of a decentralized food-waste-to-energy system with anaerobic digestion and CHP for energy utilization

Biogas derived from the decentralized anaerobic digestion (AD) of food waste may be used to generate electrical and thermal energy for nearby residents through combined heat and power generation technology. A mobile food-waste-to-energy system in conjunction with an anaerobic digester and biogas engine was developed for food waste (FW) treatment and energy output. The scale-up was simulated to explore the methane yield and energy flow at different ambient temperatures of 0 °C, 10 °C, 20 °C, 30 °C and different feedstock of 200 kg, 500 kg FW. Accordingly, the results demonstrated that the installed system with a 1 m3 digester had a methane yield of 0.55L CH4 /g VS when the feedstock load was 30 kg FW/d and the Organic Load Rate (OLR) was 5.4 g VS /L, while the thermal and electrical efficiencies of this system were 31% and 16%, respectively. The corresponding exhaust gas of the thermal energy from the biogas combustion was recovered by a heat exchanger in order to keep the digester at mesophilic conditions. The simulations carried out on the scale-up systems under loads of 200 kg FW/d and 500 kg FW/d achieved a thermal energy balance at different ambient temperatures of 0 °C, 10 °C, 20 °C and 30 °C. Improvements were proposed in the optimized system by optimizing pre-treatment facilities as well as the AD reactor, biogas engine and heat exchanger. The net thermal and electrical energy output of the optimized system at 500 kg FW/d were 175.93kWh and 163.90kWh, respectively. The energy generated by the FW-to-energy system illustrated by the Sankey diagrams depicts that was enough for operation without the need of extra heat and a power supply, moreover, the surplus energy may be utilized for its neighboring communities. In addition, the optimized system under the same OLR were increased by 87% and 135%, regards the thermal and electrical energy outputs, respectively in comparison with the current system.

The net energy ratio of microalgae biofuels production based on correlated cultivation parameters in flat plate photobioreactors

The net energy ratio (NER) of microalgae biofuels depends fundamentally on assumptions of operational energy demand and biomass yield. However, for the NER calculation, it has not previously been considered that these parameters are related. This study derives a correlation between these values from published experimental data on flat plate photobioreactors and uses it to calculate the NER. The found correlation is adapted to outdoor conditions, and the energy demand throughout the life cycle for cultivation and biogas production is added. Results show that an asymptotic correlation between the aeration rate and the photosynthetic efficiency hampers net energy output. Maximising the biomass output requires a disproportionately high aeration rate, and thus operational energy demand. Best NER is obtained at low aeration rates, however the biomethane yield at these rates cannot compensate for the total energy demand throughout the life cycle. A NER of 3.6 is calculated. Sensitivity analysis on further technological improvements, such as more efficient energy supply, reduces the NER to 1.8. A comparison of assumptions from seven previous life cycle analyses demonstrates that NER below one results from incomplete system boundaries, or unrelated parameters for operational energy demand and biomass yield. Our findings help to explain contradictory results in previous studies, and will improve the quality of future NER analyses.

Energy utilization and disposal of herb residue by an integrated energy conversion system: A pilot scale study

With huge demand of herbal medicine worldwide, herb residue (HR) treatment is attracting growing attention. This work proposed an integrated energy conversion system to treat and utilize HR, which contained a crushing and drying section to pretreat HR, a gasification section to convert HR into syngas, and a boiling section to produce hot steam for HR drying and herb steaming. A pilot scale plant was established to validate its feasibility. The results showed that HR with particle size below 10 mm and moisture content about 20 wt% was qualified as gasification feedstock. The energy efficiency, syngas heat value, and syngas yield during gasification reached 76.1%, 5.7 MJ/Nm3, and 0.6 Nm3/kgHR, respectively. When treating each kg of HR, 1.0167 kg of wastewater was emitted, which primarily came from HR dehydration and herb steaming. Meanwhile, 0.3292 kg of hot steam with 0.89 MJ of enthalpy would be produced per kg of HR as net energy output. This integrated system fully considered the upstream and downstream adaption of HR gasification technique. Highly efficient disposal and utilization of HR were thus achieved. It is hoped that this work could promisingly enhance the overall efficiency of herbal medicine production industry.

