Biomass Electric Power

Biomass is human civilisation's most ancient source of energy. It can be produced in forestry (woody biomass), in agriculture (energy crops) or form part of the waste derived from different kinds of processes (biomass residues). Biomass resources can be found or produced in almost any part of the world.

There are several technological ways to transform the energy content of biomass into electricity. The Technology Radar describes three of these ways in more detail, namely Direct biomass combustionBiomass gasification and biogas-based combustions. You can access these options by using the navigation tool on the right. Several factors are common to all biomass-based technologies for electric power generation, however, and these are highlighted below.

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1. Potential contribution to sustainable development

Global sustainable energy supply

Biomass already contributes 10% to global primary energy consumption, a proportion that is expected to remain constant or even increase. However, traditional inefficient burning still constitutes the major part of this figure and the contribution of biomass to electricity supply is marginal, about 1% of global electricity generation in 20071.

Technologies that use biomass in a more efficient way must be given priority in the sustainable energy system of the future. Modern biomass electric power technologies offer several advantages that are crucial for the sustainable supply of energy: providing base load, balancing out supply fluctuations from other renewable sources and generating heat and power on a decentralised basis. Electricity from biomass may reach up to 5% or 10% of global electricity generation by 2050 according to the IEA2 and Greenpeace3 respectively.

Climate change mitigation

Technologies for the efficient generation of electric power and heat from biomass can have a two-fold effect on climate change mitigation:

  1. Additional greenhouse gas emissions can be avoided by replacing fossil fuels with biomass.
  2. If appropriate management strategies are adopted, the production of biomass for energy could help maintain, or even increase, the overall amount of carbon that is necessary/fixed in soils, forests, agricultural lands and especially degraded lands.

Millennium development goals

The introduction of biomass-based electricity generation technologies may stimulate local development. Positive effects are derived mainly from the required supply of biomass (i.e. new income opportunities for agricultural and/or forestry activities) and from the provision of modern energy services (e.g. affordable and reliable electric power).

The participation of the local community and local organisations is essential in order to exploit local development potential and avoid detrimental effects. Particular attention should be given to specific social issues such as land use, land ownership and food security (see "Social Issues“ bellow).

Some technologies are already suitable for use by households or small communities i.e. those technologies using biogas and vegetable oil. This factor may facilitate the direct participation of local organisations in the development of energy projects. These electricity generation technologies represent a powerful tool to address energy poverty.

2. Environmental Issues

Biomass supply activities (i.e. production, collection and transport activities), which depend on resources and the supply system, form a key part of the impact of biomass use on the environment 4. Biomass can form part of the waste derived from different kinds of processes (biomass residues), it can also be produced in forestry (woody biomass) ore in agriculture (energy crops).

Biomass residues

Biomass residues can be collected as a by-product or waste from agricultural, forestry and industrial activities as well as a fraction of municipal solid waste. The use of this source of biomass does not usually imply any significant additional environmental threat. Rather, in some cases, it represents a useful alternative to waste that becomes a source of contamination unless it is disposed of properly.

However, special attention should be given to harvest residues that are traditionally used to condition soil, as diverting these residues for energy purposes could lead to soil degradation and/or increased application of chemical additives.

Biomass from forests and crops

The potential environmental impact of the production of woody biomass and crops for energetic purposes depends on several factors, such as:

  1. the production system: monoculture, diverse cropping, agroforestry, etc.
  2. the intensity of the use of chemical fertiliser, additives and pesticides
  3. site-specific characteristics (e.g. soil, climate, slope)
  4. distances between production areas, storage points and final processing and transport requirements

Effects of biomass production

The potential negative effects resulting from increased biomass production are diverse. Some notorious examples are:

  • The emission of nitrogen dioxide due to fertiliser use, which has significant ozone depletion potential and, depending on the concentration, also represents health risks for humans
  • The transport of nutrients into water bodies, which can lead to eutrophication of water sources (also due to fertiliser and pesticides)
  • Soil degradation, for example due to less humus in the soil

Land use effects

Changes in land use patterns can result in both positive and negative effects:

  • The production of biomass for energy purposes can form part of programmes addressing both the recuperation of depleted lands and the improvement of access to energy. In this context, the increase of biomass production for energy would lead to positive environmental effects like reforestation of wastelands and the enhancement of the soil's ecological functions.
  • On the other hand, the clearing of pristine forests for energy crops or plantations is one of the most destructive options for increasing the production of biomass for energy. Such a measure represents a threat to the local ecosystem and biodiversity and can even lead to a net increase of greenhouse gases.

