Richard van den Broek

The contribution of biomass in the future global energy supply: A review of 17 studies

This paper discusses the contribution of biomass in the future global energy supply. The discussion is based on a review of 17 earlier studies on the subject. These studies have arrived at widely different conclusions about the possible contribution of biomass in the future global energy supply (e.g., from below 100 EJ yr-1 to above 400 EJ yr-1 in 2050). The major reason for the differences is that the two most crucial parameters - land availability and yield levels in energy crop production - are very uncertain, and subject to widely different opinions (e.g., the assessed 2050 plantation supply ranges from below 50 EJ yr-1 to almost 240 EJ yr-1). However, also the expectations about future availability of forest wood and of residues from agriculture and forestry vary substantially among the studies. The question how an expanding bioenergy sector would interact with other land uses, such as food production, biodiversity, soil and nature conservation, and carbon sequestration has been insufficiently analyzed in the studies. It is therefore difficult to establish to what extent bioenergy is an attractive option for climate change mitigation in the energy sector. A refined modeling of interactions between different uses and bioenergy, food and materials production - i.e., of competition for resources, and of synergies between different uses - would facilitate an improved understanding of the prospects for large-scale bioenergy and of future land-use and biomass management in general.

Exploration of the ranges of the global potential of biomass for energy

Abstract This study explores the range of future world potential of biomass for energy. The focus has been put on the factors that influence the potential biomass availability for energy purposes rather than give exact numbers. Six biomass resource categories for energy are identified: energy crops on surplus cropland, energy crops on degraded land, agricultural residues, forest residues, animal manure and organic wastes. Furthermore, specific attention is paid to the competing biomass use for material. The analysis makes use of a wide variety of existing studies on all separate categories. The main conclusion of the study is that the range of the global potential of primary biomass (in about 50 years) is very broad quantified at 33−1135 EJy −1 . Energy crops from surplus agricultural land have the largest potential contribution (0– 988 EJy −1 ) . Crucial factors determining biomass availability for energy are: (1) The future demand for food, determined by the population growth and the future diet; (2) The type of food production systems that can be adopted world-wide over the next 50 years; (3) Productivity of forest and energy crops; (4) The (increased) use of bio-materials; (5) Availability of degraded land; (6) Competing land use types, e.g. surplus agricultural land used for reforestation. It is therefore not “a given” that biomass for energy can become available at a large-scale. Furthermore, it is shown that policies aiming for the energy supply from biomass should take the factors like food production system developments into account in comprehensive development schemes.

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

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

/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.

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

Willow firing in retrofitted Irish peat power plants

/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.

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

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.

Rural electrification in Tanzania : Constructive use of project appraisal

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

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

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. (

RETROFITTED IRISH PEAT PLANTS WITH WILLOW AS FUEL

4.3/GJ LHV and 7.4¢/kW h) and could therefore be a promising option to reduce CO 2 emissions in Ireland.