Eigenfunctions and genetic algorithm based improved strategies for performance analysis and geometric optimization of a two-zone solar pond

In this paper, concept of a modified two-zone solar pond consisting lateral extraction from an extended length of convection free zone combined with thermoelectric generators for electrical power generation is proposed. In this work, a new transient-state analytical model to predict the performance of such a system is developed. Fully closed-form transient solution for performance analysis during extended length lateral heat extraction from solar ponds is not yet available in the literature. The presence of two source terms, one of which is solution dependent and mixed boundary conditions makes the present study complex to be solved analytically. The methodology based on the expansion of Eigenfunctions is proposed to predict temperature profiles within the solar pond having dual layer heat extraction. Using the temperature field, net energy output from the system for a specified period is obtained. The variation in power output and net energy for various cases of design and operating parameters during the maturation phase of the solar pond and after achieving the steady-state is analysed. The sensitivity of different operating and design parameters on the output of the system is also evaluated. Further, an inverse optimization analysis is also carried out to search for possible combinations of various design and operating parameters in the system towards meeting a specified net energy output from the thermoelectric generators. It was observed that using the inversely obtained set of parameters can significantly reduce the volume, base area, and total height of the solar pond concerning the existing convention.

Fluidized bed combustion of poultry litter at farm-scale: Environmental impacts using a life cycle approach

Combustion can concentrate phosphorus (P) from poultry litter into an ash product that is easier to transport for land application. This was the first life cycle assessment (LCA) study to investigate the efficacy and sustainability of a fluidized bed combustion (FBC) system using poultry litter to heat poultry houses and produce electricity, in the United States, to replace liquid propane gas (LPG) and natural gas (NG) use. The ‘Baseline scenario’ used results from a 16-month FBC monitoring study, and an ‘Improved scenario’ based on an increased biomass feed rate (0.246 tons/h), increased run-time (6720 h/y), and net positive electricity production. In the Baseline scenario, climate change potential was 32% and 44% lower than use of LPG and NG, respectively, for poultry house heating, but the low electricity production from the FBC system resulted in net electricity import and lower sustainability compared to LPG use in 12 of the 18 impact categories. The Improved scenario had 48–98% less environmental impacts than the Baseline scenario in the 18 categories. The sensitivity analysis showed that a 10% change in the electricity input for FBC operation resulted in the highest average change (4.8%) in the 18 impact categories, indicating the necessity of a net positive electrical energy output from the FBC unit for increased sustainability. The results also highlighted the impact of the replacement heating fuel type, as replacing NG through poultry litter combustion had a greater impact than replacement of LPG.

Enviro-energy-exergo-economic analysis of ETC augmented double slope solar still with ‘N’ parallel tubes under forced mode: Environmental and economic feasibility

In this communication, the performance of dual slope solar still augmented with parallel vacuum tubes under forced mode is analyzed, comprising energy and exergy approach at an optimal flow rate. Besides, comprehensive enviro-energy-exergo-economic analyses of the proposed system are also estimated. The respective overall energy and exergy efficiencies are estimated as ∼33.8% and ∼4.9%, at an optimal flow rate of 0.06 kg/s and 0.005 m water depth. The yearly distillate, energy and exergy productivity are obtained as ∼1627 kg, ∼1131 kWh and ∼152 kWh. Based on energy, the system mitigates ∼51.4 tCO2, 0.37 tSO2, and 0.15 tNO emissions, while based on exergy, it mitigates ∼6.4 tCO2, 0.04 tSO2, and 0.02 tNO from the atmosphere during the life span. Accounting environmental cash flow due to CO2 mitigation, the respective energy and exergy production cost are estimated as Rs 0.46 and Rs 6.6 per kWh. Accounting environmental cash flow based on the net energy and exergy outputs, the distillate production costs are found to be 0.32 R/kg and 0.61 R/kg, respectively. High distillate output, enviro cash flow, emission reduction, and low production cost make the present system compatible and feasible with small collection areas of solar flux.