Therefore, the environmental impact of the supply of biomass for power generation is very case specific. Strategies to establish sustainable biomass production systems should be assessed as early as during the formulation stage of programmes that aim to introduce biomass electric power technologies.

3. Social Issues

Biomass resources play a key role in economic and social development. Critical issues are directly related to the management of biomass resources, including food security, land use and land ownership and agricultural and forestry development. Therefore, the introduction of new energy technologies that use biomass has a direct impact on social development at the local, regional or national level 5.

Chances and risks

In best-case scenarios, the increasing demand of biomass for energy use may add value to the products of local farmers and translate into additional incomes. On the other hand, the rising demand for biomass may also result in a concentration of land ownership, competing land uses (energy vs. food crops), higher food prices and poor people facing deeper poverty.

Consideration of local social realities

The implementation of technologies may take the social realities of the target region into account, e.g. by:

  • Identifying interested parties and the populations and organisations that could be affected
  • Adopting transparent and participative communication and decision-making processes
  • Establishing adequate regulations and institutions to ensure that the application of modern biomass technologies becomes a driver of social development
  • Considering possible prejudices against use of organic waste from humans or animals

The social impacts of using of biomass for the provision of electric power are therefore case specific and have to be carefully assessed as early as during the formulation stage of programmes or projects that aim to introduce biomass electric power technologies.

4. Development status and prospects

Biomass is already being used as fuel for the cogeneration of heat and power. Some agricultural and forestry industries already use the biomass residues they produce to cover internal energy demand. Prominent examples of this are the use of bagasse in sugar and ethanol industries and chips and dust in the wood industry.

There are several technological ways to transform the energy content of biomass into electricity. The most notable examples of this are direct combustion of biomass, gasification, biogas and vegetable oil extraction.

Direct combustion of biomass

Biomass combustion and power generation using steam turbines is already a commercial option for larger applications (power capacities of several MW). (Direct biomass combustion)

Biomass gasification

The anticipated developments in biomass gasification integrated with the cogeneration of heat and power promise higher efficiency and lower emissions for larger applications. It may also be possible to improve the use of solid biomass in small applications (below 500 kW). (Biomass gasification)

Biogas for electric power

The production of biogas from domestic and industrial residues (e.g. sewage sludge gas, landfill gas), but also from energy crops, is state of the art today. The average capacity of plants in Europe is estimated to be around 100 kW of electricity. (Biogas),

Research on sustainable biomass production

In addition to the expected developments in energy technologies, the question of how to increase the uptake of biomass from natural cycles into the energy sector, while at the same time avoiding or mitigating long-term detrimental effects on the ecosystems and social structures concerned, constitutes a larger area of research and development.

Sustainable management systems and certification

Certification schemes for sustainable biomass supply chains are being developed and tested. On the other hand, research and development needs to be undertaken on optimal management systems for biomass resources. Sustainable agriculture and forest management techniques that match the specific requirements of local ecosystems and social structures must be developed.

5. Economic Issues

The technical and economic feasibility of biomass power generation is heavily influenced by the availability of biomass as well as its quality. Factors such as seasonality, proximity to the production sites, local biomass prices and global markets, and storage and pre-treatment requirements are crucial for the design of an application (e.g. selection of the optimal site and size of the plant) and for its economic viability (e.g. generation costs).

The resulting generation costs strongly depend on the source of the biomass. There is often no market price for biomass from waste flows. In such cases, only collection and transport activities have to be taken into account. The situation is substantially different for energy crops or forestry products where the variability of market prices can strongly affect the financial feasibility of a project.

References

  1. International Energy Agency (IEA) (2009): World Energy Outlook 2009
  2. International Energy Agency (IEA) (2008): Energy Technology Perspectives, Scenarios and strategies to 2050
  3. Greenpeace International and European Renewable Energy Council EREC (2008): Energy [R]evolution, a sustainable global energy outlook
  4. United Nations Environmental Programme (UNEP) (2009): Towards Sustainable Production and Use of Resources: Assessing Biofuels
  5. United Nations , UN-Energy (2007): Sustainable Bioenergy: A Framework for Decision Makers