Waste-to-energy possibilities for industrial olive and grape by-products in Extremadura

The olive and grape agro-industrial sectors have a major economic importance in Extremadura. Annual production of olive oil is more than 50×10³ t, and of wine is more than 3×10⁶ hectolitres. The large amounts of by-products are in most cases under-used, although they could be converted into a zero cost of the waste at the point of origin. In this context, the present work describes an estimate of plant size, and an economic analysis of grate firing+steam turbine (GF/ST) and fluidized bed combustion+steam turbine (FBC/ST) waste-to-energy solutions using industrial olive and grape by-products in Extremadura. The fuel is dry olive husk waste (OH), olive mill wastewater (OMW), OH+OMW sludge, and grape waste from wineries, with total calculated specific costs of 3.28, 8.09, 2.67, and 2.05 € GJ⁻¹ with respect to the lower heating value (LHV), respectively. The logistics component corresponding to trucking the biomass to the power production plant is that of greatest economic importance, even when the logistics strategy includes de-centralized drying plants.For real onsite availabilities of OH 21.084×10³ t, OMW 37.483×10³ t, olive sludge 87.462×10³ t, and grape waste 89.486×10³ t, the gross power is 19.13 MW for a GF/ST plant and 20.46 MW for an FBC/ST plant. The results are compared using standard economic indices—net present value (NPV), profitability index (PI), internal rate of return (IRR), and payback time (PBT). A sensitivity and risk analysis of the proposals showed the GF/ST option to be the better suited to the studied scenario, with better values for all the indicators.     

Energy recovery from industrial waste of a confectionery plant by means of BIGFC plant

The search of environment friendly solutions for waste management, along with increasing costs and recent regulations on waste disposal, leads toward the recovery of energy and requires research activities related to plant definition and thermo-economic comparison. On the other hand, energy recovery from waste has never been an easy task. The high pollutant level in waste combustion gases requires low maximum temperatures in thermodynamic cycles thus affecting the efficiency of the “heat to electricity” conversion process. The recent progress of high temperature fuel cells seems to bring a significant change in this scenario, thanks to the feasible combination with advanced gasification systems. A thermo-economic comparison of different solutions for energy recovery from industrial waste is reported, considering an advanced dual bed gasification-MCFC integrated plant. The solution has been applied to a confectionery plant. Even if this system seems to promise high thermodynamic efficiency, a lot of effort in research is necessary for technical analysis of the advanced plant open issues and for the thermo-economic evaluation of potential advantage over consolidated systems. The thermodynamic analysis has been conducted interfacing Aspen⁺ flowsheets developed with the integration of a proprietary numerical code. The definition of a complex plan of costs would have been presumptuous at this stage of the development; therefore, a reverse economic approach has been used and is suggested by the authors; a specific solver has been implemented for this purpose. An extensive survey of the confectionary plant has been conducted considering the present energy system, the current supplies, and the trends of the required energy needs. The results show that the proposed advanced energy system can represent a valid solution for both industrial waste management and for integration in energy supply.     

Selection of the best pretreatment for hydrogen and bioethanol production from olive oil waste products

Bioethanol is one of the most promising renewable energy sources, and it can be used as an alternative to petroleum-derived products. Agro-food residues are the substrates most frequently used for bioethanol production through anaerobic fermentation. The cultivation of olive trees and olive oil production are important economic activities throughout all Mediterranean countries. The wastes derived from olive oil production include a liquid waste, known as Olive Mill Wastewater (OMW), and a semi-solid waste, called Olive Pomace (OP), which is rich is lignin and cellulose materials. The aim of this work is to evaluate the quantity of hydrogen and bioethanol that could be extracted from an OMW-OP mixture after Saccharomyces cerevisiae anaerobic fermentation. In addition, different pretreatments (ultrasonic pretreatment, basic pretreatment, and calcium carbonate addition) have been tested to increase the glucose concentration and, consequently, the bioethanol and hydrogen production in the reaction medium and to decrease the content of inhibiting polyphenols which are mainly present in the OMW. All of the pretreatments were shown to have improved the hydrogen and bioethanol concentration at the end of the fermentation. The basic and ultrasonic pretreatments resulted in the best bioethanol and hydrogen production. These two pretreatments contributed to the hydrolysis of the lignin and cellulose and to increasing the soluble sugars (in particular glucose) content in the reaction mixture. Calcium carbonate addition decreased the polyphenol concentration; the polyphenols inhibit the fermentation mediated by S. cerevisiae.     