Influence of Moisture, Temperature and Microbial Activity in Biomass Sustainable Storage. Special Focus on Olive Biomasses

Biomass is a renewable energy source that, due to its high seasonality, needs to be stored, handled and managed in suitable conditions for its optimum use. Sustainable storage is, therefore, a key process in which biomass can lose much of its qualities as fuel. The article presents an exhaustive bibliographic review of the factors that affect the quality of biomass during storage and the interactions that occur among them. Humidity, type of product, granulometry, size of the stockpile, airflow, temperature, and microbial action are analysed as the main factors affecting biomass during storage, and the results are compared with the tests that have been carried out on biomass from olive groves and olive oil industry. Recommendations are presented so that, using a correct storage method, losses, degradation and self-ignition risks are reduced and the energy quality of the fuel could be improved, taking advantage of the storage process to optimize the net energy yield.

Evaluation of the Productivity of New Spring Cereal Mixture to Optimize Cultivation under Different Soil Conditions

The aim of the study was to evaluate grain yields, protein yields, and net metabolic energy yields of different combinations of spring types of barley, oat, and wheat arranged in 10 mixtures and grown under different soil types. Naked cultivars of barley and oat were used. The three-year field experiment was conducted at the Agricultural Advisory Centre in Szepietowo, Poland. The study showed that the major factor determining yields of the mixtures was soil quality. Within the better soil (Albic Luvisols), the highest yield was achieved by a mixture of covered barley and wheat and by a mixture of covered barley with covered oats and wheat, but only in treatments with lower sowing density. Moreover, on the better soil, significantly higher protein yields were obtained for mixtures of barley (covered or naked grains) with wheat as compared to the mixture of covered barley with covered oats, or the mixture of covered barley with naked oats and wheat. The highest yields of net metabolic energy, regardless of soil type, were obtained from a mixture of naked barley with wheat, while the lowest from a mixture of covered barley with naked oats and wheat. Mixed sowings increase biodiversity of canopies, which allows a better use of production space. They also increase health and the productivity of plants.

Effect of temperature on the anaerobic digestion of cardboard with waste yeast added: Dose-response kinetic assays, temperature coefficient and microbial co-metabolism

Effective co-metabolism of microbes has been reported as an available method to achieve better performance of digestion. In order to identify the optimal synergetic living conditions of microbes and obtain the highest methane production, co-digestion of cardboard and waste yeast at 15, 25 and 35 °C were investigated in batch test. The results showed that it facilitated to establish the efficient metabolism with 0.05 g yeast/g TS sludge added, which obtained the maximal biomethane production of 228.91 mL/gVS at 35 °C (C0.5). However, the addition of excessive yeast caused a serious decline in biomethane due to the accumulation of VFA. Temperature played significant roles in co-metabolism of microbes, and temperature coefficient (Q10) which can reflect the effect of temperature on microbial activity showed the trend of increasing firstly, and then decreasing with the yeast added. The biggest difference was obtained after 0.2 g yeast/g TS sludge was added with the Q10 of 2.67. RDA analysis showed that yeast dosage and temperature are dominant driving factors, which seriously affect microbial community structure. Syntrophic VFA-oxidizing bacteria (f_Synergistaceae) and Methanosaeta were enriched in C0.5. Energy flowing analysis revealed the energy generated in C0.5 was much greater than the others, and its net energy yield has increased by 60.1% compared with 15 °C. The results indicated that co-digestion of cardboard and yeast was beneficial to achieve the reduction and stabilization of the waste for cleaner production, and realizes highest economic benefits from energy yield at 35 °C.

