Ad van Wijk

Gasification of biomass wastes and residues for electricity production

Abstract The technical feasibility and the economic and environmental performance of atmospheric gasification of biomass wastes and residues integrated with a combined cycle for electricity production are investigated for Dutch conditions. The system selected for study is an atmospheric circulating fluidized bed gasifier-combined cycle (ACFBCC) plant based on the General Electric LM 2500 gas turbine and atmospheric gasification technology, including flue gas drying and low-temperature gas cleaning (similar to the Termiska Processer AB process). The performance of the system is assessed for clean wood, verge grass, organic domestic waste, demolition wood and a wood-sludge mixture as fuel input. System calculations are performed with an ASPEN plus model. The composition of the fuel gas was derived by laboratory-scale fuel reactivity tests and subsequent model calculations. The net calculated efficiencies for electricity production are 35.4–40.3% (LHV) for the fuels studied, with potential for further improvement. Estimated investment costs, based on vendor quotes, for a fully commercial plant are 1500–2300 ECU per kW e installed. Electricity production costs, including logistics and in some cases negative fuel price, vary between minus 6.7 and 8.5 ECUct/kWh. Negative fuel costs are obtained if current costs for waste treatment can serve as income to the facility. Environmental performance is expected to meet strict standards for waste incineration in the Netherlands. The system seems flexible enough to process a wide variety of fuels. The kWh costs are very sensitive to the system efficiency but only slightly sensitive to transport distance; this is an argument in favour of large power-scale plants. As a waste treatment option the concept seems very promising. There seem to be no fundamental technical and economic barriers that can hamper implementation of this technology.

Biomass combustion for power generation

An overview is given of the state of the art of biomass combustion power generation technologies with a capacity of more than 10 MWe. Biomass combustion technologies have been compared on a qualitative basis and a selection of individual biomass combustion power plants has been compared on a quantitative basis. Collected data were modified for comparison of the various power plants in the quantitative analysis. The qualitative analysis focused on the following technologies: pile, grate, suspension and fluidised-bed combustion. Fluidised-bed systems are found to have relatively high efficiencies and are also flexible with regard to fuel properties. Both fluidised-bed systems and vibrating grates are successful in limiting thermal NOx formation. Some recently built plants and some planned concepts are compared quantitatively on the basis of efficiency, investment costs and emissions. All electric efficiencies are close to or above 30% (at lower heating value). Of the plants fired solely by biomass, vibrating grates and circulating fluidised beds turn out to have the highest efficiency at the moment. Co-firing of 4.5% biomass in a pulverised coal boiler has an efficiency of about 37% (LHV). Expected efficiencies for large-scale (100 to 250 MWe) promising concepts are in the 39–44% (LHV) range. Investment costs range from 1200 to 2900 (1992)US

CHARACTERISTICS AND AVAILABILITY OF BIOMASS WASTE AND RESIDUES IN THE NETHERLANDS FOR GASIFICATION

/kWe. High costs are often caused by additional features such as the firing of difficult fuels or combined heat and power production. None of the existing technologies is found to be superior with respect to all the criteria selected.

Electricity generation from eucalyptus and bagasse by sugar mills in Nicaragua: A comparison with fuel oil electricity generation on the basis of costs, macro-economic impacts and environmental emissions

Abstract Characteristics and availability of biomass waste streams and residues for power production by means of integrated gasification/combined cycle technology (BIG/CC), are evaluated for The Netherlands. Four main categories are investigated: streams from agriculture; organic waste; wood; and sludges. Altogether 18 different streams are distinguished. Gross availability and net availability are inventorized. Various properties (composition, heating value, supply patterns) are analysed and the suitability of these streams for conversion in a BIG/CC unit is studied. The costs at which various streams are likely to be available are assessed. The gross energetic availability amounts annually to approximately 190 PJ (HHV) primary energy. Because of competing useful and higher value applications than fuel of various streams, such as fodder and fertilizer, the net availability is slightly less than 90 PJ (HHV). For a number of streams the costs are negative due to present waste-treatment costs. Costs of waste streams vary from — 10-5 ECU/GJ. For a small fraction the costs are higher than for energy crops (estimated to be approximately 4.5 ECU/GJ). Because there are large variations in properties and contaminants between various streams, the conversion system needs to flexible when a diversity of streams is treated in one installation. Some streams require mixing with cleaner fuels to make them suitable for use in a direct atmospheric biomass integrated gasifier/combined cycle system. Important technical limits for the use of biomass fuels in the system studied, are the moisture content (maximum 70% of wet fuel) and ash content (maximum 20% dry matter content) of the fuel.