Comparison of physicochemical characteristics and photofermentative hydrogen production potential of wastewaters produced from different olive oil mills in Western-Anatolia,Turkey

Olive oil extraction produces a dark-colored wastewater that contains nutrients that can be further processed using biotechnology, in parallel with treatment for disposal. For instance, olive mill wastewater (OMW) can be used as a substrate for photofermentative hydrogen production by purple bacteria. A comparative study was investigated with several OMW samples from different olive oil mills in Western-Anatolia, Turkey. The composition of OMW varies significantly for each mill; thus, a detailed physicochemical analysis of each sample has been carried out. Subsequently, samples were assessed for their functioning in anaerobic photofermentative hydrogen production by Rhodobacter sphaeroides O.U.001. The highest hydrogen production potential (19.9 m³ m^?3) was obtained by the OMW sample with the highest organic content (mainly acetic acid, 9.71 kg m^?3) and the highest carbon-to-nitrogen (C/N) molar ratio (73.8 M M^?1). The organic content was found to be composed of primarily acetic, aspartic, and glutamic acids. There was a linear relationship between C/N ratio and hydrogen production potential across the different OMW samples. This study is unique due to the wide range of analyses of OMW samples and the comparison of many parameters for hydrogen production from wastewater. The results obtained throughout this study can aid in the design of systems using wastewater for biohydrogen production. Particularly, the C/N ratio was found to be the best parameter for choosing a proper substrate.     

Estimation of animal and olive solid wastes in Jordan and their potential as a supplementary energy source: An overview

Biomass is a potential source of energy that can reduce our dependency on oil as the main source of energy. In addition to municipal solid waste, animal and olive wastes are the main sources of organic waste in Jordan. In 2005, there were more than 2.4 million heads of sheep, about 72 thousand cows, and 40 million hens being raised in farms distributed in all governorates of Jordan. These animals produce 5.3 million tons (as exerted) of solid waste per year. If these quantities can be effectively collected they may constitute a valuable source of energy. This paper is aiming to estimate the amounts of animal and solid wastes generated in Jordan and their energy potential.The total amount of BOD from animal waste is estimated at 200,000 tons per year. Significant quantities of organic waste can also be collected from olive mills distributed in the country. This waste known locally as “Jift” is currently being collected and used for heating during the winter. The amount of olive waste produced in 2005 was about 27,000 tons. The potential for energy recovery from these wastes was investigated. Assuming an overall waste collection efficiency of 70%, the total heating value of these wastes was found to be 6600 million MJ. This quantity is equivalent to 157 thousand tons of oil equivalent (toe). This quantity represents 84% of Jordan's local crude oil and natural gas production. However, it only represents 2% of the total primary energy consumption of 7187 thousand toe. In addition, the scattering of farms and olive mills in the country will make the collection of their waste costly. Therefore, any potential project for energy recovery from animal and olive wastes in a centralized plant may have low economic merit; however, its environmental benefits are tangible. Decentralized collection and processing of these wastes may be a better option.     

Life cycle assessment of a PPV plant applied to an existing SUW management system

The huge amount of wastes produced by modern and developed countries involves important aspects of economical, social and technical fields and also of the environment. For this reason, different technologies have been proposed for trying to reduce the impact of waste management and disposal. Generally waste management system consists of different steps like selective collection, recycling and reuse operation, energy recovery from waste and landfilling. A new technology proposed for thermal waste treatment is the plasma pyrolysis vetrification (PPV). This system seems to have interesting perspective due to the possibility of thermal treatment of dangerous slag or waste producing inactivate vetrified substances that can be landfilled or used as building materials with no impact on the environment. In this study, the effect of the application of a PPV plant on an existing waste management system was evaluated with a life cycle assessment (LCA) analysis. All the activities connected to the existing system have been carefully analysed by collecting a large quantity of experimental data. Some assumptions have been made, in particular, on the PPV plant performance. LCA analysis results illustrate how the environmental benefits arising from the adoption of the new technology, concerns only few aspects of the whole system. Copyright © 2003 John Wiley & Sons, Ltd.     