The effect of microwave pretreatment on anaerobic co-digestion of sludge and food waste: Performance, kinetics and energy recovery

This paper studied the effect of microwave (MW) pretreatment on anaerobic co-digestion of sludge (SS) and food waste (FW). Using SS and FW as digestive substrates, the MW pretreatment method was used to determine the changes in the substrate matrix by means of batch anaerobic digestion at 37 °C. The kinetics of methane production were calculated, and the changes in organic matter during anaerobic co-digestion, the properties of the anaerobic-digested effluent, and the net energy output of the co-digestion system were determinated. The results showed that MW pretreatment was beneficial to the dissolution of organic matter, conversion of protein to NH4+-N, cumulative methane production, unit biomethane yield, and reaction rate of methane production in the SS and FW anaerobic co-digestion system. The highest cumulative methane production in the co-digestion system reached 3446.3 ± 172.3 mL (35 days), which was 19.93% higher than that of the control. Furthermore, MW pretreatment significantly increased the accumulation of VFAs and the content of butyric acid in the anaerobic-digested effluent, which was beneficial to the methanogenesis process. The MW pretreatment of all co-digested substrates produced a greater net energy output than the control, and the MW-SS + MW-FW group yielded the highest net energy output, which was 76.25 kJ/g Fed VS. The results indicated that MW pretreatment prior to SS and FW anaerobic co-digestion is an effective way to improve the anaerobic digestion efficiency and energy recovery rate.

Elaboration of an algae-to-energy system and recovery of water and nutrients from municipal sewage.

Increasing pressure is being exerted on the peri‐urban space that has elevated the demand for electricity, affects the global water resource, and impacts the potential to produce food, fiber, and commodity products. Algae‐based technologies and in particular algae‐based sewage treatment provides an opportunity for recovery of water for recycle and re‐use, sequestration of greenhouse gases, and generation of biomass. Successful coupling of municipal sewage treatment to an algae‐to‐energy facility depends largely on location, solar irradiance, and temperature to achieve meaningful value recovery. In this paper, an algae‐to‐energy sewage treatment system for implementation in southern Africa is elaborated. Using results from the continued operation of an integrated algal pond system (IAPS), it is shown that this 500‐person equivalent system generates 75 kL per day water for recycle and re‐use and, ∼9 kg per day biomass that can be converted to methane with a net energy yield of ∼150 MJ per day, and ∼0.5 kL per day of high nitrogen‐containing liquid effluent (>1 g/L) with potential for use as organic fertilizer. It is this opportunity that IAPS‐based algae‐to‐energy sewage treatment provides for meaningful energy and co‐product recovery within the peri‐urban space and, which can alleviate pressure on an already strained water–energy–food nexus.

Enhancing the synergistic interaction of microalgae and bacteria for the reduction of organic compounds in petroleum refinery effluent

Abstract Biocathode microbial desalination cell represent an energy yielding technology for reducing the organic compounds of petroleum refinery effluent (PRE) coupled with sea water desalination and bioelectricity production. The synergistic interaction between the microalgae Scenedesmus abundans and the bacteria played the major role in reduction of organic compounds present in PRE. It was observed that microalgae grown in 50% PRE produced maximum growth absorbance of 2.058, chlorophyll and carotenoid concentration of 2.78 and 1.365 μ g mL−1 respectively. The presence of PRE in cathode chamber significantly increased the bioelectricity generation, ionic separation rate and microalgae growth and also reduced the addition of BG11 commercial media to greater extent. The maximum power density of 0.573 Wm−3 was generated during the single batch operation using algae grown in PRE as biocathode. The study analyzed the desalination efficiency using microalgae grown in PRE as an electron acceptor and the ability to act as bioresource for bacterial growth in anode. The net energy output of the present study reveals that the microbial desalination cell (MDC) can save 1.245 kWhm−3 of power.

Mechanical pretreatment of lignocellulosic biomass to improve biogas production: Comparison of results for giant reed and wheat straw