Green Energy or Organic Food?: A Life‐Cycle Assessment Comparing Two Uses of Set‐Aside Land

Two sugar mills in Nicaragua plan to generate electricity from bagasse during the sugarcane season and eucalyptus during the rest of the year, and to sell it to the national grid. This study compared this concept with the most logical alternative at the moment, which is electricity generated from fuel oil. Costs, macro-economic impacts and environmental emissions are considered. The low cost of land and labour means that eucalyptus can be produced more cheaply than fuel oil (1.7 as compared to 3.2

Heat supply in the netherlands: A systems analysis of costs, exergy efficiency, CO2 and NOx emissions

/GJLHV). Consequently, it was calculated that a sugar mill can produce electricity from biomass for 4.9 mc/kWh as compared to 5.8 mc/kWh for electricity from an oil fired plant. About 64% of the money spent on biomass power stays within Nicaragua, thus contributing to its GDP, whereas in the case of fuel oil 83% goes abroad. The employment generated by the production of electricity from fuel oil is 15 person yr/MW yr, compared to 32 person yr/MW yr for biomass. Comparing biomass with fuel oil, emissions of CO2 and SO2 equivalents are, respectively, 67 and 18 times lower. Particulate emissions can be much higher in the biomass case because of lack of flue gas cleaning. We can conclude that biomass electricity generation by sugar mills in Nicaragua can compete with power generation from fuel oil. Moreover, it has an overall better environmental performance, creates double the amount of jobs, and contributes about four times as much to the GDP of Nicaragua.

Willow firing in retrofitted Irish peat power plants

Summary Bioenergy has a large worldwide potential in future climate change abatement, although its application may become limited by demands for land for other functions. The aim of this study was to make an environmental assessment of the use of energy crops in the Netherlands in a context that incorporates scarcity of land. A base case system was defined, consisting of conventional winter wheat production, set-aside land (1 hectare, together), and the production of coal-based electricity. Using life-cycle assessment, we compared this system with (1) a green energy system in which willow is cultivated on the set-aside land to replace the coal-based electricity and (2) an organic agriculture system in which the full hectare produces wheat under the Dutch EKO organic agriculture standard. In this way, the functional unit and the amount of land used is the same in each system. The final system comparison was based on normalized scores per environmental theme. The green energy system scored the best with respect to acidification, climate change, and energy carrier depletion. The organic food system scored best on terrestrial eco-toxicity and slightly better on the mutually related themes of seawater and seawater sediment eco-toxicity. The base case system performed slightly better with regard to eutrophication. Preferences, from an environmental point of view, for one of the systems should be determined by environmental policy priorities and the severity of local environmental problems. The case studied here shows that when climate change, energy carrier depletion, and acidification are the main drivers behind environmental policy, one should focus not on the extensification of agriculture, but rather dedicate more land to energy crops. Extensification of agriculture would be the preferred system when toxicity from pesticides is considered the main problem.

Electricity from energy crops in different settings—a country comparison between Nicaragua, Ireland and the Netherlands

About 50% of the primary energy supply in The Netherlands is used for heat production. To achieve a sustainable heat-supply system, it is necessary to obtain insight into costs, efficiency and environmental impacts for existing and possible future technologies. We have performed a comparative system analysis on six possible heat-supply chains (distribution and conversion) providing low-temperature heat to households to obtain a clear picture of their likely long-term economic, energetic and environmental performance to the year 2030. The systems studied are based on natural gas distribution [local condensing boilers or micro-cogeneration (indoors)] and on electricity (heat-pumps) and heat-distribution (district heat and small-scale cogeneration). A systems analysis was used. A heat-supply system based on district heating and/or electricity distribution turns out to be a good alternative to the present gas-based system. In addition, introduction of these systems will facilitate the future sustainability of energy sources.

Farm-based versus industrial eucalyptus plantations for electricity generation in Nicaragua.

Abstract Concerns about CO 2 emissions have caused renewed interest in biomass electricity in Ireland. A low-investment-cost option is the firing of locally grown willow in retrofitted Irish peat plants. Various options for such a biomass energy system were evaluated. All steps in the supply chain were integrated in a model and optimised economically. Retrofitting of existing peat plant was compared with building new biomass combustion and gasification plants. All conversion technologies considered are able to co-fire biomass and peat. The study focused on possibilities in the short term. To reflect uncertainties, all costs were presented in ranges. Neither agricultural subsidies nor possible CO 2 taxes were included. The lowest cost retrofit option with a proven technology was the conversion of unit 3 of the Lanesborough peat plant into a bubbling fluidised bed. The willow costs at the plant gate ranged between 4.4 and

Optimisation of the final waste treatment system in The Netherlands

15/GJ LHV and the kW h costs between 7.5 and 21¢/kW h. The not yet proven options of gasification and the retrofit into a whole-tree energy plant showed slightly lower costs. The large ranges in the costs were mainly caused by the difference between the low and high estimation of the willow yields and the farmers annual income. It can be concluded that in the lowest cost estimate, willow firing in retrofitted Irish peat plants has about the same cost as peat firing. (