Life cycle assessment of waste to energy micro‐pyrolysis system: Case study for an Italian town

Waste disposal represents an important aspect of the policies of politics of developed countries. It is well known that waste management entails several social, economical and environmental aspects. Many different technical solutions have been proposed and evaluated, more or less complicated, from a social and economic point of view, but the environmental burden linked to these solutions still remains an open problem not definitively resolved yet. One of the most promising ways for investigating and comparing the environmental consequences connected to different human activities seems to be represented by the LCA analysis. In this work the LCA analysis of a micro‐pyrolysis with micro‐gas turbine waste to energy plant, has been performed with the aid of a commercial simulation code. The scenario is analysed with regard to a small, isolated, Italian town. A comparison between the current and proposed case has also been carried out. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermodynamic analysis of olive oil mill wastewater steam reforming

A thermodynamic analysis of the steam reforming of olive oil mill wastewater (OMW) was performed in a traditional reactor (TR). The equilibrium compositions are calculated employing the Gibbs free energy minimization method (using Aspen Plus V8.8^® software). The simulations were performed at different temperatures (300–1000 °C), different pressures (1–20 bar) and different compositions of the OMW, which might differ considerably. It was found that the H₂ yield increases with the temperature up to a maximum value, while it continuously decreases with the pressure. In opposition, the water content in the feed increases the H₂ yield, thus providing opportunity to take advantage of the waste aqueous matrix. The optimum operating conditions for several OMW compositions, corresponding to either real or simulated effluents from different areas, were determined; this is a very important aspect that allows to assess, in advance, the potential of such waste valorization into green hydrogen production. Moreover, it was found a good agreement between the maximum H₂ yield obtained for each wastewater and the ones predicted based on their compositions. Coke formation was also accounted, which increases when decreasing either temperature or water content in the feed. However, for a water content in the feed greater than 60 wt.% (which is the case of most OMWs) there is no coke formation whatever the temperature and pressure (within the ranges used in this study) and for all the effluent compositions considered.     

Integrated waste management as a mean to promote renewable energy

Management of municipal solid waste is an efficient method to both increase resource efficiency (material and energy recovery instead of landfill disposal) and to replace fossil fuels with renewable energy sources (waste is renewable in itself to a large extent as it contains paper, wood, food waste etc.). The paper presents the general outline and results from a comprehensive system study of future waste management. In the study a multifunctional waste management system integrated with local energy systems for district heating and electricity, wastewater treatment, agriculture and vehicle fuel production is investigated with respect to environmental impact and financial economy. Different waste technologies as well as management strategies have been tested. The treatment is facilitated through advanced sorting, efficient treatment facilities and upgrading of output products. Tools used are the ORWARE model for the waste management system and the MARTES model for the district heating system. The results for potential global warming are used as an indicator for renewable energy. In all future scenarios and for all management strategies net savings of CO₂ is accomplished. Compared to a future reference the financial costs will be higher or lower depending on management strategy.     

优化系统,废热蒸汽资源化

本文介绍了一个将废热利用与改善环境相结合,成功实施的案例。该项目既提高了企业的经济效益,又改善了环境。通过案例实施技术、经济和环境效益的分析表明：废热利用和改善环境相结合的技术是一种最佳的能量回收技术,应在企业大力推广。     

Analysis of olive grove residual biomass potential for electric and thermal energy generation in Andalusia (Spain)

As fossil fuels are not only a limited resource, but also contribute to global warming, a transition towards a more sustainable energy supply is urgently needed. Therefore, today's environmental policies are largely devoted to fostering the development and implementation of renewable energy technologies. One important aspect of this transition is the increased use of biomass to generate renewable energy. Agricultural residues are produced in huge amounts worldwide, and most of this residue is composed of biomass that can be used for energy generation. Consequently, converting this residue into energy can increase the value of waste materials and reduce the environmental impact of waste disposal. This paper analyses the situation of biomass energy resources in Andalusia, an autonomous community in the south of Spain. More specifically, biomass is the renewable source which most contributes to Andalusian energy infrastructure. The residual biomass produced in the olive sector is the result of the large quantity of olive groves and olive oil manufacturers that generate byproducts with a potentially high energy content. The generation of agricultural and industrial residues from the olive sector produced in Andalusia is an important source of different types of residual biomass that are suitable for thermal and electric energy since they reduce the negative environmental effects of emissions from fossil fuels, such as the production of carbon dioxide.     