The effects of a mechanical pretreatment were determined on the methane yield of giant reed stems (Arundo Donax) and wheat straw. The feedstocks were pretreated using a two stages dry milling device, whose working capacity - up to 1,2 t h−1- can meet the requirements of medium and large-scale biogas plants. Untreated and pretreated materials were anaerobically digested in batch reactors under mesophilic conditions for 28 days. The cumulative biogas production from the pretreated giant reed stems exceeded 212 Nm3 t−1 of volatile solids, showing a 137% gain as compared to the raw material; furthermore, a significant decrease in the acid detergent fiber content was observed in the processed material. Pretreated straw reached a cumulative methane yield of 250.3 Nm3 t−1 of volatile solids, gaining a 49.1% as compared to the feedstock; no statistically significant differences were observed in physicochemical composition following pretreatment. The aforementioned gains resulted far above the known range for mechanical pretreatments. The specific electric energy requirement for pretreatment decreased from 76.5 kWh t−1 of processed giant reed stems to 66.0 kWh t−1 for straw. With reference to the use of biogas in CHP plants, the net electric energy output from pretreated materials was enhanced by about 111.7% and 38.3% as compared to the feedstocks for reed and straw, respectively. The cost for the extra electric energy produced by pretreatment was estimated at 0.034 and 0.048 € kWh−1 for giant reed and straw, respectively, resulting fully compatible with the selling price for the electric energy produced from biogas in force in Italy.

Vacuum pyrolysis incorporating microwave heating and base mixture modification: An integrated approach to transform biowaste into eco-friendly bioenergy products

The escalating consumption of fossil fuels and dumping of palm kernel shells (PKS) drives biofuel production to improve supply and waste disposal. To convert PKS into modified biochar (MBC) value-added solid fuel, we use microwave vacuum pyrolysis accompanied by sodium-potassium hydroxide mixture modification. First, PKS underwent microwave vacuum pyrolysis to produce biochar, and then it was chemically activated using sodium-potassium hydroxide mixture. The MBC surface morphology, porous characteristics, proximate content, and energy properties depended on microwave irradiation period and power. High yields (79 ± 1.5 wt%) were recorded at microwave power 700 W and irradiation period of 10 min, giving a high BET surface area (1320 m2/g) and pore volume (0.70 cm3/g). The MBC had acceptable low content of ash, nitrogen, and no sulphur, demonstrating its potential as an environmental friendly fuel to replace conventional coal in combustion. The MBC shows high energy yield (≤90.5%), fuel ratio (≤26.47), and heating value (≤28.69 MJ/kg) comparable to conventional fuels, thus showing desirable solid fuel properties. Energy balance analysis shows positive energy ratio of up to 10 and net energy output of up to 24.47 MJ/kg, recovering a product with a higher energy content compared to electrical power input for the pyrolysis operation. These findings demonstrate the exceptional potential of the MBC produced by this innovative approach for bioenergy generation that per se will reduce the emissions of greenhouse gases and thereby reducing global warming and climate change.

Up-concentration of wastewater to maximize biogas potential: A step towards positive energy wastewater treatment

This study demonstrates a feasible and novel design of the up-concentration of domestic sewage through the Biosorption-Sedimentation Process (BSP). In this study, the system was operated at relatively shorter ratios of anoxic to anaerobic hydraulic retention times (Tano/Tan) with an infinite sludge retention time (SRT) to obtain an up-concentrated stream in terms of chemical oxygen demand (COD) and total phosphorous (TP) and ammonium-nitrogen removal in the effluent. Results indicate that the system has a potential of net energy yield up to 15.5 kW h/m3. Tano/Tan of 60 min/60 min was selected as an optimized run based on Carbon: Nitrogen: Phosphorous (C:N:P) ratio, ammonium-nitrogen concentration, and the maximum energy potential in terms of COD. For process optimization, Response Surface Methodology (RSM) was applied. The optimized run predicted by RSM against the required responses (COD, TP, NH4+-N and TKN) was almost the same as obtained from C:N:P ratio. To conclude, BSP system is not only capable of producing an up-concentrated effluent stream but also has a potential to yield biogas via anaerobic digestion (AD).

Comparison of the energetic, environmental, and economic performances of three household-based modern bioenergy utilization systems in China

The methods of life cycle assessment and cost-effectiveness analysis were employed to compare the energetic, environmental, and economic performances of three household-based modern bioenergy (MBE) utilization systems: biogas utilization (BGs), biomass briquette utilization for energy only (BBs), and biomass briquette utilization for energy and biochar (BCs). The results showed that all the three MBEs performed positive results in net energy output, which ranged from 0.86 to 3.75 MJ (kg crop residues)−1. The positive greenhouse gas reductions also can be acquired when using these three MBEs to substitute for traditional energy, respectively. The cost-effectiveness values of three MBE systems ranged from 343 RMB (tCO2e)−1 for BGs to 598 RMB (tCO2e)−1 for BCs (the CO2e indicates the CO2 equivalent). Considering the supply index analysis results furtherly, the BGs is regarded as the best strategy for the development of MBE in rural households. However, BG leakage during BG digester operations should be received much greater attention to avoid adverse impacts on GHG mitigation.