Estonian electricity supply scenarios for 2020 and their environmental performance

Estonia is the only country in Europe with significant environmentally intensive oil shale-based energy production. However, the legal obligations of the EU will make substantial changes over the coming years to current electricity production technology. Increasing the use of alternative energy carriers for responding to future requirements has also been in focus. In this study, three different future electricity supply scenarios for Estonia in 2020 are considered and compared to the situation in 2002. They are based on domestic oil shale, imported natural gas, and imported nuclear power. According to the aims of the national energy policy, renewable energy sources were raised to 10% in all scenarios. Using the LCA methodology, the least damaging impact on the environment occurs in the ‘nuclear scenario’, with nuclear energy as the main energy source. The best scenario, however, depends on the weight or acceptance of accidental releases or other impacts not defined in this context. The ‘Oil shale scenario’ would be a slightly more damaging alternative than the ‘Natural gas scenario’ even if new technical solutions will remarkably improve the environmental performance of oil shale electricity production. Land use and waste disposal are crucial issues, particularly for oil shale and nuclear electricity production. However, the depletion of oil shale is not as critical an issue as the depletion of natural gas and uranium. According to the significance analysis of impact categories, climate change is the most significant impact on the environment in the scenarios. Future decisions on the development of the Estonian energy sector are most likely to be based on technological, economical and political aspects. Political aspects are likely to be the most significant. However, this type of study can give additional value to the discussion due to the increasing role of sustainability in energy issues.     

径向热管换热器在天然气工业炉低温烟气中的应用

当前我国的能源形势紧张,能源利用状况令人担忧.在一些高耗能的企业,工业生产中排放的中低温烟气余热由于回收难度高、回收成本大等问题,一直得不到合理的利用,如何合理回收成为亟待解决的难题之一.简要介绍了一种新型余热利用换热设备——径向热管换热器,提出了计算热管换热器经济性评价指标的方法,并以某工厂低温烟气余热回收工程为实例,对烟气余热的回收利用进行了技术和经济效益分析.实践应用证明,径向热管换热器在工业低温烟气余热回收中有很好的实用性和可行性.     

Cleaner bioprocesses for promoting zero-emission biofuels production in Vojvodina

In this study, the policy, market conditions and food security of biomass energy sources are assessed for supplying the future needs of Vojvodina. The Autonomous Province of Vojvodina is an autonomous province in Serbia, containing about 27% of its total population according to the 2002 Census. It is located in the northern part of the country, in the Pannonia plain, in southeastern Europe. Vojvodina is an energy-deficient province. The incentives to invest human and financial resources in the research and development of cleaner bioprocesses are high, considering the benefits which might be achieved in terms of environment protection and manufacturing costs. In the near and medium tenu, the development of bioprocesses for waste recycling and resource recovery might be one of the most viable options, considering much research work has already been done. In Vojvodina, there are technological solutions that biofuels produced in a closed cycle, so that the quantity of waste reduced to a minimum. These solutions include the stillage (remainder after distillation) used for fattening cattle, and cattle excrement to produce biogas and manure as fertilizer. The energy required for the production of bioethanol is obtained combustion lignocelullose residual waste from the production of basic raw materials starch, or biogas. Ash from the burned biomass returned to soil as a source of minerals for plants and replacement of mineral fertilizer. Such a closed cycle is economical for small farms in Vojvodina.     

Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO2 photocatalysis and solar photo-Fenton

Olive mill wastewater (OMW), a highly polluted wastewater from the olive oil industry, was treated by solar photocatalysis and solar photo-Fenton. Among the tested systems the application of titanium dioxide alone was not successful. The addition of peroxydisulphate as an electron acceptor had only limited effect on degradation performance and led to high salt concentrations (30 g/l sulphate generated) and a pH value near zero. The photo-Fenton method successfully removed up to 85% COD and up to 100% of phenol index of OMW with different initial concentrations and from different sources. Two solar photocatalytic pilot-plant reactors were used; one of conventional CPC type and an open non-concentrating Falling Film Reactor. The latter, newly designed reactor worked properly and yielded comparable results to the CPC in terms of degradation rate referred to incident UV radiation energy per solution volume. The suspended solids in the OMW hinder light from entering the reactor. Therefore, flocculation induced by a commercial flocculation agent was successfully applied to remove suspended solids. Application of this pre-treatment led to considerable increase of degradation rates and decrease of hydrogen peroxide consumption.     

Adsorption heat pumps for providing coupled heating and cooling effects in olive oil mills

The olive oil mill wastewater presents serious environmental threats. In this study, adsorption heat pumps utilizing zeolite coatings were proposed for olive oil mills as a helping tool for the treatment of wastewater, as well as for providing a cooling effect, which may especially be useful to prevent thermal deterioration of the olive oil. The performance of a heat pump using two adsorbers operating with waste heat was determined for different operating conditions. It was established that a sufficiently high amount of olive oil wastewater might be treated in such a system when a suitable source of waste heat is used for heating the adsorbers of the heat pump. Copyright © 2007 John Wiley & Sons, Ltd.     

Chemical, physical and spectroscopic characterization of Posidonia oceanica (L.) Del. residues and their possible recycle

Posidonia is an endemic marine plant of the Mediterranean Basin forming wide grasslands involved in the oxygenation of seawaters, fauna protection and littoral erosion prevention. Starting from September-October, leaves and part of rhizomes detach off the marine plant and reach the beaches. Onshore residues represent a great environmental, economical, social and hygienic problem in all coastal zones of Mediterranean Basin because of the great disturb to the bathers and population, and the high costs for their removal and disposal to landfill.Authors characterized the onshore residues by means of physical, chemical and spectroscopic analyses in order to propose alternative solutions to the landfill and to reutilize them in agricultural applications as well as a source of energy.Physical, chemical and spectroscopic features of posidonia residues indicated a possible utilization in agriculture in their raw state. In facts, provided a reduction in the electrical conductivity and Na content, plant residual materials may be directly used as growing media or appropriately composted with raw materials of different provenance and basically opposite characteristics. In particular, the fibrous debris showed features similar to a bulking agent, while the leaves residues closely resembled a green waste. The fibrous portion of posidonia residues can be also utilized as biofuel according to their lower heating values (LHV) ranging between 13.6 and 15.7 MJ kg⁻¹, whereas leaves debris are not so suitable for the energy recovery because their LHV were around 10 MJ kg⁻¹.     

Energetic approach of waste water processing using dry kernel as a fuel

The aim of this paper is to identify a suitable usage of the enormous amount of dry kernel, a biomass derived from olive-oil processing, as a combustible fuel in the disposal process of waste water. The method recommended besides the disposal of waste water, allows the recovery of the diluted substances with a remarkable reduction of functional costs. The method is supported by a two-year long experimental campaign during which more than 13,000 tons of waste water were processed.     

Modelling the impact of energy taxation

Energy taxation in Sweden is complicated and strongly guides and governs district energy production. Consequently, there is a need for methods for accurate calculation and analysis of effects that different energy tax schemes may have on district energy utilities. Here, a practicable method to analyse influence of such governmental policy measures is demonstrated. The Swedish Government has for some years now been working on a reform of energy taxation, and during this process, several interest groups have expressed their own proposals for improving and developing the system of energy taxation. Together with the present system of taxation, four new alternatives, including the proposed directive of the European Commission, are outlined in the paper. In a case study, an analysis is made of how the different tax alternatives may influence the choice of profitable investments and use of energy carriers in a medium‐sized district‐heating utility. The calculations are made with a linear‐programming model framework. By calculating suitable types and sizes of new investments, if any, and the operation of existing and potential plants, total energy costs are minimized. Results of the analysis include the most profitable investments, which fuel should be used, roughly when during a year plants should be in operation, and at what output. In most scenarios, the most profitable measure is to invest in a waste incineration plant. However, a crucial assumption is, with reference to the new Swedish waste disposal act, a significant income from incinerating refuse. Without this income, different tax schemes result in different technical solutions being most profitable. An investment in cogeneration seems possible in only one scenario. It is also found that particular features of some alternatives seem to oppose both main governmental policy goals, and intentions of the district heating company. Copyright © 2002 John Wiley & Sons, Ltd.     

Treatment of olive mill wastewater by different physicochemical methods and utilization of their liquid effluents for biological hydrogen production

In this study various two-stage processes were investigated for biological hydrogen production from olive mill wastewater (OMW) by Rhodobacter sphaeroides O.U.001. Two-stage processes consist of physicochemical pretreatment of OMW followed by photofermentation for hydrogen production. Explored pretreatment methods were chemical oxidation with ozone and Fenton's reagent, photodegradation by UV radiation, and adsorption with clay or zeolite. Among these different two-stage processes, strong chemical oxidants like ozone and Fenton's reagent have the highest color removal (90%). However, their effluents were observed to be unsuitable for both hydrogen production and bacterial growth. On the other hand, clay treatment method was selected as the optimum process that allows fast and low-cost treatment as well as its effluent found to have the highest hydrogen production potential (31.5 m³ m^?3). Spent-clay regeneration was also investigated on the grounds that solid waste minimization is important for the overall efficiency of this process.