Design and evaluation of degassed anaerobic membrane biofilm reactors for improved methane recovery

Anaerobic treatment of domestic wastewater (DWW) produces dissolved methane that needs to be recovered for use as an energy product. Membrane-based recovery systems have been reported in the literature but are often limited by fouling. The objective of this study was to develop a methane producing biofilm on the shell side surface a membrane to allow for immediate recovery of methane as it was produced, negating mass transfer resistance caused by fouling. Between 89 and 96% of total methane produced was recovered via in-situ degassing without the need for fouling control or cleaning throughout 72 weeks of operation. High methane recovery efficiencies led to predictions of net positive energy yield in one reactor and a 32–61% reduction in energy demand in the others compared to the control. This research demonstrates the feasibility and usefulness of combining attached growth anaerobic wastewater treatment processes with hollow fiber membrane methane recovery systems for improved operation.

Bioelectrochemical system for the enhancement of methane production by anaerobic digestion of alkaline pretreated sludge

An increasing interest is devoted to combined microbial electrolysis cell-anaerobic digestion (MEC-AD) system which could convert waste activated sludge into biogas. In this study series tests were initially conducted to study the effect of alkaline pretreatment on AD system and the results showed that alkaline pretreatment could promote the dissolution of organic matters in the sludge and thus improve the methane production. Then, the methane production in combined MEC-AD system fed with alkaline-pretreated sludge was investigated. The results indicated that the methane productions increased by 37% and 42% when applied voltage was 0.5 V and 0.8 V. The microbial electrochemical system strongly promoted the growth of Euryarchaeota (Methanosaeta and Methanobacterium). Meanwhile, the abundance of Paraclostridium increased from 17.9% to 38.5% when applied voltage was 0.8 V, suggesting an enhanced fermentation and acetogenesis process. The results of energy balance estimation indicated that MEC-AD system at 0.5 V could achieve higher net energy output.

The The Potential of Sustainable Energy Resources in Eritrea: Solar Energy - An Overview

Energy is the prerequisite and most universal measure of all kinds of work by human beings. Everything in this world is the expression of flow of energy in one of its forms. Sustainable resources of energies are those that do not deplete the Earth’s natural resources and are as environmentally benign as possible. These sources are sustainable in that they can be managed to ensure they can be used indefinitely without degrading the environment (Renewable Energy Association, 2009). The energy resources available can be divided into three types. These are primary energy sources (coal, oil, natural gas, uranium) which provide a net supply of energy, secondary energy sources (solar energy, wind energy, hydro energy etc.) which provide no net energy, and supplementary energy sources (geothermal and tidal) whose net energy yield is zero. Energy is an important input in all sectors of any country’s economy. The standard of living of any given country can be directly related to per capita energy consumption. Energy crisis is due to the rapid growth of world population and the improved standard of living of human beings. The per capita energy consumption is a measure of the per capita income or it is a measure of the prosperity of the nation. As the world population is growing at a faster rate, so the conventional sources of energy are depleting on the one hand and its uses are adversely affecting the environment on the other hand. If it will be continued with the same pace, it may be exhausted by the beginning of the next century. Nuclear energy requires skilled technicians and poses the safety as regards to radioactive waste disposal. Therefore, solar energy and other non-conventional energy sources are the sources; those which are to be utilized in the future. In this paper an attempt has been made to investigate the Potentials of sustainable energy resources in Eritrea with special reference to solar energy. The present study will also explore the intensity of global solar radiation reaching on a horizontal surface over Eritrea. This will be purely done by assessing the degree of solar energy penetration on Eritrea. The paper aims at discussing the cheaper and cleaner use of which is vital to the Eritrean economy and the environment as well.